The Zebrafish (Danio rerio) Embryo Model as a Tool to Assess Drinking Water Treatment Efficacy for Freshwater Impacted by Crude Oil Spill.

Traditional approaches toward evaluating oil spill mitigation effectiveness in drinking water supplies using analytical chemistry can overlook residual hydrocarbons and treatment byproducts of unknown toxicity. Zebrafish (Danio rerio) were used to address this limitation by evaluating the reduction in toxicity to fish exposed to laboratory solutions of dissolved crude oil constituents treated with 3 mg/L ozone (O3 ) with or without a peroxone-based advanced oxidation process using 0.5 M H2 O2 /M O3 or 1 M H2 O2 /M O3 . Crude oil water mixtures (OWMs) were generated using three mixing protocols-orbital (OWM-Orb), rapid (OWM-Rap), and impeller (OWM-Imp) and contained dissolved total aromatic concentrations of 106-1019 µg/L. In a first experiment, embryos were exposed at 24 h post fertilization (hpf) to OWM-Orb or OWM-Rap diluted to 25%-50% of full-strength samples and in a second experiment, to untreated or treated OWM-Imp mixtures at 50% dilutions. Toxicity profiles included body length, pericardial area, and swim bladder inflation, and these varied depending on the OWM preparation, with OWM-Rap resulting in the most toxicity, followed by OWM-Imp and then OWM-Orb. Zebrafish exposed to a 50% dilution of OWM-Imp resulted in 6% shorter body length, 83% increased pericardial area, and no swim bladder inflation, but exposure to a 50% dilution of OWM-Imp treated with O3 alone or with 0.5 M H2 O2 /M O3 resulted in normal zebrafish development and average total aromatic destruction of 54%-57%. Additional aromatic removal occurred with O3 + 1 M H2 O2 /M O3 but without further attenuation of toxicity to zebrafish. This study demonstrates using zebrafish as an additional evaluation component for modeling the effectiveness of freshwater oil spill treatment methods. Environ Toxicol Chem 2022;41:2822-2834. © 2022 SETAC.

Water quality monitoring with purpose: Using a novel framework and leveraging long-term data.

Water quality monitoring programs are developed to meet goals including attaining regulatory compliance, evaluating long-term environmental changes, or quantifying the impact of an emergency event. Methods for developing these programs often fail to address multiple aspects of development (hazard identification, parameter selection, monitoring locations/frequency) simultaneously. We develop a framework for monitoring program development that is both versatile and systematic, the Hazard Based Water Quality Monitoring Planning framework, and apply it to the Quabbin watershed in Massachusetts, USA. We use a novel application of dataset deconstruction of long-term water quality datasets and the Seasonal Kendall test for trends to evaluate the effects of sampling frequency on long-term trend detection at several watershed sites. Results showed that when sampling frequency is decreased, ability to detect statistically significant trends often decreases. Absolute error in trend slopes between biweekly (twice monthly) and reduced sampling frequencies was relatively small for specific conductance and turbidity but was high for total coliform, likely due to interannual variation in rainfall and temperature We found that no one sampling reduction method resulted in a consistently lower absolute error compared to the "truth" (biweekly sampling), highlighting the importance of evaluating conditions that may affect water quality at sites in different parts of a watershed. We demonstrate the framework's usefulness, particularly for parameter and sampling frequency selection, using methods that can be readily applied to other watershed systems.

Comparison of ferrate and ozone pre-oxidation on disinfection byproduct formation from chlorination and chloramination.

This study investigated the effects of ferrate and ozone pre-oxidation on disinfection byproduct (DBP) formation from subsequent chlorination or chloramination. Two natural waters were treated at bench-scale under various scenarios (chlorine, chloramine, each with ferrate pre-oxidation, and each with pre-ozonation). The formation of brominated and iodinated DBPs in fortified natural waters was assessed. Results indicated ferrate and ozone pre-oxidation were comparable at molar equivalent doses for most DBPs. A net decrease in trihalomethanes (including iodinated forms), haloacetic acids (HAAs), dihaloacetonitrile, total organic chlorine, and total organic iodine was found with both pre-oxidants as compared to chlorination only. An increase in chloropicrin and minor changes in total organic bromine yield were caused by both pre-oxidants compared to chlorination only. However, ozone led to higher haloketone and chloropicrin formation potentials than ferrate. The relative performance of ferrate versus ozone for DBP precursor removal was affected by water quality (e.g., nature of organic matter and bromide concentration) and oxidant dose, and varied by DBP species. Ferrate and ozone pre-oxidation also decreased DBP formation from chloramination under most conditions. However, some increases in THM and dihaloacetonitrile formation potentials were observed at elevated bromide levels.

Proactive modeling of water quality impacts of extreme precipitation events in a drinking water reservoir.

Extreme precipitation events are of concern to managers of drinking water sources because these occurrences can affect both water supply quantity and quality. However, little is known about how these low probability events impact organic matter and nutrient loads to surface water sources and how these loads may impact raw water quality. This study describes a method for evaluating the sensitivity of a water body of interest from watershed input simulations under extreme precipitation events. An example application of the method is illustrated using the Wachusett Reservoir, an oligo-mesotrophic surface water reservoir in central Massachusetts and a major drinking water supply to metropolitan Boston. Extreme precipitation event simulations during the spring and summer resulted in total organic carbon, UV-254 (a surrogate measurement for reactive organic matter), and total algae concentrations at the drinking water intake that exceeded recorded maximums. Nutrient concentrations after storm events were less likely to exceed recorded historical maximums. For this particular reservoir, increasing inter-reservoir transfers of water with lower organic matter content after a large precipitation event has been shown in practice and in model simulations to decrease organic matter levels at the drinking water intake, therefore decreasing treatment associated oxidant demand, energy for UV disinfection, and the potential for formation of disinfection byproducts.

Oxidation of manganese(II) with ferrate: Stoichiometry, kinetics, products and impact of organic carbon.

Manganese is a contaminant of concern for many drinking water utilities, and future regulation may be pending. An analysis of soluble manganese (Mn(II)) oxidation by ferrate (Fe(VI)) was executed at the bench-scale, in a laboratory matrix, both with and without the presence of natural organic matter (NOM) and at two different pH values, 6.2 and 7.5. In the matrix without NOM, the oxidation of Mn(II) by Fe(VI) followed a stoichiometry of 2 mol Fe(VI) to 3 mol Mn(II). The presence of NOM did not significantly affect the stoichiometry of the oxidation reaction, indicating relative selectivity of Fe(VI) for Mn(II). The size distribution of resulting particles included significant amounts of nanoparticles. Resulting manganese oxide particles were confirmed to be MnO2 via X-ray photoelectron spectroscopy. The rate of the Mn(II) oxidation reaction was fast relative to typical time scales in drinking water treatment, with an estimated second order rate constant of approximately 1 × 10(4) M(-1) s(-1) at pH 9.2 and > 9 × 10(4) M(-1) s(-1) at pH 6.2. In general, ferrate is a potential option for Mn(II) oxidation in water treatment.

Bromide oxidation by ferrate(VI): The formation of active bromine and bromate.

Ferrate (VI) (abbreviated as Fe(VI)) has long been considered as a green oxidant that does not produce any known hazardous byproducts. However, this work shows that Fe(VI) can slowly oxidize bromide forming active bromine (HOBr/OBr(-)) and bromate, and in natural waters total organic bromine (TOBr) can also be detected. Results showed that the highest levels of active bromine and bromate were formed at lower pHs and in the absence of phosphate. Hydrogen peroxide, which forms from the reaction of Fe(VI) and water, plays an essential role in suppressing bromate formation by reducing active bromine back to bromide. Fe(VI) decomposition products (assumed to be particulate phase Fe(III)) can catalyze the decomposition of hydrogen peroxide by Fe(VI). Phosphate had a substantial inhibiting effect on the formation of active bromine, but less so on bromate formation. The presence of the raw water matrix in natural water suppressed bromate formation. For a natural water spiked with 0.1 mg/L of bromide, the bromate and TOBr concentrations after Fe(VI) oxidation were below 3.0 and 15 µg/L, respectively. No consistent trend regarding the effect of pH or buffer ions on TOBr formation was observed due to the competition between Fe(VI), hydrogen peroxide, and natural organic matter (NOM) for reaction with active bromine. Under environmentally relevant conditions, the formation of bromate and TOBr would not be a problem for Fe(VI) application as their concentration levels are quite low.

Impacts of ferrate oxidation on natural organic matter and disinfection byproduct precursors.

This study investigated the effectiveness of ferrate (Fe(VI)) oxidation in combination with ferric chloride coagulation on the removal of natural organic matter (NOM) and disinfection byproduct (DBP) precursors. Twelve natural waters were collected and four treatment scenarios were tested at bench-scale. Results showed that intermediate-ferrate treatment (i.e., coagulation and particle removal followed by ferrate oxidation) was most effective followed by pre-ferrate treatment (i.e., ferrate oxidation followed by coagulation and particle removal (conventional treatment)) or conventional treatment alone (i.e., no oxidation), and the least effective was ferrate oxidation alone (i.e., no coagulation). At typical doses, direct ferrate oxidation of raw water decreased DBP formation potentials (DBPFPs) by about 30% for trihalomethanes (THMs), 40% for trihaloacetic acids (THAAs), 10% for dihaloacetic acids (DHAAs), 30% for dihaloacetonitriles (DHANs), and 5% for haloketones (HKs). The formation potential of chloropicrin (CP) consistently increased after direct ferrate oxidation. Pre-ferrate followed by conventional treatment was similar to conventional treatment alone for NOM and DBP precursor removal. Ferrate pre-oxidation had positive effects on subsequent coagulation/particle removal for THM and THAA precursor removal and may allow the use of lower coagulant doses due to the Fe(III) introduced by ferrate decomposition. On the other hand, intermediate-ferrate resulted in substantially improved removal of NOM and DBP precursors, which can be attributed to initial removal by coagulation and particle removal, leaving precursors that are particularly susceptible to oxidation by ferrate. The Fe(III) resulting from ferrate decay during intermediate-ferrate process was primarily present as particulate iron and could be effectively removed by filtration.

Characterization of particles from ferrate preoxidation.

Studies were conducted evaluating the nature of particles that result from ferrate reduction in a laboratory water matrix and in a natural surface water with a moderate amount of dissolved organic carbon. Particle characterization included size, surface charge, morphology, X-ray photoelectron spectroscopy, and transmission Fourier transform infrared spectroscopy. Characteristics of ferrate resultant particles were compared to particles formed from dosing ferric chloride, a common water treatment coagulant. In natural water, ferrate addition produced significantly more nanoparticles than ferric addition. These particles had a negative surface charge, resulting in a stable colloidal suspension. In natural and laboratory matrix waters, the ferrate resultant particles had a similar charge versus pH relationship as particles resulting from ferric addition. Particles resulting from ferrate had morphology that differed from particles resulting from ferric iron, with ferrate resultant particles appearing smoother and more granular. X-ray photoelectron spectroscopy results show ferrate resultant particles contained Fe2O3, while ferric resultant particles did not. Results also indicate potential differences in the mechanisms leading to particle formation between ferrate reduction and ferric hydrolysis.

Effect of different solutes, natural organic matter, and particulate Fe(III) on ferrate(VI) decomposition in aqueous solutions.

This study investigated the impacts of buffer ions, natural organic matter (NOM), and particulate Fe(III) on ferrate(VI) decomposition and characterized Fe(VI) decomposition kinetics and exposure in various waters. Homogeneous and heterogeneous Fe(VI) decomposition can be described as a second- and first-order reaction with respect to Fe(VI), respectively. Fe(VI) decay was catalyzed by Fe(VI) decomposition products. Solutes capable of forming complexes with iron hydroxides retarded Fe(VI) decay. Fractionation of the resulting solutions from Fe(VI) self-decay and ferric chloride addition in borate- and phosphate-buffered waters showed that phosphate could sequester Fe(III). The nature of the iron precipitate from Fe(VI) decomposition was different from that of freshly precipitated ferric hydroxide from ferric chloride solutions. The stabilizing effects of different solutes on Fe(VI) are in the following order: phosphate > bicarbonate > borate. The constituents of colored and alkaline waters (NOM and bicarbonate) inhibited the catalytic effects of Fe(VI) decomposition products and stabilized Fe(VI) in natural waters. Because of the stabilizing effects of solutes, moderate doses of Fe(VI) added to natural waters at pH 7.5 resulted in exposures that have been shown to be effective for inactivation of target pathogens. Preformed ferric hydroxide was less effective than freshly dosed ferric chloride in accelerating Fe(VI) decomposition.

Fouling indices for low pressure hollow fiber membrane performance assessment.

This study evaluated the use of fouling indices to describe low pressure membrane fouling. One critical aspect of this study was the use of a bench-scale hollow fiber membrane system that imitated full-scale operation (constant flux with automatic hydraulic backwash and chemical cleaning). Fouling indices were based on a resistance-in-series model. Two different hollow fiber membrane types (membrane A and B) were tested with water from two water utilities (A and B) and three other natural sources (oligotrophic, algal bloom impacted, and wastewater impaired). The bench-scale testing included use of the same membrane as utilized at Utility B. Most fouling was reversible by hydraulic backwash and chemical cleaning. Specific flux and fouling indices for the bench-scale system were higher than those determined from full-scale data but fouling index ratios were comparable, suggesting a similar fouling nature. At similar organic loading, fouling was specific to water source and membrane type, i.e., no generalization on the impact of water source was possible. Full-scale data were compared with bench-scale data to validate the use of fouling indices. Fouling indices based on a resistance-in-series are useful tools to describe membrane performance data for both raw and pretreated water, for different water sources, and different membrane types.

Removal of arsenic from high ionic strength solutions: effects of ionic strength, pH, and preformed versus in situ formed HFO.

Arsenic sorption to hydrous ferric oxide (HFO) is an effective treatment method for removing dissolved arsenic from fresh drinking water sources. However, detailed information is limited regarding arsenic removal from solutions of high ionic strength such as brackish groundwater, seawater, or high-pressure membrane process residuals. Bench-scale treatment experiments were conducted exploring arsenic removal from simple solutions with ionic strengths ranging from 0.008 to 1.5 M by addition of ferric chloride followed by solid/liquid separation (microfiltration or ultrafiltration). Arsenic removal from these solutions during in situ iron precipitation was approximately 90% at Fe:As molar ratios of 10 to 15 and > 95% for Fe:As molar ratios greater than 20. Arsenic removal at iron doses of 10(-6) to 10(-4) mol-Fe/L improved when pH was lowered from 8 to less than 6.5 at ionic strength 0.2 M; this improvement was not as significant at ionic strength 0.7 M. Arsenic removal diminished when alkalinity was increased from 400 to 1,400 mg/L as calcium carbonate; however, arsenic removal at the higher alkalinity improved when pH was lowered from approximately 8 to less than 7. Arsenic removal with preformed HFO solids and subsequent microfiltration was significantly less than that observed with in situ HFO precipitation. Increased removal by in situ precipitation compared to that of preformed solids is explained by an increased number of adsorption sites due to uptake during iron oxy-hydroxide polymerization as well as an increase in surface area resulting in diminished surface charge effects. Model simulations of arsenic uptake by in situ precipitation adequately captured these effect by changing the model parameters used to model arsenic uptake by preformed HFO, specificallythe total number of surface sites and surface area.

Particles in filter effluent: the roles of deposition and detachment.

Particles in the effluent of granular media filters can be classified as influent particles that were never removed or as particles that detached after prior deposition. To determine the effects of particle size, filter media depth and filter run duration on the relative fraction of each class, laboratory experiments were performed using suspensions of four sizes of polystyrene particles (0.2, 1.2, 2.5, and 4.0 microm diameters) that were destabilized with 0.04 M calcium chloride and continuously supplied to filters after flocculation. To investigate particle attachment alone, three sizes (1.4, 4.0, and 9 microm) of fluorescent microspheres (FM) were periodically pulse injected immediately ahead of the filter media. Detachmentwas assessed as the difference between net removal (particle counts) and deposition (FM counts). FM deposition followed theory, while results show that particle detachment was significant from an early phase of filtration (100 minutes). The detached fraction of effluent particles increased with particle size (1 to 12 microm range) and filter depth. These model system results suggest that detachment plays a significant role in the origin of filter effluent particles in full-scale water treatment systems.