Treatment of high-fat-containing dairy wastewater in a sequential UASBR system: influence of recycle

BACKGROUND: Raw cheese whey originating from white cheese production results in a strong and complex wastewater excessively rich in organic matter (chemical oxygen demand, COD=28-65 g L(-1)), fatty matter (14-24.5 g L(-1)) and acidity (3.9-6.1 g L(-1)). It was treated in a three-stage configuration consisting of a pre-acidification (PA) tank and sequential upflow anaerobic sludge bed reactors (UASBRs) at 2.8-7 g COD L(-1) day(-1) organic loading rates, during which the effects of effluent recycling at low rates and promoted SRB activity were investigated. Acidification, volatile fatty acids (VFA), COD and fatty matter removal and volatile solids were monitored throughout the system during the study.