Landfill leachate remains one of the most defying liquid wastes and is formed by the degradation of solid wastes and the percolation of rainfall through landfill   . Leachate greatly changes in features and includes complicated constituents like organic amalgams, inorganic chemicals, heavy metals, and emerging contaminants, that way making a dangerous ecological effect and public health worry if it is not treated completely     . For dealing with leachate, largely examined techniques comprise biological treatment  -  , advanced oxidation    , membrane filtration  -  , physical separation (involving adsorption, coagulation and flotation), and electrochemical treatment     . More importantly, electrochemical techniques are of brilliant attention thanks to their inherent benefits of plain running, ecological affinity, and validity with regard to the variability of the quality and quantities of leachate      .
As one of the electrochemical techniques, electrocoagulation (EC)  has been tested for dealing with landfill leachate  . Through an EC method, a sacrificial anode generates metal ions in situ via electrolytic oxidation below an applied electrical potential. Such metal ions attach with water molecules to constitute hydrated metal ions, which may form polymeric hydroxides that act as the coagulants and neutralize the ionic species in leachate to generate flocs. The pathways of pollutant elimination implicate chemical reactions, absorption, precipitation, and flotation  . Since the EC technique produces the coagulants in situ, it does not need an external introduction of chemicals  . Further, it is more efficient in separating suspended solids and organic matters than traditional coagulation  -  . With a large success, the EC technology has been implemented to remedying leachate thanks to its capacity of eliminating both color  , turbidity  , and a set of pollutants in the complicate leachate     . For instance, it was noted that the EC technique could attain almost 70% of the decolorization in landfill leachate employing stainless steel as the electrodes below the situation of 10 V and 120-min reaction time  . Eliminating performance of chemical oxygen demand (COD) and ammonia is hugely changing, for example among 17% and 70% (COD reduction) and 0% - 16% (ammonia reduction), as it is touched via the parameters like electrode materials, residence period, and current density  .
Since landfill leachate frequently includes an elevated level of chloride ions, the response of chloride oxidation to chlorine gas would take place as a secondary influence at the anode of EC. This reaction is accompanied by additional production of active chlorine species like free chlorine and integrated chlorine  . The co-presence of such active chlorine species and organic matters may conduct to the generation of greatly carcinogenic disinfection by-products (DBPs)  -  . Numerous investigations have mentioned the formation of active chlorine     in the electrochemical devices like electroflotation   , electrochlorination, and electrodisinfection     . For instance, chloroform, dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were found in the water samples treated by the merged EC and electrooxidation device ; however, it was possible that most DBP generation was provoked via electrooxidation    . Until now, scarce researches have frankly followed the generation of DBPs through the EC remediation of landfill leachate. Moreover, the importance of the discrete DBP category towards their poisoning contribution has not been shown until now. Consequently, there is a requirement for these studies  .
This work presents a brief view on the DBBs generation throughout EC of landfill leachate, dye and humic acid.
2. DBBs Generation throughout EC of Landfill Leachate
As discussed above, in the course of the EC handling of landfill leachate, the generation of chlorine species may conduct to the production of poisonous DBPs. This production was followed by Xu et al.  via observation of five classes of DBPs (haloacetic acids-HAA, trihalomethanes-THM, haloacetonitriles-HAN, haloketones-HK, and halonitromethanes-HNM) in two leachate samples remedied by EC (Figure 1). They proved that the applied current has catalyzed the production of DBPs, which were prevailed by unregulated DBPs. Applying a current density of 100 mA/cm2, the unregulated HK prevailed the weight-based DBP concentration (96% in Leachate A and 44.3% in Leachate B), while the unregulated HAN contributed to >80% of the DBP additive toxicity in both leachates. The in situ formation of active chlorine has conducted to the DBP production, as proved in the scavenging test. Employing granular activated carbon as a post-treatment stage could efficiently minimize the total DBP concentration from 295.33 to 82.04 μg/L in Leachate A, conducting to a total DBP abstraction of 72.2% and a toxicity elimination of 50% (Figure 2). Considering the prevailing concentration and shortage of toxicity data, the unregulated DBPs should attract more focus  .
3. DBBs Generation throughout EC of Dye and Humic Acid
Keyikoglu et al.  compared the effects of different supporting electrolytes on the treatment of a dye solution by EC technology    . They mentioned the likely hazard of the formation of DBPs which must be considered.
There is no doubt that the chloride (Cl−) ions in water containing humic acid may induce formation of carcinogenic chemicals (DBPs)  . For this reason, the favorable supporting electrolyte type would be sodium sulfate   .
Figure 1. The schematic of an EC cell with DBP formation  .
Figure 2. Leachate treatment by EC: (a) the change of color in Leachate A with different current densities applied after 60-min EC treatment (a: raw leachate, b: 5 mA/cm2, c: 10 Ma/cm2, d: 50 mA/cm2, e: 100 mA/cm2); (b) the change of color in Leachate A with different reaction times under the current density of 100 mA/cm2 (f: 15 min, g: 30 min, h: 60 min); (c) pH and conductivity changes in Leachate A with different current densities applied after the 60-min EC treatment; and (d) chemical oxygen demand (COD) and ammonium removal efficiency in two leachates when current density was 100 mA/cm2and reaction time was 60 min  .
From this work, the following conclusions can be drawn:
1) During the last three decades, the EC process has known an exemplary renaissance in the field of water and wastewater treatment. Several researchers focused on applying this electrochemical technology in removing diverse pollutants such as organic matters. During EC application, the hazards of formation of highly toxic DBPs are more and more proved especially in water containing organic matter and halogens especially chloride.
2) An investigation has uncovered the possibility of DBP production in the EC handled leachates, where unregulated DBPs prevailed both concentrations and toxicity  . Higher current densities encouraged the generation of unregulated DBPs. HKs prevailed the weight based DBP concentration while HANs prevailed the DBP additive toxicity in most of the situations. Scavenging trials proved that free chlorine possessed a fundamental contribution in producing DBPs. Using granular activated carbon post-treatment could hugely diminish the levels and toxicity of both regulated and unregulated DBPs.
3) The EC method fully eliminated the largest molecular size part of humic acid; nevertheless, the lowest molecular size portions of humic acid were a little diminished at tried pHs levels  . As a result, the EC reactor was performed in eliminating humic acid     .
4) Great efforts remain to be accomplished towards the comprehension of the inherent phenomena related to removing both microorganisms and organic matters in the EC method. Further, safe multi-barrier methods, such as distillation and membrane processes, have to be adopted.
 Xu, B., Iskander, S.M. and He, Z. (2020) Dominant Formation of Unregulated Disinfection by-Products during Electrocoagulation Treatment of Landfill Leachate. Environmental Research, 182, Article ID: 109006.
 Tsai, C.T., Lin, S.T., Shue, Y.C. and Su, P.L. (1997) Electrolysis of Soluble Organic Matter in Leachate from Landfills. Water Research, 31, 3073-3081.
 Ghernaout, D. (2017) Environmental Principles in the Holy Koran and the Sayings of the Prophet Muhammad. American Journal of Environmental Protection, 6, 75-79. https://doi.org/10.11648/j.ajep.20170603.13
 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.
 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
 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
 Ghernaout, D. and El-Wakil, A. (2017) Requiring Reverse Osmosis Membranes Modifications—An Overview. American Journal of Chemical Engineering, 5, 81-88.
 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.
 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.
 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.
 Fernandes, A., Pacheco, M.J., Ciríaco, L. and Lopes, A. (2015) Review on the Electrochemical Processes for the Treatment of Sanitary Landfill Leachates: Present and Future. Applied Catalysis B: Environmental, 176-177, 183-200.
 Foo, K.Y. and Hameed, B.H. (2009) An Overview of Landfill Lea-chate Treatment via Activated Carbon Adsorption Process. Journal of Hazardous Materials, 171, 54-60. https://doi.org/10.1016/j.jhazmat.2009.06.038
 Miao, L., Yang, G., Tao, T. and Peng, Y. (2019) Recent Advances in Nitrogen Removal from Landfill Leachate Using Biological Treatments—A Review. Journal of Environmental Management, 235, 178-185.
 Ghernaout, D. (2013) The Best Available Tech-nology of Water/Wastewater Treatment and Seawater Desalination: Simulation of the Open Sky Seawater Distillation. Green and Sus-tainable Chemistry, 3, 68-88. https://doi.org/10.4236/gsc.2013.32012
 Ghernaout, D., Badis, A., Ghernaout, B. and Kellil, A. (2008) Ap-plication of Electrocoagulation in Escherichia coli Culture and Two Surface Waters. Desalination, 219, 118-125. https://doi.org/10.1016/j.desal.2007.05.010
 Ding, J., Wei, L., Huang, H., Zhao, Q., Hou, W., Kabutey, F.T., Yuan, Y. and Dio-nysiou, D.D. (2018) Tertiary Treatment of Landfill Leachate by an Integrated Electro-Oxidation/Electro-Coagulation/Electro-Reduction Process: Performance and Mechanism. Journal of Hazardous Materials, 351, 90-97.
 Mollah, M.Y.A., Morkovsky, P., Gomes, J.A.G., Kesmez, M., Parga, J. and Cocke, D.L. (2004) Fundamentals, Present and Future Perspectives of Electrocoagulation. Journal of Hazardous Materials, 114, 199-210.
 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 Elec-trochemical Water Treatment. Desalination, 270, 9-22.
 Ghernaout, D., Gher-naout, 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.
 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.
 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
 Ghernaout, D., Al-Ghonamy, A.I., Naceur, M.W., Ait Messaoudene, N. and Ai-chouni, M. (2014) Influence of Operating Parameters on Electrocoagulation of C.I. Disperse Yellow 3. Journal of Electrochemical Science and Engineering, 4, 271-283.
 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.
 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.
 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.
 Emamjomeh, M.M. and Sivakumar, M. (2009) Review of Pol-lutants Removed by Electrocoagulation and Electrocoagulation/Flotation Processes. Journal of Environmental Management, 90, 1663-1679.
 Ilhan, F., Kurt, U., Apaydin, O. and Gonullu, M.T. (2008) Treatment of Leachate by Electrocoagulation Using Aluminum and Iron Electrodes. Journal of Hazardous Materials, 154, 381-389. https://doi.org/10.1016/j.jhazmat.2007.10.035
 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.
 Grellier, J., Rushton, L., Briggs, D.J. and Nieuwenhuijsen, M.J. (2015) Assessing the Human Health Impacts of Exposure to Disinfection by-Products—A Critical Review of Concepts and Methods. Environment International, 78, 61-81.
 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
 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 & Development in Chemistry, 1-27.
 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
 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
 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
 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
 Ghernaout, D., Naceur, M.W. and Ghernaout, B. (2011) A Review of Electroco-agulation as a Promising Coagulation Process for Improved Organic and Inorganic Matters Removal by Electrophoresis and Electro-flotation. Desalination and Water Treatment, 28, 287-320. https://doi.org/10.5004/dwt.2011.1493
 Ghernaout, D., Benblidia, C. and Khemici, F. (2015) Microalgae Removal from Ghrib Dam (AinDefla, Algeria) Water by Electroflotation Using Stainless Steel Electrodes. Desalination and Water Treatment, 54, 3328-3337.
 Huang, X., Qu, Y., Cid, C.A., Finke, C., Hoffmann, M.R., Lim, K. and Jiang, S.C. (2016) Electrochemical Disinfection of Toilet Wastewater Using Wastewater Electrolysis Cell. Water Research, 92, 164-172.
 Sun, J., Hu, C., Zhao, K., Li, M., Qu, J. and Liu, H. (2018) Enhanced Membrane Fouling Mitigation by Modulating Cake Layer Porosity and Hydrophilicity in an Elec-tro-Coagulation/Oxidation Membrane Reactor (ECOMR). Journal of Membrane Science, 550, 72-79. https://doi.org/10.1016/j.memsci.2017.12.073
 Keyikoglu, R., Can, O.T., Aygun, A. and Tek, A. (2019) Comparison of the Effects of Various Supporting Electrolytes on the Treatment of a Dye Solution by Electrocoagulation Process. Colloid and Interface Science Communications, 33, Article ID: 100210. https://doi.org/10.1016/j.colcom.2019.100210
 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
 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.
 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.
 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
 Barhoumi, A., Ncib, S., Chibani, A., Brahmi, K., Bouguerra, W. and Elaloui, E. (2019) High-Rate Humic Acid Removal from Cellulose and Paper Industry Wastewater by Combining Electrocoagulation Process with Adsorption onto Granular Activated Carbon. Industrial Crops and Products, 140, Article ID: 111715.
 Kac, F.U., Kobya, M. and Gengec, E. (2017) Removal of Humic Acid by Fixed-Bed Electrocoagulation Reactor: Studies on Modelling, Adsorption Kinetics and HPSEC Analyses. Journal of Elec-troanalytical Chemistry, 804, 199-211.
 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.
 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.
 Ghernaout, D., Mariche, A., Ghernaout, B. and Kellil, A. (2010) Electro-magnetic 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.
 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.