| The treatment of micro-polluted raw water using biological pretreatment technology was investigated in a waterworks of Guangzhou. The biological pretreatment technology using immobilized nitrobacteria pellets (10% pellets stuffing ratio in volume) in airlift loop reactor was investigated with the system operated continuously. The results in the bench scale experiment showed that it could remove low concentration NH4+-N quickly and effectively. When the influent concentration of NH4+-N was 2.13mg/L, the average effluent concentration of NH4+-N was 0.33 mg/L with HRT remaining 30min under the condition of the first kind of raw water. When feeding the second kind of raw water with concentration of NH4+-N of 0.54mg/L ,the average effluent concentration of NH4+-N was 0.18mg/L with HRT remaining 10min The immobilized nitrobacteria pellets'specific gravity is 1.02-1.04 g/cm3.The biological activity and the fluidiza- bility is fine. This system is easy to be operated and suitable for waterworks.Pilot-scale experiment using the second kind of raw water was investigated under the following operational conditions: flow rate 3m3/h and HRT 30min. The result showed that biological pretreatment technology using immobilized nitrobacteria pellets can remove low concentration NH4+-N quickly and effectively. When the influent concentration of NH4+-N was 0.46mg/L, the average effluent concentration of NH4+-N was 0.24 mg/L. When the influent concentration of NH4+-N increased unexpectedly, immobilized nitrobacteria pellets showed the ability of shock resistance .The influence of biological pretreatment on coagulate progress was also investigated. The effluent of biological pretreatment can reduce the dosage of coagulant , which would contribute to the reduction of drinking water production cost.According to the result of economic and technical analysis, the operation cost was 12.5 cent when treating one ton raw water using biological pretreatment.
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