HIGH-RATE ANAEROBIC TREATMENT OF MALTING WASTE-WATER IN A PILOT-SCALEEGSB SYSTEM UNDER PSYCHROPHILIC CONDITIONS

The feasibility of the expanded granular sludge bed (EGSB) system for the treatment of malting waste water under psychrophilic conditions wa s investigated by operating a pilot-scale 225.5 dm(3) EGSB-reactor sys tem in the temperature range from 13 to 20 degrees C. The concentratio n of chemical oxygen demand (GOD) in the malting waste water was betwe en 282 and 1436 mg dm(-3). The anaerobically biodegradable COD of the waste water was about 73%, as determined in the batch bioassays. Durin g reactor operation at 16 degrees C, the COD removal efficiencies aver aged about 56%, at organic loading rates (OLR) ranging between 4.4 and 8.8 kg COD m(-3) day(-1) and a hydraulic retention time (HRT) of appr oximately 2.4 h. At 20 degrees C, removal efficiencies were approximat ely 66% and 72%, respectively, at OLRs of 8.8 and 14.6 kg COD m(-3) da y(-1), corresponding to HRTs of 2.4 and 1.5 h. The specific methanogen ic activity with the sludge from the reactor, assessed on acetate and volatile fatty acids mixture as substrates, significantly increased (8 0%) in time, indicating an enrichment of methanogens and acetogens eve n at the low temperatures applied. These findings are of considerable practical importance because they indicate that anaerobic treatment of low strength waste waters at low temperature might become a feasible option.