RESEARCH THEMES

Conventional Wastewater Treatment

Environmental Water Quality and Treatment

Natural Wastewater Treatment Systems

Rural Ecological Sanitation

Waste Management and Cleaner Production

Wastewater Reuse in the MENA Region

Water Resources Management

Anaerobic pre-treatment of sewage under low temperature (15 ºC) conditions in an integrated UASB-Digester system

Dr. Nidal Mahmoud

The upflow anaerobic sludge bed (UASB) reactor is the most widely and successfully used high rate anaerobic system for sewage treatment. It has been successfully used for sewage treatment in several tropical countries like India, Colombia and Brazil, both at pilot scale and full scale. The ambient temperature in these countries is rather high and constant along the year ranging between 20 and 30 °C. With respect to regions of cold climates, like Palestine in the Middle East, where sewage is also characterised of high solids content, further development of the reactor technology is needed. The performance of the one-stage UASB systems at low temperature climates (5-20 °C) is highly limited by the slow hydrolysis of entrapped solids, which accumulate in the sludge bed when high loading rates are applied. Consequently, the amount of excess sludge will increase leading to a lower solids retention time (SRT) which might limit methanogenic growth resulting in a poor soluble COD removal and deterioration of sludge stability. An alternative technology, the UASB- digester system, was proposed and investigated. Results showed that this system is technically viable and can be operated for sewage treatment in Palestine, at an overall hydraulic retention time (HRT) of 8.60 hours as compared to 24 hours when applying a conventional UASB-reactor.