Enhancing Denitrification and Total Nitrogen Removal in Aeration Basin Retrofitted with Entrapped Biomass

氮化物是造成水體優養化的主要因子，亦是推動水再生資源化利用的關鍵水質，過去並未嚴格管制，以致既有廢污水處理廠多未具備除氮能力，除非特別加設無氧/厭氧/好氧(Anoxic/Anaerobic/Oxic, A2O)設施或厭氧脫硝設備。隨著廢污水再生利用已成為國際上因應氣候變遷對水資源衝擊之調適策略，提昇廢污水處理廠之氮化物處理效能已是環境保育及水再生利用之關鍵課題。 本研究目的在改善傳統活性污泥槽之除氮功能，利用包埋生物技術製備固定式包埋生物污泥板(Entrapped Biomass Plate, EBP)，由於溶氧之質傳限制，能於單一槽體空間內製造A2O微體空間，同時達到硝化(Nitrification)與脫硝作用(Denitrification)，增進總氮(Total Nitrogen, TN)之去除效能，可提高水再生資源化之可行性。 研究方法透過假說(Hypothesis)設定，進行實驗設計與驗證，採實廠生活污水與工業園區廢水進行連續流攪拌反應試驗，探求各影響變因對硝化與脫硝反應之效應，如水力停留時間(Hydraulic Retention Time, HRT)、填充率(Packing Ratio, PR)、曝氣模式、添加鹼度(Alkalinity, ALK)、電子供應者(Electron Donor, ED)等，從實際污水試驗中優化控制變數，進而改善脫硝除氮效能。 研究結果顯示，EBP在HRT為6小時下即能有效處理實際生活污水之氮化物，在進流水NH3-N濃度21~30 mg/L，包埋生物量約7500 mg/L時 (PR=31%)，添加ALK與ED，放流水NH3-N濃度可降至1 mg/L以下，硝化率達98%，脫硝除氮率達58%，氮處理負荷量(NRC)可達 56 g TN/m3•d，EBP氮負荷(EWL)為8.7 g TN/kg•d。在HRT 12小時下硝化率達98%，脫硝除氮率達64%，SCOD亦有80%以上之去除率。驗證EBP能在單一槽體內同時進行除碳、硝化與脫硝反應。 而將EBP與傳統活性污泥程序(Activated Sludge Process, ASP)結合操作時，在HRT 12小時、添加ALK與ED、NH3-N進流濃度21~54 mg/L下之硝化率達99%，脫硝除氮率達70%，氨氮放流濃度介於N.D ~3 mg/L，總氮濃度介於7~15 mg/L。在HRT 6小時之硝化率達98%，脫硝除氮率達63%。平均氮處理負荷量(NRC)可達 68 g TN/m3•d，EBP氮負荷(EWL)為17.4 g TN/kg•d，具更佳的除氮效果。 以EBP結合ASP處理工業低碳氮比廢水以延伸除氮效用之驗證，生物包埋技術仍具良好的適用性。在HRT為12小時、PR為30% (等效MLSS為15000 mg/L)、添加ALK與ED下，硝化率達88%，脫硝率達58%，NH3-N濃度可從98 mg/L處理至27 mg/L。當延長HRT為18小時後硝化率可達99%，脫硝率可達63%，NH3-N濃度約從80 mg/L處理至2 mg/L。此結合處理程序可促使活性污泥槽成為AO或A2O環境。 本研究顯示包埋生物處理技術能將傳統好氧環境改造為AO或A2O系統，有效促進生活污水與工業廢水之硝化與脫硝反應，在不需擴增既有硬體空間與操作之限制條件下，能於既有槽體空間內改善除氮效能。在好氧環境中EBP載體表層進行好氧硝化反應，內層因氧氣傳輸受限而進行無氧/厭氧之脫硝反應，系統同時進行生物硝化與脫硝除氮作用，溶氧是影響硝化、脫硝反應與除氮效能之最主要關鍵因子。而當ASP結合EBP處理廢污水時，ASP進行好氧硝化作用與除碳作用，同時消耗溶氧，當系統溶氧濃度降低，可促進EBP生物載體創造更多無氧/厭氧環境，兩者之協力作用提昇了系統之脫硝除氮效能。Nitrogen is not only the main factor of causing eutrophication in water body, but also the crucial water quality of carrying out reclaimed wastewater. It has not been restricted stringently on total nitrogen (TN) effluent standards in the past so that most conventional municipal wastewater treatment plants (WWTP) provide little TN removal unless the treatment system is upgraded to an anaerobic/anoxic/oxic (A2O) or an anaerobic denitrification unit is placed after the secondary clarifier. Increasing wastewater reuse to adapt capacity for water resources under climate change imperatively calls for an upgraded capacity of WWTP to remove TN, which would preserve environment and promote treated water more amenable to beneficial uses. This study employed entrapped biomass technology to augment a traditional aerobic activated sludge process with AO/A2O function for removal of TN. The entrapped biomass plates (EBP) were fabricated in the format of carrier plates on which microbial cells were entrapped. Due to mass transport limitations, anoxic and anaerobic conditions were created within the bioplates where denitrification could proceed. The study method was by way of devising experiments from 10 research hypotheses to verify their effects. The authentic domestic wastewater and industrial wastewater were collected to test in a continuous-flow stirred tank reactor. Factors influencing nitrification and denitrification such as the bioplate packing ratio (PR), hydraulic retention time (HRT), alkalinity (ALK; with Na2CO3), electron donor (with CH3OH), and aeration mode were investigated. With a reactor installed entrapped biomass (equivalent to as high as 7500 mg/L of biomass) to treat for an influent domestic wastewater containing 21-30 mg/L of NH3-N, the results showed 98% of ammonia nitrogen being converted to nitrate and 58% of TN removal at HRT of 6 h, and the effluent concentration of NH3-N was under 1 mg/L. EBP has exhibited its’ good performance on TN removal. The nitrogen removal capacity (NRC) was 56 g TN/m3•d and EBP weight loading (EWL) was 8.7 g TN/kg•d. The other further result was 98% of ammonia nitrogen would be converted to nitrate, 64% of TN removal, and 80% of SCOD removal at HRT of 12 h. It revealed organic carbon removal, nitrification and denitrification were concurrent in a single pass. When EBP coupled with the activated sludge process (ASP) for TN removal, nitrification efficiency exceeded 99% and TN removal of 70% was achieved for an influent domestic wastewater containing 21-54 mg/L of NH3-N at HRT of 12 h, and the effluent concentration of NH3-N was N.D.-3 mg/L, the effluent concentration of TN was 7-15 mg/L. The other result was 98% of ammonia nitrogen would be converted to nitrate, and 63% of TN removal at another HRT of 6 h. The NRC was 68 g TN/m3•d and EWL was 17.4 g TN/kg•d. The performance of TN removal was much better. While expanding ASP coupled with EBP for TN removal from industrial wastewater containing low carbon-nitrogen ratio, entrapped biomass technology could still display good applications. The coupled system enabled over 88% of nitrification and promoted denitrification that led to 58% removal of TN at HRT of 12 h with 15000 mg/L of entrapped biomass as well as MLSS 1500-2400 mg/L, and the concentration of NH3-N would descend from 98 mg/L to 27 mg/L. The coupled process readily upgraded an activated sludge aeration basin to an AO or A2O reactor. The study has demonstrated that entrapped biomass technology creates anoxic/anaerobic zones that are capable of carrying out denitrification, requiring no substantial modifications of the vessel as well as operation, and thus providing improved treatment in terms of nitrogen removal in conventional suspended-growth process. In aeration basin, nitrification can be proceeded in the outer part of the EBP. The intra space of the bioplate becomes anaerobic environment where denitrification process occurs due to mass transport limit. DO is the critical factor affecting the performance of nitrification and denitrification. When ASP coupled with EBP, ASP carried out nitrification, organic carbon removal, and depleted DO in the system, where enabled EBP creating more anoxic/anaerobic environments in the intra space that augmented coupled nitrification/denitrification processes to occur. Their synergy empowered conventional aeration basin for TN removal.口試委員會審定書 I 誌謝 II 中文摘要 III Abstract V 目錄 VII 圖目錄 X 表目錄 XII 第一章 前 言 1 1.1 研究緣起 1 1.2 研究目的 2 1.3 研究內容 4 第二章 文獻回顧 5 2.1 水體中氮化物之質量變異特性 5 2.2 水體中氮化物造成之影響 7 2.3 各國對水體氮化物之管制現況 11 2.4 生物除氮技術理論 19 2.4.1硝化作用之生化反應機制 20 2.4.2影響硝化作用之變因 28 2.4.3脫硝作用之生化反應機制 32 2.4.4影響脫硝反應之變因 35 2.4.5其他除氮路徑理論 39 2.5 生物除氮技術之發展與應用 41 2.5.1傳統硝化脫硝二段式除氮技術 41 2.5.2以部分硝化(Partial Nitrification)為途徑之除氮技術應用 47 2.5.3固定生物除氮技術 49 2.6 生物包埋技術理論 58 2.6.1生物包埋技術除氮原理 58 2.6.2生物包埋技術之發展 60 2.7 生物除氮技術相關反應動力 65 2.7.1基質與溶氧質量傳輸動力 65 2.7.2硝化/脫硝生化反應動力 68 第三章 研究架構與實驗方法 71 3.1 研究構想 71 3.1.1問題與假說(Hypothesis) 74 3.1.2實驗架構與流程 80 3.2 實驗設備之設計、建置與操作系統 82 3.2.1反應槽系統 82 3.2.2包埋生物污泥板(EBP)製備 87 3.3 包埋微生物馴養與穩定試驗 90 3.3.1基質馴養穩定試驗 90 3.3.2試驗水樣穩定試驗 91 3.4 試驗操作模式與控制變數設計 91 3.4.1處理都市生活污水之試驗控制變數 92 3.4.2處理工業綜合廢水之試驗控制變數 95 3.5 檢驗分析方法 96 3.5.1水質檢驗方法 96 3.5.2數據分析處理方法 99 第四章 結果與討論 105 4.1 廢污水處理廠背景資料與採樣分析 105 4.2 EBP的硝化脫硝反應效能 109 4.2.1 EBP的硝化反應效能 109 4.2.2 EBP的脫硝反應與除氮效能驗證 111 4.3 系統空間之質量傳輸效應 114 4.3.1 EBP載體間生物濃度(PR)效應 114 4.3.2 EBP載體內部溶氧傳輸效應 117 4.4 EBP外部環境添加效應 124 4.4.1鹼度(Alkalinity) 124 4.4.2電子供給者(Electron Donor) 127 4.5 系統操作反應的時間參數效應 128 4.5.1反應系統HRT參數 128 4.5.2 EBP的SRT參數 131 4.6 EBP結合ASP處理生活污水之協力效應(Synergy) 132 4.7 EBP處理工業廢水之效能 137 4.7.1 EBP的硝化脫硝反應效能 138 4.7.2 EBP結合ASP之協力效應 139 4.7.3 EBP的啟動時效與穩定性 141 4.8 總氮處理負荷綜合評析 143 4.8.1 處理生活污水之總氮負荷率探討 143 4.8.2 延伸應用於工業廢水處理之總氮負荷率探討 146 第五章 結論與建議 149 5.1 結論 149 5.2 建議 152 參考文獻 155 附錄 17