82Tawan LIMPIYAKORN83Sojiphong CHATRAPHORNIn situ Activity Investigation of Ammonia-oxidizing Archaea and Bacteria in Water Recirculation Systems of Aquaculture Ponds using DNA-Stable Isotope Probing Technique (Project 2015)Graded band gap CuIn1-xGaxSe2 thin film solar cells fabricated from bilayer thin films of CuInSe2 and CuGaSe2 (Project 2015)62Direct application of anaerobic digestion to municipal wastewater is easy if the concentration of organic mat-ter is increased. Although microfiltration membranes can concentrate organic matter in raw municipal waste-water, severe membrane fouling is likely to occur. In this study, efficient physical cleaning methods for direct membrane filtration (DMF) of municipal wastewater were investigated. Agitation of the tank, vibration of membrane modules and use of granular materials were examined. Aeration was not tested because it leads to microbial degradation of organic matter (loss of recoverable energy). No single cleaning method worked well for DMF. However, a combination of membrane vibration and agitation of the tank was found to be effective. When the effective physical cleaning was performed with chemically enhanced backwash using citric acid and an adequate membrane flux, DMF of real municipal wastewater could be continued for almost one month without conducting any off-line membrane cleaning. The increase in transmembrane pressure was almost per-fectly controlled in the long-term operation, during which 75% of organic matter was successfully recovered and 50-fold concentration (based on volume) of wastewater was continuously achieved with hydraulic reten-tion time of 3.1 hours.The oxidation of ammonia to nitrite is considered to be the rate-limiting step of biological nitrogen removal in recirculating aquaculture system (RAS). Recent evidence from natural environments suggest that beside the long thought ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), affiliated to Thaumarcheota, a new phylum of the domain Archaea, participate in ammonia oxidation in the global nitrogen cycle. In addition to the natural environments, modern data indicate that these microorganisms exist also in RAS. Progress in AOA knowledge has started with the qualitative and quantitative identification of these microorganisms in RAS. However, data from in situ activity investigation are not available thus far. In this study, the abundances and autotrophic ammonia oxidation activity of AOA and AOB in the RAS were investigated. qPCR shows that the abundance of AOA amoA genes was 2-700 times higher than AOB in both high and low salinity RAS. DNA-stable isotope probing was conducted in continuous flow reactors with 1 mM 12C and 13C-bicarbonate to investigate the autotrophic growth of AOA and AOB. The results demonstrated that AOA and AOB assimilated 13C as a carbon source which indicates that both microorganisms performed autotrophic ammonia oxidation.The depositions of CIS/CGS bilayer and CGS/CIS/CGS trilayer were employed for the fabrication of CIGS thin film solar cells in order to enhance the efficiency of the devices when compared with those fabricated by the commonly used three-stage deposition process. The back and double Ga-grading were obtained from the depositions of the bilayer and trilayer absorbers, respectively, leading to the grading in the conduction band of the absorbers due to the different diffusivities of In and Ga in the absorbers. The CIS/CGS bilayer absorbers with back Ga-grading showed the increasing trend of the average value of the short-circuit current density (Jsc) due to assisting back surface field, but the average open-circuit voltage (Voc) was significantly low due to the reduction of Ga content at front surface. On the other hand, the CGS/CIS/CGS trilayer absorbers showed double Ga-grading resulting in the increase of the Voc when compared with the bilayers. The highest efficiencies of the devices fabricated from the 1.8 µm thick CIS/CGS bilayer and CGS/CIS/CGS trilayer absorbers showed the maximum value of 12.5% and 15.5%, respectively. The external quantum efficiency (EQE) of the 1.8 µm thick bilayer and trilayer absorbers showed the enhancement in both visible
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