Treatment of Concentrated Black-water and Kitchen Organic-wastes in Accumulation Systems

The feasibility of two accumulation-systems (AC) for anaerobic digestion and storage of concentrated black-water with (AC1) or without (AC2) urine + kitchen organicwastes were investigated. The wastewater was collected by two vacuum toilet/transport systems. The influent-total chemical oxygen demand (COD) of the AC2 (53000 mg/L) was more concentrated by 4 times than that of the AC1. The AC systems demonstrated stable performance. There was no inhibition effect of ammonia (NH4) and volatile fatty acids (VFA) concentration decreased in time. Total-COD removal of 58 % was achieved in both systems, after 105 days at 20C. Moreover, if the supernatant in the AC1 is only withdrawn and the settled sludge stays for the next runs, only 20% of the influent total-COD will be in the supernatant. In the AC2, 74 % of influent orthophosphate was removed by precipitation. A mathematical model based on anaerobic digestion model no. 1 showed that the design filling-period for both AC systems should be higher than 100 days at 20C for obtaining >50% conversion of the wastewater to methane.