Acidogenesis in two-phase anaerobic treatment of dairy wastewater

This study investigated the effects of variations in hydraulic retention time (HRT) on volatile fatty acid (VFA) production and on the behavior of the microbial ecology in the anaerobic reactor during acido-genesis of a dairy wastewater. A laboratory-scale, continuous flow-completely mixed anaerobic reactor, coupled with a conventional gravity settling tank, was operated at a HRT range between 24 and 12 hours. The degree of acidification and the rate of acid production gradually increased, proportionally to the organic loading rate, with respect to decreases in HRT. The highest degree of acidification and the rate of acid production were achieved at 12 hours. The numbers of total bacterial community and autofluorescent methanogens decreased significantly, as HRT was decreased. Due to continuous recycling and no pH control, the methanogens were not completely washed out from the reactor, however, their activity was suppressed by monitoring of HRT.