Impact of ozone pre-treatment on the performance of upflow anaerobic sludge blanket treating pre-treated grain distillery wastewater

Two 2 L laboratory-scale upflow anaerobic sludge blanket (UASB) reactors were operated for 277 days. The substrate of the control reactor (R_c) contained grain distillery wastewater (GDWW) that had undergone coagulant pre-treatment, and the substrate of the second UASB reactor consisted of GDWW that had undergone coagulant pre-treatment and ozone pre-treatment (R_o). Both reactors treated pre-treated GDWW successfully at ca. 9 kgCOD m⁻³ d⁻¹. Chemical oxygen demand (COD) reductions of ca. 96% for R_c and 93% for R_o were achieved. Fats, oils and grease (FOG) reductions (%) showed variations throughout the study, and reductions of ca. 88 and 92% were achieved for R_c and R_o, respectively. R_c produced more biogas, and the methane percentage was similar in both reactors. UASB granule washout in R_c suggested possible toxicity of unsaturated fatty acids present in non-ozonated substrate. The feasibility of FOG removal was demonstrated as both reactors successfully treated pre-treated GDWW. Better results were obtained for R_o effluent during post-ozonation. The ozone pre-treatment possibly led to easier degradable wastewater, and better results could potentially be obtained when other post-treatment steps are applied. Ozone pre-treatment did not, however, show an added benefit in the reactor performance results.