Effect of pH on Acidification of Whey, Yeast and Yolk Wastewaters

Abstract

The acidification of protein wastewaters was investigated under different operational pH values (4.14 - 7.09) at ambient temperature. Synthetic whey, yeast and yolk wastewaters were used as the substrates. Three lab-scale continuously stirred tank reactors (CSTRS), each with a working volume of 2 L, were employed as acidogenic reactors. They were operated at a hydraulic retention time (HRT) of 4 h with a substrate concentration around 2 gCOD/L, corresponding to organic loading rates (OLRs) of 12.9 - 14.7 gCOD/Lㆍ d. Whey wastewater was the most sensitive to pH with the maximum acidification efficiency of 30.9% and acidification rate of 3.88 gCOD/Lㆍ d at pH 4.14. The highest acidification etficiency and acidification rate of yeast wastewater were found in neutral pll range (7.09) at 4.6% and 0.52 gCOD/L d, respectively. Yolk wastewater was better acidified in slightly acidic condition (pH 5.52 with the maximum eficiency and rate at 4.6% and 038 gCODL d,respectively. When comparing the system performance with no pH control condition of each wastewater, pH adjustment is not necessary. The results of this study confirmed that pH adjustment cost could be saved in the acidogenic CSTR of the two-phase anaerobic treatment of the protein wastewaters.