| 摘要: | 本研究建構一好氧沈浸式薄膜生物反應槽SMBR(Submerged Membrane Bioreactor，簡稱SMBR)反應槽，處理石化業ABS樹脂製程廢水，固定污泥停留時間(Sludge retention time，簡稱SRT) 30天，改變水力停留時間(Hydraulic retention time，簡稱HRT)12、18、24、30小時，探討各項水質參數之去除效果，建立各水質參數氣滌影響之逸散模式並推估其逸散量，計算氮化物質量平衡及各水質參數之實際去除率，並針對系統微生物相進行觀察與探討。
實驗結果顯示，HRT之改變對MLSS濃度影響極大，HRT=18小時之生物濃度為最高，生物處理槽及薄膜槽之MLSS濃度各為26.3 g/L與30.9 g/L。HRT=30小時之生物濃度為最低，生物處理槽與薄膜槽MLSS濃度各為 7.4 g/L與6.3 g/L。四個HRT操作下之總去除率，BOD5皆可達90 %以上，以HRT=18小時之97.9 %為最高；COD除HRT=12小時之86.7 % 以外，其餘皆達92 % 以上，其中以HRT=24小時之95.6 %為最高；TOC之處理成效皆可達88 %以上，HRT=18小時高達93.7 %。濁度去除率，除了操作HRT=12小時外(去除率94.2%，濁度低於16NTU以下)，其餘之操作去除率皆達98.6%以上，出流水體濁度低於3 NTU，且無SS測出。SOUR (Specific oxygen uptake rate，簡稱SOUR)方面，生物處理槽最高達117-121 mg-O2/g.hr範圍間，薄膜槽則介於73-76 mg-O2/g.hr，相較於傳統活性污泥程序(30-70 mg-O2/g.hr)，好氧式SMBR系統有較高之SOUR。HRT=18、24小時之操作結果，生物處理槽之食微比介於0.23-0.26 kg BOD5 / kg MLVSS-day，為活性污泥之對數增值期；薄膜槽之食微比介於0.08-0.11 kg BOD5 / kg MLVSS-day，為活性污泥之遲滯期；系統總體積負荷方面，HRT=18小時之操作穩定平均值高達2.0 kg BOD5 / m3-day，為一般傳統活性污泥程序(0.3-0.6 kg BOD5 / m3-day )之3-6倍。
為了解曝氣作用對SMBR各項水質指標物種逸散之影響，本研究建立氣滌影響之逸散模式並推估其逸散量，經實驗並推估後，
生物處理槽之逸散模式為：
VOC@ b=(8.33ARb^1.095×0.736＋6.450)×(Xb/10)^－0.632×@×Vb×HRTb
式中BOD5 @為0.113×0.95^(Tb-28.5)，COD之@為0.423×0.95^(Tb-28.5) ，TOC之@為0.275×0.95^(Tb-28.5) 。
薄膜槽之逸散模式為：
VOC@ m=(16.70ARm^0.720×0.280＋34.450)×(Xm/15)^－0.228×@×Vm×HRTm
式中BOD5@為0.179×0.95^(Tm-28.5)，COD之@為0.157×0.98^(Tm-28.5)，TOC之@為0.151×1.0 5^(Tm-28.5)。
系統各HRT(HRT=12、18、24、30小時)之理論總逸散量，BOD5依序為232.5、323.4、449.4及858.7 mg/HRT；COD依序為355.6、497.7、923.1及1547.4 mg/HRT；TOC依序為285.4、400.4、613.8及1203.5 mg/HRT。
氮質量平衡方面，HRT=24小時之硝酸氮與生物生長用氮各佔系統總氮量35%及20%，有機氮佔系統總氮量7%。HRT=18小時下，隨有機氮化物之轉換，亞硝酸與硝酸顯著增升，硝酸氮與生物生長攝氮各佔系統總量41%及24%，未分解之有機氮低於1%，硝化作用進行明顯，而HRT=12小時下，系統硝化現象明顯被抑制。
經由系統質量平衡換算(總去除效果扣除理論總逸散量之影響)，求得整體之實際去除成效，BOD5以HRT=18小時之94.1%為最高。COD最高可達近91.5%。TOC則有近86.0%之去除效果。氣滌去除效果之影響方面，隨著系統HRT之增長顯著上升，過長之操作(HRT=24與30小時) ，易造成為物理性逸散現象之形成。
HRT=18、24小時之操作，微生物具多樣性，且有多種指標性微生物。系統微生物觀察方面，HRT=12小時之操作，系統負荷過大，造成蕈頂蟲(Arecella vulgaris)表面組織破壞受損，並且出現絲狀菌體(Beggiatoa alba)，活性污泥有逐漸澎化之跡象。
SMBR實驗過程中進行物理性與化學性清洗，清洗頻率與方式受MLSS濃度影響甚鉅，一般而言MLSS濃度低於6 g/L，只需物理性清洗，但濃度高於24 g/L以上，則需進行物理與化學性清洗，帷本研究薄膜單元套件連續操作達204天，只進行兩次化學性清洗。顯示適當操作模式可有效降低薄膜之阻塞問題。
由本研究結果得知，好氧性SMBR系統對於ABS樹脂廢水水質之改善，具有極佳之處理成效，可作為石化工業製程廢水回收再利用之替代方案。
An aerobic submerged membrane bioreactor (SMBR) is constructed for the treatment of ABS resin wastewater. Sludge retention time (SRT) of this system is set at 30 days and the influence of hydraulic retention time (HRT) , 12, 18, 24 and 30 hours respectively, is examined. This study aims to investigate the treatment performance of SMBR system, including the establishment of evaporation model caused by air stripping, evaluation of evaporated amount during SMBR operation, mass balance of nitrogen-containing compounds and the biotic efficiency. Finally, the microbial observation of SMBR system is also carried out in this study.
The results of this study shows that the effect of HRT on MLSS concentration is significantly. The highest value of MLSS concentration, 26.3 g/L for biological treatment tank and 30.9 g/L for membrane tank, is found when HRT is 18 hours. At the condition of 30 hours, the lowest MLSS concentration, 7.4 g/L for biological treatment tank and 6.3 g/L for membrane tank, is obtained. The removal efficiency of BOD5 for each HRT is above 90% and the highest value of 97.9% is obtained with a HRT of 18 hours. All COD removals are above 92% except the HRT of 12 hours (86.7%). The removals of TOC are above 88% and with the highest value of 93.7% (HRT=18 hours). Turbidity removals were above 98.6% and no SS was detected in the effluent. As for SOUR, a range of 117 to 121 mg-O2/g•hr is found in biological treatment tank and 73~76 mg-O2/g•hr in membrane tank. The F/M ratio of biological treatment tank and membrane tank is with a range of 0.23 to 0.26 and 0.08 to 0.11 kg-BOD5/kg-MLVSS-day. The volumetric loading of this system can be as high as 2.0 kg BOD5/m3-day. This value is 3~6 times higher than the value of traditional AS treatment system.
The evaporation model for pollutants of biological treatment tank is
VOC@ b=(8.33ARb^1.095×0.736＋6.450)×(Xb/10)^－0.632×@×Vb×HRTb
For membrane tank, the general equation is
VOC@ m=(16.70ARm^0.720×0.280＋34.450)×(Xm/15)^－0.228×@×Vm×HRTm
According to the results of evaporation calculation, the biotic removal efficiency of SMBR system at different HRT conditions can be obtained in this study. As for the condition of 18 hours, the biotic efficiency of BOD5, TOC and COD is 94.1%, 86.0% and 91.5% respectively.
For mass balance of nitrogen, the results show that nitrification is significant in SMBR system with the HRT of 18 and 24 hours. About 99% Org-N is converted and the dominant nitrogen species in SMBR system is nitrate. However, the nitrification is significantly inhibited with the HRT of 12 hours
The microbial observation of SMBR system revealed that short HRT (12 hours) operating causes damage on the surface of Arcella vulgaris. Beggiatoa alba is found and bulking occurred under this condition. However, high microbial diversity is observed under long HRT operating.
When MLSS concentration is lower than 6 g/L, only water cleaning was operated. When MLSS concentration was operating up to 24 g/L, water cleaning is not as well as chemical cleaning. However, within 204 days operation, only two times of chemical cleaning was performed to remove the floc from hollow fiber membrane in this study. |
