Algal-bacterial ponding systems for municipal wastewater treatment in arid regions

A pilot plant was constructed to investigate the use of algal-bacterial systems to treat municipal wastewaters in acid regions. The pilot plant consists of sand and oil traps, weir tanks, two facultative ponds (250 m³ holding capacity each), two high-rate ponds (25 m³ holding capacity each), four sedimentation tanks, a sludge digestor, and such auxiliary facilities as a pumping station for wastewater supply, drainage systems, and a site laboratory. The main objectives of the study are to determine the design parameters needed for large-scale algal-bacterial ponds in hot climates and to determine the degree of treatment and disinfection attained in the system by operating the pilot plant. After the algae is separated from the treated water, the final effluent will be used for irrigation, and algae will be used as a soil conditioner. Investigations during start-up, test runs and experiments completed so far focused on the growth of algae and removal of biochemical oxygen demand, chemical oxygen demand, and suspended solids. During the 20-month experimental program, various operating patterns, including series operation of facultative and high-rate ponds, will be investigated. Results obtained so far indicate significant reductions in pollution concentrations.