| With the development of paper industry,the problems such as water consumption and wastetwater discharge become more serious,so it is important to strengthen the advanced treatment of paper mill wastewater and promote the wastetwater reuse.This work studied the advanced treatment of paper mill wastewater by combined process of ozone-biological aerated filter.The impact of operating parameters on the treatment effect such as air-to-liquid ratio,hydraulic loading and operation period were investigated.The quick start-up situation of BAF,degradation characteristics of conventional pollutants and particular pollutants in paper mill wastewater were also analyzed.Furthermore,the effect of the improvement of biodegradability by preozonation and the degradation effect of combined process on pollutants were researched.Results show that air-to-liquid ratio 3:1,hydraulic loading 0.23m3/(m3·h), backwash period 7～8 days were the optimum operating condition.The removal of CODCr,NH3-N and turbidity by BAF were mainly focused in the range of 0～60cm, 20～80cm,0～40cm,respectively.It demonstrated that biological aerated filter had quick start-up capability.After preozonation of 8 minutes,the biodegradability of wastewater was substantially increased,where B/C ratio was increased from 0.21 to 0.45.Pollutants could be deeply removed by combined process of ozone-biological aerated filter,under conditions of ozone dose 50mg/L,contact time 8min,BAF air-to-liquid ratio 3:1 and hydraulic loading 0.23m3/(m3·h),the removal of CODCr, UV254,NH3-N,turbidity,colority and DIBP reached 54.9%,74.5%,88.3%,92.2%, 88.8%and 46.9%,respectively.The effluent could meet the newly issued discharge standard of water pollutants for pulp and paper industry(GB3544-2008).The treatment cost for such combined process was 1.25 yuan/t.
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