A novel and cost-effective sewage treatment system consisting of UASB pre-treatment and aerobic post-treatment units for developing countries

A novel sewage treatment system was proposed, which consists of a UASB anaerobic pretreatment unit and the following DHS (downflow hanging sponge-cubes) aerobic posttreatment unit, as a low-cost and easy-maintenance process for developing countries. Over six months experiment by feeding sewage our proposed system achieved 94% of total-COD removal, 81% of soluble-COD removal. and nearly perfect SS removal and total-BOD removal at the overall HRT of 8.3 hr (7 hr in UASB and 1.3 hr in DHS unit). Moreover, the DHS reactor was capable of performing high (73--78%) nitrification. Our whole system requires neither external aeration input nor withdrawal of excess sludge. (c) 1997 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]