Optimization of Oxidation Pond Efficiency in Animal Farm Wastewater Treatment

Animal farm wastewater is known to contain high concentrations of solids, organic matter and nutrients. Thus, operators are required to build oxidation ponds for the treatment of wastewater. However, knowledge on the performance of the different systems of ponds being installed is lacking. Therefore, in this study, wastewater quality from pond inflow and outflow of farms with two ponds (2-pond) and two ponds with separator (2-pond-sep), and three ponds (3-pond) in series was investigated. Comparing inflow and outflow concentrations, all the systems resulted in significant reduction of the parameters studied. All the systems performed better in solids and organic matter removal than nutrients. Most of the reduction of total suspended solids (TSS), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) occurred in the first two ponds. The presence of the third pond resulted in a large improvement in dissolved oxygen (DO), ammonia nitrogen (AN), total nitrogen (TN) and total phosphorus (TP). For the 3-pond system, removal of TSS, BOD5 and COD exceeded 90% but for 2-pond, 77%-83% and for 2-pond-sep, only 33%-44%. For nutrients removal, the 3-pond system achieved 85%-96% whereas 2-pond system, 8%-38%, and 2-pond-sep system, 14%-15%. The use of solid-liquid separator contributed to lowering solids, organic matter and nutrients at the inflow. Overall, the order in increasing efficiency was: 2-pond-sep 2-pond 3-pond. Effluent TSS, BOD5 and COD of the 3-pond system complied with Standard A and effluent TSS and BOD5 of the 2-pond system complied with Standard B of the Environmental Quality (Sewage and Industrial Effluents) Regulations, 1979. This indicates that even with solid-liquid separator, the sizing, number and maintenance of the ponds are still essential to ensure quality effluent and compliance to the proposed water quality standards.