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The ceramisite-zeolite-activated carbon combined medium biological aerated filter (BAF) was used to study the treatment effectiveness of the polluted surface water. Several factors affecting the performance of combined medium biological aerated filter were investigated. The factors included air to liquid ratio, hydraulic loading, temperature, ammonia nitrogen and etc. Comparative analysis of combined medium biological aerated filter and a single ceramisite BAF was made for the treatment of polluted surface water. Furthermore, pollutants removal characteristic of each medium layer was studied. The experimental results were drawn as below:(1) When hydraulic retention time was 6h, the gas to liquid ratio was 1:1, temperature varied from 16℃to 24℃, the film formation of combined medium BAF was completed after 31 days. The effluent permanganate index and ammonia nitrogen concentration reduced to about 2 mg/L and below 0.1 mg/L respectively.(2) With consideration of the influencing factors, optimal operational parameters for combined medium BAF were: the gas to liquid was 2:1, hydraulic loading was 0.382 m~3/m~2.h, temperature was 22～31℃.(3) The permanganate index removal of combined medium BAF mainly took place in the 25cm area of medium bottom and activated carbon layer; zeolite layer has a good buffering capacity of ammonia-nitrogen and ammonia-nitrogen removal effect; activated carbon layer played a role in advancing treatment for the effluent of zeolite layer.(4) When hydraulic loading was 0.382 m~3/m~2.h(hydraulic retention time was 2h ), the gas to liquid was 2:1, temperature varied from 22 to 31℃, the pollutants removal effect of the ceramisite-zeolite-activated carbon combined medium biological aerated filter (BAF) was better than a single ceramisite BAF obviously. The removal rate of permanganate index, ammonia nitrogen concentration, total nitrogen and turbidity in combined medium biological aerated filter was 65.04%, 98.53%, 20.81% and 98.24% respectively. The removal rate of permanganate index, ammonia nitrogen concentration, total nitrogen and turbidity in a single ceramisite BAF was 37.02%, 84.72%, 10.70% and 97.67% respectively.(5) Compared with a single ceramisite BAF, combined medium biological aerated filter has better anti-ammonia nitrogen shock capacity. Combined medium biological aerated filter has better stability for the pollutants removal. The ceramisite-zeolite-activated carbon combined medium biological aerated filter (BAF) was used to dispose the polluted surface water, reaching the purpose of improving the water quality, it is a high economical, high-efficient, technical feasible method.
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