Laboratory Experiments Study On The Treatment Of The Low C/N Ratio Wastewater By The Sequencing Dynamic Membrane Bioreactor

The effect and its influencing factors of the Sequencing Dynamic Membrane Bioreactor to treat the low C/N ratio wastewater under laboratory conditions were investigated in this article.Firstly, the dominant bacterial strain for the low C/N ratio wastewater was acclimated by the progressive reduction of the influent C/N ratio. After this process, the removal rates of the COD and the TN increased from68.56%to71.79%, and from56.06%to81.52%, respectively.Then, the influent concentration of COD, TN and NH4+-N were stabilized between250～300mg/L,103～156mg/L, and92～140mg/L, respectively. The experimental conditions were controlled as followed:temperature was19～21℃, MLSS was3-5g/L, aerobic time DO was2-4mg/L, anaerobic time DO was0.2～0.5mg/L, and the HRT was12h totally which included8h aerobic time and4h anaerobic one. The results showed that the reactor has efficient treatment effect for the low C/N ratio wastewater. And the average removal rates of the COD, TN and NH4+-N were76.15%,82.16%and90.13%, respectively. At the same time, the removal rate of the TN is lower than the one of the NH4+-N because of the lack of the carbon sources. Within a whole HRT period, the concentrations of the COD and the TN both showed obvious phenomenon of reduction. The nitrification rate of sludge in the reactor is0.101d-1which was measured by the degradation of NH4+-N, and0.091d-1measured by the accumulation of NO3--N, and both of them are higher than the ones of the activated sludge in the conventional processing devices. Which indicated that the filtration of the membrane has effectively intercepted the slow-growing nitrobacteria, thus ensured the nitrification of the reactor and provided the denitrification process with the advantages.Finally, according to the results of the orthogonal tests, the order of the relevant factors on the COD removal rate in the light of their significance is HRT, MLSS, water temperature and pH value. The optimal operating parameters for the best COD removal rate conditions are as followed:the HRT is18h, the water temperature is22℃, the influent pH value is8and the MLSS is5g/L. The order of the relevant factors on the TN removal rate in accordance with their significance is pH value, water temperature, HRT and MLSS. The optimal operating parameters for the best TN removal rate conditions are as followed:the HRT is15h, the water temperature is24℃, the influent pH value is8and the MLSS is5g/L. At the same time, the optimal operating parameters of the reactor to treat the low C/N ratio wastewater were determined by the comprehensive analysis of the groups of the optimal operating parameters from the experiments are as followed:HRT is15h, water temperature is22℃, influent pH value is8and MLSS is5g/L.