Use of Environmental Friendly Carrier in Immobilized Biological Process for Removing Carbon and Nitrogen from Wastewater

微生物固定化技術為一生物處理技術，其具有高碳、氮去除效率、污泥產量少及佔地面積小之優勢，廢棄污泥的產生與處理一直是傳統活性污泥法的主要問題，其污泥處理費用約佔總廢水處理操作成本的50~60%，因此若能將此技術應用於實廠，將能夠增加傳統污水處理之效率並減少用地及污泥處理支出。 目前微生物固定化技術常使用的載體主要分為兩類：天然載體，如海藻酸鈉(Alginate)、矽藻土(Diatomaceous)，其為天然製成，但缺點為易被生物分解；合成載體，如聚乙烯醇(Polyvinyl alcohol, PVA)、聚丙烯醯胺(Polyacrylamide, PAA)，其多為高分子化合物，價格昂貴且合成時需添加化學溶劑，其具生物有毒性且對環境較不友善，因此難以在實廠上大量製作及應用。 為符合永續發展之理念，本研究使用一由農業資源化材料製成之材料做為固定式生物細胞之載體。研究主要分為兩部分，載體材料基本特性分析及操作參數試驗，載體基本特性分析又分為抗壓強度試驗及溶出試驗，目的為了解固定式生物於水中之穩定性；操作參數試驗目的為，探討不同曝氣比、碳氮比(SCOD/N)及水力停留時間(HRT)對SCOD、硝化及總氮去除率之影響。 載體基本特性分析之結果顯示，此固化材料與污泥混合試體具有良好之抗壓強度，且其抗壓強度隨著試體浸泡於水中之時間而增強；初期污泥與固化材料試體有有機物(COD)、TDS溶出、高導電度及高pH之特性，然而隨著浸泡天數的增加，皆能達到降低試體COD、TDS、導電度及pH之效果。另外，體積測量結果顯示，25天內試體體積並無明顯削減現象。 操作參數實驗結果顯示，曝氣比及碳氮比對硝化及總氮去除率影響大，曝氣模式從1:1調整至1: 0.5時，硝化效率提升36%，總氮去除率提升28%；碳氮比由SCOD/N = 6調整至SCOD/N = 18時，硝化效率提升19%，總氮去除率提升31%；改變水力停留時間對去除效率影響不大，HRT = 12hr、9hr、6hr下，SCOD、硝化及總氮去除率皆可達80%以上。整體而言，在曝氣比1:0.5、SCOD/N = 18、HRT=12條件下有最佳之去除效率，SCOD去除率、硝化及脫硝效率分別為96%、98%及92%。Immobilization of microbial cells is an effective biological nitrogen removal technology that has many advantages over conventional activated sludge process including high organic carbon and nitrogen removal efficiency, low production of sludge, and small area of land use. The treatment and disposal of wasted sluge have remained as the primary challenge for conventional activated sludge process. The cost of disposing wasted sludge could amount to 50~60% of total operation cost. This research is believed to provide some insights on the potential of enhancing treatment efficiency, reducing land space requirement and minimizing wasted sludge disposal cost. There are currently two main categories of material for microbial cells immobilization: natural (alginate and diatomaceous) and synthetic (polyvinyl alcohol and polyacrylamide). The advantage of natural material is that they are naturally made but the drawback is they are decomposed by microorganisms easily. Most of the syntheticmaterials are macromolecular polymer which is proven to be more robust to withstand decomposition, but the drawbacks are that they are more expensive and not environmental friendly. For the purpose of sustainable development, we rely on an agriculture waste coagulant as the material for immobilization of microbial cells. This research is consisted of two parts: analysis of the material chraracteristic and the operating factors test. Analysis of the material chraracteristic consisted of compression test and solubility test for the purpose to realize the stability of the material. The operational aspect will focus on investigating nitrification, denitrification and total nitrogen removal efficiency under different operating conditions such as aeration mode, carbon to nitrogen ration (SCOD/N) and hydraulic retention time (HRT). The compression test showed that the immobilized cells can withstand high pressure and stress, and stress enhance as the time. The immobilized cells elute COD, TDS, and were detected with conductivity and high pH in the early stage. However, the concentration of COD, TDS and conductivity decreased with time. The integrity of the immobilized cells stay intact throughout the entire experimental period. The aeration mode appeared to impact significantly on the overall removal of nitrogen. Nitrficaion and TN removal efficiency were enhanced 36% and 28% respectivily when aereation ratio was adjusted from 1:1 to 1:0.5. Moreover, nitrficaion and TN removal efficiency were enhancedto 19% and 31% respectivily when SCOD/N was changed from 6 to 18. The variation of HRT did not demonstrtate noticeable effect on nitrification and total nitrogen removal efficiency: 80% of total nitrogen was removaed at HRTs of 12hr, 9hr, and 6hr. In conclusion, the optimum operating conditions is aeration ratio of 1:0.5, SCOD/N of 18, HRT of 12hr, which resulted in 96% SCOD removal efficiency, 98% nitrification, and 92% TN removal efficiency