TREATMENT OF RAW SEWAGE IN A TEMPERATE CLIMATE USING A UASB REACTOR AND THE HANGING SPONGE CUBES PROCESS

The treatability of raw sewage in a temperate climate (wintertime arou nd 10-20 degrees C) using an upflow anaerobic sludge blanket (UASB) re actor and the hanging sponge cubes process was evaluated. After being seeded with digested sewage sludge, a 47.1 L UASB reactor was continuo usly operated for more than 2 years by feeding raw sewage, which had a verage COD around 300 mg/L (41% soluble). During summertime at an HRT of 7 h, effluent COD approximately 70 mg/L total, 50 mg/L soluble and BOD5 20 mg/L total, 12 mg/L soluble was obtained, During wintertime al so, treatment efficiency and process stability was good. With the hang ing sponge cubes process using the effluent of the UASB reactor treati ng raw sewage, the following results were obtained. The ammonia oxidat ion rates of 1.9 and 3.5 g NH4-N.m(-2).d(-1) in a downflow hanging spo nge cubes biofilter, under natural air intake only were obtained durin g wintertime and summertime, respectively. With post-denitrification a nd an external carbon source, 84% in average N (NO3 + NO2) was removed with an HRT of less than 1 hour and in the temperature range of 13 to 30 degrees C using an upflow submerged hanging sponge bed bioreactor, under anaerobic conditions. The overall system using a UASB reactor a nd the hanging sponge cubes process could be quite an attractive treat ment alternative. (C) 1997 IAWQ. Published by Elsevier Science Ltd.