Study On Nitrogen And Phosphorus Removal In Modified UCT Process With Synthetic Wastewater

With the increase in the amount of Wastewater treatment plant (WWTP), the whole capacity of pollutant removal did not improved further and the disturbing problem such as eutrophication became deteriorated and didn’t got solved. The mechanism of nutrient removal、corresponding suitable process and other contributing factors were hotspot topic in our nation’s water treatment. A2/O process as traditional method for nutrient removal its advantage against any other process for nutrient removal include:low hydraulic retention time (HRT)、simplicity in structure、low operational cost、high constancy of activated sludge and less complexity in controlling process.However, the three primary organisms such as phosphate-accumulating organisms (PAO)、denitriying bacterium and nitrifying bacterium has different requirement in A2/O process, the problem like recycling sludge with much nitrate inhibiting anaerobic phosphorus release and competition between PAO and OHO (heterotrophic bacteria) would be the main reasons result in bad stability in A2/O process operation and low nutrient removal efficiency.The pilot-scale modified UCT reactor (50.2L) with step feed concept was proposed to tackle with synthetic wastewater with combination of activated sludge acclimation. In this study, by discussing the effect of four different influent distribution ratios on COD、NH4+-N、 TN and TP removal, we concluded the optimal inflow distribution ratio was0.35:0.35:0.3. In optimal step feeding ratio, The removal efficiency of COD、NH4+-N、TN and TP were83.67%、96.6%、80.1%and86.6%, respectively, Especially in the Run3, the ratios of denitrifying phosphate accumulating organisms (DPB) to PAO was39.6%. According to the data in DO、ORP and pH measurement, by controlling concentration of DO ranged from1.5mg/L～2.0mg/L was suitable, this concentration of DO not only guaranteed completely nitrification but also prevented inhibition from denitrification process. There were different degree of SND in aerobic zones which accounted for21.73%、17.96%、24.71%and20.84%of TN removal in four phases. Usage of biomass balance for whole reactor to calculate the COD removing load and TP removing load, the results indicated inflow distribution ratio of0.35:0.35:0.3could fully take advantage of capacity of nutrient removal in former zones which compared with other three step feeding ratios. The step feeding ratio of0.35:0.35:0.3could contribute to reduction of nutrient along the zones and reduce removal load in follow-up zones. Data in ORP from anoxic2to oxic3(Run3), the ORP value kept in wide range was proved enough COD to ensure reduction in amount of nutrient removal along the zones gradually and contributed to optimizing phosphorus and nitrogen removal due to less pollutant accumulation.