當過量的含氮污染物排放至環境時，會使承受水體氮負荷過高進而發生優養化現象，同時造成人體健康危害。隨著公共污水處理廠操作技術成熟及社會環保意識逐漸抬頭，放流水管制水質項目從原先傳統有機污染物到諸如氨氮及總氮等其他營養物質有更加嚴格要求。由於氨氮與總氮污染特性及水量之因素，於公共污水處理技術上仍是以利用生物處理程序為主，並仰賴加大曝氣量、額外碳源之添加及加大硝化液迴流方式以達到放流水水質標準，形成對於資源及能源之浪費，為目前仍待解決之重要課題。
由於營建署「公共污水處理廠設計與解說」中MLE程序設計參數於我國本土水質使用上其適用範圍有待確認，故本研究選定MLE程序以桃園北區水資源中心實廠生活污水進行模型廠試驗，探討其設計參數之合理性及彈性操作空間，同時比較在不同硝化液迴流比條件下其脫硝效果，建立適合本土水質特性之MLE程序最佳操作數據。
研究結果顯示，當生物系統有機負荷F/MBOD = 0.3 kg BOD/kg MLSS‧day條件下，相較於其他階段其各項水質去除率有明顯下降趨勢，不利於實廠上的應用。比較ASRT為15天及20天之操作成果，發現ASRT 20天呈現較佳的總氮去除率，且分析ASRT vs. MLSS操作參數關聯性，當ASRT提升至20天，操作範圍與其他操作參數可以有更加的交互關聯性，建議污水處理廠設計與解說MLE程序ASRT設計值由11~15天調整為11~20天，符合實廠操作層面之彈性。
在硝化液迴流比對於氮污染物去除率影響可知，在操作條件皆相同下，R = 2時系統可達最高的總氮去除率達74%，與理論最大總氮去除率相當，出流水濃度低於10 mg/L足以滿足未來新設公共污水廠總氮排放標準；當R = 1時出流水總氮濃度約為20.2 mg/L，達到未來既設公共污水廠總氮排放標準；當R = 0.5時發現其氨氮硝化效果降低為70%，進而總氮去除率與其它操作條件相比為最低，建議硝化液迴流比應操作在1以上以確保氨氮能有效進行硝化反應。

When excessive nitrogen-containing pollutants are discharged into the environment, it may increase the nitrogen loading of the receiving water body, but also cause eutrophication, and affect human health hazards at the same time. In addition, the government attaches great importance to environmental protection regulations and the maturity of the operation technology of public sewage treatment plants. The discharge water quality control requirements from the original traditional organic pollutants to other nutrients such as ammonia nitrogen and total nitrogen.
Due to the characteristics of ammonia nitrogen and total nitrogen pollution factors, biological treatment procedures are the most common strategy in the public sewage treatment technology. It relies on increasing the amount of aeration, adding additional carbon sources and increasing the return of nitrifying liquid to achieve The water quality standard of the effluent causes a waste of resources and energy, which is an important issue that still needs to be resolved.

According to Construction and Planning Agency Ministry of the Interior "Design and Interpretation of Public Sewage Treatment Plants". The scope of MLE process design parameters that suitable for domestic water quality in Taiwan still need to be comfirm.MLE process was selected in this study to by conducting a model plant test using the domestic sewage of the Taoyuan North District Water Resources Center. , explore the rationality and elastic space of its design parameters, and compare the denitrification effects under different inrenal ratios of nitrification liquid, and establish the best operating data of the MLE program suitable for local water quality characteristics.

In Stage 1, when the biological system operating in F/MBOD = 0.3 kg BOD/kg MLSS‧day compared with other stages, the removal rate of each water quality has a clear downward trend, so it is not conducive to the actual plant Applications. When the ASRT is 15 days and 20 days and other planning operating conditions are the same, it is found that ASRT = 20 days presents a better total nitrogen removal rate, but also shown more interactively correlated with other operating parameters in the ASRT vs. MLSS operating parameter correlation analysis diagram. It is recommended that the ASRT design value of the MLE program for the design and interpretation of sewage treatment plants should be relaxed from 11~15 days to 11~20 days.

The influence of the reflux ratio of the nitrifying liquid on the removal rate of nitrogen pollutants can be shown when R = 2 the system can achieve the highest total nitrogen removal rate of 74%, which is equal to the theoretical maximum total nitrogen removal rate. The concentration is sufficient to meet the total nitrogen discharge standard of the new public sewage plant in the future ; when R = 1, the total nitrogen concentration of the effluent is about 20.2 mg/L, which meets the total nitrogen discharge standard of the existing public sewage plant in the future; when R = 0.5, the ammonia nitrogen nitrification is found The effect is reduced to 70% and the total nitrogen removal rate is the lowest compared with other stages within the recommended operating range of more than 90%. It is recommended that the reflux ratio of the nitrifying liquid should be operated above 1 to ensure that the ammonia nitrogen can effectively carry out the nitrification reaction.

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