| 摘要: | 本研究建立一套薄膜生物反應器(Membrane bioreactor, MBR)，以人工合成廢水為基質，比較不同污泥停留時間(sludge retention time, SRT) 10、20及40天，與不同進流COD濃度300、600及900 mg/L條件下，對MBR槽中水與出流水之水質處理成效、溶解性微生物產物(soluble microbial products, SMP)的生成與特性影響。
研究結果顯示，MBR對COD處理成效於SRT 20天最好，進流COD濃度於600 mg/L去除效果最差；SMP中的蛋白質及碳水化合物含量與蛋白質及碳水化合物比值(P/C)顯示，槽中生物質的利用以蛋白質為主，產生之SMP以碳水化合物為主，且碳水化合物較蛋白質易被薄膜阻擋而累積於槽中；由SCODSMP、DOCSMP佔SCOD及DOC的比例顯示在出流水中皆大於90%，表示DOC與SCOD的主要來源為SMP，此外，由槽中水至出流水SCODSMP、DOCSMP數值增加，表示其SMP屬於易通過薄膜的小分子，將其視為與基質代謝和微生物生長相關的SMP物質（Utilization-Associated Products, UAP）；於EEM分析的SMP結果則是出流水小於槽中水，表示薄膜過濾槽中屬大分子之SMP物質，將其視為較大且難分解物質，屬與微生物衰減相關，直接由菌體產生的附帶細胞產物（Biomass-Associated Products, BAP）。
於SRT變化的結果發現，MBR槽中的水質處理成效隨SRT的增加有較好的效果，UV254、SCODSMP、DOCSMP、SCODSMP/SCOD及DOCSMP/DOC則隨SRT的增加有先增後減的趨勢，表示當SRT增加時，槽中因生物質的增長，對基質的分解利用率提升，釋出的雙鍵物質與SMP物質皆增加，當SRT達40天時，因過量的生物質增長，使槽中生物質碳源不足，因此使槽中部分生物質以容易分解之SMP為碳來源，使其濃度又有下降的趨勢；隨SRT的增加，槽中生物質對蛋白質的利用與碳水化合物的產率皆增加，因此使得蛋白質與碳水化合物的比值(P/C)隨之減少；分子量分佈情形則顯示SMP以UAP為主，且隨SRT增加，UAP及BAP的分子量分佈皆略為增加；於EEM分析可知，槽中水類SMP物質濃度隨SRT而增加，因槽中過量生物質的生長，逐漸有老化、死亡現象，使其類SMP濃度增加，且SMP物質種類於出流水中也隨之增加。
於進流COD濃度為300、600及900 mg/L變化下，MBR槽中與出流水的水質處理成效先降後升，且在基質充足的條件下，槽中生物質的增加，生長代謝的作用加劇，使SCODSMP、DOCSMP有增加的情形；蛋白質的利用則是於進流COD濃度為600 mg/L時達上限，使得蛋白質的變化於進流COD濃度為300、600 mg/L時，無明顯變化，且逐漸分解部分的碳水化合物，使其值於進流COD濃度為900 mg/L時有下降的現象；於分子量分佈的情形顯示，SMP以UAP物質為主，當進流COD濃度達900 mg/L時，SMP中BAP與UAP所佔的比例相當，且隨進流COD濃度增加，UAP及BAP的分子量分佈範圍也皆略為增加；於EEM分析可知，槽中水類SMP物質濃度，因槽中生物質生長迅速，且在基質充足的情況下，生物質釋出的SMP物質隨之增加，且因過量的進流COD濃度，使得槽中亦有老化、死亡的生物質累積，因此槽中水SMP濃度隨進流COD濃度增加而增加。關鍵字：薄膜生物反應器、溶解性微生物產物、SRT、進流COD濃度
The objectives of this study were to investigate the treatment efficiency of synthetic wastewater by membrane bioreactor (MBR) and to elucidate the characteristics of soluble microbial products (SMP) at different operation parameters, including sludge retention time (SRT) 10, 20 and 40 days and influent COD concentration 300, 600 and 900 mg/L.
The results showed that the optimum treatment efficiency was occurred at operation parameter SRT 20 days. On the characteristic effect of SMP, the major component of SMP was carbohydrate and the most utilization substrate for biomass in the MBR was protein, however, the carbohydrate was easily to block the membrane filtration than the protein resulting to the concentration accumulated in the tank of MBR. Owing to the ratio of SCODSMP/SCOD and DOCSMP/DOC in the effluent grater than 90%, that is, the main contains of SCOD and DOC is SMP in the effluent. Furthermore, the concentration of SCODSMP and DOCSMP were increased from the MBR to the effluent showed that the small molecular of SMP, which belonged to UAP (Utilization-Associated Products), was easily to pass through the membrane. On the analysis of EEM, the intensity of EEM spectra of the effluent was smaller than in the tank revealed that larger molecular of SMP, which belonged to BAP (Biomass-Associated Products), was blocked by this membrane.
The treatment efficiency of UV254, SCODSMP, DOCSMP, SCODSMP/SCOD and DOCSMP/DOC was increased with the increase of SRT. This phenomenon revealed that the substrate utilization is increased with the growth of biomass resulting in improve the release of the double bond material and SMP. Because of the excessive biomass growth and the carbon source was insufficient, therefore, SMP was utilized as the food for biomass so that the concentration of SMP was dropt down at SRT 40 days. Nevertheless, the utilization of protein and the generation of carbohydrate were improved so that the ratio of protein to carbohydrate (P/C) was decrease. On the molecular weight distribution, the range of molecular weight distribution of UAP and BAP had a slight increase when the SRT increased. In addition, the concentration of SMP-like analyzed by EEM spectrum in MBR was increased with the increase of SRT due to the decay of the excessive biomass as well as the compositions of SMP was raised in the effluent.
The treatment efficiency was initially increased and then decreased corresponding to the variation of influent COD concentration 300, 600 and 900 mg/L. Simultaneously, the concentration of SCODSMP and DOCSMP also increased when the substrate was sufficient for the metabolism of biomass in MBR. On the molecular weight distribution, the major component of SMP was UAP, however, the concentration of BAP and UAP was similar at influent COD concentration 900 mg/L. Furthermore, the range of molecular weight distribution of BAP and UAP had broadened with the increase of the influent COD concentration. Finally, the concentration of SMP-like analyzed by EEM spectra in MBR was increased with the increase of influent COD concentration due to the substrate was sufficient for the metabolism of biomass in MBR.Keyword: membrane bioreactor (MBR), soluble microbial products (SMP), sludge retention time (SRT), influent COD concentration |
