| With the development of technology society,sources water in the world has been widely polluted.The removal rate of resolvable organics and NH3-N in micro-polluted source water by conventional treatment method is rather low,and chlorination can form organic halide which will do harm to human.Biological aerated filter(BAF) has many advantages,such as small volume,little covering earth and hydraulic retention time(HRT),high treatment efficiency and effluent water quality,low investment and running cost etc,so it is of good use perspective.Using zeolite as the filling material,BAF is investigated to pretreat the micro-polluted source water of a lake.The properties of zeolite are studied,as well as the capability of static and dynamic adsorption of organic pollutants and ammonia nitrogen.The efficiency of BAF on micro-polluted source water treatment is analyzed,and the best running parameters have been searched.On the basis,the influence of the running and managing parameters such as the mode of acclimation,HRT,hydraulic loading,air-water ratio,backwashing,height of filling that affect the removal efficiency has been discussed.Using simulated water and practical micro-polluted water,in the best running state,compared experiment has been studied,which proves the treatment efficiency of zeolite BAF to contaminants.And the removal efficiency of biological zeolite filter is compared with that of biological active carbon.The main conclusions drawn from the test is following. (1) Zeolite is of "quick adsorption,slow balance".Static adsorption test is conducted by using 5.00mg/L NH3-N,the removal rate of NH3-N is up to 86.8% after 30min,after that,the concentration of NH3-N in solution is hardly changing. The removal rate of organism with Zeolite is not very high in total,after 60min's adsorption,the mean removal rate of CODMn and UV254 is 3.27%and 6.02%, respectively.(2) The best working condition determined by test:hydraulic loading 1.0 m3/(m2·h),Hydraulic retention time(HRT) 48min,gas water ratio 1:1.Under this working condition,the mean removal rate of NH3-N,CODMn and UV254 in simulated waste water with BAF is 93.8%,17.2%and 12.1%,respectively.The treatment effect to actual micro-polluted water is poorer than the treatment effect to simulated waste water,but the treatment effect is ideal,the mean removal rate of NH3-N,CODMn and UV254 is 89.2%,13.8%,10.3%,respectively.(3) This test elects the way of back wash is firstly gas wash,secondly gas and water wash,thirdly water wash.During the best working condition,that is when Hydraulic loading is 1.0 m3/(m2·h) and gas water ratio is 1:1,the cycle of back wash is about 8 days.(4) The test determines the best layer that remove NH3-N is ranging from 30cm to 60cm,at the point of 60 cm,the removal rate of NH3-N is up to 89.7%, possessing 96.8%of total layer removal rate,after 60cm,the concentration of NH3-N goes flat;The main remove region of CODMn is from the point of inflow to 50cm,the removal rate of CODMn is 18.6%,possessing 90.1%of total layer removal rate,after 50 cm,the concentration of CODMn maintains unchanged.(5) According to the comparison of active carbon and zeolite BAF,the removal rate of organism with active carbon BAF is better than with zeolite BAF, active carbon is similar to inertia materials but so expensive,and the cycle of back wash is short,the energy of back wash is high using the way of gas and water wash,so it is limited in our country's water plant.However,zeolite BAF has a good removal effect of NH3-N,better than active carbon BAF obviously,and the cycle of back wash is shorter than active carbon BAF,lowering the energy of back wash.(6) For a small water plant with everyday disposal quatity of 10000t,the fixed investment cost of the pre-treatment process is 1.15 millions yuan,the running cost is 0.1989 yuan per ton,we can draw that it is of low investment and running cost,so it is easy to put into use in middle or small water plant of city and town.In all,it is an ideal pre-treatment process for micro-polluted source water.
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