Depth filtration using novel fiber-ball filter media for the treatment of high-turbidity surface water

Abstract

Performance of the novel fiber-ball filter was investigated for the treatment of high-turbidity surface water. Impact of different operating parameters, such as coagulant type, coagulant dose and filtration velocity on the effluent turbidity, dissolved organic carbon (DOC) and head loss, as well as the particle removal characteristics were studied. The clean-bed filtration results showed that the fiber-ball filters had a great potential for the removal of turbidity matters. Addition of polymeric aluminum ferric chloride (PAFC) enhanced the removal of effluent turbidity and DOC, while the head loss was also increased. The effluent turbidity could be <0.5NTU and the removal efficiency of DOC was ∼16% when the PAFC was dosed at 12mg/L. The effluent turbidity and DOC increased slightly with increasing filtration velocities (30–50m/h) due to the greater drag forces resulted from higher filtration velocities. However, the head loss was also increased. The particle removal characteristics indicated that large particles were primarily removed in the top 30cm of the filter bed and the deep depth in the bottom 20cm played an important role in preventing the occurrence of turbidity breakthrough. It was also found that particles in the size larger than 2μm could be well removed by the fiber-ball filters, implying the potential application for the removal of protozoa like Cryptosporidium (3–15μm) to meet the desired requirement for drinking water treatment during depth filtration.