Study On Low Carbon-to-nitrogen Sewage Denitrification By Combination Bed Based On Immobilized Microorganism

Nitrogen pollution has been more and more attentions. The research about low carbon to nitrogen ratio sewage denitrification has become the focus of attention at home and abroad. Biological treatment processes for low carbon to nitrogen ratio sewage have a number of limitations. The important topic for environmental workers is to research and development advanced denitrification process, which is simple structure, convenient operation, high treatment efficiency and no secondary pollution, in order to increase the denitrification efficiency of low carbon to nitrogen ratio sewage.This paper compared the purification performance of ceramsite immobilized microorganism fixed bed (CIFB) with polyurethane foam immobilized microorganism fluidized bed (PIFB), Built O/A single-stage biological fluidized bed (O/A-BFB), ceramsite-polyurethane foam layered combination bed (CL-BMB) and zeolite-polyurethane foam layered combination bed (ZL-BMB) based on immobilized microorganisms technology. The performance of biological reactor was researched containing the medium selection, process design, operation conditions, kineties and mechanism to improve the total nitrogen removal efficiency. The main results are as following:1. Two kinds of carrier material, polyurethane foam and ceramsite, were loaded into biological filter to compare the efficiency of their microbial treatment of sawage. It was shown that under the same operating conditions, the reductions in the overall NH3-N and COD by the CIFB supported by macroporous polyurethane were higher than those of the PIFB supported by ceramsite. However, the efficiency of the CIFB with macroporous polyurethane in removing TN was lower than that of the PIFB with ceramsite.2. In order to improve the total nitrogen removal efficiency, it was reconstructed to Aerobic/anoxic immobilized microorganism aerated floating filter by adding anoxic treatment zone, and its treatment efficiency and kinetics was investigated. The results showed that the pollutants can be most effectively removed at air/water ratio of1, hydraulic load of0.47m3/(m2. h), anoxia layer high of300mm. When C/N ratio was maintained at3, the NH3-N initial concentration was about10mg/L, the removal efficiency of COD、NH3-N and TN was70.24%、97.89%and72.52%respectively. The general kinetic equation at experimental conditions was as follow:Se=SO e-0.0936t/(1+0.6593t). 3. Taking advantages of the two mediums, ceramsite and macroporous polyurethane foam, a layered biological aerated filter (CL-BMB) was built to treat the low carbon-to-nitrogen micro-polluted water. The CL-BMB was operated at air/water ratio of1, hydraulic load of0.47m3/(m2·h), C/N ratio of3and the NH3-N initial concentration about10mg/L, the removal efficiency for COD, NH3-N and TN was90.3%,99.9%and58.6%respectively. The greatest increment of COD and NH3-N removal efficiency happened on the bottom250mm of medium height. The greatest increment of TN removal efficiency happened on the bottom500mm of medium height. The kinetic performance of the CL-BMB indicated that the relationship of COD and NH3-N removal efficiency with the influent COD and NH3-N concentration could be described by ln(Co/C)=(0.0023/Q0C00.9398)H and ln(C0/C)=(0.015/Q0C00.5641)H.4. In order to improve the performance of the CL-BMB, ceramsite was replaced by zeolite, zeolite and polyurethane foam layered biological aerated filter (ZL-BMB) was built. The ZL-BMB was operated at air/water ratio of1, hydraulic load of0.47m3/(m2·h), C/N ratio of3and the NH3-N initial concentration about10mg/L, the removal efficiency for COD, NH3-N and TN was90.6%、99.6%and73.7%respectively.