| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系碩士班 === 92 === 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.
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