Study On Optimization And Efficiency Of Denitrifition And Phosphorus Removal

Aiming at solving the lack of carbon resource in sewage wastewater with low C/N ratio, this research ran and operated strengthened anaerobic / anoxic / precipitation /contact oxidation pool of denitrifying phosphorus removal reactors as long as 210 days at room temperature. During the operation, the nutrient removal effects were discussed after increasing anaerobic hydraulic residence time. Then the hypoxia hydraulic retention time was optimized and the best removal efficiency was obtained. Finally,After maintaining longer anaerobic and anoxic hydraulic residence time, the performance of system was studied further. During the reactor operation time, the routine indexes, such as COD, ammonia, nitrite, nitrate, and phosphate were monitored.In order to analyze the system efficiency further, volatile fatty acids(VFA), non-VFA organic matter, the polymer(PHA and poly metaphosphate) within cell, extracellular polymeric substances(EPS) and cell morphology were monitored after increasing the anaerobic and anoxic hydraulic residence time both in this research.In the study of anaerobic hydraulic retention time, the removal efficiency of COD,nitrogen and phosphorus were investigated with hydraulic retention time increased by adjusting the volume and the following results were obtained. When hydraulic retention time increased from 2.5h to 4.5h, COD removal rate was increased from 79.84% to82.19%, and the effluent concentrations were 37.30mg/L and 32.41mg/L respectively.However, nitrification, transformation between ammonia nitrogen, nitrite and nitrate,total nitrogen removal didn’t changed much, and the orthophosphate removal rate increased by about 2.5% with anaerobic hydraulic residence time increased when the effluent concentrations were 0.59mg/L and 0.45mg/L, respectively.In order to optimize anoxic hydraulic retention time, nutrient removal of the system was monitored. The COD removal rate didn’t increased and the ammonia nitrogen removal rate remained at 93.50% after increasing anoxic hydraulic retention time(4.3h, 6.8h and 7.7h). However, the total nitrogen removal rate increased gradually(56.96%, 59.77%, 69.85%) and phosphate removal rate increased from 87.25% to89.95%.In the enhanced denitrification and phosphorus removal system, the anaerobic and anoxic residence time both increased and the following results were obtained. PHV content were 58.81mg/(g dry sludge) and 43.04mg/(g dry sludge) respectively and PHB content were 5.95mg/(g dry sludge) and 4.304mg/(g dry sludge) respectively in the anaerobic tank and anoxic tank. Polymetaphosphate content of anaerobic and anoxic sludge were 4.6mgP/gVSS and 11.02mgP/gVSS respectively. The protein and polysaccharide content in the extracellular polymeric substances of anaerobic sludgewere 95.78mg/gMLSS and 31.6mg/gMLSS respectively, and the protein and polysaccharide in anoxic sludge were 72.05mg/gMLSS 37.28mg/gMLSS respectively.