Optimisation of electrocoagulation process in the treatment of poultry slaughterhouse wastewater

Abstract

Due to rapid urbanisation and industrial growth, the production and discharge of raw and poorly treated poultry slaughterhouse wastewater increase yearly. This has serious environmental and health consequences because it disrupts ecosystems' normal operations. As a result, the development of efficient and long-lasting wastewater treatment methods is becoming increasingly important. When compared to traditional processes, electrocoagulation is one of the more promising approaches because it is efficient and simple, has short treatment times, and produces little sludge. The biological approach employs the synergistic application of biological pre-treatment using low-cost hydrolytic enzymes, is an efficient, cost-effective, sustainable, and environmentally friendly technology for treating high strength lipid-rich wastewater. The primary goal of this research was to look into the feasibility of biological pre-treatment using hydrolytic enzymes in combination with the electrocoagulation technique to reduce pollutants in poultry slaughterhouse wastewater. The feasibility of the electrocoagulation technique in removing chemical oxygen demand (COD) and fats, oils and grease (FOG) was studied using iron electrodes. A screening design of the experiment (DoE) was used to identify the most important factors influencing the electrocoagulation removal process. These variables were identified as current density, pH, reaction time, and Ecoflush™ (with or without). The central composite design (CCD) with forty runs was used in the present study. The biological treatment resulted in 85-99% FOG reduction and 20-50% COD reduction, odourless effluent, indicating that PSW was biodegradable. The EC process produced a high-quality clarified effluent without solids in suspension with 92.4% COD reduction and 99% FOG reduction after 60 minutes of reaction. The best conditions were obtained by using a pH of 3.05, a current density of 66.9 A/m2, 74-minutes of treatment time and without Ecoflush™. The combination of both processes did not perform as expected when compared to the separate processes. Despite the low removal percentages of some pollutants, the present study proved the ability of the biological treatment with novel Ecoflush™ for treating lipid-rich wastewater such as PSW largely for the removal of FOG. This proves the capability of its use as a pre-treatment for other conventional methods such as anaerobic digestion. This study also showed that EC is a promising treatment method for PSW effluent. Even though the nitrogen removal was insufficient compared to conventional wastewater treatment technologies, there are several benefits of EC treatment, including short retention time, small footprint, no mixing, and elimination of coagulants addition. These characteristics enable EC technology to be used alone or in conjunction with other technologies for a wide variety of wastewater treatment applications. The treatment cost was also viable.