TREATMENT OF MUNICIPAL WASTE-WATER IN A CIRCOX(R) AIRLIFT REACTOR WITH INTEGRATED DENITRIFICATION

In this study it was investigated whether the CIRCOX(R) airlift techno logy with integrated denitrification was suitable to treat municipal w astewater. The standard CIRCOX(R) reactor was extended with an anoxic compartment. The sludge on carrier is circulated alternately over the anoxic and oxic compartments by means of an airlift pump. The study wa s performed in two pilot reactors, a standard CIRCOX(R) reactor and a CIRCOX(R) reactor with integrated denitrification. Concerning BOD conv ersion and nitrification, no differences between the two systems were observed. It was shown that both BOD and nitrogen were removed efficie ntly. In the effluent, mean soluble BOD concentrations of 7 mg/l were attained at varying COD loading rates. Nitrification was complete in b oth reactors at temperatures above 15 degrees C and at COD conversion rates of more than 2.5 kg COD/m(3)/d. Nitrification rates below 15 deg rees C were higher as compared to a low loaded activated sludge system . Substrate conversion rates were found to be constant throughout the denitrifying reactor. Denitrification matched the rates theoretically feasible. This could be achieved by controlling the recirculation and the aeration in relation to the loading rate. It can be concluded that the denitrifying CIRCOX(R) airlift technology seems to be an interest ing alternative to treat municipal wastewater. (C) 1997 IAWQ. Publishe d by Elsevier Science Ltd.