Water Reuse: Emerging Contaminants Elimination—Progress and Trends

This work concentrates on the review paper published by Ahmed et al. [1] which is dedicated to the elimination of emerging contaminants (ECs) using biological, chemical and hybrid techniques in effluents from wastewater treatment plants (WWTPs). Endocrine disruption chemicals (EDCs) are better reduced by a membrane bioreactor (MBR), activated sludge, and aeration processes between various biological processes. Surfactants, EDCs and personal care products (PCPs) may be well reduced using activated sludge processes. Pesticides and pharmaceuticals manifested convenient reduction performances by biological activated carbon. Microalgae treatment techniques may diminish nearly all sorts of ECs to a certain degree. Additional biological methods were observed less efficient in dealing with ECs. Chemical oxidation techniques (like ozonation/H2O2, UV photolysis/H2O2, and photo-Fenton) may greatly eliminate up to 100% of pesticides, beta-blockers, and pharmaceuticals; at the same time, EDCs may be better reduced via ozonation and UV photocatalysis. Fenton method was observed less efficient in treating any sorts of ECs. A merged setup founded on ozonation pursued by biological activated carbon was manifested hugely efficacious in eliminating pesticides, beta-blockers, and pharmaceuticals. An integrated ozonation-ultrasound device may eliminate until 100% of numerous pharmaceuticals. Next research orientations to boost the elimination of ECs have been suggested.

• Water Reuse
• Emerging Contaminants (ECs)
• Endocrine Disruption Chemi-cals (EDCs)
• Membrane Processes
• Wastewater Treatment
• Advanced Oxi-dation Processes (AOPs)

1. Introduction

Emerging contaminants (ECs) are mainly synthetic organic chemicals that have been lately found in natural mediums [1] [2] [3] [4] [5]. ECs are a huge and comparatively novel group of unregulated complexes [6] and may easily induce harmful influences in aquatic and human life at naturally pertinent levels, which are beginning an increasing worry [2] [7] [8]. They are the components predominately found in urban sewage, daily household products, pharmaceutical production facilities, wastewater, hospitals, landfills, and natural aquatic mediums [9] [10] [11]. ECs levels may extend from a few ng/L to a few hundred μg/L [10] [12]. Such levels in the aquatic medium may produce ecological hazards like interference with the endocrine system of high organisms, microbiological resistance, and accumulation in soil, plants, and animals [13], because such ECs are not totally eliminated throughout traditional wastewater treatment techniques [8] [14] [15]. ECs comprise mainly pharmaceutical organic pollutants, personal care products (PCPs), endocrine disrupting compounds (EDCs), surfactants, pesticides, flame-retardants, and industrial additives among others [1].

Pharmaceutical organic contaminants and PCPs contain analgesics, lipid regulators, antibiotics, diuretics, non-steroid anti-inflammatory drugs, stimulant drugs, antiseptics, analgesics, beta-blockers, antimicrobials, cosmetics, sunscreen agents, food supplements, fragrances, and their metabolites and transformation products [1]. They may touch water quality and greatly influence potable water supplies, ecosystem and human health [15] [16] [17]. Their environmental bioaccumulation worsens the abnormal hormonal control inducing reproductive impairments, diminished fecundity, augmented incidence of breast and testosterone cancers, and persistent antibiotic resistance [18]. More important, antibiotic residues may cause the development of antibiotic-resistant genes hugely favoring superbugs [8].

EDCs are exogenous substances or mixtures that modify the roles of the endocrine systems and then induce negative health influences in an intact organism, or its progeny or populations [19]. The impacts linked to EDCs are breakage of eggs of birds, fishes, and turtles, problems in reproductive systems, alteration in the immunologic system of marine mammals, a decrease of sperm of human organ, elevation in the incidence of breast, testicle and prostate cancers, and endometriosis [16]. Pesticides have immune-depressive impacts in fishes, mammals and may alter hemopoietic tissue of anterior kidney [20]. Surfactants can touch the physical stability of human growth hormone formulations and are responsible for the endocrine activity [1] [21].

A set of diverse physical, chemical, and biological techniques have previously been utilized to eliminate or decompose the remains of ECs during the past years [22] [23]. Biological treatment techniques remain the most largely employed for eliminating ECs, comprising activated sludge, constructed wetland, membrane bioreactor (MBR), aerobic bioreactor, anaerobic bioreactor, microalgae bioreactor [24] [25], fungal bioreactor, trickling filter, rotating biological reactor, nitrification, enzyme treatment, and biosorption. Several non-biodegradable organic micropollutants cannot be enough reduced employing biological treatment techniques [5] [26] [27]. Chemical treatment processes are also largely employed for decomposing such micropollutants [26] [27], involving traditional oxidation techniques like Fenton, ozonation, photolysis, and advanced oxidation processes (AOPs) [28] [29] like ferrate [30] [31] [32], photo-Fenton, photocatalysis, solar-driven processes, ultrasound process, and electro-Fenton method. Furthermore, numerous hybrid systems have newly been implemented to improve the elimination of a large span of ECS. Table 1 lists the benefits and dares of diverse methods for eliminating ECs [1].

The plurality of polar and semi-polar pesticides and pharmaceuticals will stay partitioned in the aqueous phase because of their comparatively elevated water solubility; for this reason, their reduction via physical processes like sedimentation and flocculation is not efficient [67] as it has been mentioned to be less than 10% [68] [69]. As a result, additional debates of those methods are not revised here. The debate of extra physical treatment techniques like membrane [70], reverse osmosis (RO), ultrafiltration (UF), microfiltration (MF), NF, and adsorption methods is also kept out from this work, even if such physical approaches can be a piece of hybrid or integrated treatment techniques for eliminating ECs [1] [71].

Therefore, this work aims to deeply assess the viability of biological, chemical, and hybrid treatment processes as a tool to eliminate ECs from wastewater. Particularly, the paper presents an outline of the efficacy of diverse wastewater treatment techniques for eliminating ECs. It also estimates traditional wastewater treatment methods along with amelioration and hybrid treatment techniques for reducing ECs. It also assesses the dares and the actual comprehension inabilities restricting the performance of biological and chemical treatment technologies. Several of the future research trends are as well proposed.

2. Biological Treatment Techniques

Biological treatment techniques have been largely used for eliminating ECs mostly via the pathway of biodegradation. Biodegradation is the method during which large molecular weight ECs are decomposed by microorganisms like bacteria [72] [73] [74] [75], algae [76] [77], and fungi into small molecules [6], and even biomineralized to simple inorganic molecules like water and carbon dioxide. During the traditional biodegradation method, microorganisms employ organic complexes as first substrates for their cell development and induce

Table 1

Benefits and dares of diverse techniques in eliminating ECs [ 1 ]

Treatment method	Benefits	Dares
Traditional Biological activated carbon	A large variety of ECs reduction from wastewater. Reduction of remaining disinfection/oxidation products [33] [34] [35] [36] . Not producing hazardous active products.	Comparatively elevated cost in running and maintenance. Regeneration and disposal hurdles of high sludge. Processing of sludge may elevate global cost by 50% - 60%.
Microalgae reactor	Resource recovery of algal biomass, employed as fertilizer [37] [38] [39] . Elevated quality effluent & no acute toxicity danger linked with ECs.	Reduction efficiencies touched by cold season. EDCs cannot be decomposed conveniently.
Activated sludge	Lower capital and operational costs than AOPs. More environmental friendly than chlorination [40] [41] [42] .	Low efficiencies for pharmaceuticals and beta-blockers. Large amount of sludge containing ECs. Unsuitable where chemical oxygen demand levels are greater than 4000 mg/L.
Non-traditional Constructed wetland	Low energy consumption and low operational & maintenance costs. High performance on removal of estrogens, PCPs, pesticides and pathogens.	Clogging, solids entrapment and sediments formation. Biofilm growth, chemical precipitation and seasonal dependent. Needs large area of lands and long retention time.
MBR	Effective for the removal of bio-recalcitrant and ECs. Small footprint.	High-energy consumption, fouling, and control of heat and mass transfer. High aeration [43] cost and roughness of membrane [44] [45] . Pharmaceutical pollutants have low efficiencies.
Chemical process Coagulation	Reduced turbidity arising from suspended inorganic and organic particles [46] [47] [48] . Increased sedimentation rate through suspended solid particles formation [49] [50] [51] .	Ineffective micropollutants removal [52] [53] [54] . Large amount of sludge [55] [56] [57] . Introduction of coagulant slats in the aqueous phase [58] [59] [60] [61] .
Ozonation	Strong affinity to ECs in the presence of H2O2. Selective oxidant favoring disinfection and sterilization properties [62] .	Interference of radical scavengers.
AOPs	Major ancillary effects on removal of ECs such as EDCs, pharmaceuticals, PCPs and pesticides. Short degradation rate.	Energy consumption issues, operational & maintenance cost. Formation of toxic disinfection by-products [63] [64] . Interference of radical scavengers.
Fenton and photo-Fenton	Degradation and mineralization of ECs. Sunlight can be used by avoiding UV light.	Decrease of ●OH forming chloro and sulfato-Fe(III) complexes or due to scavenge of ●OH forming Cl2● and SO4●− in the presence of chloride and sulfate ions.
Photocatalysis (TiO2)	Degrading persistent organic compounds. High reaction rates upon using catalyst. Low price and chemical stability of TiO2 catalyst and easier recovery.	Difficult to treat large volume of wastewater. Cost associated with artificial UV lamps and electricity. Separation and reuse of photocatalytic particles from slurry suspension.
Physical process Micro-orultra-filtration	Can remove pathogens. Applicable for heavy metal removal.	Not fully effective in removing some ECs as pore sizes vary from 100 to 1000 times larger than the micropollutants. High cost of operation.
Nanofiltration (NF)	Useful for treating saline water and wastewater treatment plants (WWTPs) influents. Can remove dyestuff and pesticides.	High-energy demand, membrane fouling and disposal issue [65] . Limited application in pharmaceutical removal.
Reverse osmosis	Useful for treating saline water and WWTP influents. Can remove PCPs, EDCs and pharmaceuticals.	High-energy demand, membrane fouling and disposal issue [66] . Corrosive nature of finished water & lower pharmaceutical removal.

enzymes for their ingestion [12] [78] [79] [80]. Several ECs are poisonous and resistant to microbial development thus blocking biodegradation, in which situation a growth substrate is required to keep microbial development for biodegradation, a phenomenon recognized as cometabolism [12]. Biodegradation techniques have conventionally been utilized in wastewater treatment devices for eliminating ECs [81] [82]. They may be classified into aerobic and anaerobic techniques. Aerobic implementations involve activated sludge, MBR, and sequence batch reactor. Anaerobic techniques implicate anaerobic sludge reactors and anaerobic film reactors. The wastewater features have a fundamental contribution in choosing biological techniques [9] [83]. The wastewater treatment methods may be largely categorized as traditional processes and non-traditional processes, which are depicted in next sections [1] [66] [84].

The decomposition potential of ECs is a function of the chemical and biological persistence of ECs, their physicochemical characteristics, the technique applied and running parameters. For the highly polar substances (such as most pharmaceuticals and their corresponding metabolites), the most substantial removal mode is via the biological conversion or mineralization by microbes. The elimination yields greatly depend upon the treatment method, the working factors, and pointed pollutants [85]. Distinguishing decomposition products in environmental samples is hard work since not only are they found at so small concentrations but also they are existing in complex matrices that may interfere with detection [85] [86].

More details about progress and challenges in traditional treatment methods may be found in [1].

3. Chemical Treatment Techniques

Biological wastewater treatment techniques may be efficacious in eliminating several categories of ECs following the target chemicals, nature of wastewater, and running parameters [1] [87]. For instance, polar pharmaceuticals and beta-blockers depicted changing reduction performances in diverse biological techniques. Thus, chemical treatment processes have to be examined as replacements with the objective of discovering appropriate finishing technologies to more eliminate ECs [88] [89]. Such techniques are largely described as aqueous phase oxidation processes founded on the intermediary of highly reactive chemical species [90]. Oxidation reactions have mainly been employed to complete rather than substitute classical setups and to ameliorate removing ECs [91]. Chemicals like chlorine, hydrogen peroxide, ozone as well as the integration of these oxidants involving transition metals and metal oxides based catalysts in the so-called AOPs are needed for eliminating ECs from wastewater [92] [93]. Moreover, an energy source like UV-vis radiation, electric current, solar [94], gamma-radiation, and ultrasound are also utilized [95] [96]. In AOPs, oxidizing ECs is founded on generating free radicals, especially, hydroxyl radicals that ease the transformation of contaminants to less poisonous and more decomposable compounds [95] [97]. The final goal of chemical oxidation is the mineralization of contaminants, with their transformation to carbon dioxide, water, nitrogen, and other minerals. The rate constants for most reactions implying hydroxyl radicals in water are frequently in the order of 106 - 109 M⁻¹∙s⁻¹ [1]. Chemical oxidation techniques may modify pharmaceuticals’ polarity and the number of functional groups, which in turn influence their functionality in the organisms.

Progress and dares in classical oxidation methods are well explained by Ahmed et al. [1].

4. Progress and Challenges in Hybrid Systems

The classical wastewater treatment methods are not appropriate for eliminating efficiently several ECs [98]. A collection of hybrid treatment techniques is mentioned in the literature. Throughout the past decade, huge ameliorations have been reached in their usage in wastewater treatment, to avoid the liberation of ECs into the aquatic environment by effluent discharge [99]. Most of the hybrid systems are composed of biological-based treatment setup pursued by some physical or chemical treatment devices. Chemical oxidation founded treatment, as ozonation is the most largely employed method to merge with the biological processes. Several illustrations of these integrations comprise ozonation assisted by biological activated carbon, MBR-RO/UF/MF/ozonation, filtration and activated sludge pursued by UF [1]. MF and UF are ever more being viewed as replacements to granular media filtration [100].

5. Future Tendencies

Diverse biological and chemical-founded processes may efficiently eliminate distinct ECs; however, there are up to this time insufficiencies in the total elimination of ECs. Several additional research domains are proposed in Table 2 [1].

6. Conclusions

The main points drawn from this work may be given as:

1) Various biological techniques were observed to boost the reduction performance of diverse categories of ECs. As an illustration, the traditional activated sludge method has manifested better reduction performances for surfactants, EDCs, and PCPs than trickling filter and biofilm reactors, nitrification and denitrification techniques. Biological activated carbon method has been mentioned with ameliorated performances in the reduction of pesticides, analgesics, and antibiotics. MBR process has been detected to be hugely efficient in eliminating EDCs, PCPs, and beta-blockers than constructed wetlands. The new microalgae founded technique has the most elevated performance in eliminating diverse classes of ECs particularly pharmaceuticals and PCPs, even if no information was published on their elimination of beta-blockers, antibiotics, and surfactants [1] [110].

Table 2

Ten investigation areas suggested for the future [ 1 ]

Research field	Description
Research field #1	There is a shortage of elaborated knowledge about the decomposition pathways implicated, the effect of running factors on ECs elimination, reaction kinetics and reactor conception for excellent efficiency.
Research field #2	Amalgamation of present treatment setups with nanoscale science and technology.
Research field #3	Dares related to wastewater sample preparations, analytical methods and validation protocols for the reliable analysis of ECs in complicated environmental samples [101] [102] .
Research field #4	Reduction efficiency of various WWTP techniques at changing working situations has to be re-estimated employing appropriate sampling procedures.
Research field #5	Employing solar irradiation has to be examined as a substitutional AOP technique for diminishing the prices of huge-scale commercial implementations.
Research field #6	Composite techniques founded on merged chemical and biological treatment methods (like UV photolysis in the existence of H2O2 pursued by MBR or biological activated carbon, ozonation in the existence of H2O2 pursued by MBR or biological activated carbon, photo-Fenton pursued by MBR or biological activated carbon) have to be more tried.
Research field #7	Integrating physical methods (like gamma radiation and ultrasound with adsorption on activated carbon) may as well be performed inside the actual wastewater treatment setups [103] [104] .
Research field #8	Ferrate method is a comparatively green technology and has to be more widely investigated for industrial-scale utilizations [105] [106] [107] [108] .
Research field #9	Fresh comprehension in genetic engineering has to be inserted to choose and develop the most efficient microbes for decomposing ECs, which will decrease hydraulic contact period and economize capital cost in reactor conception.
Research field #10	The hardiness and feasibility of full-scale chemical oxidation techniques require to be widely studied to guarantee ECs elimination performances and reduce poisonous by-products [109] .

2) Chemical oxidation processes (like ozonation/H₂O₂, UV photolysis/H₂O₂, and photo-Fenton) have been observed to be the best techniques for reducing pesticides, beta-blockers, and pharmaceuticals. Ozonation and UV photocatalysis techniques are greatly efficacious in eliminating EDCs. The Fenton process has been illustrated to be the minimum efficient between all sorts of classical and AOPs treatment techniques. Reducing surfactants and PCPs via chemical techniques has not so far been well-tried [1].

3) Merged setups (like MBR pursued by RO, NF or UF) are better for eliminating EDCs and pharmaceuticals; however, they are less performant in reducing pesticides. Ozonation pursued by a biological activated carbon hybrid system has been found to be efficient in decreasing pesticides, beta-blockers, and pharmaceuticals. Ozonation pursued by ultrasound hybrid system may eliminate to 100% of some pharmaceuticals like salicylic acid, ibuprofen, naproxen, acetaminophen, cocaethylene, benzoylecgonine, enalapril, nor-benzoylecgonine, ketoprofen, atorvastatin, bezafibrate, clindamycin, sulfamethazine, and 4-aminoantipyrine. Additional hybrid systems founded on activated sludge pursued by UF or activated sludge pursued by gamma radiation are cost-effective for eliminating some EDCs, pesticides, and analgesic pharmaceuticals. Combined setups employing ultrafiltration, activated carbon pursued by the ultrasound process may be a better technology to deal with a large variety of ECs; however, they may not be cost-effective.

Conflicts of Interest

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

Abbreviations

AOPs Advanced oxidation processes

ECs Emerging contaminants

EDCs Endocrine disruption chemicals

MBR Membrane bioreactor

MF Microfiltration

NF Nanofiltration

PCPs Personal care products

RO Reverse osmosis

UF Ultrafiltration

WWTP Wastewater treatment plants

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40. 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

41. 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.

42. 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

43. Balc?o?lu, I.A. and ?tker, M. (2003) Treatment of Pharmaceutical Wastewater Containing Antibiotics by O3 and O3/H2O2 Processes. Chemosphere, 50, 85-95.https://doi.org/10.1016/S0045-6535(02)00534-9

44. Comninellis, C., Kapalka, A., Malato, S., Parsons, S.A., Poulios, I. and Mantzavinos, D. (2008) Advanced Oxidation Processes for Water Treatment: Advances and Trends for R & D. Journal of Chemical Technology & Biotechnology, 83, 769-776.https://doi.org/10.1002/jctb.1873

45. 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

46. 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

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

48. Zhou, J.L., Zhang, Z., Banks, E., Grover, D. and Jiang, J.Q. (2009) Pharmaceutical Residues in Wastewater Treatment Works Effluents and Their Impact on Receiving River Water. Journal of Hazardous Materials, 166, 655-661.https://doi.org/10.1016/j.jhazmat.2008.11.070

49. Barceló, D. and Petrovic, M. (2008) Conclusions and Future Research Needs. In: Emerging Contaminants from Industrial and Municipal Waste, Springer, New York, 265-274. https://doi.org/10.1007/978-3-540-79210-9_9

50. Ghernaout, D. (2017) Water Reuse (WR): The Ultimate and Vital Solution for Water Supply Issues. International Journal of Sustainable Development Research, 3, 36-46. https://doi.org/10.11648/j.ijsdr.20170304.12

51. Raj, D.S.S. and Anjaneyulu, Y. (2005) Evaluation of Biokinetic Parameters for Pharmaceutical Wastewaters Using Aerobic Oxidation Integrated with Chemical Treatment. Process Biochemistry, 40, 165-175. https://doi.org/10.1016/j.procbio.2003.11.056

52. Ghernaout, D., Elboughdiri, N. and Al Arni, S. (2019) Water Reuse (WR): Dares, Restrictions, and Trends. Applied Engineering, 3, 159-170.

53. Ghernaout, D., Elboughdiri, N. and Ghareba, S. (2019) Drinking Water Reuse: One-Step Closer to Overpassing the “Yuck Factor”. Open Access Library Journal, 6, e5895.

54. 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

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

56. Ghernaout, D., Alghamdi, A. and Ghernaout, B. (2019) Microorganisms’ Killing: Chemical Disinfection vs. Electrodisinfection. Applied Engineering, 3, 13-19.

57. 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.

58. 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

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

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

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

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

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

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

65. Westerhoff, P., Yoon, Y., Snyder, S. and Wert, E. (2005) Fate of Endocrine-Disruptor Pharmaceutical, and Personal Care Product Chemicals during Simulated Drinking Water Treatment Processes. Environmental Science & Technology, 39, 6649-6663. https://doi.org/10.1021/es0484799

66. Snyder, S., Lei, H., Wert, E., Westerhoff, P. and Yoon, Y. (2008) Removal of EDCs and Pharmaceuticals in Drinking Water. Water Environment Research Foundation.

67. Stackelberg, P.E., Gibs, J., Furlong, E.T., Meyer, M.T., Zaugg, S.D. and Lippincott, R.L. (2007) Efficiency of Conventional Drinking-Water-Treatment Processes in Removal of Pharmaceuticals and Other Organic Compounds. Science of The Total Environment, 377, 255-272. https://doi.org/10.1016/j.scitotenv.2007.01.095

68. 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

69. 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 Advanced and Applied Sciences, 5, 116-122.

70. 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.

71. 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

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

73. 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

74. 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

75. 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

76. 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

77. Ghernaout, D., Simoussa, A., Alghamdi, A., Ghernaout, B., El-boughdiri, 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 Advanced and Applied Sciences, 5, 61-70. https://doi.org/10.21833/ijaas.2018.05.008

78. 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

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

80. 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

81. 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

82. 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

83. 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.

84. 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.

85. 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

86. 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

87. 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

88. 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

89. 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 Advanced and Applied Sciences, 5, 60-64. ttps://doi.org/10.21833/ijaas.2018.02.010

90. 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

91. Ghernaout D. ,et al. (2019)Aeration Process for Removing Radon from Drinking Water—A Review Applied Engineering 3, 32-45.

92. Ghernaout, D. (2018) Magnetic Field Generation in the Water Treatment Perspectives: An Overview. International Journal of Advanced and Applied Sciences, 5, 193-203. https://doi.org/10.21833/ijaas.2018.01.025

93. 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

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

95. 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

96. 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

97. 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

98. 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

99. 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

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

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

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

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

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. 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

106. 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

107. 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

108. 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

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

110. 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