PRODUCTION AND SEPARATION OF ALGAE IN A HIGH-RATE PONDS SYSTEM

Pilot scale high-rate algal ponds followed by settling tanks were deve loped to produce algal biomass from wastewater for greenery developmen t and agricultural use in arid zones, like Kuwait. The high-rate ponds designed and operated by instructions resulting from the authors' res earch work can produce algal biomass of 300-400 kg/ha.d in summer and 200-300 kg/ha.d in winter seasons. The actual yield depends on the eff iciency of the floc formation and settling. A minimum of a 2-h residen ce time in the settling tanks is needed to achieve adequate separation of the phases, assuming healthy algae culture that are susceptible to flock formation. The flock formation and settling properties are sens itive to the weather and operational parameters (e.g., sunshine, hydra ulic conditions in settling tank, variations of the flow rate, and pon d depth). If conditions are inadequate, 20-30% of the biomass can be l ost. Satisfactory biomass production can be achieved only with careful plant operation and maintenance. The sensitivity of the algae separat ion by settling operation indicated the development of a modified sand filter system for algae trapping.