Treatment of urban wastewater with pure moving bed membrane bioreactor technology at different filling ratios, hydraulic retention times and temperatures

Abstract

Studies investigating the functioning and possible utility of new wastewater treatment technologies are urgently needed if the requirements of European Directive 91/271/EEC are to be met. Here, moving bed biofilm reactor-membrane bioreactor (MBBR-MBR) technology was studied in a pilot plant of 445 L volume with ultrafiltration membrane (ZW-10) under 10 h and 24 h of hydraulic retention time (HRT) and three filling ratios (20 %, 35 % and 50 %) at temperatures between 2.5 °C and 17.3 °C. Biofilm density ranged between 1510 ± 127 and 3775 ± 247 mg/L carrier. Temperature was the operative variable with most influence in the behaviour of biomass and in organic matter and nitrogen oxidation whereas the filling ratio affected mainly biofilm density. Removal of organic matter and nitrogen increased with the amount of biofilm in the carrier. The amount of biofilm attached under the highest filling ratio was reduced as a consequence of increased collision between carriers, indicating that an optimum rate of filling ratio in this process can be determined. The organic matter removal rate reached 86.4 % and 91.5 % in terms of COD and BOD5, respectively, and no less than 13.9 % and 13.7 % ammonia and total nitrogen content, respectively, was removed by the system.