Experimental Research Of Improved A2/O Sewage Treatment Process

Nitrogen and phosphorus in sewage are two important elements which causingwater pollution. They are both nutrient elements of water ecosystems nutrients,nitrogen and phosphorus are the nutrient limiting but essential for plant growth. Withthe development of social economy, the rise of the population, the increasing amountof nitrogen fertilizer, phosphate fertilizer using in agricultural production, theincreasing quantity of detergent using in living and parts of the city sewage treatmentdischarging fail to reach the standards, the number of phosphorus, nitrogen, etc. innatural water also rises and the ratio of nutrients imbalance. Once eutrophication inwater body, governance is quite difficult, eutrophication becomes a current urgentwater environment problem. Therefore, it is very important to develop a highlyefficient treatment process of nitrogen and phosphorus removal in sewage.Currently sewage treatments at home and abroad are based on activated sludgeprocess, from the principle analysis of microbial nitrogen and phosphorus removalshould include three stages: anaerobic, anoxic and aerobic. In initial activated sludgetreatment process, nitrogen removal and phosphorus removal are not simultaneous, inthe1960s, denitrification process was first put forward by Ettinger and Luclzack, inthe1970s, Barnard developed the initial A2/O process on its basis, with thecontinuous perfection and improvement， technology of biological nitrogen andphosphorus removal develop rapidly, such as UCT process, improved UCT process,new oxidation ditch technology, etc..The significance of this experiment is to develop a new sewage treatment processsystem which can improve the efficiency of sewage treatment effectively and open upa whole new direction for activated sludge process system. Compared with the oldactivated sludge process system, new system leads to the following advantages:simple operation, less investment, easy management, etc., and also provide anefficient, fast way to the factories which want to upgrade the old activated sludgeprocess system. It has a far-reaching significance of the new system, it not onlyprogresses the activated sludge process, but also transforms old systems. It has a wide market prospect and good social economy value.Through the development and the pilot test of improved A2/O treatment process,it has been better comprehended, and we got conclusions as follow:(1) In the aspect of TN removal, improved A2/O treatment process has distinctadvantages than traditional A2/O treatment process, efficiency of TN removal can beimproved by more than10%.(2) In the aspect of CODcr and NH3-N removal, removal rate of improved A2/Otreatment process is slightly better than the traditional A2/O treatment process, theadvantage is not obvious.(3) In the aspect of TP removal, since each reaction tank is fitted with mud tubesin improved A2/O treatment process, removal rate of improved A2/O treatmentprocess is better than the traditional A2/O treatment process, but in practicalengineering, cost of civil engineering and operating is more than traditional A2/Otreatment process.(4) Reflux ratio of sludge is too low， that will lead to anaerobic digestion insedimentation tank, product methane and carbon dioxide, and bubbles will drive thesludge floating, that will affect water quality, as a word, sludge reflux ratio should notbe too low.(5) By comparing test, when the sludge reflux ratio is100%, adjust the nitrifyingliquid reflux ratio to200%，300%, the output water quality of this system improvedunobvious, considered integrated operating costs and other factors, the optimumoperating parameters for the sewage reflux ratio is100%， the optimum operatingparameters for nitrifying liquid reflux ratio is200%.