THE DESIGN, OPERATIONS AND ECONOMICS OF MUNICIPAL WWTF USING NATURAL SYSTEMS IN MEXICO

摘要

This report describes the performance of two municipal wastewater treatment systemsrnin Mexico serving 4000 and 14,000 people. Both systems are low energy systems (inrnone case energy input for treatment is zero) relying on reed beds and vertical andrnhorizontal flow constructed wetlands. These systems provide complete treatment forrnboth wastewater and sludge. Water quality has exceeded Mexican Federal standardsrnfor BOD, SS and fecal coliforms. Total BOD and TSS removal rates are in excess ofrn95%. Primary Treatment is accomplished with modified Imhoff tanks in one case andrnprimary settling in the second case. Sludge is dewatered and treated in reed bedsrnplanted with Arundo donax. Sludge loading rates are reported. The larger of the twornsystems uses a roughing filter to lower BOD loading rates on the horizontal flowrnconstructed wetlands and to provide for nitrification and denitrification. Minimizingrnenergy and maintenance costs were a significant part of the design and construction.rnEnergy efficiency calculations are presented for both systems showing BOD removal inrnkilograms per KwH, and compared to other technologies. Both systems providernsignificant habitats for migrating waterfowl.