Flexible fibre filter: potential for algae removal

When algae is present in surface water it becomes an important issue in the production of drinking water, causing problems such as the interruption of coagulation and sedimentation processes and blockage of the filter. Dissolved air flotation is generally considered to be the most effective process available for the removal of algae from surface water. In this research, an evaluation is carried out on the effectiveness of an innovative fibre filter as an alternative method for algae removal. The fibre filter has been known as an effective particle separator through flexible polyamide fibres. This filter might apply for production of drinking water as well as for tertiary treatment of wastewater. The removal of particles can reduce the turbidity of the surface water and simultaneously remove microorganisms such as algae. The experiments were performed with a field-scale filter installed close to the Nak-dong River. An improvement was achieved in the removal efficiency through the in-line injection of a coagulant (PAC: 11% as Al₂O₃). With a low optimum coagulant dosage of 1 mg l⁻¹, the filter was able to achieve 90% algae removal with an effluent turbidity of less than 1 NTU when operated at a high velocity of 120 m h⁻¹.