| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 105 === Compared with aerobic biological processes, anaerobic biological treatment processes (ABTPs) have the advantage of low energy consumption, low waste sludge production, and can produce methane as biogas. However, from the perspective of the application of the actual sewage plant, how to avoid the loss of anaerobic microorganisms under short HRT becomes a significant point because of the slow-growing anaerobic microorganisms. Therefore, this study combined with an immobilization biotechnology of entrapped mixed microbial cell (EMMC) and ABTPs, so that anaerobic sludge in the form of fixed bio-plates in the reactor, can not only enhance biomass concentration, but also greatly improve the sludge residence time (SRT). This way makes the microorganisms not easily to wash out. Thus, the required hydraulic retention time can be shortened in order to overcome the restriction of ABTPs while treating low-strength domestic wastewater.
An anaerobic immobilized bio-plates reactor (AnIBPR) was used to treat low-strength synthetic and domestic wastewater at 25℃. The effective volume was 15.6 L, the sludge biomass was 42.4 g/L, and the influent COD concentration was 200 mg/L at a hydraulic retention time (HRT) of 6 and 8 hours. Then we discuss the COD removal rate, methane production rate, methane yield, methane recovery rate and dissolved methane as a performance evaluation project.
The results showed that there was no significant sludge loss in the AnIBPR reactor for more than one year. The synthetic and domestic wastewater could each reach 86% and 70% COD removal rate, and 56% and 28% methane content which can produce energy of 0.494 kWh/m3 and 0.128 kWh/m3. The energy also can be converted to the electricity energy of 0.163 kWh/m3 and 0.042 kWh/m3 or more. Considering the carbon source conversion, the synthetic wastewater have 13.8% went out with the outflow, 21.0% converted to gaseous methane, and 41.9% transformed to dissolved methane which stayed in the water as an oversaturated state, and the measured concentration of dissolved methane was 1.49 larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH_4 partial pressure. On the other hand, the domestic wastewater have 24.9% - 30.6% went out with the outflow, 2% - 3% converted to gaseous methane, 6.9% - 10.0% was used by sulphate, and 14.9% - 22.8% transformed to dissolved methane which stayed in the water as an oversaturated state, and the measured concentration of dissolved methane was 1.16-1.63 larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH_4 partial pressure.
In general, anaerobic immobilized organisms have a better treatment effect than a typical anaerobic treatment system, but a large proportion of methane discharged with the effluent in dissolved phase, not only wasted energy, but impacted the environment. Therefore, how to recover or reduce dissolved methane, is also one of the important issues of future application of anaerobic organisms.
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