Biological Aerated Filter Treatment Polluted River Water

The study adopts ceramic biological aerated filters analysis of different size ceramic impact on biofilm formation and the effects of polluted river water treatment. And explore different ratio of air and water, different hydraulic retention time, different filter height, different water concentration and lower inlet water temperature on the treatment effect.The conclusions of this study are summarized as follows.(1) Biological aerated filter forms the biofilm under the condition of inoculation sludge. In the early stage of biofilm formation, larger particle ceramsite BAF achieves a better removal efficiency on COD which reaches stability faster. While at the end of this stage, small particle ceramsite achieves it.Either reactors had a lower ammonia nitrogen removal rate at the outset of biofilm formation. After 43 days, both the ammonia nitrogen removal rate stabilized at more than 80%, and nitrifying bacteria culture matures, showing stability, high removal efficiency.(2)When the hydraulic retention time is 4 hours, with the increasing of air-water ratio, there is no simple trend of increase or decrease in either reactors on COD and total nitrogen removal rate. When the air-water ratio is 2:1, large particle ceramsite BAF achieved the best TN removal efficiency, and the small particle achieved better in various air-water ratios, which shows small particle ceramsite BAF fits better to the air-water ratio. Filter layer height for about 70cm would meet the requirements of removing nitrogen pollutants from polluted river water.(3)When the air-water ratio is 2:1, and HRT is between 0.8h⁸h, according to the TN removal efficiency, the best HRT is around 1.6h. When the filter layer height is 70 85cm, it would satisfy the demand of removing nitrogen pollutants from polluted river water. Based on this HRT range, both BAF achieved excellent TN removal efficiency, while the small one achieved better. And they fitted better to HRT changes. The change of HRT affected little to COD removal rate. (4)When pH varied around 6⁹, removal efficiencies of different pollutants were good, and both the reactors adapted the pH change very well. Small particle ceramsite showed a better shock-resistant capability than the large one. The TN and COD removal efficiencies of both the reactors are better in weak acid inlet water than in weak alkaline inlet water.(5)The higher the inlet water COD concentration, the higher that of outlet water, but the removal efficiency changed little. BAF showed a very good shock-resistant capability which remove organic compounds steadily. With the increasing of COD concentration, nitrification ability of the two reactors increased obviously, and there is little difference between the reactors.When the inlet-water ammonia nitrogen concentration is higher, for AN shock-resistant capability, small particle ceramsite BAF is weaker than large one, while for self-regulation capability, small one is better. The outlet water COD showed a stronger AN shock-resistant capability, and high AN concentration affected little to the removal efficiency.When increased inlet water nitrate nitrogen concentration to 26mg/L, the outlet water nitrate nitrogen concentration increased obviously, and the removal efficiency decreased obviously. The outlet water nitrate nitrogen concentration was still over 15mg/L after running for 5days. The inlet water nitrate nitrogen concentration affected little to outlet water COD concentration.(6)In low temperature conditions, the TN removal efficiency of BAF decreased significantly, but the effect of AN and COD removal rate is little. When the inlet water temperature dropped below 10℃, within 5 days of the trial, both the reactors COD removal efficiency remained at 90%, AN removal efficiency at 85%, and TN removal efficiency decreased to 52.3% and 62.76% separately. This showed TN removal efficiency was the most sensitive factor to temperature.(7)The nitrosation activities of large and small particle ceramsite BAF were 0.013 mg(O₂)/(g(MLSS) ?min) and 0.024 mg(O₂)/(g(MLSS) ?min); Nitrification activity were 0.15 mg(O₂)/(g(MLSS)?min) and 0.338 mg(O₂)/(g(MLSS)?min); Denitrification activity were 14.35 mg (NO₃^-)/g(MLVSS)/h and 30.53 mg (NO3-)/g(MLVSS)/h.The Nitrification performance and Denitrification performance of small particle ceramsite BAF were better than large one obviously.