Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 2

treatment undergoes a two-stage procedure with integrated anaerobic digestion and electrocoagulation to determine its efficiency (231). Both anaerobic digester and electrocoagulation serve as primary and secondary treatments, respectively. The result of the study showed that the integration of anaerobic digestion and electrocoagulation simultaneously enhances untreated slaughterhouse wastewater treatment. This indicated that the combined process exhibited removal efficiencies greater than 79% for COD, 95% for nitrate, and 90% for turbidity, respectively. A similar study is carried out by (232) but this time, an anaerobic filter and constructed wetland is used for the same poultry slaughterhouse effluent. The result showed that this system has efficient removal of organic matter of BOD 5 at 88.9%, COD at 92.9%, TSS at 93.4%, and FOG at 87.3%, respectively. o) Microbial Electrolysis Cells Treatment of Food Processing Effluents Microbial electrolysis cells(MECs) are one of the most favorable contraptions amid bio-electrochemical systems for the production of biohydrogen. A large collection of wastewater and organic wastes can be used as substrates in microbial electrolysis cells as they allow for the production of valuable chemicals like hydrogen gas. MECs can obtain clean and viable hydrogen production from a large collection of renewable biomass to displace fossil fuel (233). Cross- feeding is a possible design for treating industrial food processing wastewater samples (234). The study shows that reactor inoculated with domestic wastewater attained identical removal at a remarkably lesser time than MECs which is accustomed only to industrial wastewater, then possessing a lower wastewater treatment. Microbial electrolysis cell is used for the treatment of methanol-rich and food-processing industrial wastewaters under inexpensive cathode catalysts (235). The outcome indicated that molybdenum disulfide catalyst exhibited a better result than stainless cathode for the dual wastewater, while platinum catalyst usage displayed the best result during biogas production. This shows that molybdenum disulfide is in the best position to undergo cathode catalyst in MECs utilized for effluent treatment. Similar research showed that nickel-foam exhibited the best result (Table 5) for inexpensive electrodes during hydrogen production in the MEC system together with the treatment of food processing industrial effluents (236). Microbial electrolysis cell is simultaneously used to treat sugar factory wastewater and produce bio- hydrogen with electrodeposited cathodes (40). The result indicated that constructed cathodes exhibited better efficiency and Ni-co-p co-deposit displays the best cathode in both situations. This method generallytransforms organic waste into hydrogen gas and further degrades microorganisms(237-233). Table 5: Rundown of Results from Mecs at the Applied Voltage 1.0 V for the 3 Cathodes in the 2 Sugar Industrial Effluents [236] Substrate Cathode COD removal (%) CE (%) CHR (%) OHR (%) HPR (%) Ƞ ɛ (%) CSW SS mesh 40.59 45.11 13. 86 6.25 0.817 121.26 Ni plate 48.11 54.52 15.73 8.57 1.329 124.49 Ni foam 49.56 59.18 16.88 9.99 1.594 126.76 RSW SS mesh 30.43 44.09 8.95 3.95 0.613 113.54 Ni plate 38.99 54.67 9.39 5.13 1.022 114.54 Ni foam 40.06 56.64 12.35 6.99 1.431 119.20 Note: COD=chemical oxygen demand, CE=coulombic efficiency, CHR=cathode hydrogen recovery, OHR=overall hydrogen recovery, HPR=hydrogen production rate, and Ƞ ɛ = energy recovery As part of this study to contribute to the 2030 United Nations sustainable development goals (SDGs), primarily to SDG 6 (ensure availability and sustainable management of water and sanitation for all) and SDG 7 (ensure access to affordable, reliable, sustainable and modern energy for all), efficient management of wastewater and generation of green energy from this effluent can ensure the target of these two goals. Utilizing untreated wastewater to irrigate farms with edible crops constitutes a risk to the agricultural production system and humans. By so doing, SDG 2 (end hunger, achieve food security, improve nutrition and promote sustainable agriculture) is under threat. Also, generating wealth (value-added byproducts) from the waste dump contributes immensely to SDG 2. In Nigeria, most of these SDGs are hard to achieve due to the government's attitude towards ameliorating the poverty level of its citizens. For instance, the government has not adopted any known engineering bio-treatment technologies to solve the problem of effluent disposal treatment from food processing industries. All effluents from food processing industries are channelled into fresh waters and sometimes into dumpsites, and the destruction is unprecedented in both environmental and groundwater pollution (SDG 7 not achievable in the near future). Utilizing untreated wastewater to irrigate farms with edible crops constitutes a risk to the agricultural production system and humans. By so doing, SDG 2 (end hunger, achieve food security, improve nutrition and promote sustainable agriculture) is under threat. © 2023 Global Journals 1 Year 2023 42 Global Journal of Science Frontier Research Volume XXIII Issue ersion I VII ( H ) An Overview on Engineering Bio-Treatment Methods for Effluent in Food Processing Industries