Because the watershed surrounding domestic sewage, industrial effluents, (由於流域周圍生活汙水、工業廢水排放，)agricultural runoff, and animal husbandry, fisheries, tourism, can cause the nitrogen, phosphorus and organic matter, nutrients numerous water bodies such as lakes, reservoirs),農業徑流以及畜牧、水產、旅遊的影響，可造成氮、磷、有機物等營養元素大量進入水體（如湖泊、水庫）， aquatic organisms in particular some characteristic algae, plankton exception propagation, decomposition of organic matter in water consumption of large amounts of dissolved oxygen, dissolved oxygen, biological barriers to anxious to death, a large number of organisms in the role of microbial oxidation releasing methane, and hydrogen sulfide, carbon dioxide, etc. make water quality deterioration in market, leading to eutrophication of water bodies, so that water ecosystems and water damage to and destruction is to speed up the waters of the aging process. 使水生生物特別是某些特征性藻類等浮遊生物異常繁殖，有機物的分解消耗水中大量的溶解氧，溶解氧的降低，生物窒急而死，大量的有機體在微生物的作用下分解氧化釋放出甲烷、硫化氫、二氧化碳等使水質變壞發臭，導致水體的富營養化，使水體生態系統與水體功能受到損去與破壞，加速水體老化過程。State-of-the-art pollution indicate organic pollution, eutrophication is the current Administration's major problem, although developed countries has been eliminates organic pollution, eutrophication persists, eutrophication is worldwide are facing a common problem.國內外的水汙染現狀都表明有機物汙染、富營養化是當前水汙染治理中存在的主要問題，發達國家雖然己經消除了有機物汙染，但富營養化依然存在，富營養化是世界範圍內所面臨的***同課題。
A large number of research results show: feed ao have carbon source utilization high, nitrogen efficiency, without internal circulation, MLSs high, running adjustable.大量研究成果顯示：分段進水AO工藝具有碳源利用率高、脫氮效率高、無需內循環、汙泥濃度高、運行調節靈活等優勢。 However, the actual running of the project in the Central Plains water temperature are constantly changing and processing from many uncertainties.但是，在工程實際運行中原水水質水溫不斷變化，處理效果受到諸多不穩定因素的影響 Therefore, the test looks at the long-run conditions, multilevel AO reactor handles the actual urban wastewater, various objective factors on reactor effects.因此，該試驗考察了在長期運行條件下，多級AO反應器處理實際城市汙水時，各種客觀因素對反應器脫氮效果的影響。
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