Organic Compounds and Phosphorus Removal from Dairy Wastewater by Biofilm on Iron-Containing Supports

Abstract

This study investigated treatment of dairy wastewater in one-stage anaerobic moving biofilm reactors (AMBRs) at ambient temperature. To support biological treatment with abiotic processes (iron corrosion), metallic iron was included in the porous structure of supports. The AMBRs were operated at a hydraulic retention time of 5.5 days and organic loading rate (OLR) of 3.9 and 7.5 kgCOD (chemical oxygen demand)/(m3×day). At OLR 3.9 kgCOD/(m3×day), COD removal was significantly higher with 2% iron in the support structure than without iron (86.6±7.8% versus 81.3±9.0%). Adding Fe to the supports did not influence biogas productivity or the biogas production rate. Fe addition significantly increased phosphorus removal from about 50% in AMBRs without added Fe to 72.1±8.4% with 2% iron. Further increasing Fe content to 3% did not increase COD or P removal. In all reactors, acetoclastic methanogens predominated over hydrogenotrophic methanogens; however, Fe promoted growth of Methanobacteriaceae.