Assessment of a biological nutrient removal process for the remediation of edible oil effluent

Abstract

Eutrophication is a natural process that is greatly aggravated by the action of man in the natural environment. Deterioration of South Africa's natural water resources results directly or indirectly from the discharge of industrial effluent rich in nutrient nitrogen and phosphorus. The South African edible oil refmeries generally discharge poor quality effluent which impacts negatively on the water resources and wastewater treatment installations. The main aim of this study was to assess the capacity of a laboratory scale effluent treatment process that will produce final effluent of acceptable quality with regards to organic load and phosphate concentration prior to its discharge into the municipal sewerage system. The study was conducted in three stages: wastewater characterization, treatability studies, and laboratory scale treatment investigations. After analysing various effluent parameters, treatability studies were conducted using an aerobic-anaerobic sequencing batch reactor with a total hydraulic retention time of 24 hours. The results showed an average of 75 % reduction of COD and more than 90 % removal of fats, oils and grease (FOG). Based on the results of effluent characterisation and treatability studies, a laboratory scale activated sludge effluent treatment process was designed and operated with two bioreactors (aerobic and anaerobic) in series. The system was operated for a period of one-month resulting in 70 % removal of COD and 4% reduction in phosphate (P04-P). After some structural and operational changes from the original design configuration, the system was the operated continuously for the duration of the study period. An optimum COD removal of 75 % and 107 mgll P04-P reduction was achieved during the last operational phase of the system. More than 95 % reduction in fats, oils and grease (FOG) had been achieved in both semi-continuously and continuously operated systems.b.7