This research project was aimed at developing a ponding system for municipal wastewater treatment adapted to arid regions. High-rate algal ponds preceded by facultative ponds create a combined biological system that can provide treated effluent suitable for landscape irrigation or, after being upgraded, for agricultural irrigation; the system can also provide algae for soil conditioning or animal feed. A pilot plant was designed and constructed to study the operation and performance of the system, an intensive experimental program was introduced with in-situ measurements of the daily pond conditions and laboratory analysis of the pond effluents to evaluate the system and determine the design parameters.

The algal-bacterial ponding system performed satisfactorily providing treated effluent with less than 20 mg/l BOD, 130 mg/l COD, 40 mg/l total nitrogen and 25 mg/l NH3N. The average production of algal biomass was 250 kg/ha.d. Proper disinfection was achieved, indicated by average bacterial count of 5 N/ml total coliforms and 1000 N/ml total bacteria. The area's seasonal weather variations, dense wastewater and fluctuating organic and hydraulic load, did not adversely effect the system. The pilot operation proved the advantages and efficiency of the algal-bacterial pond system in arid regions.

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