Dissolved Air Flotation Process for Algae Removal

  • W. O. Mulaku Department of Civil Engineering, University of Nairobi, Kenya
  • E. Nyangeri Nyanchaga Department of Civil Engineering, University of Nairobi, Kenya
Keywords: Dissolved Air Flotation, Types of Algae, Algae removal


Sedimentation is the most widely used primary clarification stage before filtration for the production of potable water. Raw water that is algae laden is difficult to clarify by sedimentation, as gravitational forces are largely ineffective due to algae stability. Algae form low-density particles that exist in a colloidal state and have a tendency to float hence causing solid-liquid separation problems in the sedimentation stage. Additionally, their low turbidity, soft and high color nature produces very light flocs which settle very slowly. This study investigated the performance of the Dissolved Air Flotation (DAF) process as an alternative to sedimentation for algae removal in surface water treatment in Kenya. Batch DAF experiments were carried out in the laboratory using algae laden surface water samples collected from the river and laboratory cultured algae water samples. The performance and effectiveness of the process were assessed for algae and turbidity removal and color improvement. Experimental results showed that clarification of surface water laden with different types of algae such as blue-green, green, diatom and dinoflagellates was effective. At optimum coagulant dosage, algae removal from 70 percent to 90 percent, turbidity reduction of over 80 percent and color improvement of about 75 percent was achieved.

Journal of Civil Engineering Research and Practice Vol.1(2) 2004: 27-38

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eISSN: 1729-5769