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Abstract: A membrane bioreactor (MBR) and nanofiltration (NF) membrane processes were developed for municipal wastewater reclamation, and their performances, in terms of trace contaminant control and fouling mitigation, were evaluated and designed to meet water quality criteria and minimize flux decline. The dissolved contaminants in wastewater were poorly degraded by MBR but the microbial nitrification in MBR could greatly contribute to nitrogen removal in the MBR permeate through the addition of a NF membrane. Furthermore, most dissolved contaminants were efficiently removed by the NF membrane. However, the NF membrane was ineffective in the removal of boron. The org-N/C molar ratio was inversely correlated to SUVA and directly corresponded to the 3D FEEM, structural analysis, and IR spectra of organic matter in raw and treated water, and desorbed foulants. The observations obtained from rigorous characterization revealed that the hydrophilic fractions, which were comprised of polysaccharides and amino groups, played a major role in fouling formation of the MBR–NF system. In addition, strong amide IR peak in the NF-base supported the notion that amino groups were primarily responsible for the fouling formation of the NF membrane relative to the polysaccharides groups. [Copyright &y& Elsevier]

One of the two main objectives of this work is to oxidize MBR effluents with ozone/peroxide in high pH conditions in order to improve oxidation of pharmaceuticals, which could efficiently be rejected by the nanofiltration (NF) stage. The other main objective is to effectively oxidize of dissolved organic carbon (DOC) in MBR effluents in order to decrease fouling in the filtration stage. In this work, ozone/peroxide oxidation was applied to the MBR effluents in high pH conditions in order to improve the formation of OH radicals, and oxidized effluents were filtered by the NF membrane (NE90) in order to investigate fouling potentials and the removal of pharmaceuticals. Natural and synthetic wastewater samples were used as feed solutions for the MBR system, which was equipped with a U-shaped hollow fiber membrane module. The flux decline was decreased from 29% to 15% when 9 mg/L of ozone was used, the same decline was also observed when 6 mg/L ozone and hydrogen peroxide (1/1 ozone/peroxide mol ratio) were used. A further decrease in flux decline was observed when pH was adjusted to 9.00 (29% to 9%) prior to the ozone/peroxide oxidation. In most cases, the increase in the ozone dose, the addition of hydrogen peroxide and the adjustment of the pH level led to an increase in the removal of pharmaceuticals. Iopromide, TCEP and Naproxen were found to be more resistant to the oxidation when pH was increased. [ABSTRACT FROM AUTHOR]

Abstract: Boron (B) is an important element which should be considered seriously for drinking water production. Boron removal from seawater using nanofiltration (NF) and reverse osmosis (RO) membranes was investigated. Increase in salt concentration effects boron removal positively when RO membranes and negatively when NF membranes were used. Time dependencies of membrane processes for boron removal were also investigated. Based on the boron concentration in seawater and treated seawater, toxicity tests were conducted using Western Blotting method. HEK 293, human embryonic kidney cell line and antibodies, Bcl-2 and β-actin were used for boron toxicity tests. [Copyright &y& Elsevier]

Abstract: Reverse osmosis (RO) desalination process is an efficient and reliable membrane technology for the production of drinking water from seawater. However, some serious limitations had recently been discovered during the field practice. Boron problem is one of them. According to the WHO regulations, the boron concentration should be lower than 0.5mg/L in drinking water. It is still difficult to reduce boron level to 0.5mg/L or lower with the conventional reverse osmosis desalination plants equipped with commercially available RO membranes. Therefore, more efficient separation technologies are needed for boron removal. In this study, the performance of the boron-selective ion exchange resins containing N-methyl glucamine groups, as Diaion CRB 02 and Dowex XUS 43594.00, have been tested for boron removal from model seawater. The kinetic performances of these resins were compared. The kinetic data obtained were evaluated using Lagergren pseudo-first-order and second-order models. Also, the process kinetics were predicted by using diffusion models. In addition, column-mode tests have been carried out for boron removal from model seawater. [Copyright &y& Elsevier]

Salinity gradient processes, such as Forward Osmosis and Pressure Retarded Osmosis, have been proven to be promising technologies for reducing the energy consumption in water treatment processes, for energy production, and for energy recovery. Based on the thermodynamic concepts, specifically Gibbs' Free Energy of Mixing, the concentration of the draw solution plays an important role in determining whether the selected salinity gradient process is economically feasible or not. An increase in the salinity of a draw solution does not only increase the osmotic pressure difference between the draw and feed solutions, but also allows a higher hydraulic pressure to be applied on the draw solution, which together greatly increases the volumetric flux of the draw solution per single pass when PRO is used. Even though higher power densities can be achieved by applying higher hydraulic pressures on the draw solution, this requires greater mechanical stability of the membrane to be able to withstand these higher hydraulic pressures. In order to increase the mechanical stability of the membranes, generally, thicker support layers can be applied, which have a direct negative impact on membrane permeability. Therefore, there is a limitation to the salinity of the draw solution which can be used in the PRO processes. This being dependent on the concentration of the hypersaline solution and hence overall hydraulic pressure, necessitating the use of an ultra-thick support layer for maximum energy production and/or recovery. In this theoretical and simulative optimization of the PRO process, we achieved the optimum energy recovery from a hypersaline solution (TDS ~ 300,000 mg/l) by using a multistage PRO (MPRO) system which included implementing variable applied feed pressures to each stage. The results showed that the volumetric flow rate of the hypersaline draw solution increased by up to a factor of 10 during the MPRO process in single pass, and the concentration of the hypersaline draw solution diluted up to 10× accordingly. Energy conversion efficiency of osmotic pressure to hydraulic pressure was found to be around 10% without variable feed pressure and approximately 20% with variable feed pressure. • The optimum osmotic energy recovery from a hypersaline solution was theoretically achieved by using a MPRO system. • Using variable feed pressures to MPRO process further increased the theoretical energy recovery from a hypersaline solution. • The simulation results showed that the volumetric flow rate of the hypersaline draw solution can increase by up to a factor of 10 during the MPRO process in single pass. [ABSTRACT FROM AUTHOR]

During algal bloom, it's a challenge to provide good quality feed water, and ensure sustainable RO plant operations without an adequate pre-treatment of seawater. In this paper, the effectiveness of the coagulation process with the individual and dual coagulants, using alum, FeCl 3 and chitosan, were explored aiming to remove microalgae from seawater. The coagulation-flocculation-sedimentation (C-F-S) experiments were conducted by optimizing multiple process strategies to reduce the amounts of coagulants and also to shorten the sedimentation process time. The coagulation-flocculation-dissolved air flotation (C-F-D) experiments were performed to generate the process data in order to evaluate the dual coagulation process performance of the C-F-S system. C-F-S experiments using FeCl 3 coagulant gave better process performance (20 ppm FeCl 3 dose, 8.2 pH, 30 min sedimentation time and 98% microalgae removal efficiency) when compared to alum and chitosan based individual coagulations. The process time of the coagulation process was significantly reduced by the addition of chitosan as a flocculent aid. For dual coagulation using alum (10 ppm) as coagulant and chitosan (1 ppm) as flocculent aid improved microalgae removal efficiency to 98% at a reduced process time of 5 min, making C-F-S process as attractive as C-F-D process. [ABSTRACT FROM AUTHOR]

Ten white-rot fungal isolates were evaluated for the decolorization potential of pulp and paper mill effluent. Trametes elegans PP17-06, Pseudolagarobasidium sp. PP17-33, and Microporus sp.2 PP17-20 showed the highest decolorization efficiencies between 42 and 54% in 5 d. To reveal the mechanisms involved in decolorization and assess the long-term performance, PP17-06, which showed the highest decolorization efficiency, was further investigated. It could reduce the ADMI color scale by 63.6% in 10 d. However, extending the treatment period for more than 10 d did not significantly enhance the decolorization efficiencies. The maximum MnP activity of 3.27 U L−1 was observed on the 6 d during the biodegradation. In comparison, laccase activities were low with the maximum activity of 0.38 U L−1 (24 d). No significant LiP activities were monitored during the experiment. Dead fungal biomass showed an optimum decolorization efficiency of 44.18% in 8 d employing the biosorption mechanism. No significant changes in the decolorization efficiency were observed after that, suggesting the equilibrium status was reached. These results revealed that PP17-06 has the potential to decolorize pulp and paper mill effluent by employing both biodegradation and biosorption processes. [ABSTRACT FROM AUTHOR]

Oil concentration levels in municipal waste water effluent streams are stringently regulated in most parts of the world. Apart from municipal waste, stricter oil/grease discharge limits are also enforced in oil and gas sectors as large volumes of produced water is being discharged to open ocean. One of the feasible, practical and established methods to remove oil substances from waste water sources is by gas flotation. In this overview, gas flotation technologies, namely dissolved and induced flotation systems, are discussed. Physico-chemical interaction between oil–water-gas during flotation is also summarized. In addition to a brief review on design advancements in flotation systems, enhancement of flotation efficiency by using pre-treatment methods, particularly coagulation-flocculation, is also presented. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) is a developing technology, which is thought to have a potential of producing potable water in an energy-efficient manner. FO is driven by the natural osmotic pressure difference across a semi-permeable membrane. Despite a number of patents and peer-reviewed papers published for different methods and systems for water desalination by FO, this technology is still in its infancy because of some serious limitations and challenges. Due to many environment and energy related challenges, FO-based desalination has recently gained worldwide attention because it operates at low levels of pressure and temperature. Compared to traditional pressure-driven membrane processes, FO offers recognized advantages including reversible membrane fouling, and potentially less operation energy. The purpose of this review paper is to provide the state-of-the-art of the physical principles, recent developments, and applications of forward osmosis in the area of water desalination. Strengths and limitations of the applications of FO processes in the area of water desalination are highlighted and the future of FO technology is considered. [ABSTRACT FROM AUTHOR]

The water flux of several draw solutions (DSs, solutes: KCl, NaCl, CaCl 2 , Na 2 SO 4 ) and fouling propensity of two different organic foulants (humic acid and alginate) were systematically investigated using forward osmosis (FO) and unpressurized pressure-retarded osmosis. In addition, reverse solute selectivity was evaluated to characterize the water and salt transport mechanisms at different temperatures and in the presence of four different inorganic DS compounds. The influence of solution viscosity has significant implications in FO applications, because the water molecules easily penetrated and diffused throughout the FO membrane active layer (AL) and supporting layer (SL) with increasing temperatures, which is mainly correlated with the lower water viscosities with increasing temperatures. The results indicated that the water flux on average significantly increased from 9.5 to 13.7 and 24.9 LMH when the operating temperature was increased from 5 to 20 and 45 °C, which corresponded to a 44 and 262% increase in the water flux, compared to the FO mode at 5 °C. However, the water flux and viscosity exhibited generally constant trends with respect to the elevating temperature. In addition, elevating temperature increased the reverse solute flux selectivity (RSFS), not only by decreasing the internal concentration polarization (the AL and SL) and the wettability within the effective porosity of the SL, but also via the improvement of water molecule diffusion kinetics rather than solute diffusion. In addition, the RSFS was inversely related to the solute permeability of the different DSs and followed the order Na 2 SO 4 > CaCl 2 > NaCl > KCl. These results have significant implications for the prediction of water flux behavior and the selection of DSs at different temperatures in osmotically driven FO processes. [ABSTRACT FROM AUTHOR]

Abstract: Water shortages are anticipated to occur all over the world and are likely to have a significant effect on the availability of water for processes such as photocatalysis and electrolysis, as well as for drinking and industrial water. To overcome this problem, it has been suggested that seawater could be used as an alternative resource for the various water industries, such as hydrogen production, industrial and drinking water. Seawater contains a large amount of dissolved ion components, thus allowing it to be utilized as an electrolyte in photoelectrochemical system for producing hydrogen. Especially, the concentrated shows higher salinity (total dissolved solids, TDS) than the general seawater fed to the membrane process, because the permeate has a lower salinity and the retentate is more concentrated than the original seawater. For these reasons, the hydrogen evolution rate was investigated in a photoelectrochemical system, including anodized tubular TiO2 and platinum as the photoanode and cathode, an external bias (solar cell) and the use of various types of seawater prepared by the nanofiltration membrane process as the electrolyte in the photoelectrochemical system. The results showed that the rate of hydrogen evolution obtained using the relatively tight nanofiltration membrane, NF90, operated at 20MPa in the photoelectrochemical system is ca. 270μmol/cm2 h, showing that the retentate with a higher TDS than the general TDS of seawater acts as a more effective seawater electrolyte for hydrogen production. [Copyright &y& Elsevier]

Abstract: An engineered constructed wetland, fed with wastewater effluent, was investigated with respect to the control of organic micropollutants. The levels of 30 different micropollutants, including pharmaceuticals, endocrine disruptors and personal care products, were measured using solid phase extraction, followed by liquid chromatography/tandem mass spectrometer. Only 9 of the 30 chemicals exhibited relatively high concentrations in the effluent samples. Therefore, these were further characterized for their removals by the constructed wetlands. Atenolol, naproxen, and triclosan consistently showed fairly good removal trends, as measured during both May and August 2007. Sulfamethoxazole and dilantine, and carbamazepine, diazepam and triclosan exhibited medium-range and fluctuating (or somewhat low) removal behaviors, respectively. Attempts were made to determine the dominant removal mechanisms, with regard to soils and plants, using two different extraction methods. However, no substantial amounts were detected, thus it was not possible to induce potential removal mechanisms. Analyses of the removal efficiencies and two characteristic parameters (log K ow and pK a) showed no evidence supporting hydrophobic and electrostatic interactions for the control of micropollutants. [Copyright &y& Elsevier]