Ammonia Nitrogen Removaland N,N-dimethylformamide Wastewater Treatment By Facultative-aerobic Fluidized Bed

As a new biofilm technique, biological fluidized bed has many advantages such as less space, higher transfer efficiency and less excess sludge. Thus, the biological fluidized bed has been a research hotspot in the study of water treatment technology at home and abroad.In water pollution, ammonia nitrogen is the key to eutrophication and also a main DO-consumption pollutant, which has been shown to cause developmental damage in fish and some aquatic organisms. Therefore the development of a high efficiency, energy saving wastewater denitrification process is of great practical significance.N,N-dimethylformamide(DMF) is a wildly used organic solvent in synthetic leather manufacturing and chemical industry processing. The US classified DMF as a possible carcinogenic substances to humans. At present, the removal of DMF in low concentration is usually by degradation with an unsatisfied effect and inorganic nitrogens such as ammonia nitrogen appear during the degradation process. This research studied the ammonia nitrogen removal and the effect of DMF wastewater treatment using fluidized bed process, providing a reference for further academic research and engineering application.Facultative-aerobic fluidized bed was used as the experimental reactor with waste coke particles(size between 0.6 to 1.2 mm) used as media. The reactor was started at a relatively low C/N ratio(C/N=0.3) and it was found that the effluent ammonia nitrogen level reduced to 31 mg/Lafter 23 days. The inflow ammonia nitrogen level was 130 mg/L and the removal rate was approximately 75%. At the same time, many protazoa such as vorticellae and epistylis were appeared. The change of mixed liquid suspended solids(MLSS) and mixed liquor volatile suspended solids(MLVSS)in suspended phase at the early stage of startup showed that the microorganisms in the reactor were mainly composed of attached microorganisms. The suspended microorganism were few in number and had little effects on the water purification as the effluent was clear.Having a long hydraulic retention time was beneficial to the reactor for ammonia nitrogen removal, especially in the facultative zone. When the carbon nitrogen ratio C/N=1, the ammonia nitrogen removal effect was optimized. However, the Chemical Oxygen Demand(COD) removal effect increased along with the increase of the C/N ratio, but the concentration of nitrate nitrogen decreased with the increase of COD.When the concentration of ammonia nitrogen in wastewater was less than 141 mg/L, the efficiency of ammonia nitrogen removal could be significantly increased. The fluidized bed reactor had a satisfactory removal rate for the DMF wastewater with DMF concentration of 100mg/L. Effluent COD levels were low and both COD and DMF removal could be achieved in the facultative zone. When the wastewater containing DMF, the removal efficiency of ammonia nitrogen became obviously worse. One possible reason was speculated that DMF had some inhibitions of the activity of nitrifying bacteria. Under the condition of no extra carbon and nitrogen source, the facultative-aerobic fluidized bed reactor could achieve good purification effects with a low DMF concentration(100 mg/L).