Analysis of Polyvinylidene Fluoride Membranes Fabricated for Membrane Distillation.

The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different conditions by the phase inversion method and characterized to measure flux, rejection, contact angle (CA), liquid entry pressure (LEP), and pore sizes.

Retardation of wetting for membrane distillation by adjusting major components of seawater.

Wetting by fouling is phenomenon specific to membrane distillation (MD) and are regarded as challenges to the seawater membrane distillation (SWMD) process. To understand fouling and wetting, the influence of Mg and Sr crystals, which can potentially cause scaling, as well as Ca crystals deposited on the membrane surface were investigated. Mg(OH) and CaSO had significant impact on fouling and wetting.

Process stability and comparative rDNA/rRNA community analyses in an anaerobic membrane bioreactor with silicon carbide ceramic membrane applications.

This study evaluated the feasibility of using a silicon carbide (SiC) anaerobic ceramic membrane bioreactor (AnCMBR) to co-manage domestic wastewater (DWW) and food waste recycling wastewater (FRW). A pilot-scale SiC-AnCMBR was put into operation for 140 days under two different organic loading rates (OLRs): 5 kg COD m d (OLR 5) and 3 kg COD m d (OLR 3). The organic removal efficiency was 93.

Chlorination caused a shift in marine biofilm niches on microfiltration/ultrafiltration and reverse osmosis membranes and UV irradiation effectively inactivated a chlorine-resistant bacterium.

The effect of chlorine disinfection on marine biofilm populations and communities formed on membrane surfaces was investigated under two feedwater conditions: raw seawater and deep bed filtration-treated seawater. As a result of chlorination, the structure of the biofilm community on the microfiltration/ultrafiltration and reverse osmosis membrane coupons shifted significantly at the genus level. However, the total bacterial population was not reduced under the two feedwater conditions.

Negligible seeding source effect on the final ANAMMOX community under steady and high nitrogen loading rate after enrichment using poly(vinyl alcohol) gel carriers.

This study investigated the effect of seeding source on the mature anaerobic ammonia oxidation (ANAMMOX) bacterial community niche in continuous poly(vinyl alcohol) (PVA) gel systems operated under high nitrogen loading rate (NLR) condition. Four identical column reactors packed with PVA gels were operated for 182 d using different seeding sources which had distinct community structures. The ANAMMOX reaction was achieved in all the bioreactors with comparable total and ANAMMOX bacterial 16S rRNA gene quantities.

Effective seeding strategy using flat type poly (vinyl alcohol) cryogel for anammox enrichment.

In this study, anammox enrichment reactors were operated using flat type poly (vinyl alcohol) cryogel (cryoPVAG) with precultured anammox bacteria (PAB) and activated sludge (AS) from an anoxic tack of the A2O process to evaluate the effect of different seeding sources on anammox enrichment. In addition, cryoPVAGs with different thicknesses (1, 2, and 3 mm) were used to investigate the effects of the thickness on anammox enrichment. The regression analysis with a modified Gompertz model showed that the start-up period of the anammox enrichment using PAB inoculum was approximately 14 days earlier than that of AS inoculum at a nitrogen loading rate of approximately 1 kg-N m day.

Effects of the ammonium loading rate on nitrite-oxidizing activity during nitrification at a high dose of inorganic carbon.

In this study, the effects of the ammonium loading rate (ALR) and inorganic carbon loading rate (ILR) on the nitrification performance and composition of a nitrifying bacterial community were investigated in a moving bed biofilm reactor, using poly(vinyl alcohol) (PVA) sponge cubes as a supporting carrier. Between the two ALRs of 0.36 and 2.

Effects of changes in temperature on treatment performance and energy recovery at mainstream anaerobic ceramic membrane bioreactor for food waste recycling wastewater treatment.

An anaerobic ceramic membrane bioreactor (AnCMBR) has been attracted as an alternative technology to co-manage various organic substrates. This AnCMBR study investigated process performance and microbial community structure at decreasing temperatures to evaluate the potential of AnCMBR treatment for co-managing domestic wastewater (DWW) and food waste-recycling wastewater (FRW). As a result, the water flux (≥6.

Effect of engineered environment on microbial community structure in biofilter and biofilm on reverse osmosis membrane.

Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC).

Comparison of inoculum sources for long-term process performance and fate of ANAMMOX bacteria niche in poly(vinyl alcohol)/sodium alginate gel beads.

The process performance and microbial niche of anaerobic ammonia oxidation (ANAMMOX) bacteria were compared in two identical bioreactors inoculated with different inoculum sources (i.e., pre-cultured ANAMMOX bacteria: PAB and activated sludge: AS) entrapped in poly(vinyl alcohol)/sodium alginate (PVA/SA) gel beads for a long-term period (i.

Targeted removal of trichlorophenol in water by oleic acid-coated nanoscale palladium/zero-valent iron alginate beads.

A new material was developed and evaluated for the targeted removal of trichlorophenol (TCP) from among potential interferents which are known to degrade removal activity. To achieve TCP-targeted activity, an alginate bead containing nanoscale palladium/zero-valent iron (Pd/nZVI) was coated with a highly hydrophobic oleic acid layer. The new material (Pd/nZVI-A-O) preferentially sorbed TCP from a mixture of chlorinated phenols into the oleic acid cover layer and subsequently dechlorinated it to phenol.

Assessment of bacterial community structure in nitrifying biofilm under inorganic carbon-sufficient and -limited conditions.

In this work, nitrification and changes in the composition of the total bacterial community under inorganic carbon (IC)-limited conditions, in a nitrifying moving bed biofilm reactor, was investigated. A culture-independent analysis of cloning and sequencing based on the 16S rRNA gene was applied to quantify the bacterial diversity and to determine bacterial taxonomic assignment. IC concentrations had significant effects on the stability of ammonia-oxidation as indicated by the reduction of the nitrogen conversion rate with high NH4(+)-N loadings.

Effect of anions and humic acid on the performance of nanoscale zero-valent iron particles coated with polyacrylic acid.

Effects of anions (NO3(-), HCO3(-), Cl(-), SO4(2-)) and humic acid on the reactivity and core/shell chemistries of polyacrylic acid-coated nanoscale zero-valent iron (PAA-NZVI) and inorganically modified NZVI (INORG-NZVI) particles were investigated. The reactivity tests under various ion concentrations (0.2-30mN) revealed the existence of a favorable molar ratio of anion/NZVI that increased the reactivity of NZVI particles.

High-rate partial nitritation using porous poly(vinyl alcohol) sponge.

Poly(vinyl alcohol) (PVA) has been utilized as a support material for the immobilization of nitrifying bacteria without the comprehensive survey of partial nitritation. In the present study, the activities of nitrifiers and the maximum nitrogen conversion rate of partial nitritation with PVA sponge-cubes were specified according to different conditions. The selective enrichment of ammonia-oxidizing bacteria (AOB) on PVA sponge-cubes was achieved by the competition between AOB and nitrite-oxidizing bacteria for dissolved oxygen.

Effects of washing solution and drying condition on reactivity of nano-scale zero valent irons (nZVIs) synthesized by borohydride reduction.

Washing and drying processes are essential when synthesizing nano-scale zero valent irons (nZVIs) by borohydride reduction of iron salts in aqueous phase. However, effects of these processes on nZVI reactivity have not been investigated in detail, although different washing and drying conditions might alter surface characteristics of nZVIs and thus vary their reactivity towards reducible contaminants. In this study, effects of three washing solutions and drying conditions on the reactivity of nZVIs for nitrate were investigated.

Oxidation of bisphenol A by UV/S2O8(2-): comparison with UV/H2O2.

The UV/S2O8(2-) process was applied to decompose bisphenol A (BPA), which is a representative endocrine-disrupting chemical (EDC), and was comared with the UV/H2O2 process. The BPA degradation efficiency by UV/S2O8(2-) was increased by increasing S2O8(2-) concentration or decreasing BPA concentration. The presence of humic acid caused an inhibitory effect.

Analyses of calcium carbonate scale deposition on four RO membranes under a seawater desalination condition.

Inorganic fouling is one of the critical operational issues in reverse osmosis membrane. Few researches investigated effects of membrane surface characteristics on inorganic fouling and on anti-scaling techniques although the fouling occurs on the membrane surface. The objective of this paper was to examine whether different characteristics of deposition of calcium carbonate solids would occur on four membranes having distinctive surface properties.

Chemometrics in assessment of seasonal variation of water quality in fresh water systems.

The chemometric techniques were applied for evaluation of the seasonal variation of water qualities at 17 stations along a stretch of the Bagmati river of Nepal for 23 water quality parameters measured during 1999-2003. The application of discriminant analysis confirmed the classification of the water quality measurements into three seasons: pre-monsoon, monsoon, and post-monsoon affording 93.8% correct classification.

Influence of membrane surface properties on the behavior of initial bacterial adhesion and biofilm development onto nanofiltration membranes.

In order to investigate biofouling problems, the fundamental behaviors of initial bacterial adhesion and biofilm development on four different nanofiltration (NF) membranes were evaluated using Pseudomonas aeruginosa PAO1 as a model bacterial strain. Initial cell adhesion was considerably higher on an aromatic polyamide-based NF membrane with a hydrophobic and rough surface, whereas cell aggregation on a polypiperazine-based NF membrane with a relatively hydrophilic and smooth surface was lower. Moreover, significant differences in the structural heterogeneity of the biofilms were observed among the four NF membranes.

Chemometric application in classification and assessment of monitoring locations of an urban river system.

The study presents the application of selected chemometric techniques: cluster analysis, principal component analysis, factor analysis and discriminant analysis, to classify a river water quality and evaluation of the pollution data. Seventeen stations, monitored for 16 physical and chemical parameters in 4 seasons during the period 1999-2003, located at the Bagmati river basin in Kathmandu Valley, Nepal were selected for the purpose of this study. The results allowed, determining natural clusters of monitoring stations with similar pollution characteristics and identifying main discriminant variables that are important for regional water quality variation and possible pollution sources affecting the river water quality.

Assessment of spatial-temporal patterns of surface and ground water qualities and factors influencing management strategy of groundwater system in an urban river corridor of Nepal.

This study examined the spatial-temporal variations and factors influencing the management of groundwater along a section of the Bagmati river corridor in the Kathmandu valley (Nepal). The results showed that rural areas were less polluted than urban areas. In urban areas, the biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP) concentrations ranged from 8.

Application of water quality indices and dissolved oxygen as indicators for river water classification and urban impact assessment.

The usefulness of water quality indices, as the indicators of water pollution, for assessment of spatial-temporal changes and classification of river water qualities was verified. Four water quality indices were investigated: WQI (considering 18 water quality parameters), WQI(min) and WQI(m) (considering five water quality parameters: temperature, pH, DO, EC and TSS) and WQI(DO) (considering a single parameter, DO). The water quality indices WQI(min), WQI(m) and WQI(DO) could be of particular interest for the developing countries because of the minimum analytical cost involved.

Spatial-temporal variation and comparative assessment of water qualities of urban river system: a case study of the river Bagmati (Nepal).

The study presents the assessment of variation of water qualities, classification of monitoring networks and detection of pollution sources along the Bagmati River and its tributaries in the Kathmandu valley of Nepal. Seventeen stations, monitored for 23 physical and chemical parameters in pre-monsoon, monsoon, post-monsoon and winter seasons, during the period 1999-2003, were selected for the purpose of this study. The study revealed that the upstream river water qualities in the rural areas were increasingly affected from human sewage and chemical fertilizers.

Application of QUAL2Kw for water quality modeling and dissolved oxygen control in the river Bagmati.

A stream water quality model, QUAL2Kw, was calibrated and validated for the river Bagmati of Nepal. The model represented the field data quite well with some exceptions. The influences of various water quality management strategies have on DO concentrations were examined considering: (i) pollution loads modification; (ii) flow augmentation; (iii) local oxygenation.