Preliminary Study On Denitrification With Methane As External Carbon Source

Municipal wastewater with low carbon to nitrogen(C/N) ratio is a common problem in our country, it requires adding external carbon source in the denitrification step. In order to achieve the desired removal, most wastewater treatment plants use methanol as a carbon source. However, it has many disadvantages, such as high cost, high toxicity, difficult transportation and storage. In order to find a inexpensive, non-toxic carbon. This paper we study methane as a feasible electron donor for denitrification.Through the AME-D (aerobic methane oxidation coupled denitrification) process analysis, the intermediate product of methane oxidation is methanol, the methane oxidation rate can achieve about 185.7mmol/gVSS·d, the denitrification rate reached 131.5mgNO₃^--N/gVSS·d, the consumption of oxygen to methane ratio is 1.3, methane to nitrogen ratio is 8.8 (molar ratio of CH₄-C/N), the denitrification rate slower than methanol, faster than system carbon source.Evaluate the factors that affecting AME-D analysis, the oxygen supply rate is the most important factors. When O₂/CH₄ radio rang from 1 to 1.5, the denitrification rate increases and then decreases, C/N ratio has been increasing, rising from 7.6 to 15.6. it should be strictly controlled the amount of oxygen for getting a low C/N ratio. DO impact on the AME-D is also important, when DO and solubility of CH₄ concentration is low , it can get a high denitrification rate. In the AME-D, the nitrogen removal mainly by denitrification. AME-D can also removal ammonia nitrogen, activated sludge AME-D maximum denitrification rate can reach 4.2mgN/(L·h). When the ambient temperature lower than 15℃, the basic denitrification was inhibited.Membrane aeration process can be used in AME-D for its good mass transfer, the kLa of methane can reach 0.0246min^-1. denitrification rate reach 1.6gN/m²Â·d, the lowest C/N ratio is 9.4, when the DO is 1mg/L it will get high nitrate removel efficiency, in order to simultaneously achieve the optimal denitrification rate and C/N ratio, we need to do more in-depth on the amount of oxygen supplying, ammonia nitrogen had no effect on AME-D.For the current study, the C/N ratio has been a constraining factor, comparison with methanol, AME-D process does not be economical.