Sewage clarification by dissolved air flotation and chemically assisted sedimentation

Abstract

The removal efficiencies of two physico‐chemical methods of sewage treatment, viz. dissolved air flotation (DAF) and chemically assisted sedimentation (CAS) were investigated on pilot‐plant scales. The experimental treatments were factorial combinations of chemical programmes, chemical dosages and hydraulic loadings. These were applied to both raw and settled sewage. DAF was demonstrated to be more efficient than CAS in removing suspended solids and oil/grease. Chemical dosage proved to be the most important factor in removal efficiency for both processes.

Keywords:

• Sewage treatment
• dissolved air flotation
• sedimentation
• clarification