Experimental Study Of The Biological Aerated Filter Pretreatment Guanting Reservoir Source Water

Guanting Reservoir was an important water source to Beijing in 1980's, but it loses water supply function for water source has been polluted badly. In order to improve Guanting Reservoir water quality, Ministry of Water Resources and Ministry of Science and Technology put a pilot study on Biological Aerated Filter (BAF) for Guanting Reservoir Water Source.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. BAF has been used widely for many years in the world and been used to treat several wastewater in our country.In this paper, BAF was studied on Guanting Reservoir water source treatment with pilot scale and homemade expanded clay as filtration media. Different factors that influence the growth of biofilm were studied. Treatment results and influencing factors were studied on CODMn, UV254, NH4-N and NO2-N in this paper. At the temperature 0.5~25癈, the influent concentration of CODMn and NH4-N is 6.35~41.9mg/L and 1.16-27.9mg/L, respectively. The results show that: (1) When the water temperature is over 11癈, the influent CODMnconcentration is 6.35~23.1mg/L, hydraulic loading is 4~6m3 /m2 h, the average effluent is 5.97mg/L. In winter, at the temperature of less than 5癈, the influent CODMn concentration is 7.80~41.9mg/L and the treatment result of organics is less than at the normal temperature. The treatment result of UV254 is better and treatment rate is 37.4% when the influent UV254 concentration is 0.126~0.710mg/L. (2) When the water temperature is over 6癈, hydraulic loading is 4-6 m3/m2h, the average treatment rate of NFLrN is more than 81.2%. At the temperature of 0.5-5 癈, when hydraulic loading is 3 m3/m2h the average influent ammonia concentration is 17.2mg/L and the effluent of BAF I and BAF II is 17.2mg/L and 15.2mg/L, respectively. (3) The treatment result of NO2-N is good. When the influent concentration of NO2-N is 0.01 ~2.23mg/L, the effluent is less than O.lOmg/L and the influence of temperature, hydraulic loading the total ratio of gas and water is small. (4) The active material is small in the biomass, but it participates in almost all biochemical reaction. Meanwhile the experiment shows that the activity of biofilm is lower in low temperature than in normal temperature.Guanting reservoir water source quality in winter resembles normal sewage wastewater, so the experiment provides the first-hand material of using BAF to treat low-temperature sewage wastewater in the cold area.