Treatability and kinetic analysis of anaerobic moving bed biofilm reactor treating high strength milk permeate

Abstract

High strength milk permeate wastewater with chemical oxygen demand (COD) of 50–77 g·l–1 from cheese making process was treated respectively under sub-mesophilic (20–25°C) and mesophilic (35–40°C) conditions using bench-scale anaerobic moving bed biofilm reactors (AMBBR). Organic loading rates (OLR) were gradually increased from 0.5 to 6.2 g total COD (TCOD)·l–1·d–1 and from 1.5 to 11 g TCOD·l–1·d–1, achieving maximum stable OLRs at 5.5 and 9.5 g TCOD·l–1·d–1 with corresponding hydraulic retention times (HRT) as 14 and 6.8 days, respectively, under sub-mesophilic and mesophilic condition. Within the maximum stable OLR levels, ratios of VFA (volatile fatty acids)/TA (total alkalinity) were well maintained under suggested limit of digester failure in most cases. Therefore, TCOD and soluble COD (SCOD) removal efficiencies were found to be 82% and 92% in sub-mesophilic treatment and 84% and 96% in mesophilic one. Kinetic analysis found the maximum substrate utilization rates (µmax) were 46.1 and 95.2 g SCOD·l–1·d–1 along with maximum specific methane yield (Ymax) values being 0.301 and 0.313 l CH4·g–1 SCOD removed, respectively, in sub-mesophilic and mesophilic treatments.