Modification of a polyamide reverse osmosis membrane by heat treatment for enhanced fouling resistance

The use of heat treatment to improve solute rejection and fouling resistance of a polyamide reverse osmosis (RO) membrane was investigated in this study. Heat treatment was carried out by immersing the membrane samples in Milli-Q water at 70 degrees celcius for a specific duration. Heat treatment reduced the pure water permeability from 4.1 to 2.8 L/m2 bar but improved conductivity rejection from 95.5 to 97.0 percent. As a result, a correlation was observed between changes in the two parameters. Marginal changes in the membrane surface characteristics were observed as a result of heat treatment. Heat treatment significantly improved the fouling resistance property of the RO membrane. When the secondary effluent was filtrated at an elevated permeated flux, the virgin RO membrane exhibited 30 percent flux decline while the heat-treated membrane showed only 12 percent flux decline. This is possibly because heat treatment resulted in a denser cross-linked active skin layer, thus reducing the blockage caused by small organic foulants

Hydrogen-bond-assisted syndiotactic-specific radical polymerization of N-isopropylacrylamide : The solvent effect on the stereospecificity

Radical polymerizations of N-isopropylacrylamide (NIPAAm) in several solvents at low temperatures in the absence or presence of hexamethylphosphoramide (HMPA) or 3-methyl-3-pentanol (3Me3PenOH) were examined. The isotacticities of the poly(NIPAAm)s obtained in the absence of HMPA and 3Me3PenOH at lower temperatures slightly increased as the polarities of the solvents used increased. The addition of HMPA significantly induced the syndiotactic-specificity even in polar solvents such as tetrahydrofuran and acetone, although the use of the solvents having proton-donating ability, such as chloroform, prevented the induction of the syndiotactic-specificity, even if their polarities are low. In the presence of 3Me3PenOH, a good correlation between the polarities of the solvents used and the syndiotacticities of the obtained poly(NIPAAm)s was observed, and poly(NIPAAm) with r = 73% was obtained using the toluene/methylcyclohexane mixed solvent

Dialysis as a new pre-treatment technique for online bacterial counting

Real-time bacteriological counting technology is capable of providing an online profile of bacterial removal during the wastewater treatment process, and can enhance the safety of recycled water for potable water reuse. However, autofluorescence emanating from dissolved organic compounds present in treated wastewater interferes with the analysis. In this study, a novel approach is adopted, viz., dialysis treatment for the removal of dissolved interfering substances from treated wastewater, and the efficiency of this treatment protocol is evaluated as a pre-treatment technique for real-time bacteriological counting. Dialysis using membranes having a molecular weight cut-off (MWCO) of 1000 kDa and 6?8 kDa were found to successfully reduce the intensity of autofluorescence emitted from the interfering substances; whereas the courser dialysis membrane having a MWCO of 1000 kDa was found to be more effective in removing the interfering substances. Here we demonstrate for the first time that continuous online dialysis treatment aids in the direct determination of the bacterial counts in ultrafiltration- and membrane bioreactor-treated wastewaters. The results of the study indicate that the dialysis pre-treatment technique is effective for continuously reducing the concentration of interfering substances in treated wastewater, and thus allows for direct online counting of bacteria

Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC

Tetraneutron ($^4n$) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. $^4\mathrm{He}({\pi}^- , {\pi}^+)$, as an alternative way to populate tetraneutron. An intense ${\pi}^-$ beam with the kinetic energy of ~850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, will open up a possibility to improve the experimental sensitivity of the formation cross section, which will be much smaller than hitherto known DCX cross sections such as $^9\mathrm{Be}({\pi}^-, {\pi}^+)^9\mathrm{He}\ (g.s.)$.Comment: 4 pages, 1 figure; proceedings of the 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto, Japan, 25-30 July 201

Fouling substances causing variable rejection of a small and uncharged trace organic chemical by reverse osmosis membranes

The safety of recycled water for potable water reuse can be enhanced by improving the reliability of reverse osmosis (RO) treatment for the removal of trace organic chemicals. This study assessed the mechanisms underlying the variable rejection of a carcinogenic N-nitrosamine, namely N-nitrosodimethylamine (NDMA), caused by RO membrane fouling. Foulants that cause the variable rejection were evaluated through rejection tests and foulant characterization. The RO treatment of wastewaters with and without pre-treatment using an ultrafiltration or nanofiltration membrane showed that NDMA rejection commonly increased with increasing membrane fouling. The characterization of organics in the treated wastewater samples revealed that increased NDMA rejection can be caused by foulants composed of low-molecular-weight organics (<300 Da), including tryptophan (or tryptophan-like substances). It is speculated that small organics such as tryptophan form a densely packed cake layer on the membrane surface, which may function as an additional barrier for the membrane transport of NDMA. The results of this study indicate that RO membrane fouling that occurs during long-term wastewater treatment can increase NDMA rejection. The enhanced separation performance can yield positive consequences for the credibility of RO treatment in potable water reuse

Online monitoring of bromate in treated wastewater: implications for potable water reuse

Continuous monitoring of bromate ions, a disinfection by-product of the ozonation of wastewater, may improve the safety of recycled water for potable use. A recently developed elemental analyzer can determine bromate ion concentrations online. However, dissolved organics present in wastewater interfere with the detection of bromate ions. The aim of this study was to develop a nanofiltration (NF) membrane-based pre-treatment system to remove the interfering substances present in treated wastewater prior to the online analysis. The NF pre-treatment system was optimized to ensure the removal of the interfering substances from the membrane bioreactor (MBR)-treated wastewater without altering the bromate ion concentration. We determined a permeate flux of 1 L m−2 h−1 and a feed temperature of 35 °C as optimal pre-treatment conditions for online analysis. Furthermore, the continuous monitoring of MBR-treated wastewater, containing different bromate ion concentrations (0-12 μg L−1), for three days revealed a strong correlation between the concentrations determined using the online analyzer and liquid chromatography coupled with tandem mass spectrometry. Thus, this study demonstrates the potential utility of the online bromate ion analyzer coupled with NF pre-treatment system to monitor the rate of bromate ion formation during ozonation

Online assessment of sand filter performance for bacterial removal in a full-scale drinking water treatment plant

Microbiological risks associated with drinking water can be minimized by providing enhanced integrity monitoring of bacterial removal by water treatment processes. This study aimed to evaluate the efficacy of real-time bacteriological counters for continuously assessing the performance of a full-scale sand filter to remove bacteria. Over the course of an 8-day evaluation, online counting of bacteria was successfully performed, providing continuous bacterial counts in the sand filter influent and effluent over approximate ranges from 17 × 10 4 to 94 × 10 4 and from 0.2 × 10 4 to 1.3 × 10 4 counts/mL, respectively. Periodic variations were observed with online bacterial counts in the sand filter influent because of the changes in the performance of flocculation and sedimentation processes. Overall, online removal rates of bacteria determined during the full-scale test were 95.2?99.3% (i.e., 1.3?2.2-log), indicating that online bacterial counting can continuously demonstrate over 1.3-log removal in the sand filter. Real-time bacteriological counting technology can be a useful tool for assessing variability and detecting bacterial breakthrough. It can be integrated with other online water quality measurements to evaluate underlying trends and the performance of sand filters for bacterial removal, which can enhance the safety of drinking water

コウナイホウ LeFort IIガタ コツキリジュツ ニヨリ チュウガンメン ノ カンオウ オ カイゼン サセタ コッカクセイ カガク ゼントツショウレイ

The patient was a 15-year 6-month female, and her chief complaint was severe nasomaxillary hypoplasia with anterior crossbite. After extraction of bilateral upper and lower third molars, the preoperative orthodontic treatment was initiated at 15-year and 7-month old. After 10-month orthodontic treatment, she received a surgery of intraoral LeFort II midfacial advancement using a piezoelectric braze. The naso-maxillary LeFort II segment was placed forward and downward by 8.0 mm using a Rigid External Distractor (RED) system, and internal rigid fixation was performed. For the mandible, the bilateral intraoral vertical ramus osteotomy was also performed, resulting in 6.0 mm mandibular setback. After 6-month of postoperative treatment, multi-bracket appliances were removed. At 7-month after surgery, the satisfactory facial profile and acceptable occlusion were obtained

N-nitrosamine rejection by nanofiltration and reverse osmosis membranes: The importance of membrane characteristics

The influence of membrane characteristics on the rejection of eight N-nitrosamines was investigated using one nanofiltration (NF), one seawater reverse osmosis (SWRO) and six low pressure reverse osmosis (LPRO) membranes. The rejection of the two lowest molecular weight N-nitrosamines, namely N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA), varied in the range from 8-82% to 23-94%, respectively. In general, the rejection of NDMA and NMEA increased with decreasing membrane permeability. The impact of membrane characteristics became less important for higher molecular weight N-nitrosamines. Among the four LPRO membranes (i.e. ESPA2, LFC3, TFC-HR and 70LW) that are commonly used for water reclamation applications, similar rejections were obtained for NDMA (37-52%) and NMEA (69-82%). In addition, rejection values of NDMA and NMEA among two LPRO membranes (i.e. ESPA2 and 70LW) were almost identical when compared under variable permeate flux and feed temperature conditions. However, it is noteworthy that the ESPABmembrane could achieve very high rejection of NDMA (as high as 71%) despite having a similar permeability to the LPRO membranes. Results reported here suggest that membrane characteristics associated with permeability such as the pore size and thickness of the active skin layer can be a key factor determining N-nitrosamine rejection

Assessment of 265-nm UV-LED for direct photolysis and advanced oxidation of N-nitrosamines and 1,4-dioxane

The advanced oxidation process (AOP), using conventional low-pressure mercury (LP Hg)-vapor UV lamps, forms a critical barrier for pathogens and contaminants of emerging concern (CECs) in potable water reuse. In recent years, UV-light-emitting diode (UV-LED) has attracted considerable attention as an alternative UV source because it has a long lifetime and is mercury-free. This study assesses the effectiveness of 265-nm UV-LED in removal of characteristic CECs, 1,4-dioxane (100 μg/L) and N-nitrosamines (500 ng/L), including N-nitrosodimethylamine (NDMA), in recycled potable water. Direct photolysis using a UV-LED lamp, at the maximum UV dose of 900 mJ/cm2, achieved a maximum of 31% NDMA reduction, as opposed to a 93% reduction by a conventional LP Hg UV lamp. We attributed this to the longer emission wavelength of the UV-LED (265 nm) than that for the LP Hg UV lamp (254 nm). Both UV lamps failed to photolyze 1,4-dioxane. Using hydrogen peroxide or monochloramine remarkably enhanced the effectiveness of the LP Hg UV-based AOP in removing 1,4-dioxane, and the percentage of NDMA removed also increased slightly; however, it did not improve the effectiveness of the UV-LED-based AOP. We conclude from this study that despite the advantages of the UV-LED over the conventional LP Hg UV lamp, the former performs ineffectively at attenuating major CECs in recycled water