Search

Freshwater represents one of the most precious resources on the planet, so it is fundamental to preserve it. In this work, an innovative sunlight‐driven device composed of bismuth oxybromide (BiOBr) grown on a material derived from natural sources, i.e., Lightweight Expanded Clay Aggregates (LECA), is developed to clean surface waters under natural solar light irradiation. For this purpose, the photodegradation of two non‐steroidal anti‐inflammatory drugs, ibuprofen, and diclofenac, is investigated under varying operative conditions. Laboratory‐ and real‐scale experiments reveal that the fabricated floating BiOBr/LECA photocatalyst fully degrades diclofenac, whereas limited abatement of ibuprofen is observed. Based on the identification of specific transformation products (TPs) during the degradation, this behavior seems to be strongly related to the different structures of the two drugs. In fact, the main TP produced during diclofenac degradation derives from dechlorination and ring condensation: this type of photocatalytic degradation pathway is generally favored over the C─C bonds's cleavage, which is a unique possibility for IBU abatement. Moreover, the potential partial adsorption of these species on the photocatalyst's active sites can cause their deactivation. Finally, reusability tests demonstrate the high stability of the floating composite. [ABSTRACT FROM AUTHOR]

The requirements for water intended for domestic and economic purposes prompt the search for new solutions in surface water treatment technologies. In this study, the enhancement of coagulation processes by connections with adsorption and/or ozonation for surface water treatment was studied. The possibility of a reduction in natural organic matter (NOM) content in modified surface water was analysed regarding changes in colour, turbidity, oxidisability (OXI), total and dissolved organic carbon (TOC, DOC) and absorbance at 254 nm (UV254). Additionally, the changes in copper and zinc ion content during the modified surface water treatments studied were analysed for initial metal concentrations of 0.5 or 1.0 mg/L. Studies of modified surface water were carried out with doses of medium-basicity PAX coagulant (C2) 5 mg/L and PAC 100 mg/L. During the coagulation process, the colour decreased by 86–90%, turbidity by 85–90%, OXI by 65–77%, TOC by 65–76% and UV254 absorbance by 73–84%. The enhancement of coagulation with adsorption and/or ozonation resulted in an increased efficiency of colour and turbidity removal by 2 and 4%, respectively. The highest increase in efficiencies of OXI, TOC, DOC and UV254 removal, by 12, 12, 11 and 11%, was observed for the connection of ozonation with coagulation and adsorption. The efficiency of metal ion removal from modified water observed for the single coagulation process was 58 and 55% for copper and 46 and 43% for zinc, respectively, for initial concentrations of 0.5 and 1.0 mg/L. The intensification of coagulation with ozonation and adsorption resulted in metal removal on the level of 66 and 62% for copper and 62 and 54% for zinc. [ABSTRACT FROM AUTHOR]

This is the first study to describe a novel, patented process for the on-site synthesis and subsequent direct utilisation of Polyferric Chloride (PFC) at low Fe concentration dosing, which aims to facilitate the potential replacement of Polyaluminium Chloride (PAC) during surface water treatment (e.g., from reservoirs) for drinking water production. For this purpose, the PFC was synthesised and subsequently used as a coagulant in simulated surface water samples under different synthesis and coagulation/flocculation conditions, namely for different pre-hydrolysed Fe concentrations, pre-hydrolysis pH, coagulation pH, and flocculation times. The effectiveness of PFC was examined mainly in terms of total organic carbon (TOC) removal and the residual Fe concentration. The obtained results showed that the pre-hydrolysed Fe concentration at 0.5 ± 0.25%, pre-hydrolysis at pH 2.5 ± 0.25, coagulation at pH 5.5–7.0 and a flocculation time of 5 min could result in the highest TOC removal (i.e., residual values < 0.60 mg/L) and the lowest residual Fe concentration (<5 μg Fe/L), which is acceptable for a water quality assessment. These values are also substantially lower when compared to the respective TOC and residual metal concentrations using PAC (usually, the relevant obtained values are around TOC > 1 mg/L and Al > 50 μg/L). [ABSTRACT FROM AUTHOR]

Copyright of Applied Chemical Industry is the property of Shaanxi Research Design Insitute of Petroleum & Chemical Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Here, multifunctional heterogeneous ion-exchange metal nanocomposite membranes were prepared for surface water desalination and bacterial inactivation under low-pressure (0.05 MPa) filtration conditions. Ultrafiltration (UF) heterogeneous ion exchange membranes (IEMs) were modified with different concentrations of AgNO3 and CuSO4 solutions using the intermatrix synthesis (IMS) technique to produce metal nanocomposite membranes. Scanning electron microscopy (SEM) images revealed that the metal nanoparticles (MNPs) (Ag and Cu) were uniformly distributed on the surface and the interior of the nanocomposite membranes. With increasing metal precursor solution concentration (0.01 to 0.05 mol·L−1), the metal content of Ag and Cu nanocomposite membranes increased from 0.020 to 0.084 mg·cm−2 and from 0.031 to 0.218 m·cm−2 respectively. Results showed that the hydrodynamic diameter diameters of Ag and Cu nanoparticles (NPs) increased from 62.42 to 121.10 nm and from 54.2 to 125.7 nm respectively, as the metal precursor concentration loaded increased. The leaching of metals from metal nanocomposite membranes was measured in a dead-end filtration system, and the highest leaching concentration levels were 8.72 ppb and 5.32 ppb for Ag and Cu, respectively. The salt rejection studies indicated that ionic selectivity was improved with increasing metal content. Bacterial filtration showed higher antibacterial activity for metal nanocomposite membranes, reaching 3.6 log bacterial inactivation. [ABSTRACT FROM AUTHOR]

The utilization of biochar holds promise as a viable method for the preservation of water resources and the remediation of wastewater. The objective of this study is to evaluate the advancements achieved in the field of biochar research pertaining to the remediation of surface water. The review was conducted by systematically collecting data from Scopus and doing bibliometric analysis. This study utilized the Scopus database to retrieve data pertaining to countries, institutions, highly cited articles, keywords, emerging subjects, and prospective research directions. Furthermore, the VOSviewer bibliometric software was utilized to assess the scholarly citations in this research paper. The results indicate that significant advancements have been achieved in this area of study during the year 2015. A total of 48 works has been indexed by Scopus, a renowned academic database, across 28 distinct international journals. A significant proportion of researchers primarily operate within the United States, often engaging in collaborative efforts with their counterparts from China. This article attempts to study the bibliography on the biochar for surface water treatment, identify popular topics, and discern the fields of future studies in this discussion. Furthermore, it investigates future research in the field of biochar will primarily concentrate on optimizing the synthesis of biochar and exploring its potential use in the treatment of heavy metals and organic chemicals. [ABSTRACT FROM AUTHOR]

Organic matter present in natural water is a serious problem during water treatment in terms of the possibility of creating disinfection by-products (DBP). The new materials and processes are still analyzed in order to improve the efficient removal of organic matter as well as other pollutants from water intended for human consumption. The aim of the presented study was to evaluate the efficiency of using various combined processes: (a) coagulation and adsorption, (b) oxidation with ozone and coagulation, (c) oxidation with ozone, coagulation and adsorption, and (d) oxidation with ozone, UV irradiation, coagulation and adsorption for treatment of the modified surface water. In the presented study, the changes in pH, turbidity, color, organic matter content (evaluated as oxidizability, total and dissolved organic carbon content, UV 254 and 272 absorbances), and Ni2+, Cd2+, and Pb2+ ions content were determined during modified surface water purification. Supporting the coagulation process by adsorption with additional ozonation and UV irradiation of the water sample improved the treatment processes of modified surface water. Processes associated with coagulation increased the efficiency of removing color by 4–16% and reduced the value of UV254 and UV272 absorbance by 10–20%. Using ozonation did not significantly change the content of total organic matter. Heavy metal ions were mostly removed by coagulation and adsorption processes (40–60%). Including ozone, oxidation resulted in insignificant changes in the concentration of metal ions in the purified water (less than 5%). During the treatment of the tested, modified surface water, the best efficiency was observed after the use of coagulation and adsorption processes enhanced with ozone oxidation. The additional involvement of UV irradiation did not have a significant effect on the removal of the analyzed pollutants. [ABSTRACT FROM AUTHOR]

Steam system water inventory is mainly supplied by surface sources, such as lakes or rivers. The incoming surface water is highly contaminated with organic matter and mineral salts. Inadequate treatment of such water sources results in severe and widespread deposits and water-side corrosion. This paper studied the Fenton oxidation with coagulation as pretreatment of the surface water from Nile River (Ismailia Channel) used as makeup boiler water. The incoming water has been analyzed and characterized for one year; the examined characteristics in this work are pH, total dissolved solid (TDS), total hardness (TH), chlorides, total alkalinity (TA), and organic matter (OM). Additionally, the effect of two types of coagulants and Fenton oxidation process on the reduction of the above characteristics has been studied. Moreover, the effect of the combination of Fenton/coagulation process was investigated. The influence of Fe2+ concentration and coagulant dosages was studied. The experimental work was carried out by using Jar test. The results proved that coagulation with ferric chloride is more beneficial than alum at similar doses. It is also found that treatment by Fenton oxidation with coagulation is more effective than coagulation or Fenton oxidation, under operating conditions ([Fe2+] = 10 mg/L; Fe2+:H2O2 = 1.25:1; initial pH = 2.8; followed by coagulation at initial pH 8 with 5 mg/L ferric chloride). [ABSTRACT FROM AUTHOR]

The goal of the research was to determine the effects of artificial infiltration as an initial water treatment process at the river water intake. The effects were determined with respect to removal of chemical admixtures as well as lowering microbiological parameters. The impact of the seasons and operating conditions of the intake on the achievement of stabilized infiltration effects was investigated. The research was carried out on a water intake for a town with a population of 500,000 in Central Poland. The field research installation was used for the tests. The metering wells (piezometers) were drilled along the water flow path from the pond to the collecting well. The effects of infiltration were assessed in terms of the changes of the physical, chemical and microbiological parameters of infiltration water, compared to river water. The test results confirmed that the infiltration process improves the physicochemical and microbiological parameters of water. The water after the infiltration process exhibits similar characteristics to groundwater. The infiltration effects are affected by the phase of the pond operation cycle. This was visible in the case of organic compounds, the removal of which were the lowest at the beginning of pond operating cycle. [ABSTRACT FROM AUTHOR]

In the current study, aluminum formate was synthesized in various molar ratios (formic acid to aluminum) from 1 to 2.5 using aluminum hydroxide and formic acid. The coagulation ability of synthesized compounds was evaluated and compared with alum. All the aluminum formates synthesized with various molar ratios (i.e., 1-2.5) were performed similar to alum except molar ratio 1. The influence of coagulant dose, pH, and alkalinity-turbidity combinations on coagulation behavior of aluminum formates was determined using jar test. The optimum coagulant dose for aluminum formate was found as 80 mg/L. The optimum pH for lower residual turbidity was achieved at pH 6 using aluminum formate. The residual aluminum concentration of aluminum formate synthesized with molar ratio 2.5 was within the limits. In addition to that for higher OH-, CO3 2-, and HCO3 - alkalinity and turbidity combination relatively small quantity of coagulant was sufficient to remove turbidity effectively than with low OH-, CO3 2-, and HCO3 - alkalinity and turbidity combination. [ABSTRACT FROM AUTHOR]

The study investigated the effects of pre-ozonation on the parameters such as turbidity, color, chlorophyll a and TOC on a pilot scale. The investigation results indicate that the amount of required ozone to remove TOC, color and turbidity depends on the quality of inlet water, and the efficiency of water ozonation depends on the process factors such as ozone dose, temperature, pH and ozone-water contact time. The study likewise shows that the lower amount of turbidity, TOC, temperature and higher alkaline pH of sample water boost the ozonation effect on removing the variables in question. The results also demonstrate a direct relationship between pH, ozone dosage and contact time, as well as an indirect relationship between temprerature and the removal of parameters. [ABSTRACT FROM AUTHOR]

This study presents the preparation of a novel inorganic-biological composite flocculant, termed PAFC-CBF, which is composed of polymeric aluminum ferric chloride (PAFC) and compound bio-flocculant (CBF). It was investigated under different PAFC/CBF weight ratios. The turbidity and total organic carbon (TOC) removal efficiency were also investigated, when PAFC-CBF was added to the surface water. Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were performed to characterize PAFC-CBF. Finally, floc properties including floc strength and recoverability were investigated using Mastersizer 2000. The results of the investigation indicated that CBF was successfully embedded into PAFC, forming a novel flocculant with the characteristic structure of PAFC and CBF. Considering the flocculation efficiency and economic cost, PAFC-CBF demonstrated a superior flocculation performance at the flocculant dosage of 25 mg/L, with an optimal turbidity removal efficiency of 90.28%, and a TOC removal efficiency of 26.75%. During the flocculation process, charge neutralization, adsorption bridging and sweep mechanisms served in the main role of colloidal destabilization and aggregation. [ABSTRACT FROM AUTHOR]

The impact of feed water quality on biofilm formation during membrane distillation (MD) was investigated in this study, particularly emphasizing the interrelationship between organics, salts, and microbes. Two types of typical natural surface waters in Nanjing, China, were chosen as feed solutions for long-term MD operation, including the Qinhuai River and Xuanwu Lake. The biofilms that developed under different feed water qualities exhibited distinct Foulant compositions and structures, causing different flux decline trends for the MD system. Accordingly, two typical patterns of biofilm formation were suggested for the MD operation of the two different kinds of surface waters in this study. Organics from a primal feed solution and dead bacteria were the key to the establishment of a biofilm on the membrane, and this needs to be effectively removed from the MD system through pre-treatment and process control strategies. Finally, a feasible strategy for MD biofouling control was suggested. [ABSTRACT FROM AUTHOR]

Port Said Canal is one of the man-made Nile branches in Egypt that gain its water supply via the Ismailia Canal. The canal extended parallel to the Suez Canal navigation route providing the surrounding region the necessary drinking and irrigation waters. The water treatment plants along the canal use the surface water as a crude supply without preliminary pre-filtration process, and chlorination is applied in two phases, which may impose some health hazards. The study aims to ensure that the finished water is safe to drink and meet the international drinking water regulations. The public water purification systems in four treatment plants along Port Said Canal were tested for their efficiency and chlorination by-products. Raw and treated waters in these plants were analyzed for organic, toxic, trace, and heavy elements. Flow measurements were implemented at five sections along the main canal course during the summer and the winter seasons. Results indicated that the treated water suffers from low filtering effectiveness and exceeds the drinking water standards for the trihalomethane species. Furthermore, the change of canal flow from influent to effluent conditions during the winter season increases the contaminants' concentrations. Also, the heavy metal concentrations in the treated water samples from all treatment works were much higher than that of the raw water samples, especially for those higher in suspended particulate matter. The study proposed a better purification system including, sedimentation and gravel pre-filtration combined with slow sand filtration and underground water passage for the elimination of the existing pollution problems. [ABSTRACT FROM AUTHOR]

Environmental context: Contamination of surface water by micropollutants is a major environmental concern because of their high persistence and toxicity. Micropollutants are only partially removed in nanofiltration water treatment systems, encouraging the investigation of more complex systems involving partitioning with membrane materials, organic matter and ion exchange resins. This study elucidates the micropollutant partitioning mechanisms in this complex water treatment system. The accumulation of micropollutants, such as steroid hormones, in magnetic ion exchange resin-nanofiltration (MIEX-NF) poses a risk to the environmental contamination of surface water where the treated water is discharged. In this study, the partitioning of the steroid hormone estradiol (E2) with humic acid (HA), MIEX and the membrane is investigated at different feed water conditions (e.g. pH and presence of calcium). The transport and adsorption of E2 in NF is not affected significantly by the E2-HA interaction. Indeed, E2 partitions with HA between 8 % and 25 % at different pH. This is attributed to the presence of calcium ions, which reduces the number of HA molecules available to interact with E2 molecules. The calcium interference is evident especially at pH > 10, where calcite and HA precipitate to result in irreversible membrane fouling. In the hybrid MIEX-NF process, the E2-MIEX interaction occurs at all pH conditions. Approximately 40 % of the E2 total mass partitions with MIEX. This is significantly higher than E2 accumulation in NF. Since the partitioning is at least partially reversible, this poses a risk for accidental E2 release into the process streams. Environmental context. Contamination of surface water by micropollutants is a major environmental concern because of their high persistence and toxicity. Micropollutants are only partially removed in nanofiltration water treatment systems, encouraging the investigation of more complex systems involving partitioning with membrane materials, organic matter and ion exchange resins. This study elucidates the micropollutant partitioning mechanisms in this complex water treatment system. [ABSTRACT FROM AUTHOR]

The present study highlights the effect of the periodical cleaning by backwashing and forward flushing, on fouling mitigation in a pressurized ultrafiltration (UF) membrane process treating high turbid surface water. The results showed that coupling backwashing and forward flushing has a better effect on membrane permeability recovery than applying only one cleaning technique. Moreover, during periodical cleaning, starting by backwashing followed by forward flushing would allow a better membrane recovery. A cake formation model was used to simulate the global trend of the relative membrane permeability. The modelling study enabled to quantify the effect of different cleaning strategy on fouling mitigation. [ABSTRACT FROM AUTHOR]

The primary problem for the application of microfiltration (MF) and ultrafiltration (UF) membrane technology is membrane fouling. Such is the case that understanding membrane fouling has become one of the major factors driving MF and UF membrane technology forward. Nevertheless, identifying the constituents that most contribute to membrane fouling and quantifying how they are detached when backwashing (BW) and cleaning-in-place (CIP) are applied still remains a challenging task. The aim of the present study was to quantify membrane fouling development during filtration and membrane fouling detachment during BW and CIP in terms of membrane permeability changes and masses of inorganic and organic constituents accumulated on the membrane. The study was conducted using bench-scale MF and UF modules fed with coagulated and settled water coming from a drinking water treatment plant and operated under dead-end and cross-flow operation modes. The experiments consisted inconsecutive permeation (20 min) alternated with BW with permeate water (1.0 min) (periodically chemically assisted with NaClO and NaOH) and followed by a two-stage CIP consisting first in an oxidising and basic step (NaClO and NaOH) and second in an acidic step (citric acid). Feed, permeate, retentate (when present) and cleaning discharge streams were monitored for turbidity, total and dissolved organic carbon (TOC and DOC, respectively), UV254and inorganic ions (Al, Fe, P). DOC was fractionated by high-performance size exclusion chromatography to gain insight into the behaviour of the different organic fractions. Results showed that both MF and UF membranes successfully removed turbidity, Al and Fe, whereas UV254was moderately removed and TOC and DOC poorly removed, with removal percentages higher for UF than for MF. With regard to the organic fractions, the largest molecular weight compounds were moderately removed while the smallest organic fractions seemed to totally permeate through both membranes. The results also showed that foulants were poorly washed out from the membrane by BW, but better extracted by the two-stage CIP up to a complete detachment for some foulants. [ABSTRACT FROM AUTHOR]

Filtration characteristics in surface water treatment using tubular microfiltration and ultrafiltration membranes made of polypropylene or ceramic were investigated. A series of filtration experiments were performed to examine the flux behaviors and fouling propensity. When the initial flux was set to be same, the fouling rates were similar regardless of the membrane materials and pore size, suggesting that the hydrodynamic effect was dominant compared with physicochemical interactions between foulants and membranes. Based on theoretical analysis of critical flux, the major foulants were identified to be colloidal particles which size ranges from 0.01 to 0.1 μm. To control the membrane fouling, three methods were compared including (1) periodic backwashing; (2) intermittent operation (periodic pump stop); and (3) the mixed operation of dead end and cross-flow modes. Considering the anti-fouling effect and energy consumption, the mixed operation of dead end and cross-flow modes was better than other operation methods. [ABSTRACT FROM AUTHOR]

Membrane fouling is an inherent phenomenon in ultrafiltration (UF) membrane processes, making it necessary to periodically perform backwashes (BW) and chemical “cleanings in place” (CIP) to restore the initial permeability of the membrane. The objective of this study was (1) to explore systematically the effect of distinct BW-related variables (BW transmembrane pressure, duration, frequency and composition) on the reversibility of UF membrane fouling and on the permeate quality (in terms of total organic carbon, turbidity and UV absorbance) over successive filtration/BW cycles; and (2) to identify which organic fractions were most removed by the membrane and, of these, which were most detached after BW, alkaline and oxidant CIP and acid CIP episodes. For this purpose, a bench-scale outside-in hollow fibre module operated under dead-end filtration mode at constant transmembrane pressure and treating settled water from a drinking water treatment plant was employed. Dissolved organic carbon fractionation was performed by high-performance size-exclusion chromatography. Results showed that, in general, the more intensive the BW was (in terms of high transmembrane pressure, shortened frequency and prolonged duration) the more effective it was in removing fouling from the membrane. Concerning the composition of the water used for the BW, the addition of NaClO led to maximum fouling reversibility, closely followed by the combination of NaOH + NaClO, while citric acid and NaOH contributed little compared to water alone. However, results also showed that irreversible fouling was never completely avoided whatever the BW regime applied, leading to a gradual increase in the total resistance over time. Larger differences in the behaviour of the different organic fractions were observed. UF membrane preferentially retained the heaviest fraction of biopolymers (BP), while the intermediate fraction of humic substances (HS) was removed at a lower percentage and the lighter fractions seemed to entirely pass through the UF membrane. The successive application of BW and CIPs resulted in the detachment from the membrane of a significant percentage of the retained BP, whereas only a modest percentage of the retained HS. [ABSTRACT FROM PUBLISHER]

BACKGROUND The aim of this work was the investigation of background water matrix impact on the effectiveness of a hybrid process, combining ceramic membrane microfiltration with oxidation processes for the treatment of surface water. The implementation of ozone-based oxidation during membrane filtration is expected to improve the overall process effectiveness, to enhance the permeate quality and to mitigate membrane fouling. RESULTS The novel hybrid reactor consisted of a submerged ceramic membrane, while the gas-containing ozone was introduced with the aid of ceramic gas spargers, producing fine bubbles. Total consumption of ozone during the experiments was achieved. Single ozonation experiments and ozonation in the presence of hydrogen peroxide were performed, as well as single microfiltration ( MF). The novelty of this study is connected with the specific investigation of the carbonates and background ions influence on the effectiveness of various membrane hybrid treatment processes; the fouling process and mechanism during the application of membrane filtration was also examined. The connection between permeate quality and the extent of membrane fouling was also discussed. CONCLUSIONS In the absence of carbonates in the treated water the hybrid processes resulted in a TOC removal up to 75%, while membrane fouling was substantially reduced. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Coagulation with sludge flotation and rapid filtration was selected as a surface water treatment technology to be optimised with a full-scale investigation, which was carried out in Poland between August and October 2013. The river water treated was characterized by low alkalinity, high-temperature variability and a high organic matter content. In the course of technological studies, the processes of coagulation with sludge flotation and rapid filtration were analysed. The studies were performed in the most adverse conditions for the applied technology i.e. during the period of algal bloom and subsequent decomposition of dead plankton. Throughout the study, the river water contained mainly dissolved organic matter, with occasional increases in the concentration of the undissolved fraction during algal bloom. The undissolved total organic carbon (TOC) fraction was effectively removed through coagulation while small doses of ClO2 added prior to coagulation enhanced the process. The process of coagulation using high-coagulant doses at pH = 6.5 did not provide a reduction in the TOC value below the level of 4 mg C/L required for treated water. The effect was achieved by adding powdered activated carbon (PAC) before the filters. The coagulation products were characterised by low-hydraulic resistance which should be taken into account at the stage of water delivery to the filters, after flotation. [ABSTRACT FROM AUTHOR]

The removal of natural organic matter (NOM) is a critical aspect of potable water treatment because NOM compounds are precursors of harmful disinfection by-products, hence should be removed from water intended for human consumption. Ultrafiltration using ceramic membranes can be a suitable process for removal of natural substances. Previously reported experiments were dedicated to evaluating the suitability of ultrafiltration through ceramic membrane for water treatment with a focus on the separation of natural organic matter. The effects of the membrane operating time and linear flow velocity on transport and separation properties were also examined. The experiments, using a 7-channel 300 kDa MWCO ceramic membrane, were carried out with model solutions and surface water at trans-membrane pressure of 0.2-0.5 MPa. The results revealed that a loose UF ceramic membrane can successfully eliminate natural organic matter from water. The permeability of the membrane was strongly affected by the composition of the feed stream, i.e. the permeate flux decreased with an increase in the NOM concentration. The permeate flux also decreased over the period of the operation, while this parameter did not influence the effectiveness of separation, i.e. the removal of NOM. It was observed that the increased cross-flow velocity resulted in the decrease in the membrane-fouling intensity and slightly improved the retention of contaminants. [ABSTRACT FROM AUTHOR]

The kinetic formation of biofilms developing on nanofiltration (NF) membranes was studied for 2 years in the water production unit of Méry-sur-Oise, France. New membranes were set up in a pilot train integrated to the plant and autopsied after operation for 7, 80, 475 and 717 days. The biofouling layer was studied by confocal laser scanning microscope after 4′,6-diamidino-2-phenyindole dihydrochloride and lectin staining, and by attenuated total reflectance-Fourier transform infrared spectroscopy and rheology experiments. Three stages of biofilm growth were discriminated: (1) the presence of sessile microcolonies embedded in an exopolymeric matrix (after filtration for seven days); (2) membrane coverage expansion through microcolony development and biofilm growth in three dimensions (up to 80 days filtration); and (3) biofilm maturation by densification (after filtration for 80–717 days). Biofilm maturation resulted in total coverage of the membrane surface and matrix residue diversification, development of the polysaccharide network, and the strengthening of matrix cohesion through viscosity and elasticity increases. The wettability and permeability of the fouled NF membranes decreased quickly and continuously throughout the biofilm development process. The longitudinal pressure drop (LPD) increased only after the biofilm reached a quantitative threshold. The decline in membrane permeability may be the result of contributions from many fouling mechanisms but the LPD was more substantially influenced by biofilm development. [ABSTRACT FROM PUBLISHER]

This research details the effects of ozone pretreatment on flux of a reverse osmosis membrane. Initial tests were conducted to determine the effects of ozonation on solids removal, turbidity, and chemical oxygen demand concentrations using various doses on a simulated surface water. These initial tests showed that the best reduction of solids in the 2-5 microns range was at 0.30 mg/L of ozone. Next, a series of bench scale tests was run for 62.5 hours using a standard reverse osmosis system under constant pressure with three pre-ozonation doses and a no ozone baseline dose. Temporal models were developed using the flux data from these tests to determine the effects of operating hours and ozone dosage on flux. It was found that the laboratory data were not linear and followed power law models. Statistical analysis was used to determine the significance of each ozone dose on the four developed models. The change in flux over the 62.5 operating hours with an ozone dosage of 0.30 mg/L showed the lowest flux change. Last, the models were tested using Hermia's filtration models and resistance versus time data to determine the type of membrane fouling that existed. It was concluded that the major fouling was pore blockage. This work demonstrated that ozone pretreatment is effective prior to use with reverse osmosis since it shows a better solid and organic removal rate as well as decreased flux and resistance changes over time. [ABSTRACT FROM AUTHOR]

Surface flow constructed wetlands (SFCWs) can be effectively used to treat agricultural drainage waters, reducing N and P surface water pollution. In the Venice Lagoon drainage basin (northeastern Italy), an SFCW was monitored during 2007–2013 to assess its performance in reducing water, N, and P loads more than 10 years after its creation. Nitrogen concentrations showed peaks during winter due to intense leaching from surrounding fields. Phosphorus concentrations were higher after prolonged periods with no discharge, likely due to mobilization of P of the decomposing litter inside the basin. Over the entire period, N removal efficiency was 83% for NO3–N and 79% for total N; P removal efficiency was 48% for PO4–P and 67% for total P. Values were higher than in several other studies, likely due to the fluctuating hydroperiod that produced discontinuous and reduced outflows. Nitrogen outlet concentrations were reduced by the SFCW, and N removal ratios decreased with increasing hydraulic loading, while no strong correlations were found in the case of P. The SFCW was shown to be an effective long-term strategy to increase water storage and reduce N and P loads in the Venice Lagoon drainage basin. [ABSTRACT FROM AUTHOR]

Natural water treatment techniques combined with engineered solutions were investigated at demonstration sites in Europe within the AquaNES project. Ultrafiltration is well-established in water treatment, but is not feasible for many water utilities due to its high operational costs compared to conventional treatment. These differences in cost are caused by membrane fouling and the associated cleaning required. This study aims to assess the economic and energetic operation factors based on studies of an out/in ultrafiltration treatment plant for river water and bank filtrate. The fouling potential of both raw water sources was investigated as well as the quality of the resulting water. In addition, the results show the potential utility of a combined approach utilizing bank filtration followed by ultrafiltration in drinking water treatment. In a separate consideration of the treatment process, the water quality does not fulfill the requirements of the German drinking water ordinance. A new method for the removal of dissolved manganese from the bank filtrate is presented by inline electrolysis. While this improves water quality, this also has a significant influence on fouling potential and, thus, on operating costs of ultrafiltration. These aspects lead to a fundamental decision for operators to choose between more costly ultrafiltration with enhanced microbiological safety compared to cost-effective but less stringent drinking water treatment via open filtration. [ABSTRACT FROM AUTHOR]