The Optimal Treatment For Micro-polluted Water With BAF

This subject was supported by the biological pretreatment technology research and demonstration, leading under the major science and technology projects of national water pollution control and management (2008ZX07422-003).The BAF was used in pre-treatment of micro-polluted water, and optimized this treatment.In this paper, BAF was studied on the micro-polluted water of high concentration of pollutants with polit scale and homemade expanded clay and lava as filtration media. The results show that:(1)a contrastive study was made on the start-up, biofilm formation in different temperature, and two BAFs in low tmperature. This study shows that the time needed for the start-up and biofilm formation of BAF in different temperature were different, there need 20 days in normal temperture,and 30 days was needed in low temperture (5-10℃) with high concentration of pollutants and low filtration rate.(2) The factors included hydraulic loading, air to liquid ratio,pH, influent organic concentration and temperture. The study shows that when the filtration rate is 4-6m/h, hydraulic loading is 0.38-1.00m3/m2-h, air to liquid ratio is 1:1,pH is 6.5-8.0, the influent CODMn is 10.0mg/L, and the influent NH4+-N is 6.5mg/L, the average treatment rate of NH4+-N is 85%, the average treatment rate of CODMn is 50%.When the temperature is over 15℃,the average treatment rate of CODMn and NH4+-N is 50% and 80%, respectively. But when the temperture down to 5-10℃,both of the treatment of CODMn and NH4+-N were cut down. There were 28% and 70%, respectively.(3) the head loss of the BAF was studied by using the tube. The study shows that with the reactor running time increases, and the head loss will gradually increase.the rate in 0-80cm was faster than the later part of the BAF.(4) the backwashing was studied in different wash rate. The results show that when the water wash rate is 15L/(s.m2),the air wash rate is 20L/(s.m2), the BAF can achieve a better bachwash effect.(5)when the temperture is in 5-10℃,the influent CODMn and NH4+-N were 4-5mg/L and 6-8mg/L,the filtration rate is 5m/h,air to liquid ratio is 1:1,the results show that the average treatment rate of NH4+-N is 65.4%,the treatment rate of CODMn is in 19.6%-22.6% in the clay BAF;the average treatment rate of NH4+-N is 66.3%,the treatment rate of CODmn is in 20.4%-23.6% in the lava BAF.By comparing, the treatment effect of the lava BAF was better than the clay BAF,but it was almost.By studying the biofilm activity,it shows that the different of the biofilm activity is consistent with the operation effect.