Electrochemically and Ultrasonically-Enhanced Coagulation for Algae Removal

At the global level, the augmenting presence of harmful algae blooms constitutes important dares to water treatment plants (WTPs). In WTPs, coagulation remains the primary process of the applied procedure to treat algae-contaminated water. Such a chemical process influences the following techniques; thus, regulating coagulation parameters to eliminate algae at the maximum degree without provoking cell deterioration is more than crucial. This work aims to review coagulation-founded methods for algae elimination. First, investigations concentrating on algae elimination using the chemical process are discussed. The introduction presents the widespread algae encountered in the water treatment field. Then, habitually utilized experimental techniques and emerging methods in coagulation investigations are summarized with typical findings. Next, the newest expansions in improved algae elimination, launched by electrochemically and ultrasonically-enhanced coagulation, are discussed. Workable thoughts for applying coagulation to eliminate algae in WTPs are also debated. The paper finishes by defining restrictions and dares related to the present literature and suggesting trends for subsequent studies. The charge neutralization mechanism efficiently removes solubilized microcystins (MCs), and enhanced coagulation configuration is also found to be more efficient for their removal. However, considerations should be taken to avert that the acid introduction has no unwanted effect in killing algae treatment to avoid the solubilized MCs level elevation. If such techniques are well-optimized and controlled, both algae and solubilized MCs could be efficaciously removed by ultrasound-enhanced coagulation and electrocoagulation/electrooxidation.

• Harmful Algal Blooms (HABs)
• Electrocoagulation (EC)
• Electrooxidation (EO)
• Ultrasound (US)
• Machine Learning (ML)
• Reactive Oxygen Species (ROSs)

1. Introduction

A flourishing population of phytoplankton microorganisms in aquatic ecosystems, like eukaryotic algae and cyanobacteria, is more than an essential constituent [1] [2] [3] . Nonetheless, harmful algal blooms (HABs) could exist below some ecological circumstances conducting to immoderate aggregation of algal biomass, exhaustion of dissolved oxygen, and inherent formation of toxins [4] [5] [6] . In water treatment and human safeguard, some algal types that form toxins remain of noteworthy worry [7] [8] . Such poisonous substances could provoke unfavorable human health influences [9] [10] . Several HAB-producing species generate disagreeable taste and odor (T&O) substances [11] . Even if cyanobacteria repeatedly remain the most difficult harmful algal category, numerous other eukaryotic algae also worsen water quality by forming toxins [12] . Table 1 presents the frequent algae of interest and their likely influences on water quality. Even if HABs could exist naturally, the effects of human activities (e.g., expanded nutrient charge and hydrologic change) have been related to the augmenting recurrence of HAB cases [13] [14] . The severe effects of HABs on water safety have been confirmed broadly in many instances, during which potable water supply had to be suspended because of poisonous HABs [15] [16] . Since climate alteration is foreseen to modify the recurrence, distribution, and gravity of HABs, vigorous management procedures must be elaborated to dominate the harmful impacts of HABs in natural waters and furnish enough supplies of protected potable water [1] .

Water treatment plants (WTPs) use a multi-barrier procedure to deal with algae-infected source water [1] [19] [20] . In traditional potable water treatment techniques, coagulation remains largely the opening treatment unit [8] [21] [22] . However, its performance immediately influences all downstream treatment stages [23] [24] [25] . Destroyed algal cells could liberate toxins, T&O compounds, and additional cellular metabolites that generate disinfection by-products (DBPs) [15] [26] [27] . Thus, the main objective of coagulation, besides the following solid-liquid separation methods (i.e., clarification and filtration), remains to increase the elimination of algae without touching the cell integrity [7] [10] [28] . The significance of coagulation in treating algae issues overpasses treatment plants [2] [3] [5] .

Regarding water management, the basic procedure to stop and dominate eutrophication and algae-linked troubles is to decrease the nutrient charges into waterbodies [6] [11] [19] . Comparatively, defining point-source nutrients related

Table 1

Frequent algae of interest to water treatment [ 1 ] [ 17 ] [ 18 ]

Classification	Common genera of interest	Biological characteristics	Importance
Cyanobacteria (blue-green algae)	Anabaena, Aphanizomenon, Cylindrospermopsis, Lyngbya, Microcystis, Oscillatoria, Phormidium, Planktothrix	• Cell walls are composed of peptidoglycan and a layer of lipopolysaccharide (Gram-negative) • Pigments include chlorophylls, phycobilins, and carotenoids • Contain specialized structures: aerotopes, heterocytes, and akinetes • Various morphologies: unicellular, colonial, filamentous	• Produce cyanotoxins (cyclic peptides, alkaloids, and endotoxins) • Produce T&O compounds • Clog water intake and filter • Increase in organic matter
Chlorophyta (green algae)	Chara, Cladophora, Hydrodictyon, Pithophora, Scenedesmus	• Have flagella in at least one life stage • Various morphologies: unicellular, colonial, filamentous	• Some genera produce T&O compounds
Bacillariophyta (diatoms)	Aulacoseira, Cyclotella, Melosira, Nitzschia, Pseudonitzschia, Synedra, Tabellaria	• Cell walls are made of silica • Two forms: centric and pennate • Many have spines or stellate	• Only one marine genus (Pseudonitzschia) produces a toxin (domoic acid) • Some genera produce T&O compounds
Dinophyceae (dinoflagellates)	Ceratium, Peridinium	• Unicellular with two dissimilar flagella • Many have lorica made of cellulose	• Many marine genera produce toxins • Only one freshwater toxin-producing species (Peridiniopsis polonicum) • Some genera produce T&O compounds
Chrysophyceae (golden algae)	Chrysosphaerella, Dinobryon, Uroglen	• Unicellular with one or two dissimilar flagella • Unique siliceous cyst • Some have lorica	• Some genera produce T&O compounds
Euglenophyceae (euglenoids)	Euglena, Phacus	• Generally, spindle-shaped • No cell walls, but enveloped by a proteinaceous pellicle	• A few species (e.g., Euglena sanguinea) produce a toxin (euglenophycin)
Haptophyta	Prymnesium	Usually with two flagella and a unique haptonema	• Prymnesium parvum produces a toxin (prymnesin)
Phaeophyceae Xanthophyceae Rhodophyta		• Commonly known as brown, yellow-green, and red algae, respectively.	• Rarely in large quantities, not a concern

to urban and industrial wastes stays simple and satisfies regulatory discharge limits using advanced processes for improved nutrient elimination [12] [14] [29] . Nonetheless, attempts at point-source nutrient lowering are frequently useless because of the primarily unregulated nutrient inputs from nonpoint sources (e.g., agricultural drainage, soil erosion, urban runoff, and household septic systems) [30] . Actions to decrease nonpoint-source nutrients (e.g., applying best management practices in agriculture) could be expensive, and it could take several years to depict marks of amelioration [1] . This can follow from the internal cycling of nutrients aggregated in the sediment because of constant external charge. Therefore, there is an augmenting agreement that geoengineering actions are indispensable to deal with the internal legacy phosphorus (P) charge inside a water body [1] [13] . Processes founded on coagulation and precipitation have set significant capacity in decreasing eutrophication and dominating algal blooms [31] [32] [33] . This method uses coagulants with ballast materials to sink agglomerated algal flocs into the sediment [1] . P-sorbent materials could be used in integration to eliminate P in the water column and diminish its liberation from the deposit. These in-lake actions will be more and more significant to water management because they can engender a direct amelioration in water quality and consequently reduce the time gap until the long-term preventive precautions (like external nutrient decrease) enter into impact [34] .

Coagulation remains one of the most proven water treatment methods; however, applying coagulation stays utterly dependent on an experimental procedure, the jar test [1] [21] [35] . Several depending parameters, including those from water matrices and running circumstances, make the coagulation phenomenon more complex [22] [23] [24] . The various biological properties of algae complicate the situation [19] [36] . The conventional colloidal models and flocculation principles occasionally need to be revised to define the relationship pathways in the coagulation method. They remain as well of restricted employment in anticipating the results when treating complex water matrices [25] [37] [38] . Even with the expanding investigation campaign in this domain, empirical circumstances are frequently similar in such investigations [6] [14] . In addition, numerous publications are short of an explained illustration of practical cases, rendering the juxtaposition among various coagulation setups hard [39] [40] [41] . Nevertheless, traditional coagulants have been primarily utilized for several decades and provided acceptable efficiencies under below-optimized circumstances [42] [43] [44] . Nonetheless, coagulants frequently require algae-laden water injections at a bigger dosage to satisfy the regulatory targets [6] [7] [10] . Such a procedure produces a considerable quantity of sludge that needs substantial treatment before disposal and adds to the global working costs [45] . Also, there has been an unceasing discussion about the long-term security and ecological effects of such usual coagulants (like the inherent negative impacts of aluminum [29] [46] [47] and synthetic polymer coagulants) [48] [49] .

Consequently, the demand for novel kinds of coagulants, which are secure, performant, and cost-effective, has pushed the expansion of new coagulants founded on materials of natural origin [1] [50] [51] . Another fresh progress in algae elimination is integrating coagulation methods with emerging processes like electrochemical techniques [6] [52] [53] and sonication [54] . Such combined treatment technologies can be powered via renewable energy and decrease the chemical need in the coagulation method. However, even if encouraging outcomes have been noticed in lab-scale experiments performed below well-controlled parameters, such strategies must be reliable for field deployment [1] .

Recently published review papers present significant comprehensions on the observation and elimination of cyanobacteria and cyanotoxins [4] [15] [55] ; however, the field of such publications, which include several treatment technologies, does not furnish a complete survey of coagulation-founded techniques [1] . Also, surveys focusing on the global implementation of the coagulation method [56] [57] do not treat the specific dares of algae-infected water. Researchers [58] discuss the effects of algal features on the solid-liquid separation of algae and illustrate the significance of regulating coagulation in the following clarification stage. Ghernaout et al. [2] presented some ameliorations in this domain and shortly displayed the contribution of coagulation in algae and cyanotoxins elimination. The field has progressed highly over the last twelve years by suggesting novel methodologies, improving diverse coagulant materials, and combining new technologies with coagulation. Therefore, even with writing this work, there is a need for a review paper furnishing a thorough survey of the latest advance in algae elimination and domination via coagulation-founded methods. Thus, this work aims to include the usage of coagulation for algae elimination in water treatment and its implementation to deal with eutrophic water bodies. Coagulation/flocculation-founded methods are among the most common processes for harvesting algal biomass [59] .

Nonetheless, it must be mentioned that coagulation’s principal aim is to recover high-purity algal biomass efficiently. Besides, algae-related troubles in water treatment, like toxins and T&O substances, are no longer a worry because algal species are frequently preselected and cultivated in a controlled medium. Consequently, this work will not examine investigations concerning coagulation in algal biomass harvesting. However, a more detailed overview of this subject may be found in such references [1] [59] .

Ren et al. [1] recently discussed the savoir-faire in utilizing coagulation-founded methods to deal with algae-impacted water. They defined the interfacial phenomena in the coagulation process regarding colloidal chemistry and algal properties. They also outlined the empirical procedures frequently utilized in coagulation investigations to estimate floc characteristics, distinguish and observe algal cells, and describe coagulant materials. Also, they debated the advance in the expansion of coagulant materials. In this work, we display the emerging coagulation methods founded on the electrochemical phenomenon and sonication for enhanced algae removal. Further, we focus on the troubles related to coagulation-founded techniques for algae removal in water treatment and in-lake algae control. Lastly, we display the restrictions of existing coagulation investigations and suggest opportunities for future study.

2. New Coagulation Method for Algae Elimination

2.1. Electrochemical Process

2.1.1. Electrooxidation

In an electrochemical cell, the oxidation of a matter may be initiated by either direct electron transfer to the anode (anodic oxidation) or a chemical reaction with species electrogenerated at the anode surface (mediated oxidation) [60] [61] [62] . The oxidation route is mainly controlled by the features of the electrode and solution chemistry [63] [64] [65] . Following the strength of interaction with hydroxyl radicals produced in the electrooxidation (EO) of water, anode materials could be classified into active and non-active anodes (Table 2) [66] [67] [68] . The active anodes boost strong chemisorption of ^•OH and could advance higher oxidation states on the surface [1] . An excellent instance is the mixed metal oxide electrodes prepared by coating the titanium substrate with a film of mixed oxides (like RuO₂, IrO₂, and Ta₂O₅) [69] . Such materials are valuable anodes for the oxygen evolution reaction (OER) thanks to their low overpotential for OER yet show low oxidizing power, conducting to partial oxidation of substances. Further, at the non-active anodes, the interaction with physisorbed ^•OH is weak, leading to poor OER efficiency; even so, a strong oxidizing power promotes total oxidation [60] [70] . On the other hand, boron-doped diamond (BDD) electrodes produce a considerable quantity of loosely adsorbed ^•OH that is so efficacious at oxidizing refractory pollutants and demobilizing algal cells [71] [72] .

The current density (current per unit area of the electrode, mostly expressed as mA/cm²) is a critical parameter determining the EO reaction rate [1] . At low current intensities, the electrochemical method is under current control; thus, an augmentation in the present leads to a more considerable elimination of algal cells [6] . Nonetheless, as the current keeps augmenting, the elimination efficiency attains a plateau because the reaction becomes kinetically restricted by algae’s mass transfer to the anode surface. An additional elevation in current raises the competing OER, decreasing the current efficiency [73] [79] . Most EO tests on algae were performed in lab-scale tank reactors mixed by continuous stirring [74] [85] . Specially engineered flow reactors have presented noticeable amelioration over tank reactors in treating wastewater samples [87] . To favor the mass transport of algae in the EO method, a commercial filter-press flow cell reactor (Electro MP-Cell) was employed, and the hydrodynamics of the reactor was assessed and modeled as a continuous stirred-tank reactor [82] . Even if the device was not optimized, it revealed the large capacity of flow reactors in eliminating algal cells [1] .

Table 2

Experiments on algae demobilization categorized by anode materials utilized in electrooxidation (EO) [ 1 ]

Anode type	Composition	Oxidation potential (V)#	Overpotential of OER (V)#	Studies on algae inactivation
Active	RuO2/Ti	1.4 - 1.7	0.18	[73] [74] [75] [76] [77]
	IrO2-Ta2O5/Ti	1.5 - 1.8	0.25	[78]
	Pt	1.7 - 1.9	0.30	[78]
	Graphite	1.7	-	[74] [79]
	BDD	2.2 - 2.6	1.3	[72] [78] [80] - [85]
Non-active	Magnéli oxides (Ti4O7-Ti5O9-Ti9O17)	2.2 - 2.7	1.3	[86]

^#Potential values (vs. normal hydrogen electrode) are obtained from references [1] [69] [86] .

In electrochemical engineering, the occurrence of electrolytes remains necessary for the electrochemical method to progress [1] [88] . In lab-scale trials, NaCl or Na₂SO₄ is frequently injected into the algae suspension as the supporting electrolyte to reach the desired conductivity [89] . If chloride (Cl⁻) exists, EO forms chlorine (Cl₂) [90] [91] , hypochlorous acid (HClO) [92] , and/or hypochlorite (ClO⁻), following the aqueous pH (Figure 1(a)) [52] [69] [70] . Such active chlorine species can accelerate the oxidation rate through numerous reaction pathways in addition to the coexisting direct oxidation at the anode surface and reactive oxygen species (ROSs)-mediated oxidation [1] [64] . Researchers [80] examined the EO demobilization of Microcystis aeruginosa employing a sandwich-type device with a solid polymer electrolyte. They illustrated that the synergistic influence of in-situ produced ozone (O₃) [93] and Cl₂ species boosted the demobilization of cells and decomposition of microcystins (MCs) when 30 mg/L Cl⁻ was introduced. Scientists [83] likewise demonstrated that the main route of M. aeruginosa demobilization was provoked by the electrogenerated active chlorine, and the level of oxidants was highly dependent on the Cl⁻ (100 - 1000 mg/L). Practically, the BG-11 medium, primarily utilized for cultivating freshwater algae, carries approximately 18 mg/L Cl⁻ [1] [94] .

In addition to the active chlorine, different chlorine oxoacids and oxyanions (e.g., chlorine dioxide (ClO₂), chlorite ( ClO 2 − ), chlorate ( ClO 3 − ), and perchlorate ( ClO 4 − ) could be generated via either direct oxidation of chloride or reaction with hydroxyl radicals formed by the oxidation of water [70] . Among these, chlorine dioxide and chlorite frequently exist considerably lower than active chlorine. Further, chlorate and perchlorate have insufficient oxidizing capabilities than hypochlorite, so the generation of such species competes for chloride and is expected to diminish the oxidation performance [69] . Also, since chlorite, chlorate, and perchlorate could cause toxicity and harmful health impacts, their maximum levels are regulated or considered for regulation [95] [96] [97] . One more dare related to the occurrence of chlorides in EO, particularly at more significant levels, is the possible generation of toxic organochlorinated DBPs like trihalomethanes and haloacetic acids [87] . The typical chloride concentration in freshwater ranges from 1 to 250 mg/L [87] . For example, increased chloride levels have been detected in U.S. rivers during the last years, particularly in urban areas, influenced by anthropogenic sources like road salt and wastewater [98] . As a result, it is not a suitable procedure to use EO for algae demobilization in chloride-rich source water or add extra chlorides as a supporting electrolyte [1] .

The actual efficacy in generating active chlorine is likewise influenced by the characteristics of the anode [1] . Mixed metal oxide electrodes (especially those founded on RuO₂ and IrO₂) are seen to be the most performant in the occurrence of chloride. The RuO₂-founded anode was proven to boost hypochlorite generation [69] . Investigators [77] tested algae demobilization utilizing a RuO₂-Ti anode in simulated surface waters with low Cl levels (0 - 18 mg/L). They demonstrated that active chlorine and hydrogen peroxide (H₂O₂) were the main species inhibiting M. aeruginosa cells. While the level of chorine augmented with the elevation in Cl⁻ level, the level of H₂O₂ diminished. The occurrence of Cl⁻ ameliorated the oxidation performance because of the considerable efficacy of RuO₂-founded anode in forming active chlorine. In the absence of chloride, the generation of hydroxyl radicals and related ROSs from the EO of water dominates. As discussed previously, such a mechanism promotes non-active anodes like BDD. When source water carries additional salts (like sulfates, phosphates, and carbonates), BDD anodes could form persulfate, perphosphate, and percarbonate, and a greater oxidation efficacy can be obtained [87] [99] . As an illustration, researchers [78] juxtaposed the demobilization efficacy of M. aeruginosa below three electrode materials (BDD, IrO₂-Ta₂O₅/Ti, and Pt) with various electrolytes (Na₂SO₄, NaNO₃, and Na₂HPO₄). BDD anode achieved a much greater demobilization efficacy (about 99%) than the other two (10% - 20%) below the identical working circumstances. The most excellent effectiveness was reached with 30 mM Na₂SO₄ as the electrolyte. The in-situ electrochemical formation of persulfate was proved, and ^•OH and reactive sulfate species like SO 4 · − both participated in the increased oxidation of algal cells.

EO mainly implies the phenomena on the anode [100] [101] [102] . To completely take advantage of the electrochemical setup, cathodic phenomena (like the in-situ formation of H₂O₂) may be combined with EO [1] [103] . When iron ions are introduced into the electrolyte [104] [105] [106] , a hybrid setup consisting of EO and the electro-Fenton (E-F) [107] technique can considerably boost the oxidation efficacy (Figure 1(a)). Long et al. [84] examined an electrochemical device with a BDD anode, and a carbon felt cathode for demobilizing M. aeruginosa. When 0.2 mM Fe²⁺ was introduced, the elimination rate was augmented 15 times. The significant amelioration was attributed to the synergistic impact among radicals generated by the BDD anode and the E-F technique. The Fe²⁺ was regenerated on the anode surface [108] [109] [110] ; thus, the Fe²⁺/Fe³⁺ cycle persisted in the device to transform electrogenerated H₂O₂ to ^•OH. The EO/E-F apparatus was efficient in a large pH interval, and the elimination rate was hardly influenced by the pH interval of 3 to 9 [1] .

A large plurality of experimentation on EO demobilization of algae has been performed in lab-scale setups [1] [69] [87] . As a stand-alone process, EO is not a functional technique for algae elimination, at least in terms of water treatment, due to likely side contamination troubles like the generation of DBPs throughout the method. One of the main barriers to scaling up the EO technique for functional exercise is linked to the decay of anode activity. During persistent running, a polymer film of oxidation by-products may aggregate on the electrode surface, leading to the passivation of the anode. BDD is less susceptible to electrode fouling thanks to its inert surface, even if it is still vulnerable to corrosion from anodic oxidation [60] . The first surface can be oxidized through duration, becoming more hydrophilic [111] . The alteration in surface chemistry may affect the electron transfer with redox couples on the electrode that, in turn, can influence the EO performance. EO could be better appropriate as a pre-oxidation stage to be integrated with electrocoagulation (EC) (debated in Section 2.1.2), chemical coagulation, or membrane filtration [112] [113] [114] . The following study can be dedicated to developing such a combined treatment technique and examining the contribution of EO to it.

2.1.2. Electrocoagulation (EC)

In the classic disposition of an electrocoagulation (EC) device (Figure 1(b)), the dissolution of sacrificial anodes (usually in iron or aluminum) liberates metal ions that form flocs in coagulation [115] [116] [117] . Table 3 summarizes the main routes encountered in EC using Fe and Al electrodes [118] [119] [120] .

For instance, in the case of an Al anode, following the aqueous pH, the electrogenerated Al³⁺ ions could be converted into different monomeric and polymeric Al species [1] . Among them, Al(OH)₃ is the predominant species (Reaction (13) and Reaction (14), Table 3) that results in the production of precipitates [123] [124] [125] . Theoretically, the amount of metal ions liberated from the anodic oxidation is stoichiometrically linked with the number of electrons passing across the electrode [126] [127] [128] . Supposing the EC technique is run under constant current, the quantity of coagulant m may be quantified by Faraday’s laws of electrolysis (Equation (16)):

Table 3

Electrocoagulation (EC) mechanisms using Fe (pH 2, 7, and 12) and Al (pH 7) electrodes [ 61 ] [ 109 ] [ 121 ] [ 122 ]

Fe Mechanisms	Medium	Reaction
Mechanism # 1 (pH 2)	Anode	2Fe ( s ) − 4e − → 2Fe ( aq ) 2 + (E˚ = +0.447 V) (1) 2H 2 O ( l ) − 4e − → O 2 ( g ) + 4H ( aq ) + (E˚ = −1.229 V) (2)
	Solution	2Fe ( aq ) 2 + + 4OH ( aq ) − → 2Fe ( OH ) 2 ( s ) (3)
	Cathode	8H ( aq ) + + 8e − → 4H 2 ( g ) (E˚ = 0.000 V) (4)
	Total	2Fe ( s ) + 6H 2 O ( l ) → O 2 ( g ) + 4H 2 ( g ) + 2Fe ( OH ) 2 ( s ) (5)
Mechanism # 2 (pH 7)	Anode	2Fe ( s ) − 4e − → 2Fe ( aq ) 2 + (E˚ = +0.447 V) (1) Fe ( aq ) 2 + − e − → Fe ( aq ) 3 + (E˚ = −0.771 V) (6) Fe ( s ) − 3e − → Fe ( aq ) 3 + (E˚ = +0.037 V) (7)
	Solution	2Fe ( aq ) 2 + + 4OH ( aq ) − → 2Fe ( OH ) 2 ( s ) (3) 2Fe ( aq ) 3 + + 6OH ( aq ) − → 2Fe ( OH ) 3 ( s ) (8)
	Cathode	8H 2 O ( l ) + 8e − → 4H 2 ( g ) + 8OH ( aq ) − (E˚ = −0.828 V) (9)
	Total	3Fe ( s ) + 8H 2 O ( l ) → Fe ( OH ) 2 ( s ) + 2Fe ( OH ) 3 ( s ) + 4H 2 ( g ) (10)
Mechanism # 3 (pH 12)	Anode	Fe ( s ) − 3e − → Fe ( aq ) 3 + (E˚ = +0.037 V) (7)
	Solution	2Fe ( aq ) 3 + + 6OH ( aq ) − → 2Fe ( OH ) 3 ( s ) (8)
	Cathode	8H 2 O ( l ) + 8e − → 4H 2 ( g ) + 8OH ( aq ) − (E˚ = -0.828 V) (9)
	Total	2Fe ( s ) + 6H 2 O ( l ) → 2Fe ( OH ) 3 ( s ) + 3H 2 ( g ) (11)
Al Mechanism (pH 7)	Anode	Al ( s ) − 3e − → Al ( aq ) 3 + (E˚ = +1.660 V) (12) 2H 2 O ( l ) − 4e − → O 2 ( g ) + 4H ( aq ) + (E˚ = −1.229 V) (2)
	Solution	Al ( aq ) 3 + + 3OH ( aq ) − → Al ( OH ) 3 ( s ) (13) Al ( OH ) 4 ( aq ) − → OH ( aq ) − + Al ( OH ) 3 ( s ) (14)
	Cathode	8H 2 O ( l ) + 8e − → 4H 2 ( g ) + 8OH ( aq ) − (E˚ = −0.828 V) (9)
	Total	Al ( s ) + 5H 2 O → O 2 ( g ) + ( 7 / 2 ) H 2 ( g ) + Al ( OH ) 3 ( s ) (15)

m = I × t × M M n × F (16)

where: I is the applied current, t is the electrolysis time; F is the Faraday’s constant (96,485 C/mol); m, M_M, and n are the mass, molar mass, and valence of the anode materials, respectively [129] [130] [131] . The actual amount of dissolved metal ions has mainly been observed to be bigger than the theoretical value, and this could be affected in part by the chemical dissolution of the anode as expressed in Reaction (1) and Reaction (7) for Fe and Reaction (12) for Al [132] [133] [134] . The chemical dissolution is promoted at acidic pH, which can be induced by OER at the anode [1] . Also, the pitting corrosion of the anode in the occurrence of electrolyte anions can participate in the augmentation of dissolved metal ions (this is why EC is defined as accelerated corrosion) [135] .

The anodic dissolution of the Fe anode mostly liberates ferrous ions (Fe²⁺) (see Mechanism #1 (pH 2), Table 3), accompanied by a negligible quantity of ferric ions (Fe³⁺) (see Mechanism #2 (pH 7), Table 3). The coexistence of Fe²⁺ and Fe³⁺ (Mechanism #2 (pH 7), Table 3) leads to a more complex system than what is presented with the Al anode (Al Mechanism, Table 3). In a neutral media (Mechanism #2 (pH 7), Table 3), soluble Fe²⁺ ions could be oxidized into Fe³⁺, followed by the subsequent formation of Fe(OH)_3(s) [1] . At higher pH (Mechanism #3 (pH 12), Table 3), Fe³⁺ is transformed to Fe(OH)_3(s). Even if Fe(II) species could lead to floc generation, Fe(III) species, especially Fe(OH)_3(s), are the favored species for performant coagulation. The occurrence of Fe(II) species is commonly related to the lower current efficiency of the Fe anode in EC devices. Several investigations established that below the identical circumstance, Fe anode could attain only 70% - 80% of the performance of Al anode in dealing with M. aeruginosa cells [136] [137] .

The flocs produced in EC can precipitate like in the traditional coagulation-decantation technique [138] . Electrolysis of water can take place as minor reactions forming oxygen gas (Reaction (2)) at the anode and hydrogen gas (Reaction (4), Reaction (9)) at the cathode. In addition, the microbubbles may attach to the flocs and carry them to the surface [6] [139] . Integrating such two methods is known as electrocoagulation-flotation (ECF). The combined setup may be run either in one electrochemical cell or independently in two units [1] . As an illustration, researchers [140] assessed the elimination of Chlorella vulgaris employing an ECF apparatus with Al electrodes for the EC module and IrO₂-Ti electrodes in a separate electroflotation (EF) chamber. The gas/solid ratio in ECF was lower than that in traditional dissolved air flotation, showing that the smaller bubbles electrogenerated in ECF were more performant in interacting with algal cells. When non-sacrificial electrodes are utilized, the device is run mainly by EF, as no metal ion-induced flocs are produced. As a result, the elimination performance of algal cells is lower than those with sacrificial anodes [141] . Non-sacrificial electrodes also need higher current densities; thus, this may only apply to sensitive metal contamination, such as algae harvesting for food products.

Ren et al. [1] listed new investigations on eliminating algal cells by EC/EF techniques. In addition to the kind of anode, the reduction efficacy is related to more parameters, comprising the current density, inter-electrode distance, and the occurrence of electrolyte salts [6] . Identical to the EO method, the elimination of algal cells in EC is increased with the elevation in current density to some level where an additional augmentation boosts the secondary reactions, which can provoke serious harm to algal cells and excessive remaining metal ions [137] . A shorter gap between the anode and cathode reduces the internal resistance of the electrochemical cell, decreasing the energy compulsion [142] . Moreover, a short inter-electrode gap is helpful for the mass transfer between algal cells and electrogenerated species. EC elimination performance is considerably improved with chlorides [143] . As mentioned above concerning the EO method, algal cells can be destabilized because of the oxidation impact of active chlorine species formed at the anode. In addition, the activity of an Al electrode decays over time because of the generation of a passive oxide film [1] . The pitting corrosion provoked by active chlorine may efficiently eliminate the oxide film and form porous structures on the anode surface [143] . Consequently, more metal species can be dissolved for coagulation when chloride exists.

Juxtaposed to chemical coagulation, EC needs less coagulant, forming less sludge [8] [144] . This could be related to numerous distinctive benefits of the EC system: 1) metal ions are in-situ formed and consumed, so averting the overdoing of coagulant; 2) algal cells may be destabilized as a consequence of their interactions with electrogenerated active species; 3) charged algal cells could migrate to the oppositely charged electrode; and 4) the electric field itself could likewise harm cells via inducing transient pores in the membrane [67] [131] [145] . Besides, the alkalinity consumption associated with the generation of flocs is buffered by the OH⁻ formation at the cathode; thus, alkalinity adjustment could not be indispensable in EC devices [1] .

For ideal water sources that need no amendment of electrolytes [88] , electrochemical techniques comprising EO and EC may be run without injecting coagulants or oxidants, so avoiding the necessity for storage and handling of chemical products [1] . Further, electrochemical devices are compact in size and simple to adapt to automation juxtaposed to traditional techniques [69] [139] . Also, renewable energy from sources like solar photovoltaics [146] [147] [148] , wind, and biomass [5] [19] could be employed to power the electrochemical methods [29] [149] . For example, a hybrid device using the power produced from a microbial fuel cell with nitrifying and denitrifying biocathodes and a sacrificial Fe anode was proved for the EC elimination of M. aeruginosa cells [150] [151] . Such distinctive properties can align well with the interests of decentralized treatment needs or small-scale facilities in rural areas [152] [153] [154] . In general, eliminating algae via electrochemical methods stays at the early step of technology expansion [6] [11] . Even if the idea and individual parameters of the technique have been validated in lab studies, some of the simulated conditions could not satisfy the demand of real-world utilizations. More research remains to be performed on actual circumstances in algae-laden water sources. Thus, knowledge could be efficiently transferred to pilot and full-scale operations [1] .

2.2. Ultrasound (US)-Enhanced Coagulation

By applying ultrasound (US, with a frequency higher than 20 kHz) into an algae-laden suspension, cavity bubbles are formed via nucleation from pre-existing bubbles or surface crevice sites [1] . Bubbles then contract and expand along with the acoustic wave and induce cavitation effects in two distinct modes: stable cavitation (where bubbles oscillate over many cycles); and transient cavitation (where bubbles proliferate in a few cycles and collapse in a burst) [155] [156] . In the former case, a streaming flow driven by bubble oscillation forms a shear force, provoking mechanical destruction to cells. Transient cavitation is interesting in sonochemistry-related methods. The violent collapse of cavitation bubbles produces micro-jetting close to the surface. More importantly, the energy liberated from the rapid collapse is highly localized to a hotspot that could attain around 5000 K and 1000 bar [155] [157] . Extreme temperature and pressure break bonds, forming free radicals that initiate chemical reactions. Following the solution chemistry, a series of ROSs (like ^•OH, · O 2 − ) and H₂O₂ may be produced and harm different components of cells via oxidation [157] [158] [159] .

The sonochemistry activity could be adjusted by changing the device parameters that then control the impact of US on algae [1] . The frequency of the US is linked with the amount and size of cavitation bubbles. At lower frequencies, mechanical impacts resulting from the collapse of bubbles dominate. At higher frequencies, the augmented nucleation and short time of growth lead to smaller bubbles, and a shorter bubble lifetime permits more radicals to liberate and migrate to the interface. The chemical influences begin to be dominant [155] [157] [158] . The impact of frequency on algae elimination and demobilization has been established in numerous investigations [79] [160] [161] [162] . As an illustration, Wu et al. [160] depicted that sonication at 20 kHz induced harm to M. aeruginosa primarily via direct rupture of cells; however, at 580 kHz, more radicals were generated, conducting to the demobilization of cells with less mechanical deterioration. The frequency impact is particularly significant in the experiments on cyanobacteria with gas vacuoles. The size of the gas vacuole is mostly below one μm, and the resonance size of a bubble is inversely related to the frequency of US [1] . Sonication at 1700 kHz was observed to be more performant in pushing gas vacuoles to collapse and cell inhibition as the frequency is closer to the resonance frequency of gas vacuoles [157] [162] [163] . Nonetheless, it must be remembered that as the cavitation threshold is elevated at higher frequencies, higher power intensities are requested to cause cavitation [79] [157] [158] .

As a rule, a higher power density is directly linked with the elevation in cavitation bubbles and sonochemical activity [156] [164] . US intensity is determined by measuring the acoustic power entering the system via calorimetry and expressed as power supplied per unit volume, W/mL [1] . US dosage (J/mL) considers the duration of exposure and is obtained by multiplying density (W/mL) by time (s). While a higher intensity can boost the ultrasonic impact on algae, the intensity must be augmented with care since the necessary liberation of algal organic matter (AOM) resulting from cell harm and death was observed at higher US intensities [79] [163] [165] . US has as well been assessed for eliminating algal toxins and T&O compounds. Effective decompositions of MCs, 2-methylisoborneol, and geosmin via sonication were detected in some reports [166] [167] . Since the decomposition was solely attained at relatively higher US intensities, enhancing coagulation with concomitant elimination of toxins could not be a practical procedure. More AOM, comprising toxins and T&O compounds, can be liberated at such intensities as established in lab-scale tests [79] [165] .

Ren et al. [1] listed fresh investigations concerning eliminating algae with US-enhanced coagulation. Using sonication below the suitable dosage can change the cell surface structure and destabilize the cells by decreasing the zeta potential. Thus, a similar or even better coagulation reduction could be attained at a low coagulant injection [79] . Different system components touch the best favorable circumstances; however, various investigations could still detect some general tendencies. It has been depicted that mid-range frequencies of about 500 kHz are more performant at demobilizing algal cells, and high US density and dosage could elevate the possibility of severe cell deterioration [157] [160] . Considering functional parameters involving reduction rate (turbidity, total organic carbon, or cell count), US dosage and coagulant dosage furnish a more thorough indicator to estimate the performance of US-enhanced coagulation [1] .

The key sonication parameters (frequency, density, and dosage) dominate the pivotal working conditions [1] . Also, the sonication performance may be affected by additional factors in the sonication system. For example, higher dissolved gas concentrations participate in the augmentation of nucleation bubbles and lower the cavitation threshold. Dissolved gas can also directly influence the reaction mechanisms at the interface of collapsing bubbles; for instance, oxygen concentration can dictate the type and proportion of ROSs formed in the sonochemical process [155] [156] . Likewise, the occurrence of solid particles could intervene with neighboring bubbles and furnish nucleation sites for cavitation via crevices and defects on the surface of the particles. As an illustration, Wang et al. [168] utilized TiO₂/biochar as a catalyst in the sonication pretreatment to boost ROSs generation. They depicted that the catalyst increased the oxidation impact on the cell membranes of M. aeruginosa and augmented the following coagulation elimination of cells [168] . A subsequent investigation may be performed to suggest new materials to promote the US-enhanced coagulation technique. Practically, a hybrid material with a core-shell structure can be carefully conceived so that the granules can boost the demobilization of algal cells as a sonocatalyst in the sonication pretreatment. In addition, the coating shell may be perforated and eroded by the mechanical shear force and micro jetting of sonication, so liberating the core component as a coagulant to eliminate cells in the following coagulation method [1] .

Using the US as a stand-alone technique to dominate algal blooms in natural waterbodies has failed, particularly with lower US employment intensities [169] [170] . Eliminating algal cells only lasted briefly before the population recovered to its original level [158] . Higher powers proved efficacious in inactivating algae; however, different aquatic organisms (like Daphnia magna, a phytoplankton grazer) were also demobilized at these intensities [169] . Also, the related energy consumption and high operating cost may be a worry for the implementation in large open water areas. The following research may focus on the possibility of US-enhanced coagulation to reduce algal blooms. Integrating low-intensity US for cell demobilization and low coagulant injection for cell elimination can be a cost-saving strategy to treat algal blooms in natural waterbodies [1] .

3. Applied Features of Algae Elimination in Water Treatment Technologies

WTPs embrace a multi-barrier procedure to treat water damaged by algae-related troubles (see Figure 2). The train of solid-liquid separation processes (i.e., coagulation, flocculation, sedimentation or flotation, filtration [171] [172] ) remains so efficient in eliminating algal cells when run below-optimized circumstances [173] [174] [175] .

Nonetheless, such methods can potentially eliminate low-molecular-weight dissolved organic substances like cyanotoxins and different cellular metabolites, which could result in DBPs generation [176] [177] . Consequently, the global objective of solid-liquid separation treatment is to maximize the elimination of algal cells while preserving cell integrity [1] [178] [179] .

3.1. Pretreatment

In some WTPs, pretreating using oxidants increases algae elimination in coagulation [180] [181] [182] . The oxidants tested are chlorine, chlorine dioxide, ozone, permanganate, and ferrate [56] [57] . If employed at a proper dosage, pre-oxidation ameliorates algae removal primarily via four routes: first, pre-oxidation modifies the structure of algal cells, and such impact is very significant for demobilizing the motile species that can get away from agglomerated flocs [183] [184] ; second, pre-oxidation decreases the surface charge of algal cells, so augmenting the agglomeration of destabilized cells [56] [185] ; third, pre-oxidation detaches the surface-bound extracellular organic matter (EOM) from algal cells [186] , and the desorbed EOM may assist cell bridging to produce larger flocs [1] [187] ; fourth, in the examples of permanganate and ferrate, in-situ produced MnO₂ or Fe(III) precipitate particles could adsorb onto the cell surface, and boost agglomeration and such amorphous species possess a large surface area that can as well adsorb some dissolved organic substances [188] [189] . However, overdosing on oxidants could lead to grave cell lysis and intracellular organic matter (IOM) liberation (involving toxins) regardless of the kind of oxidant implied [56] . IOM is more hydrophilic and includes more organic nitrogen compounds (like amino acids and proteins) [21] . Also, IOM is a more potent precursor than EOM for carbonaceous and nitrogenous DBPs [1] [188] . Since pre-oxidation can constitute a danger of liberated toxins and DBPs precursors to downstream techniques, pre-oxidation must regularly be accompanied by strict control to determine the oxidant demand that attains cell modification without compromising cell integrity. New advances in the pretreatment of algae-laden water proposed that methods founded on advanced oxidation processes could be feasible options for traditional oxidants [190] . Pre-oxidation employing Fe(II)-mediated UV/H₂O₂ and UV/persulfate depicted encouraging findings in eliminating algal cells and decreasing the liberation of AOM and toxins [191] [192] . More studies are requested to estimate the efficiency of such methods in complex water matrices and evaluate the practicability in actual cases.

Researchers proposed that powdered activated carbon (PAC) comes after pre-oxidation to diminish the hazard of liberated toxins [1] [193] . As a rule, PAC is injected before coagulation (e.g., raw water intake, rapid mixing) to guarantee an adequate contact time. However, the PAC performance in retaining toxins could be influenced by the dose, carbon type, contact time, and interference from organic matter [194] . Besides, PAC particles can work as ballast compounds in coagulation and benefit flocs’ aggregation and settling [57] [195] . Therefore, pre-oxidation and PAC must be considered when utilizing a jar test to find the optimal coagulation circumstance.

3.2. Coagulation-Flocculation

Below appropriate circumstances in the coagulation-flocculation technique, algae interact with coagulants to form flocs that could be retained in the next clarification treatment stage [1] [2] [7] . Even if most investigations have been dedicated to the critical contributions of coagulants and working pH in the coagulation reduction of algae (Figure 3), the impacts of mixing circumstances still need to be considered [10] [14] . Scientists proposed that rapid mixing [24] might not be indispensable when the WTPs are run under sweep flocculation circumstances [174] [196] . However, appropriate mixing circumstances remain significant in that enough energy must be furnished to guarantee the mixing of coagulant and the development of flocs while averting the floc breakup because of overmixing [197] . Because the target of the jar test is to simulate the wanted circumstances in the full-scale operation, the mixing process is envisaged to mirror the actual events to the extent possible. A usual jar tester is equipped with multiple overhead stirrers, and the mixing energy input could be reached from the chart depicting the relationship between velocity gradient (G value, s⁻¹) and paddle rotation speed (rpm) [1] . Even though it is primarily employed in laboratories, there are better instruments than the magnetic stirrer for mixing in the coagulation test. The rotating speed of the stirring bar noted in numerous investigations cannot be correlated to the mixing energy. Also, the flow pattern formed by a magnetic stirrer is characterized by a strong vortex with upwelling

at the outer wall and downwelling in the axial core [198] . The introduced dye was observed to accumulate around the vortex axis with magnetic stirring [198] , proving that this flow pattern could result in the inefficacious mixing of coagulants near the vortex funnel [1] .

When pre-oxidation is not applied, it is usually trusted that coagulation does not provoke algae deterioration [199] . Nonetheless, there has been proof proposing that cell rupture and lysis can happen below low pH or mechanical stress [200] [201] [202] . Ghernaout et al. [7] proved that the jar tests of enhanced coagulation (pH 6 and alum dose 15 mg/L) as only one stage of water treatment, without chlorination and filtration, ameliorate the elimination of organic matter and algae at 97% and 99%, respectively. Notable cell deterioration and metabolite liberation were detected with Anabaena circinalis and Cylindrospermopsis below low pH circumstances (pH < 5), while M. aeruginosa depicted higher resistance to acidic events [201] . Scientists [200] observed compromised cell integrity and metabolite liberation with A. circinalis, even if the hydraulic cases in the mixing satisfied the adopted guidelines. Such findings reveal the significance of fundamental coagulation parameters, and plants must inspect and regulate operations to avert cell harm resulting from localized acidic environmental or excessive shear stress [1] .

Numerous reverse osmosis (RO) desalination plants are in regions susceptible to marine algal blooms [1] . Without suitable pretreatment, the algae and related AOM in RO feed water may lead to irreversible membrane fouling [203] , provoking severe negative impacts on the plant’s operation. Therefore, coagulation pursued by a clarification method is frequently implemented in desalination plants to ameliorate the feed water quality [204] .

Nonetheless, because of seawater’s elevated salinity and alkalinity, coagulants could require to be injected at a higher dosage or even become inefficient [1] . Seawater possesses an average salinity of 35‰ (i.e., ~ 0.7 M in ionic strength), and freshwater typically contains an ionic strength lower than 0.01 M [205] . Such dissimilarity influences metal salt hydrolyzing species’ concentrations and distribution profiles in coagulation methods. For example, Al is more dissolvable in seawater as the minimum solubility of Al augments with augmented ionic strength. The minimum solubility of Al salts is also higher in warmer waters, attaining ~ 270 μg/L at 35˚C [205] . Since several desalination plants are located in warm water areas (like the Mediterranean region and the Gulf countries), the elevated concentration of residual Al can be carried over to RO membranes, provoking precipitative scaling as aluminum hydroxides or aluminum silicates. Further, the solubility of Fe salts is less influenced and stays under 1 μg/L below an extensive range of circumstances. Thus, Fe salts are constantly employed in full-scale RO desalination plants to avert scaling trouble [204] .

3.3. Clarification

When sedimentation is employed, the coagulation-flocculation is mostly run below the sweep flocculation pathway to produce large and compact flocs of algae that can defeat the fluid drag and buoyancy [1] [2] [174] . As a substitute clarification method, dissolved air flotation (DAF) has been adopted as distinctly convenient for dealing with algae-laden water thanks to the fact that the density of algal cells is usually low and numerous species with gas vacuoles possess sufficient buoyancy [206] . Robust, even if smaller flocs keeping a particle size distribution of 10 - 30 μm are supposed to provide the best elimination effectiveness in DAF [207] . In DAF, large flocs are not requested, and the shear stress and turbulence when injecting air bubbles could break the large flocs. DAF is very performant in capturing small flocs, so it is a robust method relatively insensitive to the coagulant selection and operation regime [208] . The substantial efficacy of DAF in eliminating algal cells has been proved in many cases [208] [209] . In addition, a DAF device could cancel the necessity for a traditional coagulation-flocculation treatment stage. Without coagulation-flocculation, microbubbles can be functionalized with cationic surfactants or polymers to reach stronger cohesion between bubbles and algae. Cell eliminations above 90% were attained [210] .

3.4. Filtration

In the traditional treatment train, filtration is the last primary stage to eliminate algae from water physically [1] . In the filter, granular media are employed, and their characteristics could influence the filtration effectiveness. Filtration can efficiently retain algae trapped in flocs.

Free cells may escape from the filter media following the filter makeup and algae properties. Researchers [211] explored the impact of algal biodiversity on the elimination efficacy utilizing a lab-scale treatment setup comprising coagulation, sedimentation, and sand filtration. The raw water samples collected from three eutrophic lakes had cell densities of 3.93 - 13.1 × 10⁵ cells/mL, and 25 - 55 algal species were observed. Their findings proposed that species with a needle, filament, or plate-like morphologies or protruding structures like thorns or flagella harmed the global elimination efficacy. Also, higher removal efficacies were detected in raw water with more extraordinary algal biodiversity. Species with an elongated shape or larger size could interact with tiny algae through bridging or sweeping routes. The residual algae in the filtration effluent mainly consisted of smaller cells with a spherical shape, like those from the genera of Gloeocapsa and Chlorella. Identically, other scientists [212] followed the effect of cell morphonology on the filtration reduction rate with a pilot-scale in-line filtration setup (coagulation followed by filtration). The cell numbers of spherical M. aeruginosa were invariably higher than those of Aphanizomenon flos-aquae (filamentous) in filtered water. In contrast, a constant breakthrough of Aphanizomenon in filtered water was noted by researchers [213] in a traditional potable WTP that was observed during a bloom season.

4. Conclusions

Using coagulation for eliminating algae remains complicated as such a process is affected by several factors. The critical elements implicated in the coagulation method may be grouped into three classes: water quality parameters comprising those linked with algae features, coagulant parameters, and mixing circumstances. Several of such factors interact with each other via either direct or indirect relationships; thus, the variation of one parameter could touch the efficacy of the overall technology [1] . The summary and analysis of present investigations on coagulation techniques for algae elimination lead to the subsequent conclusions and recommendations for future study:

1) Most coagulation investigations concentrate on only one or two factors’ impacts while maintaining the remaining fixed conditions. One of the frequent procedures is to examine the implications of coagulation circumstances (i.e., coagulant, dosage, and operation pH) on reducing some algae species utilizing the same water parameters. The other is to contrast the elimination efficiencies of various algae below the same coagulation conditions. Until now, decisive predictions could not be made concerning how a certain algal species would respond to the modification in coagulation circumstances. Several findings published in the literature are case-specific, making it hard to directly juxtapose the different investigations’ conclusions. It is crucial to describe complete data regarding trial circumstances, like the parameters of raw or synthetic water samples, the properties and density of algal cells, the composition and features of coagulants, and the parameters of treated water. The hydraulic circumstances for mixing in the jar test must also meet the guidelines in full-scale operation. For new coagulation technologies, which imply the electrochemical process or the application of sonication, a full detailing of the reactor configuration must be comprised in the literature in addition to the usually reported water parameters and coagulation circumstances. It is also critical to study real-world conditions when performing tests if such techniques are expected to be utilized in practical applications.

2) To maximize algae elimination, the traditional water treatment train regulates the entire solid-liquid separation technology (comprising coagulation, clarification, and filtration as multiple barriers). Even if most algae elimination is realized through clarification, filtration also captures the residual algae [214] . Utilizing settled water quality in a jar test as the exclusive efficacy indicator could lead to an augmented coagulant introduction being determined as optimal without any critical benefit to the finished water quality. It could be helpful to combine a filter column into the jar tester to simulate the solid-liquid separation process in the traditional water treatment plant. The optimal running circumstance to retain algae is assessed, considering the optimized effectiveness of the global system instead of a single unit [1] .

3) Pre-oxidation must be avoided because of the possible lysis of algae cells; further, algal growth may be controlled with more frequent cleaning of the basins, especially in summer periods, and coverage of open sedimentation basins would be avoided to benefit from solar radiation disinfection and oxygen diffusion from the air. Chlorine can be maintained as a final disinfectant if organic precursors are sufficiently removed. It remains to be seen that the conventional water treatment (clarification + filtration + chlorination) will continue to be a viable solution for drinking water from source waters containing organic matter as their quality deteriorates and water quality standards become more difficult to achieve [3] .

4) During the previous years, with the fast expansion of machine learning (ML), there has been an increasing interest in employing ML algorithms to deal with complicated troubles in environmental science and engineering [215] . ML is superior to conventional statistical analysis in modeling complex systems (like the coagulation phenomenon) with weak or nonlinear relationships between numerous variables [1] . In some preliminary trials, ML algorithms were trained to predict the treated water quality founded on the coagulant injection or assess the coagulant injection to attain the wanted effluent quality [215] . Also, ML algorithms can be trained with various monitoring data [216] [217] [218] to ameliorate the forecasts for HABs and estimate the threat to water utilities and the general public [219] [220] [221] . Until now, employing ML to explore the coagulation elimination of algae has been rare [222] . The following studies may concentrate on leveraging ML to divulge the interactions between different factors and elucidate the divergent behaviors of algal species in response to the alteration of coagulation circumstances. One more crucial aspect of ML is that a robust algorithm can only be obtained when a broad and diverse range of data sets are utilized in the training process. A large dataset concerning the troubles and solutions related to algal blooms needs cohesive efforts from monitoring systems, water utilities, and research communities. The development of ML algorithms must concentrate on predicting the coagulation circumstances in response to the changing algal features and water parameters, diminishing the need for trial-and-error optimization procedures such as jar tests. In the future, intelligent control systems powered by ML will be combined with the entire water treatment process [1] .

Acknowledgements

The Research Deanship of the University of Ha’il, Saudi Arabia, has funded this research through Project RG-23 030.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

Abbreviation

AOM Algal organic matter

BDD Boron-doped diamond

DAF Dissolved air flotation

DBPs Disinfection by-products

E-F Electro-Fenton

EC Electrocoagulation

ECF Electrocoagulation-flotation

EF Electroflotation

EO Electrooxidation

EOM Extracellular organic matter

HABs Harmful algal blooms

IOM Intracellular organic matter

MCs Microcystins

ML Machine learning

OER Oxygen evolution reaction

PAC Powdered activated carbon

RO Reverse osmosis (RO)

ROSs Reactive oxygen species

T&O Taste and odor

US Ultrasound

WTPs Water treatment plants

References

1. Ren, B., Weitzel, K.A., Duan, X., Nadagouda, M.N. and Dionysiou, D.D. (2022) A Comprehensive Review on Algae Removal and Control by Coagulation-Based Processes: Mechanism, Material, and Application. Separation and Purification Technology, 293, Article ID: 121106. https://doi.org/10.1016/j.seppur.2022.121106

2. Ghernaout, B., Ghernaout, D. and Saiba, A. (2010) Algae and Cyanotoxins Removal by Coagulation/Flocculation: A Review. Desalination and Water Treatment, 20, 133-143. https://doi.org/10.5004/dwt.2010.1202

3. Ghernaout, D., Moulay, S., Ait Messaoudene, N., Aichouni, M., Naceur, M.W. and Boucherit, A. (2014) Coagulation and Chlorination of NOM and Algae in Water Treatment: A Review. International Journal of Environmental Monitoring and Analysis, 2, 23-34. https://doi.org/10.11648/j.ijema.s.2014020601.14

4. Westrick, J.A. and Szlag, D. (2018) A Cyanotoxin Primer for Drinking Water Professionals. Journal—American Water Works Association, 110, E1-E16. https://doi.org/10.1002/awwa.1088

5. Ghernaout, D. and Ghernaout, B. (2012) On the Concept of the Future Drinking Water Treatment Plant: Algae Harvesting from the Algal Biomass for Biodiesel Production—A Review. Desalination and Water Treatment, 49, 1-18. https://doi.org/10.1080/19443994.2012.708191

6. Ghernaout, D., Benblidia, C. and Khemici, F. (2015) Microalgae Removal from Ghrib Dam (Ain Defla, Algeria) Water by Electroflotation Using Stainless Steel Electrodes. Desalination and Water Treatment, 54, 3328-3337. https://doi.org/10.1080/19443994.2014.907749

7. Ghernaout, D., Badis, A., Braikia, G., Mataam, N., Fekhar, M., Ghernaout, B. and Boucherit, A. (2017) Enhanced Coagulation for Algae Removal in a Typical Algeria Water Treatment Plant. Environmental Engineering and Management Journal, 16, 2303-2315. https://doi.org/10.30638/eemj.2017.238

8. Ghernaout, D., Ghernaout, B. and Kellil, A. (2009) Natural Organic Matter Removal and Enhanced Coagulation as a Link between Coagulation and Electrocoagulation. Desalination and Water Treatment, 2, 203-222. https://doi.org/10.5004/dwt.2009.116

9. Merel, S., Walker, D., Chicana, R., Snyder, S., Baurès, E. and Thomas, O. (2013) State of Knowledge and Concerns on Cyanobacterial Blooms and Cyanotoxins. Environment International, 59, 303-327. https://doi.org/10.1016/j.envint.2013.06.013

10. Kellali, Y. and Ghernaout, D. (2019) Physicochemical and Algal Study of Three Dams (Algeria) and Removal of Microalgae by Enhanced Coagulation. Applied Engineering, 3, 56-64.

11. Ghernaout D. ,et al. (2019)Electrocoagulation Process for Microalgal Biotechnology—A Review Applied Engineering 3, 85-94.

12. Ghernaout, D. and Elboughdiri, N. (2020) Eliminating Cyanobacteria and Controlling Algal Organic Matter—Short Notes. Open Access Library Journal, 7, e6252. https://doi.org/10.4236/oalib.1106252

13. Paerl, H.W., Gardner, W.S., Havens, K.E., Joyner, A.R., McCarthy, M.J., Newell, S.E., Qin, B. and Scott, J.T. (2016) Mitigating Cyanobacterial Harmful Algal Blooms in Aquatic Ecosystems Impacted by Climate Change and Anthropogenic Nutrients. Harmful Algae, 54, 213-222. https://doi.org/10.1016/j.hal.2015.09.009

14. Ghernaout, D., Elboughdiri, N., Ghareba, S. and Salih, A. (2020) Coagulation Process for Removing Algae and Algal Organic Matter—An Overview. Open Access Library Journal, 7, e6272. https://doi.org/10.4236/oalib.1106272

15. He, X.X., Liu, Y.L., Conklin, A., Westrick, J., Weavers, L.K., et al. (2016) Toxic Cyanobacteria and Drinking Water: Impacts, Detection, and Treatment. Harmful Algae, 54, 174-193. https://doi.org/10.1016/j.hal.2016.01.001

16. Qin, B., Xu, P., Wu, Q., Luo, L. and Zhang, Y. (2007) Environmental Issues of Lake Taihu, China. In: Eutrophication of Shallow Lakes with Special Reference to Lake Taihu, China, Springer, Berlin, 3-14. https://doi.org/10.1007/978-1-4020-6158-5_2

17. Southard, G.M., Fries, L.T. and Barkoh, A. (2010) Prymnesium parvum: The Texas Experience. Journal of the American Water Resources Association, 46, 14-23. https://doi.org/10.1111/j.1752-1688.2009.00387.x

18. Zimba, P.V., Huang, I.S., Gutierrez, D., Shin, W., Bennett, M.S. and Triemer, R.E. (2017) Euglenophycin Is Produced in at Least Six Species of Euglenoid Algae and Six of Seven Strains of Euglena sanguine. Harmful Algae, 63, 79-84. https://doi.org/10.1016/j.hal.2017.01.010

19. Al Arni, S., Amous, J. and Ghernaout, D. (2019) On the Perspective of Applying of a New Method for Wastewater Treatment Technology: Modification of the Third Traditional Stage with Two Units, One by Cultivating Microalgae and Another by Solar Vaporization. International Journal of Environmental Sciences & Natural Resources, 16, Article ID: 555934. https://doi.org/10.19080/IJESNR.2019.16.555934

20. Ghernaout, D. (2020) Enhanced Coagulation: Promising Findings and Challenges. Open Access Library Journal, 7, e6569.

21. Ghernaout, D. (2014) The Hydrophilic/Hydrophobic Ratio vs. Dissolved Organics Removal by Coagulation—A Review. Journal of King Saud University—Science, 26, 169-180. https://doi.org/10.1016/j.jksus.2013.09.005

22. Ghernaout, D., Al-Ghonamy, A.I., Boucherit, A., Ghernaout, B., Naceur, M.W., Ait Messaoudene, N., Aichouni, M., Mahjoubi, A.A. and Elboughdiri, N.A. (2015) Brownian Motion and Coagulation Process. American Journal of Environmental Protection, 4, 1-15.

23. Ghernaout, D., Al-Ghonamy, A.I., Naceur, M.W., Boucherit, A., Messaoudene, N.A., Aichouni, M., Mahjoubi, A.A. and Elboughdiri, N.A. (2015) Controlling Coagulation Process: From Zeta Potential to Streaming Potential. American Journal of Environmental Protection, 4, 16-27. https://doi.org/10.11648/j.ajeps.s.2015040501.12

24. Ghernaout, D. and Boucherit, A. (2015) Review of Coagulation’s Rapid Mixing for NOM Removal. Journal of Research & Developments in Chemistry, 2015, Article ID: 926518. https://doi.org/10.5171/2015.926518

25. Ghernaout D. ,et al. (2017)Entropy in the Brownian Motion (BM) and Coagulation Background Colloid and Surface Science 2, 143-161.

26. Westrick, J.A., Szlag, D.C., Southwell, B.J. and Sinclair, J. (2010) A Review of Cyanobacteria and Cyanotoxins Removal/Inactivation in Drinking Water Treatment. Analytical and Bioanalytical Chemistry, 397, 1705-1714. https://doi.org/10.1007/s00216-010-3709-5

27. Ghernaout, D. (2018) Disinfection and DBPs Removal in Drinking Water Treatment: A Perspective for a Green Technology. International Journal of Advances in Applied Sciences, 5, 108-117. https://doi.org/10.21833/ijaas.2018.02.018

28. Djezzar, S., Ghernaout, D., Cherifi, H., Alghamdi, A., Ghernaout, B. and Aichouni, M. (2018) Conventional, Enhanced, and Alkaline Coagulation for Hard Ghrib Dam (Algeria) Water. World Journal of Applied Chemistry, 3, 41-55. https://doi.org/10.11648/j.wjac.20180302.12

29. Ghernaout, D., Ghernaout, B. and Naceur, M.W. (2011) Embodying the Chemical Water Treatment in the Green Chemistry—A Review. Desalination, 271, 1-10. https://doi.org/10.1016/j.desal.2011.01.032

30. Havens, K.E., James, R.T., East, T.L. and Smith, V.H. (2003) N:P Ratios, Light Limitation, and Cyanobacterial Dominance in a Subtropical Lake Impacted by Non-Point Source Nutrient Pollution. Environmental Pollution, 122, 379-390. https://doi.org/10.1016/S0269-7491(02)00304-4

31. Li, H. and Pan, G. (2015) Simultaneous Removal of Harmful Algal Blooms and Microcystins Using Microorganism- and Chitosan-Modified Local Soil. Environmental Science & Technology, 49, 6249-6256. https://doi.org/10.1021/acs.est.5b00840

32. Miranda, M., Noyma, N., Pacheco, F.S., de Magalhaes, L., Pinto, E., Santos, S., et al. (2017) The Efficiency of Combined Coagulant and Ballast to Remove Harmful Cyanobacterial Blooms in a Tropical Shallow System. Harmful Algae, 65, 27-39. https://doi.org/10.1016/j.hal.2017.04.007

33. Noyma, N.P., de Magalhaes, L., Furtado, L.L., Mucci, M., van Oosterhout, F., Huszar, V.L.M., Marinho, M.M. and Lürling, M. (2016) Controlling Cyanobacterial Blooms through Effective Flocculation and Sedimentation with Combined Use of Flocculants and Phosphorus Adsorbing Natural Soil and Modified Clay. Water Research, 97, 26-38. https://doi.org/10.1016/j.watres.2015.11.057

34. Lürling, M., Mackay, E., Reitzel, K. and Spears, B.M. (2016) Editorial—A Critical Perspective on Geo-Engineering for Eutrophication Management in Lakes. Water Research, 97, 1-10. https://doi.org/10.1016/j.watres.2016.03.035

35. Ghernaout, D. (2020) Water Treatment Coagulation: Dares and Trends. Open Access Library Journal, 7, e6636.

36. Pieterse, A.J.H. and Cloot, A. (1997) Algal Cells and Coagulation, Flocculation and Sedimentation Processes. Water Science & Technology, 36, 111-118. https://doi.org/10.2166/wst.1997.0099

37. Nel, A.E., Madler, L., Velegol, D., Xia, T., Hoek, E.M.V., Somasundaran, P., et al. (2009) Understanding Biophysicochemical Interactions at the Nano-Bio Interface. Nature Materials, 8, 543-557. https://doi.org/10.1038/nmat2442

38. Ghernaout, D., Simoussa, A., Alghamdi, A., Ghernaout, B., Elboughdiri, N., Mahjoubi, A., Aichouni, M. and El-Wakil, A.E.A. (2018) Combining Lime Softening with Alum Coagulation for Hard Ghrib Dam Water Conventional Treatment. International Journal of Advances in Applied Sciences, 5, 61-70. https://doi.org/10.21833/ijaas.2018.05.008

39. Ghernaout, D., Alshammari, Y. and Alghamdi, A. (2018) Improving Energetically Operational Procedures in Wastewater Treatment Plants. International Journal of Advances in Applied Sciences, 5, 64-72. https://doi.org/10.21833/ijaas.2018.09.010

40. Alshammari, Y., Ghernaout, D., Aichouni, M. and Touahmia, M. (2018) Improving Operational Procedures in Riyadh’s (Saudi Arabia) Water Treatment Plants Using Quality Tools. Applied Engineering, 2, 60-71.

41. Ghernaout, D. (2020) Water Treatment Challenges towards Viruses Removal. Open Access Library Journal, 7, e6408.

42. Ghernaout, D. (2020) Natural Organic Matter Removal in the Context of the Performance of Drinking Water Treatment Processes—Technical Notes. Open Access Library Journal, 7, e6751.

43. Belhout, D., Ghernaout, D., Djezzar-Douakh, S. and Kellil, A. (2010) Electrocoagulation of a Raw Water of Ghrib Dam (Algeria) in Batch Using Iron Electrodes. Desalination and Water Treatment, 16, 1-9. https://doi.org/10.5004/dwt.2010.1081

44. Ghernaout, D. (2017) The Holy Koran Revelation: Iron Is a “Sent Down” Metal. American Journal of Environmental Protection, 6, 101-104. https://doi.org/10.11648/j.ajep.20170604.14

45. Jiang, J.-Q. (2015) The Role of Coagulation in Water Treatment. Current Opinion in Chemical Engineering, 8, 36-44. https://doi.org/10.1016/j.coche.2015.01.008

46. Ghernaout, D. (2013) The Best Available Technology of Water/Wastewater Treatment and Seawater Desalination: Simulation of the Open Sky Seawater Distillation. Green and Sustainable Chemistry, 3, 68-88. https://doi.org/10.4236/gsc.2013.32012

47. Ghernaout, D. and Elboughdiri, N. (2019) Water Disinfection: Ferrate(VI) as the Greenest Chemical—A Review. Applied Engineering, 3, 171-180.

48. Edzwald, J.K. (2020) Aluminum in Drinking Water: Occurrence, Effects, and Control, Journal—American Water Works Association, 112, 34-41. https://doi.org/10.1002/awwa.1499

49. Bolto, B. and Gregory, J. (2007) Organic Polyelectrolytes in Water Treatment. Water Research, 41, 2301-2324. https://doi.org/10.1016/j.watres.2007.03.012

50. Ibrahim, A., Yaser, A. and Lamaming, J. (2021) Synthesising Tannin-Based Coagulants for Water and Wastewater Application: A Review. Journal of Environmental Chemical Engineering, 9, Article ID: 105007. https://doi.org/10.1016/j.jece.2020.105007

51. Yang, R., Li, H.J., Huang, M., Yang, H. and Li, A.M. (2016) A Review on Chitosan-Based Flocculants and Their Applications in Water Treatment. Water Research, 95, 59-89. https://doi.org/10.1016/j.watres.2016.02.068

52. Ghernaout, D., Naceur, M.W. and Aouabed, A. (2011) On the Dependence of Chlorine By-Products Generated Species Formation of the Electrode Material and Applied Charge during Electrochemical Water Treatment. Desalination, 270, 9-22. https://doi.org/10.1016/j.desal.2011.01.010

53. Ghernaout, D., Elboughdiri, N., Alghamdi, A. and Ghernaout, B. (2020) Trends in Decreasing Disinfection By-Products Formation during Electrochemical Technologies. Open Access Library Journal, 7, e6337. https://doi.org/10.4236/oalib.1106337

54. Huang, Y., Li, L., Luan, X., Wei, X., Li, H., Gao, N. and Yao, J. (2021) Ultrasound-Enhanced Coagulation for Cyanobacterial Removal: Effects of Ultrasound Frequency and Energy Density on Coagulation Performance, Leakage of Intracellular Organic Matters and Toxicity. Water Research, 201, Article ID: 117348. https://doi.org/10.1016/j.watres.2021.117348

55. Ghernaout, D. and Elboughdiri, N. (2020) Dealing with Cyanobacteria and Cyanotoxins: Engineering Viewpoints. Open Access Library Journal, 7, e6363.

56. Xie, P.C., Chen, Y.Q., Ma, J., Zhang, X., Zou, J. and Wang, Z.P. (2016) A Mini Review of Preoxidation to Improve Coagulation. Chemosphere, 155, 550-563. https://doi.org/10.1016/j.chemosphere.2016.04.003

57. Cui, H.M., Huang, X., Yu, Z.C., Chen, P. and Cao, X.L. (2020) Application Progress of Enhanced Coagulation in Water Treatment. RSC Advances, 10, 20231-20244. https://doi.org/10.1039/D0RA02979C

58. Henderson, R., Parsons, S.A. and Jefferson, B. (2008) The Impact of Algal Properties and Pre-Oxidation on Solid-Liquid Separation of Algae. Water Research, 42, 1827-1845. https://doi.org/10.1016/j.watres.2007.11.039

59. Matter, I.A., Bui, V.K.H., Jung, M., Seo, J.Y., Kim, Y.E., Lee, Y.C. and Oh, Y.K. (2019) Flocculation Harvesting Techniques for Microalgae: A Review. Applied Sciences, 9, 3069. https://doi.org/10.3390/app9153069

60. Panizza, M. and Cerisola, G. (2009) Direct and Mediated Anodic Oxidation of Organic Pollutants. Chemical Reviews, 109, 6541-6569. https://doi.org/10.1021/cr9001319

61. Ghernaout, D. (2013) Advanced Oxidation Phenomena in Electrocoagulation Process: A Myth or a Reality? Desalination, and Water Treatment, 51, 7536-7554. https://doi.org/10.1080/19443994.2013.792520

62. Ghernaout, D. (2019) Virus Removal by Electrocoagulation and Electrooxidation: New Findings and Future Trends. Journal of Environmental Science and Allied Research, 2019, 85-90. https://doi.org/10.29199/2637-7063/ESAR-202024

63. Ghernaout D. ,et al. (2019)Electrocoagulation and Electrooxidation for Disinfecting Water: New Breakthroughs and Implied Mechanisms Applied Engineering 3, 125-133.

64. Ghernaout, D. and Elboughdiri, N. (2020) Advanced Oxidation Processes for Wastewater Treatment: Facts and Future Trends. Open Access Library Journal, 7, e6139.

65. Ghernaout, D., Elboughdiri, N., Ghareba, S. and Salih, A. (2020) Electrochemical Advanced Oxidation Processes (EAOPs) for Disinfecting Water—Fresh Perspectives. Open Access Library Journal, 7, e6257. https://doi.org/10.4236/oalib.1106257

66. Comninellis, C. and Chen, G. (2010) Electrochemistry for the Environment. Springer, Berlin. https://doi.org/10.1007/978-0-387-68318-8

67. Ghernaout, D. (2020) Electric Field (EF) in the Core of the Electrochemical (EC) Disinfection. Open Access Library Journal, 7, e6587.

68. Ghernaout, D. and Elboughdiri, N. (2021) Towards Combining Electrochemical Water Splitting and Electrochemical Disinfection. Open Access Library Journal, 8, e7445. https://doi.org/10.4236/oalib.1107445

69. Martinez-Huitle, C.A., Rodrigo, M.A., Sires, I. and Scialdone, O. (2015) Single and Coupled Electrochemical Processes and Reactors for the Abatement of Organic Water Pollutants: A Critical Review. Chemical Reviews, 115, 13362-13407. https://doi.org/10.1021/acs.chemrev.5b00361

70. Vacca, A., Mascia, M., Palmas, S. and Da Pozzo, A. (2011) Electrochemical Treatment of Water Containing Chlorides under Non-Ideal Flow Conditions with BDD Anodes. Journal of Applied Electrochemistry, 41, 1087-1097. https://doi.org/10.1007/s10800-011-0274-3

71. Marselli, B., Garcia-Gomez, J., Michaud, P.-A., Rodrigo, M. and Comninellis, C. (2003) Electrogeneration of Hydroxyl Radicals on Boron-Doped Diamond Electrodes. Journal of the Electrochemical Society, 150, D79. https://doi.org/10.1149/1.1553790

72. Wang, X., Xiang, P., Zhang, Y., Wan, Y. and Lian, H. (2018) The Inhibition of Microcystis aeruginos by Electrochemical Oxidation Using Boron-Doped Diamond Electrode. Environmental Science and Pollution Research, 25, 20631-20639. https://doi.org/10.1007/s11356-018-1977-3

73. Liang, W., Qu, J., Chen, L., Liu, H. and Lei, P. (2005) Inactivation of Microcystis aeruginosa by Continuous Electrochemical Cycling Process in Tube Using Ti/RuO2 Electrodes. Environmental Science & Technology, 39, 4633-4639. https://doi.org/10.1021/es048382m

74. Xu, Y., Yang, J., Ou, M., Wang, Y. and Jia, J. (2007) Study of Microcystis aeruginosa Inhibition by Electrochemical Method. Biochemical Engineering Journal, 36, 215-220. https://doi.org/10.1016/j.bej.2007.02.022

75. Liang, W., Wang, K., Chen, L., Ruan, L. and Sui, L. (2011) Variation of Algal Viability during Electrochemical Disinfection Using Ti/RuO2 Electrodes. Water Science & Technology, 64, 162-170. https://doi.org/10.2166/wst.2011.490

76. Lin, L., Feng, C., Li, Q., Wu, M. and Zhao, L. (2015) Effects of Electrolysis by Low-Amperage Electric Current on the Chlorophyll Fluorescence Characteristics of Microcystis aeruginosa. Environmental Science and Pollution Research, 22, 14932-14939. https://doi.org/10.1007/s11356-015-4708-z

77. Lin, L., Meng, X., Li, Q., Huang, Z., Wang, L., Lin, K., Chen, J. and Crittenden, J. (2018) Electrochemical Oxidation of Microcystis aeruginosa Using a Ti/RuO2 Anode: Contributions of Electrochemically Generated Chlorines and Hydrogen Peroxide. Environmental Science and Pollution Research, 25, 27924-27934. https://doi.org/10.1007/s11356-018-2830-4

78. Zhou, S., Bu, L., Shi, Z., Deng, L., Zhu, S. and Gao, N. (2018) Electrochemical Inactivation of Microcystis aeruginosa Using BDD Electrodes: Kinetic Modeling of Microcystins Release and Degradation. Journal of Hazardous Materials, 346, 73-81. https://doi.org/10.1016/j.jhazmat.2017.12.023

79. Huang, C., Huang, W., Xiong, J. and Wang, S. (2021) Mechanism and Excellent Performance of Graphite Felt as Anodes in Electrochemical System for Microcystis aeruginosa and Microcystin-LR Removal with No pH Limitation nor Chemical Addition. Separation and Purification Technology, 277, Article ID: 119502. https://doi.org/10.1016/j.seppur.2021.119502

80. Bakheet, B., Islam, M.A., Beardall, J., Zhang, X. and McCarthy, D. (2018) Effective Electrochemical Inactivation of Microcystis aeruginosa and Degradation of Microcystins via a Novel Solid Polymer Electrolyte Sandwich. Chemical Engineering Journal 350, 616-626. https://doi.org/10.1016/j.cej.2018.06.012

81. Bakheet, B., Islam, M.A., Beardall, J., Zhang, X. and McCarthy, D. (2018) Electrochemical Inactivation of Cylindrospermopsis raciborskii and Removal of the Cyanotoxin Cylindrospermopsin. Journal of Hazardous Materials, 344, 241-248. https://doi.org/10.1016/j.jhazmat.2017.10.024

82. Mascia, M., Vacca, A. and Palmas, S. (2013) Electrochemical Treatment as a Pre-Oxidative Step for Algae Removal Using Chlorella vulgaris as a Model Organism and BDD Anodes. Chemical Engineering Journal 219, 512-519. https://doi.org/10.1016/j.cej.2012.12.097

83. Mascia, M., Monasterio, S., Vacca, A. and Palmas, S. (2016) Electrochemical Treatment of Water Containing Microcystis aeruginosa in a Fixed Bed Reactor with Three-Dimensional Conductive Diamond Anodes. Journal of Hazardous Materials, 319, 111-120. https://doi.org/10.1016/j.jhazmat.2016.03.004

84. Long, Y., Li, H., Xing, X. and Ni, J. (2017) Enhanced Removal of Microcystis aeruginosa in BDD-CF Electrochemical System by Simple Addition of Fe2+. Chemical Engineering Journal, 325, 360-368. https://doi.org/10.1016/j.cej.2017.05.067

85. Liu, B., Zhu, T.T., Liu, W.K., Zhou, R., Zhou, S.Q., Wu, R.X., Deng, L., Wang, J. and Van der Bruggen, B. (2020) Ultrafiltration Pre-Oxidation by Boron-Doped Diamond Anode for Algae-Laden Water Treatment: Membrane Fouling Mitigation, Interface Characteristics and Cake Layer Organic Release. Water Research, 187, Article ID: 116435. https://doi.org/10.1016/j.watres.2020.116435

86. Gao, Y., Zhang, J., Bai, X. and You, S. (2018) Monolithic Ceramic Electrode for Electrochemical Deactivation of Microcystis aeruginosa. Electrochimica Acta, 259, 410-418. https://doi.org/10.1016/j.electacta.2017.10.127

87. Radjenovic, J. and Sedlak, D.L. (2015) Challenges and Opportunities for Electrochemical Processes as Next-Generation Technologies for the Treatment of Contaminated Water. Environmental Science & Technology, 49, 11292-11302. https://doi.org/10.1021/acs.est.5b02414

88. Ghernaout, D. and Ghernaout, B. (2011) On the Controversial Effect of Sodium Sulphate as Supporting Electrolyte on Electrocoagulation Process: A Review. Desalination, and Water Treatment, 27, 243-254. https://doi.org/10.5004/dwt.2011.1983

89. Ghernaout, D., Naceur, M.W. and Ghernaout, B. (2011) A Review of Electrocoagulation as a Promising Coagulation Process for Improved Organic and Inorganic Matters Removal by Electrophoresis and Electroflotation. Desalination, and Water Treatment, 28, 287-320. https://doi.org/10.5004/dwt.2011.1493

90. Ghernaout, D., Alghamdi, A., Aichouni, M. and Touahmia, M. (2018) The Lethal Water Tri-Therapy: Chlorine, Alum, and Polyelectrolyte. World Journal of Applied Chemistry, 3, 65-71. https://doi.org/10.11648/j.wjac.20180302.14

91. Ghernaout, D. and Elboughdiri, N. (2020) Is Not It Time to Stop Using Chlorine for Treating Water? Open Access Library Journal, 7, e6007.

92. Ghernaout D. ,et al. (2017)Water Treatment Chlorination: An Updated Mechanistic Insight Review Chemistry Research Journal 2, 125-138.

93. Ghernaout, D. and Elboughdiri, N. (2020) Towards Enhancing Ozone Diffusion for Water Disinfection—Short Notes. Open Access Library Journal, 7, e6253.

94. Rippka, R. (1988) Isolation and Purification of Cyanobacteria. Methods in Enzymology, 167, 3-27. https://doi.org/10.1016/0076-6879(88)67004-2

95. Boucherit, A., Moulay, S., Ghernaout, D., Al-Ghonamy, A.I., Ghernaout, B., Naceur, M.W., Ait Messaoudene, N., Aichouni, M., Mahjoubi, A.A. and Elboughdiri, N.A. (2015) New Trends in Disinfection By-Products Formation upon Water Treatment. Journal of Research & Developments in Chemistry, 2015, Article ID: 628833. https://doi.org/10.5171/2015.628833

96. Ghernaout, D. and Elboughdiri, N. (2020) Strategies for Reducing Disinfection By-Products Formation during Electrocoagulation. Open Access Library Journal, 7, e6076. https://doi.org/10.4236/oalib.1106076

97. Ghernaout, D. and Elboughdiri, N. (2020) Disinfection By-Products: Presence and Elimination in Drinking Water. Open Access Library Journal, 7, e6140.

98. Stets, E.G., Sprague, L.A., Oelsner, G.P., Johnson, H.M., Murphy, J.C., Ryberg, K., Vecchia, A.V., et al. (2020) Landscape Drivers of Dynamic Change in Water Quality of U.S. Rivers. Environmental Science & Technology, 54, 4336-4343. https://doi.org/10.1021/acs.est.9b05344

99. Canizares, P., Sáez, C., Sánchez-Carretero, A. and Rodrigo, M.A. (2009) Synthesis of Novel Oxidants by Electrochemical Technology. Journal of Applied Electrochemistry, 39, 2143-2149. https://doi.org/10.1007/s10800-009-9792-7

100. Ghernaout D. ,et al. (2017)Microorganisms’ Electrochemical Disinfection Phenomena EC Microbiology 9, 160-169.

101. Ghernaout, D. and Elboughdiri, N. (2020) Electrochemical Technology for Wastewater Treatment: Dares and Trends. Open Access Library Journal, 7, e6020.

102. Ghernaout, D., Boudjemline, A. and Elboughdiri, N. (2020) Electrochemical Engineering in the Core of the Dye-Sensitized Solar Cells (DSSCs). Open Access Library Journal, 7, e6178. https://doi.org/10.4236/oalib.1106178

103. Ghernaout, D. (2020) Demobilizing Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes by Electrochemical Technology: New Insights. Open Access Library Journal, 7, e6685. https://doi.org/10.4236/oalib.1106685

104. Ghernaout, D. and Naceur, M.W. (2011) Ferrate(VI): In Situ Generation and Water Treatment—A Review. Desalination, and Water Treatment, 30, 319-332. https://doi.org/10.5004/dwt.2011.2217

105. Ghernaout, D. and Elboughdiri, N. (2019) Mechanistic Insight into Disinfection Using Ferrate(VI). Open Access Library Journal, 6, e5946.

106. Ghernaout, D. and Elboughdiri, N. (2019) Iron Electrocoagulation Process for Disinfecting Water—A Review. Applied Engineering, 3, 154-158.

107. Ghernaout, D., Elboughdiri, N. and Ghareba, S. (2020) Fenton Technology for Wastewater Treatment: Dares and Trends. Open Access Library Journal, 7, e6045. https://doi.org/10.4236/oalib.1106045

108. Ghernaout, D., Ghernaout, B. and Boucherit, A. (2008) Effect of pH on Electrocoagulation of Bentonite Suspensions in Batch Using Iron Electrodes. Journal of Dispersion Science and Technology, 29, 1272-1275. https://doi.org/10.1080/01932690701857483

109. Ghernaout, D., Ghernaout, B., Boucherit, A., Naceur, M.W., Khelifa, A. and Kellil, A. (2009) Study on Mechanism of Electrocoagulation with Iron Electrodes in Idealised Conditions and Electrocoagulation of Humic Acids Solution in Batch Using Aluminium Electrodes. Desalination, and Water Treatment, 8, 91-99. https://doi.org/10.5004/dwt.2009.668

110. Ghernaout, D., Irki, S. and Boucherit, A. (2014) Removal of Cu2+ and Cd2+, and Humic Acid and Phenol by Electrocoagulation Using Iron Electrodes. Desalination, and Water Treatment, 52, 3256-3270. https://doi.org/10.1080/19443994.2013.852484

111. Macpherson, J.V. (2015) A Practical Guide to Using Boron Doped Diamond in Electrochemical Research. Physical Chemistry Chemical Physics, 17, 2935-2949. https://doi.org/10.1039/C4CP04022H

112. Ghernaout D. ,et al. (2019)Brine Recycling: Towards Membrane Processes as the Best Available Technology Applied Engineering 3, 71-84.

113. Ghernaout, D., Alshammari, Y., Alghamdi, A., Aichouni, M., Touahmia, M. and Ait Messaoudene, N. (2018) Water Reuse: Extenuating Membrane Fouling in Membrane Processes. International Journal of Environmental Chemistry, 2, 1-12. https://doi.org/10.11648/j.ajche.20180602.12

114. Ghernaout, D., El-Wakil, A., Alghamdi, A., Elboughdiri, N. and Mahjoubi, A. (2018) Membrane Post-Synthesis Modifications and How It Came about. International Journal of Advances in Applied Sciences, 5, 60-64. https://doi.org/10.21833/ijaas.2018.02.010

115. Ghernaout, D. (2018) Electrocoagulation Process: Achievements and Green Perspectives. Colloid and Surface Science, 3, 1-5. https://doi.org/10.11648/j.css.20180301.11

116. Ghernaout, D. (2008) élimination des substances humiques et des germes indicateurs de contamination bactériologique par électrocoagulation assistée d’un traitement magnétique de l’eau. Ph.D. Thesis, University of Blida, Blida.

117. Irki, S., Ghernaout, D., Naceur, M.W., Alghamdi, A. and Aichouni, M. (2018) Decolorization of Methyl Orange (MO) by Electrocoagulation (EC) Using Iron Electrodes under a Magnetic Field (MF). II. Effect of Connection Mode. World Journal of Applied Chemistry, 3, 56-64. https://doi.org/10.11648/j.wjac.20180302.13

118. Ghernaout, D., Touahmia, M. and Aichouni, M. (2019) Disinfecting Water: Electrocoagulation as an Efficient Process. Applied Engineering, 3, 1-12.

119. Ghernaout, D., Aichouni, M. and Touahmia, M. (2019) Mechanistic Insight into Disinfection by Electrocoagulation—A Review. Desalination, and Water Treatment, 141, 68-81. https://doi.org/10.5004/dwt.2019.23457

120. Ghernaout D. ,et al. (2019)Greening Electrocoagulation Process for Disinfecting Water Applied Engineering 3, 27-31.

121. Ghernaout, D., Alghamdi, A. and Ghernaout, B. (2019) Electrocoagulation Process: A Mechanistic Review at the Dawn of Its Modeling. Journal of Environmental Science and Allied Research, 2, 51-67. https://doi.org/10.29199/2637-7063/ESAR-201019

122. Irki, S., Ghernaout, D. and Naceur, M.W. (2017) Decolourization of Methyl Orange (MO) by Electrocoagulation (EC) Using Iron Electrodes under a Magnetic Field (MF). Desalination, and Water Treatment, 79, 368-377. https://doi.org/10.5004/dwt.2017.20797

123. Ghernaout, D. and Elboughdiri, N. (2019) Electrocoagulation Process Intensification for Disinfecting Water—A Review. Applied Engineering, 3, 140-147.

124. Ghernaout D. ,et al. (2019)Disinfection via Electrocoagulation Process: Implied Mechanisms and Future Tendencies EC Microbiology 15, 79-90.

125. Ghernaout, D. and Elboughdiri, N. (2020) Electrocoagulation Process in the Context of Disinfection Mechanism. Open Access Library Journal, 7, e6083.

126. Ghernaout, D. and Elboughdiri, N. (2021) Modeling Viruses’ Isoelectric Points as a Milestone in Intensifying the Electrocoagulation Process for Their Elimination. Open Access Library Journal, 8, e7166. https://doi.org/10.4236/oalib.1107166

127. Ghernaout, D., Badis, A., Ghernaout, B. and Kellil, A. (2008) Application of Electrocoagulation in Escherichia coli Culture and Two Surface Waters. Desalination, 219, 118-125. https://doi.org/10.1016/j.desal.2007.05.010

128. Ghernaout, D., Ghernaout, B., Saiba, A., Boucherit, A. and Kellil, A. (2009) Removal of Humic Acids by Continuous Electromagnetic Treatment Followed by Electrocoagulation in Batch Using Aluminium Electrodes. Desalination, 239, 295-308. https://doi.org/10.1016/j.desal.2008.04.001

129. Mollah, M., Morkovsky, P., Gomes, J., Kesmez, M., Parga, J. and Cocke, D. (2004) Fundamentals, Present and Future Perspectives of Electrocoagulation. Journal of Hazardous Materials, 114, 199-210. https://doi.org/10.1016/j.jhazmat.2004.08.009

130. Ghernaout, D. and Elboughdiri, N. (2020) An Insight in Electrocoagulation Process through Current Density Distribution (CDD). Open Access Library Journal, 7, e6142. https://doi.org/10.4236/oalib.1106142

131. Ghernaout, D. (2020) Electrocoagulation as a Pioneering Separation Technology— Electric Field Role. Open Access Library Journal, 7, e6702.

132. Saiba, A., Kourdali, S., Ghernaout, B. and Ghernaout, D. (2010) In Desalination, from 1987 to 2009, the Birth of a New Seawater Pretreatment Process: Electrocoagulation—An Overview. Desalination, and Water Treatment, 16, 201-217. https://doi.org/10.5004/dwt.2010.1094

133. Ghernaout, D., Al-Ghonamy, A.I., Naceur, M.W., Ait Messaoudene, N. and Aichouni, M. (2014) Influence of Operating Parameters on Electrocoagulation of C.I. Disperse Yellow 3. Journal of Electrochemical Science and Engineering, 4, 271-283. https://doi.org/10.5599/jese.2014.0065

134. Ghernaout, D., Al-Ghonamy, A.I., Irki, S., Grini, A., Naceur, M.W., Ait Messaoudene, N. and Aichouni, M. (2014) Decolourization of Bromophenol Blue by Electrocoagulation Process. Trends in Chemical Engineering, 15, 29-39.

135. Ghernaout, D., Al-Ghonamy, A.I., Ait Messaoudene, N., Aichouni, M., Naceur, M.W., Benchelighem, F.Z. and Boucherit, A. (2015) Electrocoagulation of Direct Brown 2 (DB) and BF Cibacete Blue (CB) Using Aluminum Electrodes. Separation Science and Technology, 50, 1413-1420. https://doi.org/10.1080/01496395.2014.982763

136. Gao, S.S., Yang, J.X., Tian, J.Y., Ma, F., Tu, G. and Du, M.A. (2010) Electro-Coagulation-Flotation Process for Algae Removal. Journal of Hazardous Materials, 177, 336-343. https://doi.org/10.1016/j.jhazmat.2009.12.037

137. Meetiyagoda, T. and Fujino, T. (2020) Comparison of Different Anode Materials to Remove Microcystis aeruginosa Cells Using Electro-Coagulation-Flotation Process at Low Current Inputs. Water, 12, Article No. 3528. https://doi.org/10.3390/w12123528

138. Ghernaout, D., Mariche, A., Ghernaout, B. and Kellil, A. (2010) Electromagnetic Treatment-Bi-Electrocoagulation of Humic Acid in Continuous Mode Using Response Surface Method for Its Optimization and Application on Two Surface Waters. Desalination, and Water Treatment, 22, 311-329. https://doi.org/10.5004/dwt.2010.1120

139. Visigalli, S., Barberis, M.G., Turolla, A., Canziani, R., Zrimec, M.B., Reinhardt, R. and Ficara, E. (2021) Electrocoagulation-Flotation (ECF) for Microalgae Harvesting—A Review. Separation and Purification Technology, 271, Article ID: 118684. https://doi.org/10.1016/j.seppur.2021.118684

140. Wiley, P.E. and Trent, J.D. (2016) Clarification of Algae-Laden Water Using Electrochemical Processes. Water Science & Technology: Water Supply, 16, 314-323. https://doi.org/10.2166/ws.2015.140

141. Lian, H.L., Xiang, P., Xue, Y.H., Jiang, Y.Z., Li, M.Y. and Mo, J.Y. (2020) Efficiency and Mechanisms of Simultaneous Removal of Microcystis aeruginosa and Microcystins by Electrochemical Technology Using Activated Carbon Fiber/Nickel Foam as Cathode Material. Chemosphere, 252, Article ID: 126431. https://doi.org/10.1016/j.chemosphere.2020.126431

142. An, J.K., Li, N., Wang, S., Liao, C.M., Zhou, L., Li, T., Wang, X. and Feng, Y.J. (2019) A Novel Electro-Coagulation-Fenton for Energy Efficient Cyanobacteria and Cyanotoxins Removal without Chemical Addition. Journal of Hazardous Materials, 365, 650-658. https://doi.org/10.1016/j.jhazmat.2018.11.058

143. Gao, S.S., Du, M.A., Tian, J.Y., Yang, J.Y., Yang, J.X., Ma, F. and Nan, J. (2010) Effects of Chloride Ions on Electrocoagulation-Flotation Process with Aluminum Electrodes for Algae Removal. Journal of Hazardous Materials, 182, 827-834. https://doi.org/10.1016/j.jhazmat.2010.06.114

144. Irki, S., Ghernaout, D., Naceur, M.W., Alghamdi, A. and Aichouni, M. (2018) Decolorizing Methyl Orange by Fe-Electrocoagulation Process—A Mechanistic Insight. International Journal of Environmental Chemistry, 2, 18-28. https://doi.org/10.11648/j.ijec.20180201.14

145. Drees, K.P., Abbaszadegan, M. and Maier, R.M. (2003) Comparative Electrochemical Inactivation of Bacteria and Bacteriophage. Water Research, 37, 2291-2300. https://doi.org/10.1016/S0043-1354(03)00009-5

146. Ghernaout, D., Alghamdi, A., Touahmia, M., Aichouni, M. and Ait Messaoudene, N. (2018) Nanotechnology Phenomena in the Light of the Solar Energy. Journal of Energy, Environmental & Chemical Engineering, 3, 1-8. https://doi.org/10.11648/j.jeece.20180301.11

147. Ghernaout, D. and Elboughdiri, N. (2020) Solar Treatment in the Core of the New Disinfection Technologies. Chemical Science & Engineering Research, 2, 6-11. https://doi.org/10.36686/Ariviyal.CSER.2020.02.04.014

148. Irki, S., Kasbadji-Merzouk, N., Hanini, S. and Ghernaout, D. (2020) Modelling of the Coupling of Desalination Plants with the Thermal Solar Energy System. Water Supply, 20, 1807-1822. https://doi.org/10.2166/ws.2020.092

149. Ghernaout D. ,et al. (2019)Greening Cold Fusion as an Energy Source for Water Treatment Distillation—A Perspective American Journal of Quantum Chemistry and Molecular Spectroscopy 3, 1-5.

150. Han, X., Qu, Y., Dong, Y., Chen, D., Liang, D., Liu, J., et al. (2021) Simultaneous Electricity Generation and Eutrophic Water Treatment Utilizing Iron Coagulation Cell with Nitrification and Denitrification Biocathodes. Science of the Total Environment, 782, Article ID: 146436. https://doi.org/10.1016/j.scitotenv.2021.146436

151. Dong, Y., Qu, Y., Li, C., Han, X., Ambuchi, J.J., Liu, J., Yu, Y. and Feng, Y. (2017) Simultaneous Algae-Polluted Water Treatment and Electricity Generation Using a Biocathode-Coupled Electrocoagulation Cell (Bio-ECC). Journal of Hazardous Materials, 340, 104-112. https://doi.org/10.1016/j.jhazmat.2017.06.055

152. Ghernaout, D. and Elboughdiri, N. (2019) Water Reuse: Emerging Contaminants Elimination—Progress and Trends, Open Access Library Journal, 6, e5981.

153. Ghernaout, D. and Elboughdiri, N. (2020) On the Treatment Trains for Municipal Wastewater Reuse for Irrigation. Open Access Library Journal, 7, e6088.

154. Ghernaout, D. and Elboughdiri, N. (2020) UV-C/H2O2 and Sunlight/H2O2 in the Core of the Best Available Technologies for Dealing with Present Dares in Domestic Wastewater Reuse. Open Access Library Journal, 7, e6161. https://doi.org/10.4236/oalib.1106161

155. Mason, T.J., Cobley, A.J., Graves, J.E. and Morgan, D. (2011) New Evidence for the Inverse Dependence of Mechanical and Chemical Effects on the Frequency of Ultrasound. Ultrasonics Sonochemistry, 18, 226-230. https://doi.org/10.1016/j.ultsonch.2010.05.008

156. Wood, R.J., Lee, J. and Bussemaker, M.J. (2017) A Parametric Review of Sonochemistry: Control and Augmentation of Sonochemical Activity in Aqueous Solutions. Ultrasonics Sonochemistry, 38, 351-370. https://doi.org/10.1016/j.ultsonch.2017.03.030

157. Rajasekhar, P., Fan, L., Nguyen, T. and Roddick, F.A. (2012) A Review of the Use of Sonication to Control Cyanobacterial Blooms. Water Research, 46, 4319-4329. https://doi.org/10.1016/j.watres.2012.05.054

158. Park, J., Church, J., Son, Y., Kim, K.-T. and Lee, W.H. (2017) Recent Advances in Ultrasonic Treatment: Challenges and Field Applications for Controlling Harmful Algal Blooms (HABs). Ultrasonics Sonochemistry, 38, 326-334. https://doi.org/10.1016/j.ultsonch.2017.03.003

159. Wu, X., Joyce, E.M. and Mason, T.J. (2011) The Effects of Ultrasound on Cyanobacteria. Harmful Algae, 10, 738-743. https://doi.org/10.1016/j.hal.2011.06.005

160. Wu, X., Joyce, E.M. and Mason, T.J. (2012) Evaluation of the Mechanisms of the Effect of Ultrasound on Microcystis aeruginosa at Different Ultrasonic Frequencies. Water Research, 46, 2851-2858. https://doi.org/10.1016/j.watres.2012.02.019

161. Joyce, E.M., Wu, X. and Mason, T.J. (2010) Effect of Ultrasonic Frequency and Power on Algae Suspensions. Journal of Environmental Science and Health, Part A, 45, 863-866. https://doi.org/10.1080/10934521003709065

162. Li, Y.T., Shi, X.D., Zhang, Z. and Peng, Y.Z. (2019) Enhanced Coagulation by High-Frequency Ultrasound in Microcystis aeruginosa-Laden Water: Strategies and Mechanisms. Ultrasonics Sonochemistry, 55, 232-242. https://doi.org/10.1016/j.ultsonch.2019.01.022

163. Kong, Y., Peng, Y.Z., Zhang, Z., Zhang, M., Zhou, Y.H. and Duan, Z. (2019) Removal of Microcystis aeruginosa by Ultrasound: Inactivation Mechanism and Release of Algal Organic Matter. Ultrasonics Sonochemistry, 56, 447-457. https://doi.org/10.1016/j.ultsonch.2019.04.017

164. Ghernaout, D. and Elboughdiri, N. (2020) Vacuum-UV Radiation at 185 nm for Disinfecting Water. Chemical Science & Engineering Research, 2, 12-17. https://doi.org/10.36686/Ariviyal.CSER.2020.02.04.015

165. Liu, C., Wang, J., Cao, Z., Chen, W. and Bi, H.K. (2016) Variation of Dissolved Organic Nitrogen Concentration during the Ultrasonic Pretreatment to Microcystis aeruginosa. Ultrasonics Sonochemistry, 29, 236-243. https://doi.org/10.1016/j.ultsonch.2015.09.017

166. Song, W., Teshiba, T., Rein, K. and O’Shea, K.E. (2005) Ultrasonically Induced Degradation and Detoxification of Microcystin-LR (Cyanobacterial Toxin). Environmental Science & Technology, 39, 6300-6305. https://doi.org/10.1021/es048350z

167. Song, W. and O’Shea, K.E. (2007) Ultrasonically Induced Degradation of 2-Methylisoborneol and Geosmin. Water Research, 41, 2672-2678. https://doi.org/10.1016/j.watres.2007.02.041

168. Wang, J., Li, W. and Wu, X. (2021) Microcystis aeruginosa Removal by the Combination of Ultrasound and TiO2/Biochar. RSC Advances, 11, 24985-24990. https://doi.org/10.1039/D1RA03308E

169. Lürling, M. and Tolman, Y. (2014) Beating the Blues: Is There Any Music in Fighting Cyanobacteria with Ultrasound? Water Research, 66, 361-373. https://doi.org/10.1016/j.watres.2014.08.043

170. Lürling, M. and Mucci, M. (2020) Mitigating Eutrophication Nuisance: In-Lake Measures Are Becoming Inevitable in Eutrophic Waters in the Netherlands. Hydrobiologia, 847, 4447-4467. https://doi.org/10.1007/s10750-020-04297-9

171. Ghernaout, D. and El-Wakil, A. (2017) Requiring Reverse Osmosis Membranes Modifications—An Overview. American Journal of Chemical Engineering, 5, 81-88. https://doi.org/10.11648/j.ajche.20170504.15

172. Ghernaout, D. (2017) Reverse Osmosis Process Membranes Modeling—A Historical Overview. Journal of Civil, Construction and Environmental Engineering, 2, 112-122.

173. Ghernaout, D. and Ghernaout, B. (2010) From Chemical Disinfection to Electrodisinfection: The Obligatory Itinerary? Desalination, and Water Treatment, 16, 156-175. https://doi.org/10.5004/dwt.2010.1085

174. Ghernaout, D. and Ghernaout, B. (2012) Sweep Flocculation as a Second Form of Charge Neutralisation—A Review. Desalination, and Water Treatment, 44, 15-28. https://doi.org/10.1080/19443994.2012.691699

175. Ghernaout, D. (2018) Increasing Trends towards Drinking Water Reclamation from Treated Wastewater. World Journal of Applied Chemistry, 3, 1-9. https://doi.org/10.11648/j.wjac.20180301.11

176. Ghernaout, D. and Elboughdiri, N. (2020) Disinfection By-Products (DBPs) Control Strategies in Electrodisinfection. Open Access Library Journal, 7, e6396. https://doi.org/10.4236/oalib.1106396

177. Ghernaout, D. and Elboughdiri, N. (2020) Controlling Disinfection By-Products Formation in Rainwater: Technologies and Trends. Open Access Library Journal, 7, e6162. https://doi.org/10.4236/oalib.1106162

178. Ghernaout, D. and Elboughdiri, N. (2020) Foresight Look on the Disinfection By-Products Formation. Open Access Library Journal, 7, e6349.

179. Ghernaout, D. and Elboughdiri, N. (2020) Disinfection By-Products Regulation: Zero ng/L Target. Open Access Library Journal, 7, e6382.

180. Shang, L.X., Feng, M.H., Xu, X.E., Liu, F.F., Ke, F., et al. (2018) Co-Occurrence of Microcystins and Taste-and-Odor Compounds in Drinking Water Source and Their Removal in a Full-Scale Drinking Water Treatment Plant. Toxins, 10, 26. https://doi.org/10.3390/toxins10010026

181. Mohamed, Z.A., Deyab, M.A., Abou-Dobara, M.I., El-Sayed, A.K. and El-Raghi, W.M. (2015) Occurrence of Cyanobacteria and Microcystin Toxins in Raw and Treated Waters of the Nile River, Egypt: Implication for Water Treatment and Human Health. Environmental Science and Pollution Research, 22, 11716-11727. https://doi.org/10.1007/s11356-015-4420-z

182. Bogialli, S., di Gregorio, F.N., Lucentini, L., Ferretti, E., Ottaviani, M., Ungaro, N., Abis, P.P. and de Grazia, M.C. (2013) Management of a Toxic Cyanobacterium Bloom (Planktothrix rubescens) Affecting an Italian Drinking Water Basin: A Case Study. Environmental Science & Technology, 47, 574-583. https://doi.org/10.1021/es302260p

183. Plummer, J.D. and Edzwald, J.K. (2002) Effects of Chlorine and Ozone on Algal Cell Properties and Removal of Algae by Coagulation. Journal of Water Supply: Research and Technology—AQUA, 51, 307-318. https://doi.org/10.2166/aqua.2002.0027

184. Steynberg, M., Pieterse, A. and Geldenhuys, J. (1996) Improved Coagulation and Filtration of Algae as a Result of Morphological and Behavioural Changes Due to Pre-Oxidation. Journal of Water Supply: Research and Technology—AQUA, 45, 292-298.

185. Piezer, K., Li, L., Jeon, Y., Kadudula, A. and Seo, Y. (2021) The Application of Potassium Permanganate to Treat Cyanobacteria-Laden Water: A Review. Process Safety and Environmental Protection, 148, 400-414. https://doi.org/10.1016/j.psep.2020.09.058

186. Yang, T., Xiong, H., Liu, F., Yang, Q., Xu, B. and Zhan, C. (2019) Effect of UV/TiO2 Pretreatment on Fouling Alleviation and Mechanisms of Fouling Development in a Cross-Flow Filtration Process Using a Ceramic UF Membrane. Chemical Engineering Journal 358, 1583-1593. https://doi.org/10.1016/j.cej.2018.10.149

187. Naceradska, J., Pivokonsky, M., Pivokonska, L., Baresova, M., Henderson, R.K., Zamyadi, A. and Janda, V. (2017) The Impact of Pre-Oxidation with Potassium Permanganate on Cyanobacterial Organic Matter Removal by Coagulation. Water Research, 114, 42-49. https://doi.org/10.1016/j.watres.2017.02.029

188. Dong, F.L., Lin, Q.F., Li, C., He, G.L. and Deng, Y. (2021) Impacts of Pre-Oxidation on the Formation of Disinfection Byproducts from Algal Organic Matter in Subsequent Chlor(am)ination: A Review. Science of the Total Environment, 754, Article ID: 141955. https://doi.org/10.1016/j.scitotenv.2020.141955

189. Qi, J., Ma, B., Miao, S., Liu, R., Hu, C. and Qu, J. (2021) Pre-Oxidation Enhanced Cyanobacteria Removal in Drinking Water Treatment: A Review. Journal of Environmental Sciences, 110, 160-168. https://doi.org/10.1016/j.jes.2021.03.040

190. Bai, M.D., Zheng, Q.L., Zheng, W., Li, H.Y., Lin, S.Y., Huang, L.F. and Zhang, Z.T. (2019) OH Inactivation of Cyanobacterial Blooms and Degradation of Toxins in Drinking Water Treatment System. Water Research, 154, 144-152. https://doi.org/10.1016/j.watres.2019.02.002

191. Cheng, X.X., Wu, D.J., Liang, H., Zhu, X.W., Tang, X.B., Gan, Z.D., Xing, J.J., Luo, X.S. and Li, G.B. (2018) Effect of Sulfate Radical-Based Oxidation Pretreatments for Mitigating Ceramic UF Membrane Fouling Caused by Algal Extracellular Organic Matter. Water Research, 145, 39-49. https://doi.org/10.1016/j.watres.2018.08.018

192. Jia, P.L., Zhou, Y.P., Zhang, X.F., Zhang, Y. and Dai, R.H. (2018) Cyanobacterium Removal and Control of Algal Organic Matter (AOM) Release by UV/H2O2 Pre-Oxidation Enhanced Fe(II) Coagulation. Water Research, 131, 122-130. https://doi.org/10.1016/j.watres.2017.12.020

193. Dugan, N.R., Smith, S.J. and Sanan, T.T. (2018) Impacts of Potassium Permanganate and Powdered Activated Carbon on Cyanotoxin Release. Journal—American Water Works Association, 110, E31-E42. https://doi.org/10.1002/awwa.1125

194. Newcombe, G., Ho, L. and Neto, J.C. (2021) Controlling Cyanotoxin Occurrence: Drinking-Water Treatment. In: Toxic Cyanobacteria in Water, CRC Press, Boca Raton, 591-639. https://doi.org/10.1201/9781003081449-10

195. Cho, K., An, B.M., So, S., Chae, A. and Song, K.G. (2020) Simultaneous Control of Algal Micropollutants Based on Ball-Milled Powdered Activated Carbon in Combination with Permanganate Oxidation and Coagulation. Water Research, 185, Article ID: 116263. https://doi.org/10.1016/j.watres.2020.116263

196. Edzwald, J.K. (2013) Coagulant Mixing Revisited: Theory and Practice. Journal of Water Supply: Research and Technology—AQUA, 62, 67-77. https://doi.org/10.2166/aqua.2013.142

197. Rossini, M., Garrido, J.G. and Galluzzo, M. (1999) Optimization of the Coagulation-Flocculation Treatment: Influence of Rapid Mix Parameters. Water Research, 33, 1817-1826. https://doi.org/10.1016/S0043-1354(98)00367-4

198. Halász, G., Gyüre, B., Jánosi, I.M., Szabó, K.G. and Tél, T. (2007) Vortex Flow Generated by a Magnetic Stirrer. American Journal of Physics, 75, 1092-1098. https://doi.org/10.1119/1.2772287

199. Chow, C.W.K., Drikas, M., House, J., Burch, M.D. and Velzeboer, R.M.A. (1999) The Impact of Conventional Water Treatment Processes on Cells of the Cyanobacterium Microcystis aeruginosa. Water Research, 33, 3253-3262. https://doi.org/10.1016/S0043-1354(99)00051-2

200. Clemente, A., Wilson, A., Oliveira, S., Menezes, I., Gois, A. and Capelo-Neto, J. (2020) The Role of Hydraulic Conditions of Coagulation and Flocculation on the Damage of Cyanobacteria. Science of the Total Environment, 740, Article ID: 139737. https://doi.org/10.1016/j.scitotenv.2020.139737

201. Qian, F., Dixon, D.R., Newcombe, G., Ho, L., Dreyfus, J. and Scales, P.J. (2014) The Effect of pH on the Release of Metabolites by Cyanobacteria in Conventional Water Treatment Processes. Harmful Algae, 39, 253-258. https://doi.org/10.1016/j.hal.2014.08.006

202. Pietsch, J., Bornmann, K. and Schmidt, W. (2002) Relevance of Intra- and Extracellular Cyanotoxins for Drinking Water Treatment. Acta Hydrochimica et Hydrobiologica, 30, 7-15. https://doi.org/10.1002/1521-401X(200207)30:1<7::AID-AHEH7>3.0.CO;2-W

203. Ait Messaoudene, N., Naceur, M.W., Ghernaout, D., Alghamdi, A. and Aichouni, M. (2018) On the Validation Perspectives of the Proposed Novel Dimensionless Fouling Index. International Journal of Advances in Applied Sciences, 5, 116-122. https://doi.org/10.21833/ijaas.2018.07.014

204. Villacorte, L.O., Tabatabai, S.A.A. anderson, D.M., Amy, G.L., Schippers, J.C. and Kennedy, M.D. (2015) Seawater Reverse Osmosis Desalination and (Harmful) Algal Blooms. Desalination, 360, 61-80. https://doi.org/10.1016/j.desal.2015.01.007

205. Edzwald, J.K. and Haarhoff, J. (2011) Seawater Pretreatment for Reverse Osmosis: Chemistry, Contaminants, and Coagulation. Water Research, 45, 5428-5440. https://doi.org/10.1016/j.watres.2011.08.014

206. Edzwald, J.K. (2010) Dissolved Air Flotation and Me. Water Research, 44, 2077-2106. https://doi.org/10.1016/j.watres.2009.12.040

207. Edzwald, J.K. (1995) Principles and Applications of Dissolved Air Flotation. Water Science & Technology, 31, 1-23. https://doi.org/10.2166/wst.1995.0512

208. Gonzalez-Torres, A., Putnam, J., Jefferson, B., Stuetz, R.M. and Henderson, R.K. (2014) Examination of the Physical Properties of Microcystis aeruginosa Flocs Produced on Coagulation with Metal Salts. Water Research, 60, 197-209. https://doi.org/10.1016/j.watres.2014.04.046

209. Teixeira, M.R., Sousa, V. and Rosa, M.J. (2010) Investigating Dissolved Air Flotation Performance with Cyanobacterial Cells and Filaments. Water Research, 44, 3337-3344. https://doi.org/10.1016/j.watres.2010.03.012

210. Zhang, M., Wang, Y.F., Wang, Y.Q., Li, M.T., Zhang, D.Y., Qiang, Z.M. and Pan, X.L. (2019) Efficient Elimination and Regrowth Inhibition of Harmful Bloom-Forming Cyanobacteria Using Surface-Functionalized Microbubbles. Water Research, 161, 473-485. https://doi.org/10.1016/j.watres.2019.06.035

211. Ma, J., Lei, G.Y. and Fang, J.Y. (2007) Effect of Algae Species Population Structure on Their Removal by Coagulation and Filtration Processes—A Case Study. Journal of Water Supply: Research and Technology—AQUA, 56, 41-54. https://doi.org/10.2166/aqua.2007.062

212. Dugan, N.R. and Williams, D.J. (2006) Cyanobacteria Passage through Drinking Water Filters during Perturbation Episodes as a Function of Cell Morphology, Coagulant and Initial Filter Loading Rate. Harmful Algae, 5, 26-35. https://doi.org/10.1016/j.hal.2005.04.001

213. Zamyadi, A., MacLeod, S.L., Fan, Y., McQuaid, N., Dorner, S., Sauve, S. and Prevost, M. (2012) Toxic Cyanobacterial Breakthrough and Accumulation in a Drinking Water Plant: A Monitoring and Treatment Challenge. Water Research, 46, 1511-1523. https://doi.org/10.1016/j.watres.2011.11.012

214. Drikas, M., Chow, C.W.K., House, J. and Burch, M.D. (2001) Using Coagulation, Flocculation, and Settling to Remove Toxic Cyanobacteria. Journal—American Water Works Association, 93, 100-111. https://doi.org/10.1002/j.1551-8833.2001.tb09130.x

215. Zhong, S., Zhang, K., Bagheri, M., Burken, J.G., Gu, A., Li, B., et al. (2021) Machine Learning: New Ideas and Tools in Environmental Science and Engineering. Environmental Science & Technology, 55, 12741-12754. https://doi.org/10.1021/acs.est.1c01339

216. Ghernaout, D., Aichouni, M. and Alghamdi, A. (2018) Applying Big Data (BD) in Water Treatment Industry: A New Era of Advance. International Journal of Advances in Applied Sciences, 5, 89-97. https://doi.org/10.21833/ijaas.2018.03.013

217. Ghernaout, D., Aichouni, M., Alghamdi, A. and Ait Messaoudene, N. (2018) Big Data: Myths, Realities and Perspectives—A Remote Look. American Journal of Information Science and Technology, 2, 1-8. https://doi.org/10.11648/j.ajist.20180201.11

218. Ghernaout, D., Aichouni, M. and Alghamdi, A. (2018) Overlapping ISO/IEC 17025: 2017 into Big Data: A Review and Perspectives. International Journal of Science and Qualitative Analysis, 4, 83-92.

219. Maier, H.R., Sayed, T. and Lence, B.J. (2000) Forecasting Cyanobacterial Concentrations Using B-Spline Networks. Journal of Computing in Civil Engineering, 14, 183-189. https://doi.org/10.1061/(ASCE)0887-3801(2000)14:3(183)

220. Kehoe, M.J., Chun, K.P. and Baulch, H.M. (2015) Who Smells? Forecasting Taste and Odor in a Drinking Water Reservoir. Environmental Science & Technology, 49, 10984-10992. https://doi.org/10.1021/acs.est.5b00979

221. Xiao, X., He, J., Huang, H., Miller, T.R., Christakos, G., Reichwaldt, E.S., et al. (2017) A Novel Single-Parameter Approach for Forecasting Algal Blooms. Water Research, 108, 222-231. https://doi.org/10.1016/j.watres.2016.10.076

222. Zhao, Z.M., Sun, W.J., Ray, M.B., Ray, A.K., Huang, T.Y. and Chen, J.B. (2019) Optimization and Modeling of Coagulation-Flocculation to Remove Algae and Organic Matter from Surface Water by Response Surface Methodology. Frontiers of Environmental Science & Engineering, 13, Article No. 75. https://doi.org/10.1007/s11783-019-1159-7