Studies On Optimization And Functional Enhancement Of Nitrogen And Phosphorus Removal By Ferric Enzymatic Activated Sludge

The situation of water pollution and eutrophication in our country are increasingly serious in recent years. High content of nitrogen and phosphorus nutrient substances in water body is the root cause of eutrophication. Therefore, the state developed a more stringent sewage discharge standard. But the traditional simultaneous nitrogen and phosphorus removal technology has many problems in nitrification at low temperature, changes of workload and coping with carbon source contradictions. As a new wastewater treatment process, ferric enzymatic activated sludge has advantages as higher density structure, better precipitation performance, and the process has a better effect of nitrification at low temperature, higher MLSS, stronger adaptability to shock loading conditions compare with the conventional activated sludge system. It is an efficient BNR technology which meets the reality of municipal wastewater treatment in our country.Based On the pre-existing research results, in this study, urban sewage as the research object, contrasted by conventional activated sludge, studied the functional enhancement of trace elements on activated sludge,system startup of ferric enzymatic activated sludge at low temperatures , process performances in different workload and different conditions at room temperature.The research results showed that:(1) Fe3+ has a promoting effect on pollutant removal ability in activated sludge system, and 10mg/L-20mg/L is a more economical and effective concentration range. SOUR activity of the system improved greatly compared with the comparison one .The enhanced effects of Co2+ and Ni2+ on nitrogen and phosphorus removal was not obvious, the system activity will be inhibited in case of the CoCl2 and NiCl2 concentration higher than 0.2mg/L. (2) The MLSS of ferric enzymatic activated sludge system was higher compared with ordinary activated sludge system at low temperatures So, the ferric enzymatic activated sludge system startup faster. MLVSS/MLSS, TTC-DHA, NH3-N nitrification rate and phosphate uptake rate of ferric enzymatic activated sludge system were higher than the ordinary activated sludge system. Microbial activity of ferric enzymatic activated sludge system was higher than ordinary activated sludge system at low temperature.(3) Compared with the conventional activated sludge TTC-DHA of ferric enzymatic activated sludge was increased by 28.85% and the average removal efficiency of CODCr, NH3-N, PO₄^3--P were better at the low and medium loads. Ferric enzymatic activated sludge system can also achieve good treatment results under the long sludge age.(4) Reflux ratio 200% of ferric enzymatic activated sludge system was more economic and reasonable under the long sludge age and medium load conditions. The activity of ferric enzymatic activated sludge was relatively higher. The poisoning effect can be reduced under the high ammonia load condition, and the organic pollutants removal efficiency had been promoted. Thereby the system stability and adaptability was improved. (5) Fe(OH)₃ maked a smaller impact of system than ferric citrate in the ferric enzymatic activated sludge culture, and it also shows a higher pollutant removal capabilities. Ferric citrate as supplementary iron source at a lower dosage (3%) can achieve a higher TTC-DHA activity; take a positive role to efficient and stable operation of ferric enzymatic activated sludge system.