Treatment of Wastewater from Slaughterhouses by Electrocoagulation: Case Study of Gachororo Slaughterhouse, Kiambu County, Kenya

Abstract

Wastewater from slaughterhouses is highly contaminated with high concentrations of organic materials, colloids such as proteins, cellulose, and fats, as well as suspended solids. Discharge of this water before treatment into the rivers affects the water quality and the fauna as well as microflora present in it, increases long term biological oxygen demand (BOD) and creates water treatment problems. The conventional methods including the aerobic and anaerobic biological treatment processes used to treat this water are characterized by many disadvantages including; production of high levels of sludge, high energy consumption required for aeration, sensitivity to high organic loading rates and long hydraulic retention times. It is therefore necessary to explore other alternative treatment methods such as electro-coagulation. This study therefore sought to explore slaughterhouse wastewater treatment using electro-coagulation method. The set-up included elctrocoagulation reactors using iron and aluminium electrodes of different surface areas under varying electrical voltages. pH, Electrical Conductivity, alkalinity, Chemical Oxygen Demand, Turbidity, Total Suspended Solids, and BOD of raw and treated wastewater were determined using standard methods. The results revealed that electro-coagulation method is able to reduce all these parameters in wastewater to levels that are acceptable by the Government of Kenya Standards for treated wastewater and effluent discharge into the environment. The highest removal efficiencies of 98.4% (BOD), 98.9% (COD), 53% (Total Alkalinity), 83% (conductivity), 99.9% (turbidity), and 99.4% (TSS) were obtained at voltage of 25V and surface area of 40 cm2 with aluminum electrodes and 90 cm2 with iron electrodes. ANOVA analyses demonstrated that electrocoagulation is very effective in treating slaughterhouse wastewaters at optimum voltage and surface area of electrode and that aluminium is the better option for electrode material. The study concludes that electrocoagulation is a very effective method for treating slaughterhouse wastewaters and that aluminium is the better electrode material. The treated water can be recovered and be re-used for activities such as cleaning and farming but requires further treatment for it to be used for drinking. From the findings, the study recommends further inquiry into the process through which electro-coagulation reduces total alkalinity of wastewater. It also recommends further studies to investigate other metals or materials that may be more effective and environmentally friendly as electrodes, and on use of solar or wind as sources of energy in the electrocoagulation process.