Evaluation of a laboratory-scale biological process for the treatment of edible oil effluent

The discharge of poor quality effluents by the edible oil refining industry in South Africa is posing a serious threat to water sources and wastewater treatment installations alike. The main objective of this study was to ass ess the efficiency of a laboratory scale activated sludge treatment process in producing a final effluent conforming to regulatory standards with rega rds COD and phosphate loads. The study was conducted in three principal sta ges: waste characterisation; treatability studies and laboratory-Scale inve stigations. After analysing various raw effluent parameters, treatability s tudios were conducted using an aerobic/aerobic sequencing batch reactor (SB R). The results showed 75% influent COD (S-ti) reduction and more than 90% removal of oils and suspended solids. Based on the results from waste chara cterisation and treatability studies, a continuous laboratory-scale nutrien t removal system was designed. The reactor was operated on a fed-batch basi s-for 15 d resulting in 70% S-ti and 4% phosphate reduction. Poor phosphoru s (P) removal was attributed to a small anaerobic sludge mass fraction. The system was then operated continuously with structural changes to the react or. A COD and phosphate reduction of 44% and a 36% respectively, was achiev ed at an organic loading rate of 0.5 kgCOD/kgMLSS.d(-1).