Biotrickling Filters For Nitrification Of Nitric Oxide

NO_X is a major soure of atmospheric pollutant, being harmful to human and animals, resulting in the acid mist,acid rain and the photochemistry smoke, endangering human life and environment. Although conventional solutions to NO_X have their own advantages, in the recent years, some new methods such as biofilter bring vital force to the removal of NO_X. According to the nitrification principles, this thesis uses bio-trickling filter to treat low concentration of NO under aerobic conditions.Two kinds of actived carbons are applied as packing material in this experiment. The microbe from sludge is cultured by sodium nitrite which is supplied as the only nitric source. After that the microbe is inoculated on the surface of packing material to develop the biofilm. The potential and difference of the nitrification of the biofilm on the two packing material are studied by dynamic test in the biofilter. The main effects such as the pH of recycle liquid and its flow rate, the Empty Bed Resident Time(EBRT), the NO influent concentration, the height of packing material and the organic carbon source were investigated respectively.The experiment has been carried out under the following conditions: the NO influent concentration is less than 150 mg/m~3, EBRT is 31～68 s, recycle liquid flow rate is 0.05～0.15 L/h. The results showes that:①Under the conditions of DO>2.0 mg/L, 25～30℃and pH 6.0～8.5, the bacteria which are got by cultivating could cooperate in nitrification process;②The maximum removal efficiency of NO is achieved when the pH value of recycle liquid is 7.5～8.0. The removal efficieny drops quickly with the increase of the recycle liquid flow rate or NO flow rate. The removal efficiency of NO showes a good linear relation with influent burthen. The lowest level of the bio-trickling filter has the highest removal efficiency. When the liquid flow rate is 0.05 L/h,the EBRT is 68 seconds and the influent concentration is 114.50 mg/m~3, the removal efficiency reached 58.60% and 57.03% respectively;③The removal efficiency of 84.03% and 79.26% are attained under the conditons of EBRT 68 seconds,pH 7.5～8.0 and the liquid rate 0.05～0.10 L/h, when the gas concentration declines from 127.40 mg/m~3 to 20.34 mg/m~3 and 26.42 mg/m~3;④Supplied with organic carbon source, the removal efficiency of NO is increased, because the autotrophic nitrifying activity has already been excited.