Effects of total dissolved solids and organic loadings on the chemical oxygen demand removal by yeast-activated sludge system.

Abstract

Typically, the soybean oil processing industry generates complex wastewater containing high total dissolved solids (TDS), chemical oxygen demand (COD), and fat oil and grease (FOG) contents with low pH. Therefore, treating this industrial wastewater with the conventional activated sludge (AS) wastewater treatment system is challenging. Yeast can be co-cultured with the activated sludge (AS) called yeast-activated sludge (YAS) to degrade high COD and salinity in the wastewater. However, little is known about the effects of TDS and organic loading (OLRs) on the performance of YAS system with the presence of both Rhodotorula mucilaginosa and Candida xylanilytica. In this study, we evaluated the effects of TDS and organic loading rates (OLRs) on the performances of the YAS system for soybean oil wastewater treatment. Four sequencing batch reactors (SBRs) were operated under aerobic conditions at different TDS concentrations 25%, 50%, 75%, and 100% increasing rate. The results indicated that the TDS at the loading rate of 50% resulted in maximum biomass production. The overloading of the clarifier was observed and possibly caused by the accumulation of solids contained in the influent wastewater. At the OLR of 0.67 kg BOD5/m3-day and the TDS loading rate of 15.5 kg TDS/m3-day, the YAS system achieved the average COD removal efficiencies of 71±1%