ANAEROBIC DIGESTION APPLIED TO MUNICIPAL WASTEWATER TREATMENT: FACTS AND LIMITATIONS OF AN ADAPTED TECHNOLOGY FOR LATIN AMERICA.

Although the UASB reactor has, particularly in warm climate regions, an important potential for municipal sewage treatment in a reliable and economic way, it is not yet a technology accepted among sanitary engineers. It is necessary, therefore, to establish a reference frame that may serve as technical and economic basis for dissemination of UASB technologies in this specific application. The paper presents a short bibliographic review of selected experiences with full scale UASB reactors treating municipal sewage. The advantages of anaerobic treatment of sewage respond very well to the technological needs of the region: it has very limited energy requirements and low sludge production, the operation and maintenance tasks are simple, the plant foot print is very small, and the biogas produced may provide, under certain circumstances, a local energy source. These strong points are faced to some drawbacks, the main ones being the lower effluent quality and odor generation. It is concluded that UASB reactors is a real option for municipal sewage treatment with a water temperature above of 20°C. In addition, with simple post-treatment processes, it can produce high quality secondary effluents, keeping comparatively low operation and maintenance.