Membrane distillation (MD) is a thermally driven desalination process with a hydrophobic membrane. MD process has been known to have a lower fouling potential compared to other pressure-based membrane desalination process (NF, RO). However, membrane fouling also occurs in MD process. In this study, the membrane fouling was observed in MD process according to the pre-treatment processes. The filtration and precipitation processes were applied as the pre-treatment to prevent the membrane fouling. The pore sizes of roughing filters were 0.4, 5, 10, 30, and 60 ㎛. The concentration of the coagulant was 1.2 mg/L as FeCl3. The membrane fouling on MD membrane was successfully removed with both pre-treatment processes.

Membrane distillation (MD) is a hydrid membrane process using the temperature difference as a driving force. In order to enhance the performance (flux) of the MD process, various membrane structures (asymmetric or bi-composite) and materials (PP, PVDF or PTFE) have been suggested. In this study, the support layer of the commercial PTFE/PP bi-composite membrane is modifed by forming the macro punctures in it. The size and location of macro punctures were varied according to the designed support layer porosities (50, 60, 70 and 80 %). The modified membrane test was conducted by using the DCMD configuration. The flux of a modified membranewas enhanced up to 27 % compared with that of pristine membrane when the size of the macro puncture and overall porosity of the support layer were larger than 20 mm2 and 60 %, respectively.

Membrane distillation (MD) is the thermally driven water separation process based on the vapor pressure difference across the membrane. In order to increase the water recovery of the conventional RO process, the additional MD-PRO pocess was suggested. In this study, the syntheric RO brine was used as a feed solution of the MD process. Due to the high salinity of the RO brine, the MD membrane could be fouled by the scalants. In order to mitigate the scaling on the MD membrane surface, the pre-treatment process using the column filled by natural zeolite was applied. The roughing filter was installed between the pre-treatment process and MD system in order to prevent possible particulate fouling by the debries of the natural zeolite. Moreover, in order to enhance the CEC of the natural zeolite, the NaCl soaking was conducted. The flux and electronic conductivity were monitored under given experimental conditions. And the membrane morphology and the chemical compositions were analyzed by using the SEM-EDX.

자외선 검출소자로 응용될 수 있는 우수한 특성을 지진 AlxGa1-xN 박막을 MOCVD 법으로 성장시킨 후 박막의 구조적인 특성을 조사하였다. 사파이어 기판 위에 성장된 AlxGa1-xN의 물리적인 특성을 평가하기 위해 Synchrotron Radiation XRD를 사용하였다. AlxGa1-xN의 두께가 커질수록 박막의 결정성은 증가하였으며 아래층은 Undoped GaN의 결정성과 성장된 AlxGa1-xN의 결정성이 서로 비례적인 상관관계를 가지고 있음을 알아내었다. Al 조성비는 막질에 크게 영향을 주었으며 조성비가 높아질수록 표면 형상은 매우 나빠졌다.

An experimental study was conducted to investigate the effects of chlorine dioxide and ozone on reduction of THM(trihalomethane) formation. Precursor concentration, chlorine concentration, reaction time, pH, and temperature were governing compornents of THM formation. When other conditions are constant, THM formation increased linearly with precursor concentration increased. THM formation increased when pH increased from 5 to 9. In combined treatment with chlorine and chlorine dioxide, chlorine treatment after chlorine dioxide treatment made less THM than any other case does. Ozonation reduced THMFP(THM formation potential) of THM precursor. THMFP decreased exponentially with reaction time increased. Also biodegradability of humic acid was enhanced by ozonation.