High Rate Anaerobic Digestion of Wool Scouring Wastewater in a Digester Combined with Membrane Filter

Abstract

The performance and sludge diminution property in wool scouring wastewater treatment of an anaerobic process in combination with an ultrafiltration membrane (UFM) was evaluated. With regard to TOD removal, both mesophilic (37°C) and thermophilic (53°C) digestion, without UFM, showed the same trend of decreasing sharply from about 90 % to 30 % in proportion to the increasing TOD loading rate from 3 to 45 kg/m3· d. When a digester was provided at the effluent line of a reactor with UFM separator, about two times higher concentration of biomass was retained and the quality of the effluent improved remarkably due to better filtration. TOD and grease removal improved remarkably from 45 to 90 % and 37 to 99 % respectively, at a TOD loading rate of 15 kg/m3 · d in both fermentative temperatures. Further, the effective recirculation system of rejected liquid from UFM was studied to diminish the quantity of sludge generated. The study revealed that 33 % of the incoming SS was biodegraded under the recirculation system for rejected liquid from UFM to reactor, while 17 % was achieved in one pass through the system at the same TOD loading rate. Deterioration in the flux rate of UFM was observed for the first 40 days of operation from 37 to 23 l/m2 · h which then gradually decreased to 17 l/m2 · h after 210 days of service.