| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 105 === Due to climate change and the increasing demand of water for industry, Taiwan frequently faces an acute problem of water scarcity in recent years. Therefore, much attention has been paid for using reclaimed water to solve the problem of water shortage. Based on the effluents of domestic sewage and industrial waste water are large and stable water resources, the production of reclaimed water from these effluents will have great potential.
In this study, membrane distillation was used for effluent treatment from Dihua sewage treatment plant (STP) to produce the reclaimed water. Experiments were divided into direct contact membrane distillation (DCMD) pilot test and air gap membrane distillation (AGMD) laboratory module test, the former was used for long-term data obtained while the latter was designed to implement the cleaning test for fouled membrane. In addition, simulation analysis for energy consumption of AGMD to produce reclaimed water from STP was also carried out in this study.
Pilot DCMD test using flat sheet module with ePTFE membrane was conducted under feed temperature at 60℃and Re= 9500 while the permeate side at 35℃and Re=3200.The flux decline obtained by 4 hours operation per day and 2 month continuous operation is not significant, its value being about 15 kg/m²hr. Based on the measurement of conductivity in feed and permeate, respectively, to determine the ion rejection, results showed that the ion rejection reaches 99%. By measuring the Cl- ion concentration, it appeared that the rejection was 99.9%. SEM-EDS analysis for fouled membranes showed that the fouling components are mainly from organic matters. Based on the COD, Cl- and NH4+ measured from the produced water, it clearly indicated that the water quality from MD is better than that by RO.
Experimental results of AGMD showed that 0.1 wt% NaOH or 0.8 wt% EDTA-4Na solution can wash away the fouling on the membrane surface and the cleaned membrane has flux nearly same as that from virgin membrane. Based on Memstill® concept for heat recovery, the thermal energy consumption of AGMD was also estimated. Under the given conditions of flat plate module 1x1 m2 , temperatures of feed inlet and after heater were at 80 and 30℃, respectively, and the superficial flow velocity in the module channel was 0.01 m/s, the thermal energy consumption estimated was 106.8 kWh/m3 and the flux was 5.5 kg/m2hr.
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