HIGH-RATE ANAEROBIC WASTE-WATER TREATMENT UNDER PSYCHROPHILIC AND THERMOPHILIC CONDITIONS

Anaerobic wastewater treatment is an attractive and generally accepted technology for the treatment of various types of medium- and high-str ength wastewaters. So far, this treatment technology is mostly applied at the mesophilic temperature range between 25 and 40 degrees C. Howe ver, results of recent research conducted under both psychrophilic (< 20 degrees C) and thermophilic (> 45 degrees C) conditions, reveal tha t temperature is not a limiting factor in applying anaerobic treatment , provided the appropriate process design is chosen. Temperature has a considerable impact on various biological and physical factors of the anaerobic conversion process. For instance, the biogas production rat e is reduced to a minimum at low temperatures, while it can reach extr eme values under thermophilic conditions. In sludge bed systems, the b iogas production rate determines the degree of mixing between the biom ass and the wastewater and should, therefore, be considered in the pro cess design. Other impacts of temperature are related to inhibition ef fects under thermophilic conditions and to a non-desirable accumulatio n of non- or partly degradable organic matter under psychrophilic cond itions. Obviously, these effects may hamper the utility of the commonl y applied single stage reactor systems. However, by adapting the proce ss design to the expected prevailing conditions inside the reactor, th e loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved. (C) 1997 IAWQ. Published by Elsevi er Science Ltd.