Wastewater Renovation by Flotation for Water Pollution Control

Abstract

Planning and management of water resources is more and more being based on the renovation and utilization of wastewater for use in agricultural and landscape irrigation as well as in industrial production. Conventional wastewater treatment, even when it is economically feasible, is costly because of biosolids handling and tertiary sedimentation tanks. The fact that (DAF) dissolved air flotation (with 3–5 min of detention time) can replace sedimentation (with 2–3 h of detention time) for clarification has been overlooked by environmental engineers for many decades. Modern high rate DAF clarifiers have advanced to such an extent that they could overshadow the conventional settling clarifiers in wastewater treatment. DAF hydraulic loadings increased from 1 to 2.5 L/m2/s and for a triple stacked unit to 7.5 L/m2/s; the detention time decreased from 30 to 3 min; air dissolving is improved and now requires only 10 s retention time in the air dissolving tube instead of the previous 60 s. This chapter discusses the field application of the DAF process for primary wastewater clarification, secondary separation of mixed liquor from activated sludge and the design and operation parameters for a two-stage DAF operation. The performance of the compact units in treatment of various wastewater effluents illustrates the system’s usefulness for wastewater reclamation, recycling and reuse.