Formation of Organic Fouling during Membrane Desalination: The Effect of Divalent Cations and the Use of an Online Visual Monitoring Method.

Reverse osmosis (RO) is the most popular technology for brackish, seawater and wastewater desalination. An important drawback of RO is membrane fouling, which reduces filtration effectiveness and increase the cost of produced water. This study addresses two important topics of membrane fouling: (i) the impact of different divalent ions on the formation of organic fouling and (ii) online monitoring and prediction of fouling formation. In the absence of divalent ions, dissolved organic matter had little effect on fouling formation, even at 3.5 mgC/L, in the upper range of groundwater concentration. Calcium, strontium and iron enhanced (organic) fouling formation, whereas barium had negligible effect. However, while iron affected fouling throughout the entire tested range (0-0.5 mg/L), calcium and strontium enhanced organic fouling only at high concentrations: more than 140 mg/L and 10 mg/L for calcium and strontium, respectively. An online system was developed for monitoring the formation of organic fouling, consisting of (i) an ex-situ RO cell with a transparent cover, (ii) a video camera continually monitoring the surface of the membrane and (iii) an algorithm which automatically identified changes in the color of the membrane caused by fouling, using a specially designed membrane spacer with colored reference dots. Changes in the color of the membrane surface were normalized to the reference colors, to eliminate all non-fouling related interference. The system was used to record and analyze changes in membrane color during numerous filtration tests. The data was successfully correlated to changes in specific flux (and subsequently to fouling formation rate) and can be applied to monitor and predict the formation of membrane fouling during desalination.

Detection of N-nitrosodimethylamine (NDMA) and its formation potential in hospital wastewater.

Hospital wastewaters contain high concentrations of pharmaceutical residues and other chemicals, and may present an important source for NDMA (N-nitrosodimethylamine) and its precursors in the aquatic environment. The present study evaluates the contribution of hospital wastewater to NDMA environmental load and identifies important sources within the hospital itself. For this purpose, wastewaters from five large hospitals in Israel were analyzed, and concentrations of NDMA were found in the range of 20.7-56.7 ng/L, which are similar to NDMA concentrations typically detected in domestic wastewater. The relative contribution of day surgery, oncology, laboratories, and central kitchen (in Sheba hospital) to the daily load of NDMA was calculated as 20.2%, 8.2%, 10%, and 43.2%, respectively. In addition, NDMA concentration in Sheba's mixed wastewater stream, measured throughout a complete working day, was highest at 14:00. This suggests the possible impact of lunchtime on NDMA concentration, and emphasizes the dominant contribution of central kitchen waste. Finally, formation potential of NDMA in the mixed stream was 7300 ng/L, in the upper range of domestic wastewater, but could be decreased by 70% during subsequent aerobic biological wastewater treatment.

Pseudoviruses for the assessment of coronavirus disinfection by ozone.

The COVID-19 pandemic has severely impacted public health worldwide. Evidence of SARS-CoV-2 transmission via aerosols and surfaces has highlighted the need for efficient indoor disinfection methods. For instance, the use of ozone gas as a safe and potent disinfectant against SARS-CoV-2 virus is of particular interest. Here we tested the use of pseudoviruses as a model for evaluating ozone disinfection of the coronavirus at ozone concentrations of 30, 100, and 1000 ppmv. Results show that ozone disinfection rate of pseudoviruses was similar to that of coronavirus 229E (HuCoV-229E) at short contact times, below 30 min. Viral infection decreased by 95% following ozone exposure for 20 min at 1000 ppmv, 30 min at 100 ppmv and about 40 min at 30 ppmv. This findings mean that ozone is a powerful disinfectant toward the enveloped pseudovirus even at low ozone exposure. We also showed that viral disinfection occurs on various contaminated surfaces, with a positive association between disinfection and surface hydrophilicity. Infected surfaces made of aluminum alloy, for example, were better disinfected with ozone as compared to brass, copper, and nickel surfaces. Lastly, we demonstrate the advantage of ozone over liquid disinfectants by showing similar viral disinfection on top, side, bottom, and interior surfaces. Overall, our study demonstrates the potential use of ozone gas disinfection to combat the COVID-19 outbreak.

Trace Organic Compound Removal from Wastewater Reverse-Osmosis Concentrate by Advanced Oxidation Processes with UV/O3/H2O2.

Advanced technologies, such as reverse osmosis (RO), allow the reuse of treated wastewater for direct or indirect potable use. However, even highly efficient RO systems produce ~10-15% highly contaminated concentrate as a byproduct. This wastewater RO concentrate (WWROC) is very rich in metal ions, nutrients, and hard-to-degrade trace organic compounds (TOrCs), such as pharmaceuticals, plasticizers, flame retardants, and detergents, which must be treated before disposal. WWROC could be up to 10 times more concentrated than secondary effluent. We examined the efficiency of several advanced oxidation processes (AOPs) on TOrC removal from a two-stage WWROC matrix in a pilot wastewater-treatment facility. WWROC ozonation or UV irradiation, with H2O2 addition, demonstrated efficient removal of TOrCs, varying between 21% and over 99% degradation, and indicating that radical oxidation (by HO·) is the dominant mechanism. However, AOPs are not sufficient to fully treat the WWROC, and thus, additional procedures are required to decrease metal ion and nutrient concentrations. Further biological treatment post-AOP is also highly important, to eliminate the degradable organic molecules obtained from the AOP.

UV/H2O2 advanced oxidation for abatement of organophosphorous pesticides and the effects on various toxicity screening assays.

Advanced oxidation processes (AOPs) are utilized due to their ability to treat emerging contaminants with the fast reacting and non-selective hydroxyl radical (OH). Organophosphorous insecticides are common drinking water contaminants, with 12 different compounds of this class being found on the US EPA's most recent Candidate Contaminant List (CCL4). The use of the AOP UV/H2O2 for the treatment of organophosphorous insecticides was explored in this study, by coupling biological and analytical tools to follow the abatement of the target compounds. Four insecticides were explored for advanced oxidation treatment: acephate, dicrotophos, fenamiphos, and methamidophos. All four compounds were fast reacting with OH, all reacting with second order rate constants ≥5.5 × 109 M-1s-1. Three major endpoints of toxicity were studied: estrogenicity, genotoxicity (mutagenicity) and neurotoxicity. None of the target compounds showed any estrogenic activity, while all compounds showed an active genotoxic (mutagenic) response (AMES II assay) and most compounds had some level of neurotoxic activity. AOP treatment did not induce any estrogenic activity, and reduced the compounds' neurotoxicity and genotoxicity in all but one case. Methamidophos degradation by UV/H2O2 resulted in an increase in genotoxicity, likely due to the formation of toxic transformation products. The increase in toxicity gradually decreased with time, possibly due to hydrolysis of the transformation products formed. This study provides insights into parent compound abatement and the changes in toxicity due to transformation products.

Key environmental processes affecting the fate of the insecticide chloropyrifos applied to leaves.

Chlorpyrifos (CP) is still a commonly employed organophosphorus insecticide worldwide. In semi-arid and Mediterranean climates, applied CP is expected to remain on leaves surfaces for relatively long time due to the lack of summer rains and common use of drip irrigation. The present work examines the loss rate of CP from leaves via different surface processes: evaporation, direct photolysis and reactions with ozone and OH radicals. Laboratory experiments showed that evaporation rate constant of CP increased from 0.109 to 0.492 h-1 with the increase in wind speed up to 4 m/s. First-order rate constant of direct photolysis, measured using a solar simulator, was k'UV = 1.15 (±0.01) x 10-20 cm2 photon-1. Second-order rate constants for the reaction of CP with ozone and OH were measured as 6 × 10-20 and 6 × 10-12 cm3 molecule-1 s-1, respectively. The above rate constants were applied successfully in an outdoor experiment to predict the disappearance of chloropyrifos under specific environmental conditions. Further modeling showed that the insecticide half-life time on exposed surfaces under typical Mediterranean environment will be in the range of 0.9-6.9 h. Evaporation is expected to be the dominant removal path under most environmental conditions, followed by direct photolysis and reaction with OH.

Integrative Advanced Oxidation and Biofiltration for Treating Pharmaceuticals in Wastewater.

Advanced oxidation of active pharmaceutical ingredients (APIs) in wastewater produces transformation products (TPs) that are often more biodegradable than the parent compounds. Secondary effluent from a wastewater treatment plant was treated using UV-based advanced oxidation (LPUV/H2O2 and MPUV/NO3) followed by biological aerated filtration (BAF), and different APIs and their transformation products were monitored. The advanced oxidation processes degraded the APIs by 55-87% (LPUV/H2O2) and 58-95% (MPUV/NO3), while minor loss of APIs was achieved in the downstream BAF system. Eleven TPs were detected following oxidation of carbamazepine (5) and iopromide (6); three key TPs were biodegraded in the BAF system. The other TPs remained relatively constant in the BAF. The decrease in UV absorbance (UVA254) of the effluent in the BAF system was linearly correlated to the degradation of the APIs (for the MPUV/NO3-BAF), and can be applied to monitor the biotransformation of APIs in biological-based systems.

Application of metabolite profiling tools and time-of-flight mass spectrometry in the identification of transformation products of iopromide and iopamidol during advanced oxidation.

The efficiency of wastewater treatment systems in removing pharmaceuticals is often assessed on the basis of the decrease in the concentration of the parent compound. However, what is perceived as "removal" during treatment may not necessarily mean mineralization of the pharmaceutical compound but simply conversion into different transformation products (TPs). Using liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (LC-QToF-MS), we demonstrated conversion of iopromide in wastewater to at least 14 TPs after an advanced oxidation process (AOP) using UV (fluence = 1500 mJ/cm(2)) and H2O2 (10 mg/L). Due to the complexity of the wastewater matrix, the initial experiments were performed using a high concentration (10 mg/L) of iopromide in order to facilitate the identification of TPs. Despite the high concentration of iopromide used, cursory inspection of UV and mass spectra only revealed four TPs in the chromatograms of the post-AOP samples. However, the use of METLIN database and statistics-based profiling tools commonly used in metabolomics proved effective in discriminating between background signals and TPs derived from iopromide. High-resolution mass data allowed one to predict molecular formulas of putative TPs with errors below 5 ppm relative to the observed m/z. Tandem mass spectrometry (MS/MS) data and isotope pattern comparisons provided necessary information that allowed one to elucidate the structure of iopromide TPs. The presence of the proposed iopromide TPs was determined in unspiked wastewater from a municipal wastewater treatment plant, but no iopromide and TPs were detected. Using analogous structural modifications and oxidation that results from the AOP treatment of iopromide, the potential TPs of iopamidol (a structurally similar compound to iopromide) were predicted. The same mass fragmentation pattern observed in iopromide TPs was applied to the predicted iopamidol TPs. LC-QToF-MS revealed the presence of two iopamidol TPs in unspiked AOP-treated wastewater.

Characterization of hydraulic fracturing flowback water in Colorado: implications for water treatment.

A suite of analytical tools was applied to thoroughly analyze the chemical composition of an oil/gas well flowback water from the Denver-Julesburg (DJ) basin in Colorado, and the water quality data was translated to propose effective treatment solutions tailored to specific reuse goals. Analysis included bulk quality parameters, trace organic and inorganic constituents, and organic matter characterization. The flowback sample contained salts (TDS=22,500 mg/L), metals (e.g., iron at 81.4 mg/L) and high concentration of dissolved organic matter (DOC=590 mgC/L). The organic matter comprised fracturing fluid additives such as surfactants (e.g., linear alkyl ethoxylates) and high levels of acetic acid (an additives' degradation product), indicating the anthropogenic impact on this wastewater. Based on the water quality results and preliminary treatability tests, the removal of suspended solids and iron by aeration/precipitation (and/or filtration) followed by disinfection was identified as appropriate for flowback recycling in future fracturing operations. In addition to these treatments, a biological treatment (to remove dissolved organic matter) followed by reverse osmosis desalination was determined to be necessary to attain water quality standards appropriate for other water reuse options (e.g., crop irrigation). The study provides a framework for evaluating site-specific hydraulic fracturing wastewaters, proposing a suite of analytical methods for characterization, and a process for guiding the choice of a tailored treatment approach.

Influence of wastewater particles on ozone degradation of trace organic contaminants.

In this Article, we demonstrate the influence of effluent particles (in the range of <50 µm) on ozone degradation of trace organic contaminants (TrOCs) and effluent-quality parameters. Secondary effluent was filtered through different pore-size filters and ozonated at various ozone doses. Degradation of both ozone-reactive and ozone-refractory contaminants improved following ozonation of effluent filtered with smaller pore size filters, indicating that particles in this range may adversely affect ozonation. The inhibitory effect of particles was attributed to their reaction with ozone, reducing available ozone and HO(•) radicals. In addition, increasing filtration level decreased the effluent's (instantaneous) ozone demand and increased removal of effluent UV absorbance (UVA254), further establishing that ozone reacts with effluent particles, in competition with dissolved matter. Moreover, ozone was shown to react with particles even during the first seconds of the process, suggesting a high rate of some ozone-particle reactions, comparable to ozone reaction with highly reactive dissolved organic matter moieties. Particle image analysis revealed that particle formation/aggregation and particle disintegration occurs simultaneously during wastewater (WW) ozonation. Our study implies that particles could affect the efficiency of WW ozonation, by increasing the effluent's ozone demand and decreasing contaminant degradation.

Demonstrating sucralose as a monitor of full-scale UV/AOP treatment of trace organic compounds.

Due to the large number of trace organic compounds (TOrCs) in water and wastewater, their degradation during UV-based advanced oxidation (UV/AOP) is best monitored using a conservative indicator compound. The present study demonstrates the in situ use of sucralose, a widely consumed artificial sweetener, as a conservative probe for UV/AOP degradation of TOrCs. The main qualities of sucralose in this regard are its high concentration in wastewater effluent and surface water (enabling its direct detection), its resistance to direct UV photolysis, and its relatively slow reaction with hydroxyl radical. Degradation of sucralose was compared to the degradation of commonly detected TOrCs, across two AOPs (i.e. UV/H2O2 and UV/NO3), in both lab-scale and pilot-scale systems. In all cases, UV/AOP degradation of sucralose was slower than the degradation of the examined TOrCs, and is expected to be slower than the degradation of the majority of other environmentally relevant TOrCs. These results demonstrate the potential of sucralose as a conservative probe, to monitor the transformation of TOrCs during UV/AOP treatment. Furthermore, degradation of sucralose was slower than the degradation of many transformation products (generated during oxidation of TOrCs), implying that sucralose is also a valuable indicator for the decay of primary transformation products.

Production of photo-oxidants by dissolved organic matter during UV water treatment.

Dissolved organic matter (DOM) irradiated by sunlight generates photo-oxidants that can accelerate organic contaminant degradation in surface waters. However, the significance of this process to contaminant removal during engineered UV water treatment has not been demonstrated, partly due to a lack of suitable methods in the deep UV range. This work expands methods previously established to detect (1)O2, HO•, H2O2, and DOM triplet states ((3)DOM*) at solar wavelengths to irradiation at 254 nm, typical of UV water treatment. For transient intermediates, the methods include a photostable probe combined with selective scavengers. Quantum yields for (1)O2, (3)DOM* and H2O2 were in the same range as for solar-driven reactions but were an order of magnitude higher for HO•, which other experiments indicate is due to H2O2 reduction. With the quantum yields, the degradation of metoxuron was successfully predicted in a DOM solution irradiated at 254 nm. Further modeling showed that the contribution of DOM sensitization to organic contaminant removal during UV treatment should be significant only at high UV fluence, characteristic of advanced oxidation processes. Of the reactive species studied, (3)DOM* is predicted to have the greatest general influence on UV degradation of contaminants.

Treating wastewater from a pharmaceutical formulation facility by biological process and ozone.

Wastewater from a pharmaceutical formulation facility (TevaKS, Israel) was treated with a biological activated-sludge system followed by ozonation. The goal was to reduce the concentrations of the drugs carbamazepine (CBZ) and venlafaxine (VLX) before discharging the wastewater to the municipal wastewater treatment plant (WWTP). Both drugs were detected at extremely high concentrations in TevaKS raw wastewater ([VLX]=11.72 ± 2.2mg/L, [CBZ]=0.84 ± 0.19 mg/L), and resisted the biological treatment. Ozone efficiently degraded CBZ: at an O3 dose-to-dissolved organic carbon ratio of 0.55 (O3/DOC), the concentration of CBZ was reduced by >99%. A lower removal rate was observed for VLX, which was decreased by ≈ 98% at the higher O3/DOC ratio of 0.87. Decreasing the pH of the biologically treated effluent from 7 to 5 significantly increased the ozone degradation rate of CBZ, while decreasing the degradation rate of VLX. Ozone treatment did not alter the concentration of the effluent's DOC and filtered chemical oxygen demand (CODf). However, a significant increase was recorded (following ozonation) in the effluent's biological oxygen demand (BOD5) and the BOD5/CODf ratio. This implies an increase in the effluent's biodegradability, which is highly desirable if ozonation is followed by a domestic biological treatment. Different organic byproducts were formed following ozone reaction with the target pharmaceuticals and with the effluent organic matter; however, these byproducts are expected to be removed during biological treatment in the municipal WWTP.

Sulfamethoxazole contamination of a deep phreatic aquifer.

Groundwater samples were obtained from the water table region of a phreatic aquifer (unsaturated zone depth up to 28 m) under land irrigated with wastewater effluents for about 5 decades and a relatively deep pumping well (109 m), used as a drinking water source till 2007, located downstream (1300 m) of wastewater effluent and sludge infiltration facilities. Sulfamethoxazole (SMX) concentrations in secondary effluents varied between 90 and 150 ng/L. SMX was extracted using SPE and was analyzed by HPLC-MS/MS. SMX (maximum concentration of 37 ng/L) was detected in the water table region, in two monitoring wells, after an unsaturated zone transport period of about 16 years. The maximum SMX concentration detected in the pumping well was of 20 ng/L. These results question wastewater effluent disposal strategies including the suitability of irrigation with effluents on the replenishment area of an aquifer supplying drinking water.