Impact of salinity and pH on the UVC/H2O2 treatment of reverse osmosis concentrate produced from municipal wastewater reclamation

While reverse osmosis (RO) technology is playing an increasingly important role in the reclamation of municipal wastewater, safe disposal of the resulting RO concentrate (ROC), which can have high levels of effluent organic pollutants, remains a challenge to the water industry. The potential of UVC/H₂O₂ treatment for degrading the organic pollutants and increasing their biodegradability has been demonstrated in several studies, and in this work the impact of the water quality variables pH, salinity and initial organic concentration on the UVC/H₂O₂ (3 mM) treatment of a municipal ROC was investigated. The reduction in chemical oxygen demand and dissolved organic carbon was markedly faster and greater under acidic conditions, and the treatment performance was apparently not affected by salinity as increasing the ROC salinity 4-fold had only minimal impact on organics reduction. The biodegradability of the ROC (as indicated by biodegradable dissolved organic carbon (BDOC) level) was at least doubled after 2 h UVC/H₂O₂ treatment under various reaction conditions. However, the production of biodegradable intermediates was limited after 30 min treatment, which was associated with the depletion of the conjugated compounds. Overall, more than 80% of the DOC was removed after 2 h UVC/3 mM H₂O₂ treatment followed by biological treatment (BDOC test) for the ROC at pH 4-8.5 and electrical conductivity up to 11.16 mS/cm. However, shorter UV irradiation time gave markedly higher energy efficiency (e.g., EE/O 50 kWh/m³ at 30 min (63% DOC removal) cf. 112 kWh/m³ at 2 h). No toxicity was detected for the treated ROC using Microtox^® tests. Although the trihalomethane formation potential increased after the UVC/H₂O₂ treatment, it was reduced to below that of the raw ROC after the biological treatment.     

Advanced treatment of the reverse osmosis concentrate produced during reclamation of municipal wastewater

The work investigated the treatment of the concentrate produced from the reverse osmosis treatment of an MBR effluent. Two conventional chemical processes, coagulation and activated carbon adsorption, and three advanced oxidation processes (electrochemical treatment, photocatalysis and sonolysis) were applied. Coagulation with alum gave dissolved organic carbon (DOC) removals up to 42%, while FeCl(3) achieved higher removals (52%) at lower molar doses. Adsorption with granular activated carbon showed the highest DOC removals up to 91.3% for 5 g/L. The adsorption isotherm was linear with a non-adsorbable organic fraction of around 1.2 mg/L DOC. The three oxidation methods employed, electrolytic oxidation over a boron-doped diamond electrode, UVA/TiO2 photocatalysis and sonolysis at 80 kHz, showed similar behavior: during the first few minutes of treatment there was a moderate removal of DOC followed by further oxidation at a very slow rate. Electrolytic oxidation was capable of removing up to 36% at 17.8A after 30 min of treatment, sonolysis removed up to 34% at 135W after 60 min, while photocatalysis was capable of removing up to 50% at 60 min.     

Cyclophosphamide removal from water by nanofiltration and reverse osmosis membrane

The rejection of cyclophosphamide (CP) by nanofiltration (NF) and reverse osmosis (RO) membranes from ultrapure (Milli-Q) water and membrane bioreactor (MBR) effluent was investigated. Lyophilization-extraction and detection methods were first developed for CP analysis in different water matrices. Experimental results showed that the RO membrane provided excellent rejection (>90%) under all operating conditions. Conversely, efficiency of CP rejection by NF membrane was poor: in the range of 20-40% from Milli-Q water and around 60% from MBR effluent. Trans-membrane pressure, initial CP concentration and ionic strength of the feed solution had almost no effect on CP retention by NF. On the other hand, the water matrix proved to have a great influence: CP rejection rate by NF was clearly enhanced when MBR effluent was used as the background solution. Membrane fouling and interactions between the CP and water matrix appeared to contribute to the higher rejection of CP.     

Electrochemical oxidation of reverse osmosis concentrate on mixed metal oxide (MMO) titanium coated electrodes

Reverse osmosis (RO) membranes have been successfully applied around the world for wastewater reuse applications. However, RO is a physical separation process, and besides the clean water stream (permeate) a reverse osmosis concentrate (ROC) is produced, usually representing 15-25% of the feed water flow and containing the organic and inorganic contaminants at higher concentrations. In this study, electrochemical oxidation was investigated for the treatment of ROC generated during the reclamation of municipal wastewater effluent. Using laboratory-scale two-compartment electrochemical systems, five electrode materials (i.e. titanium coated with IrO₂-Ta₂O₅, RuO₂-IrO₂, Pt-IrO₂, PbO₂, and SnO₂-Sb) were tested as anodes in batch mode experiments, using ROC from an advanced water treatment plant. The best oxidation performance was observed for Ti/Pt-IrO₂ anodes, followed by the Ti/SnO₂-Sb and Ti/PbO₂ anodes. The effectiveness of the treatment appears to correlate with the formation of oxidants such as active chlorine (i.e. Cl₂/HClO/ClO⁻). As a result, electro-generated chlorine led to the abundant formation of harmful by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs), particularly at Ti/SnO₂-Sb and Ti/Pt-IrO₂ anodes. The highest concentration of total HAAs (i.e. 2.7 mg L⁻¹) was measured for the Ti/SnO₂-Sb electrode, after 0.55 Ah L⁻¹ of supplied specific electrical charge. Irrespective of the used material, electrochemical oxidation of ROC needs to be complemented by a polishing treatment to alleviate the release of halogenated by-products.     

Advanced oxidation of the pharmaceutical drug diclofenac with UV/H2O2 and ozone

Diclofenac, a widely used anti-inflammatory drug, has been found in many Sewage Treatment Plant effluents, rivers and lake waters, and has been reported to exhibit adverse effects on fish. Advanced oxidation processes, ozonation and H2O2/UV were investigated for its degradation in water. The kinetic of the degradation reaction and the nature of the intermediate products were still poorly defined. Under the conditions adopted in the present study, both ozonation and H2O2/UV systems proved to be effective in inducing diclofenac degradation, ensuring a complete conversion of the chlorine into chloride ions and degrees of mineralization of 32% for ozonation and 39% for H2O2/UV after a 90 min treatment. The reactions were found to follow similar, but not identical, reaction pathways leading to hydroxylated intermediates (e.g. 2-[(2,6-dichlorophenyl)amino]-5-hydroxyphenylacetic acid) and C-N cleavage products (notably 2,5-dihydroxyphenylacetic acid) through competitive routes. Subsequent oxidative ring cleavage leads to carboxylic acid fragments via classic degradation pathways. In the pH range 5.0-6.0 kinetic constants (1.76 x 10(4)-1.84 x 10(4) M(-1) s(-1)) were estimated for diclofenac ozonation.     

Comparison of the removal of hydrophobic trace organic contaminants by forward osmosis and reverse osmosis

We compared the rejection behaviours of three hydrophobic trace organic contaminants, bisphenol A, triclosan and diclofenac, in forward osmosis (FO) and reverse osmosis (RO). Using erythritol, xylose and glucose as inert reference organic solutes and the membrane pore transport model, the mean effective pore size of a commercial cellulose-based FO membrane was estimated to be 0.74 nm. When NaCl was used as the draw solute, at the same water permeate flux of 5.4 L/m² h (or 1.5 μm/s), the adsorption of all three compounds to the membrane in the FO mode was consistently lower than that in the RO mode. Rejection of bisphenol A and diclofenac were higher in the FO mode compared to that in the RO mode. Because the molecular width of triclosan was larger than the estimated mean effective membrane pore size, triclosan was completely rejected by the membrane and negligent difference between the FO and RO modes could be observed. The difference in the separation behaviour of these hydrophobic trace organics in the FO (using NaCl the draw solute) and RO modes could be explained by the phenomenon of retarded forward diffusion of solutes. The reverse salt flux of NaCl hinders the pore diffusion and subsequent adsorption of the trace organic compounds within the membrane. The retarded forward diffusion effect was not observed when MgSO₄ and glucose were used as the draw solutes. The reverse flux of both MgSO₄ and glucose was negligible and thus both adsorption and rejection of BPA in the FO mode were identical to those in the RO mode.     

Evaluation of UV irradiation for photolytic and oxidative degradation of pharmaceutical compounds in water

A medium-pressure (MP) ultraviolet (UV) system was used to investigate the UV photolysis and UV/H(2)O(2) oxidation of pharmaceutically active compounds (PhACs) that belong to different therapeutic classes and were found to occur in the aquatic environment. The results obtained in laboratory-grade water (LGW) and surface water (SW) were compared with low-pressure (LP) results reported previously. Overall, MP lamps proved to be more efficient to maximize the bench-scale degradation of the selected group of compounds (ketoprofen, naproxen, carbamazepine, ciprofloxacin, clofibric acid, and iohexol) by both UV photolysis and UV/H(2)O(2) oxidation. Fundamental direct and indirect photolysis parameters obtained in LGW are reported and used to model the MP-UV photolysis and MP-UV/H(2)O(2) oxidation of the pharmaceuticals in SW, predicting the experimental results very well.     

Electrochemical oxidation of trace organic contaminants in reverse osmosis concentrate using RuO2/IrO2-coated titanium anodes

During membrane treatment of secondary effluent from wastewater treatment plants, a reverse osmosis concentrate (ROC) containing trace organic contaminants is generated. As the latter are of concern, effective and economic treatment methods are required. Here, we investigated electrochemical oxidation of ROC using Ti/Ru_0.7Ir_0.3O₂ electrodes, focussing on the removal of dissolved organic carbon (DOC), specific ultra-violet absorbance at 254 nm (SUVA₂₅₄), and 28 pharmaceuticals and pesticides frequently encountered in secondary treated effluents. The experiments were conducted in a continuously fed reactor at current densities (J) ranging from 1 to 250 A m⁻² anode, and a batch reactor at J = 250 A m⁻². Higher mineralization efficiency was observed during batch oxidation (e.g. 25.1 ± 2.7% DOC removal vs 0% removal in the continuous reactor after applying specific electrical charge, Q = 437.0 A h m⁻³ ROC), indicating that DOC removal is depending on indirect oxidation by electrogenerated oxidants that accumulate in the bulk liquid. An initial increase and subsequent slow decrease in SUVA₂₅₄ during batch mode suggests the introduction of auxochrome substituents (e.g. -Cl, NH₂Cl, -Br, and -OH) into the aromatic compounds. Contrarily, in the continuous reactor ring-cleaving oxidation products were generated, and SUVA₂₅₄ removal correlated with applied charge. Furthermore, 20 of the target pharmaceuticals and pesticides completely disappeared in both the continuous and batch experiments when applying J ≥ 150 A m⁻² (i.e. Q ≥ 461.5 A h m⁻³) and 437.0 A h m⁻³ (J = 250 A m⁻²), respectively. Compounds that were more persistent during continuous oxidation were characterized by the presence of electrophilic groups on the aromatic ring (e.g. triclopyr) or by the absence of stronger nucleophilic substituents (e.g. ibuprofen). These pollutants were oxidized when applying higher specific electrical charge in batch mode (i.e. 1.45 kA h m⁻³ ROC). However, baseline toxicity as determined by Vibrio fischeri bioluminescence inhibition tests (Microtox) was increasing with higher applied charge during batch and continuous oxidation, indicating the formation of toxic oxidation products, possibly chlorinated and brominated organic compounds.     

Rejection of pharmaceuticals in nanofiltration and reverse osmosis membrane drinking water treatment

This paper investigates the removal of a broad range of pharmaceuticals during nanofiltration (NF) and reverse osmosis (RO) applied in a full-scale drinking water treatment plant (DWTP) using groundwater. Pharmaceutical residues detected in groundwater used as feed water in all five sampling campaigns were analgesics and anti-inflammatory drugs such as ketoprofen, diclofenac, acetaminophen and propyphenazone, beta-blockers sotalol and metoprolol, an antiepileptic drug carbamazepine, the antibiotic sulfamethoxazole, a lipid regulator gemfibrozil and a diuretic hydrochlorothiazide. The highest concentrations in groundwater were recorded for hydrochlorothiazide (58.6-2548ngL(-1)), ketoprofen (85%). Deteriorations in retentions on NF and RO membranes were observed for acetaminophen (44.8-73 %), gemfibrozil (50-70 %) and mefenamic acid (30-50%). Furthermore, since several pharmaceutical residues were detected in the brine stream of NF and RO processes at concentrations of several hundreds nanogram per litre, its disposal to a near-by river can represent a possible risk implication of this type of treatment.     

Degradation of bromoxynil and trifluralin in natural water by direct photolysis and UV plus H2O2 advanced oxidation process

The degradation of two pesticides, bromoxynil and trifluralin, was investigated in ultrapure and natural water solutions under ultraviolet (UV) light and a combination of UV and hydrogen peroxide (H₂O₂). The effect of pH on the photooxidation of the pesticides was also studied. The results indicated that under direct photolysis with monochromatic light at 253.7 nm and different conditions, the photochemical rates followed first-order kinetics, with fluence-based rate constants ranging from 9.15 × 10⁻⁴ to 6.37 × 10⁻³ cm² mJ⁻¹ and 7.63 × 10⁻³ to 1.47 × 10⁻² cm² mJ⁻¹ for bromoxynil and trifluralin, respectively. Quantum yields, in the range of 0.08-0.25 for bromoxynil and 0.12-0.72 for trifluralin, were observed in experiments using ultrapure water. The study also found that the UV/H₂O₂ process enhanced the oxidation rate in comparison to direct photolysis. A 90% degradation with UV dose of 333 and 188 mJ cm⁻² was achieved for bromoxynil and trifluralin, respectively, in natural water, in presence of 8.8 × 10⁻⁴ M H₂O₂. To assess the aquatic toxicity, the Microtox^® 81.9% screening test protocol was used before and after treatment. The test results indicated a decrease in the acute toxicity of the samples after treatment for both pesticides.     

The effect of UV/H2O2 treatment on biofilm formation potential

Greater Cincinnati Water Works (GCWW) evaluated the efficacy of ultraviolet light/hydrogen peroxide advanced oxidation (UV/H₂O₂) for reducing trace organic contaminants in natural water with varying water qualities. A year-long UV/H₂O₂ pilot study was conducted to examine a variety of seasonal and granular activated carbon (GAC) breakthrough conditions. The UV pilot-scale reactors were set to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for by-product formation. Because hydroxyl radicals react non-selectively with organic compounds, unintended by-product formation occurred.Total assimilable organic carbon (AOC) concentration increased through the reactors from 14 to 33% on average, depending on water quality. Natural organic matter (NOM) contains the precursors for AOC production, so when post-GAC water (versus conventionally treated water) served as reactor influent, less AOC was produced. No appreciable difference in AOC concentration was observed between LP and MP UV reactors. The Spirillum strain NOX fraction of the AOC increased from 50 to 65% on average, depending on the quality of the water. The increase in this fraction of AOC occurred because oxidation of NOM yielded smaller more assimilable organic compounds such as organic acids that are necessary for NOX growth. The Pseudomonas fluorescens strain P17 AOC concentration increased only when conventionally treated plant water was used as pilot influent. This organism thrives in waters of differing organic energy sources, but does not thrive well in carboxylic acids alone. The CONV water had more overall TOC that could contribute to higher P17 AOC counts.Biofilm coupon studies indicated that biofilms with greater heterotrophic plate counts were observed in the granular activated carbon (GAC) effluent streams receiving UV/H₂O₂ pre-treatment. Biofilm coupon studies additionally indicated that the effluent stream of the GAC column proceeded by the MP reactor exhibited more viable biofilm than the other GAC effluent streams based on an ATP-bioluminescence method. The increased viability of the biofilm produced by the MP UV reactor is likely a result of the multiple UV wavelengths and higher energy input characteristic of this technology.     

Kinetics and mechanisms of DMSO (dimethylsulfoxide) degradation by UV/H(2)O(2) process

The objective of this study was to elucidate the degradation pathways of dimethylsulfoxide (DMSO) during its mineralization caused by UV/H(2)O(2) treatment. In order to accomplish this, we measured the concentration time-profiles of DMSO and its degradation intermediates during the UV/H(2)O(2) treatment. In addition, we proposed a kinetic model that could account for the degradation pathways of DMSO during its UV/H(2)O(2) treatment. The results show that the degradation of DMSO by the UV/H(2)O(2) treatment can be classified into two major pathways, and this is supported by both the analysis of the intermediates and total organic carbon (TOC) measurements. Firstly, DMSO was degraded into sulfate (SO(4)(2-)) through the formation of methansulfinate (CH(3)SO(2)(-)) and methansulfonate (CH(3)SO(3)(-)) as sulfur-containing intermediates. One of the two carbon constituents of DMSO was highly resistant to mineralization, due to the formation of methansulfonate, which reacted very slowly with (.-)OH k = 0.8 x 10(7) M(-1)s(-1)). Secondly, the other carbon constituent of DMSO was relatively easily mineralized through the formation of formaldehyde (HCHO) and formate (HCO(2)(-)) as non-sulfur-containing intermediates. The kinetic model proposed in this study for the degradation of DMSO by (.-)OH in the UV/H(2)O(2) process was able to successfully predict the patterns of concentration time-profiles of all components during the UV/H(2)O(2) treatment of DMSO.     

Impact of UV/H(2)O(2) advanced oxidation treatment on molecular weight distribution of NOM and biostability of water

The presence of natural organic matter (NOM) poses several challenges to the commercial practice of UV/H₂O₂ process for micropollutant removal. During the commercial application of UV/H₂O₂ advanced oxidation treatment, NOM is broken down into smaller species potentially affecting biostability by increasing Assimilable Organic Carbon (AOC) and Biodegradable Organic Carbon (BDOC) of water. This work investigated the potential impact of UV/H₂O₂ treatment on the molecular weight distribution of NOM and biostability of different water sources. A recently developed flow cytometric method for enumeration of bacteria was utilized to assess biological stability of the treated water at various stages through measurement of AOC. BDOC was also assessed for comparison and to better study the biostability of water. Both AOC and BDOC increased by about 3-4 times over the course of treatment, indicating the reduction of biological stability. Initial TOC and the source of NOM were found to be influencing the biostability profile of the treated water. Using high performance size exclusion chromatography, a wide range of organic molecule weights were found responsible for AOC increase; however, low molecular weight organics seemed to contribute more. Positive and meaningful correlations were observed between BDOC and AOC of different waters that underwent different treatments.     

The effect of UV/H2O2 treatment on disinfection by-product formation potential under simulated distribution system conditions

Advanced oxidation with ultraviolet light and hydrogen peroxide (UV/H₂O₂) produces hydroxyl radicals that have the potential to degrade a wide-range of organic micro-pollutants in water. Yet, when this technology is used to reduce target contaminants, natural organic matter can be altered. This study evaluated disinfection by-product (DBP) precursor formation for UV/H₂O₂ while reducing trace organic contaminants in natural water (>90% for target pharmaceuticals, pesticides and taste and odor producing compounds and 80% atrazine degradation). A year-long UV/H₂O₂ pilot study was conducted to evaluate DBP precursor formation with varying water quality. The UV pilot reactors were operated to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for DBP precursor formation. Two process waters of differing quality were used as pilot influent, i.e., before and after granular activated carbon adsorption. DBP precursors increased under most of the conditions studied. Regulated trihalomethane formation potential increased through the UV/H₂O₂ reactors from 20 to 118%, depending on temperature and water quality. When Post-GAC water served as reactor influent, less DBPs were produced in comparison to conventionally treated water. Haloacetic acid (HAA5) increased when conventionally treated water served as UV/H₂O₂ pilot influent, but only increased slightly (MP lamp) when GAC treated water served as pilot influent. No difference in 3-day simulated distribution system DBP concentration was observed between LP and MP UV reactors when 80% atrazine degradation was targeted.     

Photocatalytic oxidation of DBP precursors using UV with suspended and fixed TiO2

French River water (Nova Scotia, Canada) was separated into six different natural organic matter (NOM) fractions, including hydrophobic acids, bases and neutrals and hydrophilic acids, bases and neutrals. The raw water, as well as each of the NOM fractions were analysed for disinfection by-product (DBP) formation potential before and after advanced oxidation with UV/TiO₂ to determine the efficacy of this treatment for the removal of DBP precursors. The UV/TiO₂ treatment was carried out with a nanostructured thin film (NSTF), coated with TiO₂ which is compared with the use of a TiO₂ suspension. For the raw river water, removals of total trihalomethane formation potential (TTHMFP) and total haloacetic acid formation potential (THAA₉FP) were found to be approximately 20% and 90%, respectively, with 50 mJ/cm² UV exposure and 1 mg/L TiO₂. For the fractionated samples, approximately 75% of both trihalomethane (THM) and haloacetic acid (HAA) precursors were found to be associated with the hydrophobic acid fraction. For this individual fraction the same UV/TiO₂ treatments exhibited approximately 20-25% removal of both TTHMFP and THAA₉FP, suggesting that the fractionation process may have affected the treatability of HAA precursors or may have altered the results of the oxidation processes.     

Glyphosate degradation in water employing the H2O2/UVC process

Glyphosate is the organophosphate herbicide most widely used in the world. Any form of spill or discharge, even if unintentional, can be transferred to the water due to its high solubility. The combination of hydrogen peroxide and UV radiation could be a suitable option to decrease glyphosate concentration to acceptable limits. In this work, the effects of initial pH, hydrogen peroxide initial concentration, and incident radiation in glyphosate degradation were studied. The experimental device was a cylinder irradiated with two tubular, germicidal lamps. Conversion of glyphosate increases significantly from pH = 3-7. From this value on, the increase becomes much less noticeable. The reaction rate depends on the initial herbicide concentration and has an optimum plateau of a hydrogen peroxide to glyphosate molar concentration ratio between 7 and 19. The expected non linear dependence on the irradiation rate was observed. The identification of critical reaction intermediaries, and the quantification of the main end products were possible and it led to propose a plausible degradation path. The achieved quantification of the mineralization extent is a positive indicator for the possible application of a rather simple technology for an in situ solution for some of the problems derived from the intensive use of glyphosate.     

Efficiency and energy requirements for the transformation of organic micropollutants by ozone, O3/H2O2 and UV/H2O2

The energy consumptions of conventional ozonation and the AOPs O₃/H₂O₂ and UV/H₂O₂ for transformation of organic micropollutants, namely atrazine (ATR), sulfamethoxazole (SMX) and N-nitrosodimethylamine (NDMA) were compared. Three lake waters and a wastewater were assessed. With p-chlorobenzoic acid (pCBA) as a hydroxyl radical (^•OH) probe compound, we experimentally determined the rate constants of organic matter of the selected waters for their reaction with ^•OH (k_OH,DOM), which varied from 2.0 × 10⁴ to 3.5 × 10⁴ L mgC⁻¹ s⁻¹. Based on these data we calculated ^•OH scavenging rates of the various water matrices, which were in the range 6.1-20 × 10⁴ s⁻¹. The varying scavenging rates influenced the required oxidant dose for the same degree of micropollutant transformation. In ozonation, for 90% pCBA transformation in the water with the lowest scavenging rate (lake Zürich water) the required O₃ dose was roughly 2.3 mg/L, and in the water with the highest scavenging rate (Dübendorf wastewater) it was 13.2 mg/L, corresponding to an energy consumption of 0.035 and 0.2 kWh/m³, respectively. The use of O₃/H₂O₂ increased the rate of micropollutant transformation and reduced bromate formation by 70%, but the H₂O₂ production increased the energy requirements by 20-25%. UV/H₂O₂ efficiently oxidized all examined micropollutants but energy requirements were substantially higher (For 90% pCBA conversion in lake Zürich water, 0.17-0.75 kWh/m³ were required, depending on the optical path length). Energy requirements between ozonation and UV/H₂O₂ were similar only in the case of NDMA, a compound that reacts slowly with ozone and ^•OH but is transformed efficiently by direct photolysis.     

Alumina nanofibers grafted with functional groups: A new design in efficient sorbents for removal of toxic contaminants from water

A new design in efficient sorbents for the removal of trace pollutants from water was proposed: grafting the external surface of γ-alumina (γ-Al₂O₃) nanofibers with functional groups that have a strong affinity to the contaminants. This new grafting strategy greatly improves the accessibility of these sorption sites to adsorbates and thus efficiency of the fibrous sorbents. The product sorbents could capture the pollutants selectively even when the concentration of the contaminants is extremely low. Two types of γ-Al₂O₃ nanofibers with different size were prepared via facile hydrothermal methods. Thiol groups were then grafted on the γ-Al₂O₃ fibers by refluxing the toluene solution of 3-mercaptopropyltrimethoxysilane (MPTMS). The thiol group modified fibers not only can efficiently remove heavy metal ions (Pb²⁺ and Cd²⁺) from water at a high flux, but also display high sorption capacity under sorption equilibrium conditions. Similar result was obtained from the nanofibers grafted with octyl groups which are employed to selectively adsorb highly diluted hydrophobic 4-nonylphenol molecules from water. This study demonstrates that grafting nanofibers is a new and effective strategy for developing efficient sorbents.     

Effects of ozone and ozone/peroxide on trace organic contaminants and NDMA in drinking water and water reuse applications

An ozone and ozone/peroxide oxidation process was evaluated at pilot scale for trace organic contaminant (TOrC) mitigation and NDMA formation in both drinking water and water reuse applications. A reverse osmosis (RO) pilot was also evaluated as part of the water reuse treatment train. Ozone/peroxide showed lower electrical energy per order of removal (EEO) values for TOrCs in surface water treatment, but the addition of hydrogen peroxide increased EEO values during wastewater treatment. TOrC oxidation was correlated to changes in UV₂₅₄ absorbance and fluorescence offering a surrogate model for predicting contaminant removal. A decrease in N-nitrosodimethylamine (NDMA) formation potential (after chloramination) was observed after treatment with ozone and ozone/peroxide. However, during spiking experiments with surface water, ozone/peroxide achieved limited destruction of NDMA, while in wastewaters net direct formation of NDMA of 6-33 ng/L was observed after either ozone or ozone/peroxide treatment. Once formed during ozonation, NDMA passed through the subsequent RO membranes, which highlights the significance of the potential for direct NDMA formation during oxidation in reuse applications.