|摘要: ||本研究建構一實驗室級好氧薄膜生物反應槽(Membrane bioreactor，簡稱MBR)，探討處理低碳氮比進流水(化糞池出流水)之成效。
本研究探討各項水質參數之去除成效，實驗項目有：pH、溶氧(Dissolved oxygen，DO)、溫度、混合液懸浮固體物(Mixed liquid suspended solid，MLSS)、混合液揮發性懸浮固體物(Mixed liquid volatile suspended solid、MLVSS)、生化需氧量(Biochemical oxygen demand，BOD)、化學需氧量(Chemical oxygen demand，COD)、總有機碳(Total organic carbon，TOC)、比攝氧率(Specific oxygen uptake rate，SOUR)、污泥密度指標(Sludge density index，SDI)、總溶解固體物(Total dissolved solids，TDS)、胞外聚合物(extracellular polymeric substances，EPS)、總凱氏氮、氨氮、有機氮、亞硝酸鹽氮、硝酸鹽氮、鹼度、色度、濁度、過膜壓力與流通量。
研究期間為267天，共分為5個實驗階段進行，在固定操作參數方面，反應槽有效體積為12L，本系統固定水力停留時間(Hydraulic retention time，HRT)為6.48小時，薄膜抽停之模式，均以抽取5分鐘/停止1分鐘循環進行之；研究之變數主要包括NaHCO3添加濃度變化（0、250、500 mg/L）與不同之污泥停留時間(Sludge retention time，SRT)（不排泥操作、SRT=10天、SRT=20天）。
研究結果得知，反應槽中MLSS濃度以第3階段之9750 mg/L為最高，最低為第1階段之1953 mg/L，各階段平均MLSS濃度分別為3327 mg/L，5150 mg/L，9013 mg/L，6615 mg/L與4828 mg/L。比攝氧率(SOUR)方面，以第五階段(NaHCO3 500ppm，SRT 20天) SOUR值53 mg-O2/g-MLVSS-hr為最高。
出流水濁度、TDS與SDI方面，濁度去除率達99.3%，出流水濁度低於1.8 UTN以下，且無SS測出；出流TDS之濃度以第三階段1069 mg/L為最高；出流SDI值介於4〜6之間。
In this study the performances of a laboratory scale membrane bioreactor (MBR) was examined for the aerobic treatment of low carbon-nitrogen ratio wastewater (septic tank effluent) for 267 days.
The indicators employed for examining the performances of the system were as follows: pH, dissolved oxygen (DO), temperature, mixed liquid suspended solid (MLSS), mixed liquid volatile suspended solid (MLVSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), specific oxygen uptake rate (SOUR), sludge density index (SDI), total dissolved solids (TDS), extracellular polymeric substances (EPS), total Kjeldahl nitrogen (TKN), NH4+-N, Org-N, NO2- -N, NO3- -N, alkalinity, true color (ADMI), turbidity, trans-membrane pressure (TMP) and flux.
A long-term operation of 267 days was divided into 5 stages according to changes in the levels of alkalinity and sludge retention time (SRT). The reactor was with a working volume of 12 L. In continuous operation the suction pump was stopped for 1 minute to allow membrane relaxation after each 5 minutes of filtration to give an average hydraulic retention time (HRT) of 6.48 hours. The duration of each stage was 73, 64, 34, 33 and 45 days respectively. No sludge was withdrawn during the stage 1, 2 and 3 operations. The SRT of stage 4 and stage 5 was 10 and 20 days respectively. 250 mg/L of NaHCO3 was added for stage 2 and 500 mg/L for stages 3, 4 and 5.
The results showed that the highest MLSS concentration of 9750 mg/L was found at stage 1 and the lowest MLSS concentration of 1953 mg/L was observed at stage X. The average concentration of MLSS of each stage was3327 mg/L，5150 mg/L，9013 mg/L，6615 mg/L and 4828 mg/L, respectively. As for SOUR, the highest value of 53 mg-O2/g-MLVSS-hr was obtained at stage 5 ( 500 mg NaHCO3/L addition and the SRT of 20 days).
Generally, the highest removal efficiency of TCOD (total COD), SCOD (soluble COD) TOC and BOD5 was 96%, 89%, 89% and 92%, respectively.
The highest conversation of ammonia-nitrogen was found at stage 5. NO2- -N was non-detected in the influent at stage 5 and the percentages of NH4+-N, Org-N and NO3- -N was 85.9%、13.3% and 0.7%, respectively. The results indicated that the nitrification was completely and the percentages of NH4+-N, Org-N and NO3- -N in effluent was 4.7%、4.3% and 88.5%, respectively.
Regarding the effluent turbidity, all the turbidity levels in the effluent were lower than 1.8 NTU and all the removal efficiencies were higher than 99% during the operation period. The highest TDS with a concentration of 1069 mg/L was found at stage 3. The values of effluent SDI varied from 4 to 6.
The results also revealed that the alkalinity supplement and SRT control would influence the COD removal and nitrification significantly.
This study showed that the treatment of septic tank effluent using a laboratory scale aerobic membrane bioreactor was feasible and effective. The results obtained from this study could be applied to the field works and considered as an alternative of household treatment unit for the advance purification of septic tank effluent.