Anaerobic treatment of domestic sewage: established technologies and perspectives.

The use of anaerobic reactors for domestic sewage treatment has increased significantly since the UASB configuration started to be efficiently applied for this purpose in the beginning of the 1980s. Nowadays, hundreds of UASB reactors, or similar anaerobic units, are used in domestic sewage treatment systems, particularly in developing countries. These units have been operated at ambient temperature, normally higher than 20 degrees C, at hydraulic detention time in the range of 6 to 10 hours, and organic loading rates lower than 3.0 kg COD.m(-3).d(-1). They have presented COD removal efficiencies in the range of 65% to 80%. Besides, new configurations have been developed and assayed in research centres, aiming to amplify the range of application and to improve process performance. At the same time, research is being conducted on the post-treatment of anaerobic effluents attempting to offer alternatives to the existing conventional systems. It takes into consideration not only sanitation and environmental protection, but also considers resources conservation at lower construction and running costs as the main supporting concepts for further development. This text presents some aspects of the consolidated technologies and suggests on further developments in the conception of domestic sewage treatment systems having the anaerobic process as their core.