Development of Floating Plastic Media Filtration System for Water Treatment and Wastewater Reuse

摘要

Floating plastic media coupled with sand filtration system was applied for treating surface water and secondary effluent from municipal sewage treatment plant. The system employed floating plastic media for the removal of suspended solids in surface water and precipitated phosphorus from secondary effluent of sewage treatment plant. Sand filtration was then used to remove further the suspended solids. For the purposes of wastewater reuse, a zeolite layer was used instead of sand filter to absorb ammonium nitrogen. Application of system for surface water treatment suggested appropriate filtration rate of 5 m~3/m~2 h. Polyaluminum chloride was found to be the best coagulant with an appropriate plastic and sand bed depth of 40cm. The system could produce average effluent turbidity and suspended solids of 0.71 NTU and 0.94 mg/L respectively. Average turbidity and suspended solids removal efficiencies were 96.26% and 95.48% with low headloss development of 40.4cm at the end of 6h operation period. When applying 1.50 m. floating plastic media bed for the treatment of synthetic raw water, short and long-term turbidity removal efficiencies were 96.79-97.72% and 81.81-94.61% for raw water containing turbidity of 20 and 40 NTU. It could produce the effluent with turbidity less than 5 NTU while having less than 1.0m. headloss. The system was also applied for the secondary effluent treatment. An optimum filtration rate of 5 m~3/m~2 h was obtained when using plastic and sand bed depth of 60 and 20cm under direct filtration mode. Average turbidity removal was 60.3% and 59.6% after 6 and 48 h of operation. It was also found that 1 m~3/m~2h filtration rate and 50:30 cm of plastic:zeolite bed could be used to achieve both ammonium nitrogen and phosphate removal. Suspended solids, turbidity, BOD_5, NH_4~+, and PO_4~(3-) removal efficiencies were 91.9, 94.6, 95.4, 97.3, and 99.5% respectively after 24 h. As a result, the effluent from the system had average NH_4~+ and PO_4~(3-) of 0.5 mg N/L and 0.02 mg P/L.