Occurrence and removal of poly/perfluoroalkyl substances (PFAS) in municipal and industrial wastewater treatment plants.

The presence of poly- and perfluoroalkyl substances (PFAS) has caused serious problems for drinking water supplies especially at intake locations close to PFAS manufacturing facilities, wastewater treatment plants (WWTPs), and sites where PFAS-containing firefighting foam was regularly used. Although monitoring is increasing, knowledge on PFAS occurrences particularly in municipal and industrial effluents is still relatively low. Even though the production of C8-based PFAS has been phased out, they are still being detected at many WWTPs. Emerging PFAS such as GenX and F-53B are also beginning to be reported in aquatic environments. This paper presents a broad review and discussion on the occurrence of PFAS in municipal and industrial wastewater which appear to be their main sources. Carbon adsorption and ion exchange are currently used treatment technologies for PFAS removal. However, these methods have been reported to be ineffective for the removal of short-chain PFAS. Several pioneering treatment technologies, such as electrooxidation, ultrasound, and plasma have been reported for PFAS degradation. Nevertheless, in-depth research should be performed for the applicability of emerging technologies for real-world applications. This paper examines different technologies and helps to understand the research needs to improve the development of treatment processes for PFAS in wastewater streams.

Plastic toys as a source of exposure to bisphenol-A and phthalates at childcare facilities.

Infants and toddlers are constantly exposed to toys at childcare facilities. Toys are made of a variety of plastics that often use endocrine-disrupting chemicals such as bisphenol-A (BPA) and phthalates as their building blocks. The goal of this study was to assess the non-dietary exposure of infants and toddlers to BPA and phthalates via leaching. We have successfully developed wipe tests to evaluate the leachability of BPA and phthalates from toys used at several day care facilities in Philadelphia. Our studies have shown an average leaching of 13-280 ng/cm2 of BPA and phthalates. An estimate of total exposure of infants to BPA and phthalates is reported. The leaching of the chemicals was observed to be dependent on the washing procedures and the location of the day care facilities. Using bleach/water mixture two or more times a week to clean the toys seems to reduce the leaching of chemicals from the toys. There is a huge data gap in the estimated intake amounts and reported urinary concentrations; this is the first study that provides valuable information to address these data gaps in the existing literature.

Steroid hormones in environmental matrices: extraction method comparison.

The U.S. Environmental Protection Agency (EPA) has developed methods for the analysis of steroid hormones in water, soil, sediment, and municipal biosolids by HRGC/HRMS (EPA Method 1698). Following the guidelines provided in US-EPA Method 1698, the extraction methods were validated with reagent water and applied to municipal wastewater, surface water, and municipal biosolids using GC/MS/MS for the analysis of nine most commonly detected steroid hormones. This is the first reported comparison of the separatory funnel extraction (SFE), continuous liquid-liquid extraction (CLLE), and Soxhlet extraction methods developed by the U.S. EPA. Furthermore, a solid phase extraction (SPE) method was also developed in-house for the extraction of steroid hormones from aquatic environmental samples. This study provides valuable information regarding the robustness of the different extraction methods. Statistical analysis of the data showed that SPE-based methods provided better recovery efficiencies and lower variability of the steroid hormones followed by SFE. The analytical methods developed in-house for extraction of biosolids showed a wide recovery range; however, the variability was low (≤ 7% RSD). Soxhlet extraction and CLLE are lengthy procedures and have been shown to provide highly variably recovery efficiencies. The results of this study are guidance for better sample preparation strategies in analytical methods for steroid hormone analysis, and SPE adds to the choice in environmental sample analysis.

Rapid and sensitive screening of 17ß-estradiol estrogenicity using Fourier transform infrared imaging spectroscopy (FT-IRIS).

It is important to develop rapid and sensitive screening assays to assess the biological effects of emerging contaminants. In this contribution, the ability to determine the molecular level effects of 17ß-estradiol on single MCF-7 cells using Fourier transform infrared imaging spectroscopy (FT-IRIS) was investigated. The use of FT-IRIS enabled subcellular imaging of the cells and determination of a dose dependent response in mucin concentration at 24 and 48 h of incubation. The 48 h increase in mucin was comparable to increases in cellular proliferation (Pearson R = 0.978). The EC50 values for the E-screen and FT-IRIS assays were 2.29 and 2.56 ppt, respectively, indicating that the molecular changes, which are observed at the single cell level using FT-IRIS, are reflective of physiological changes that are observed as the cell population responds to 17ß-estradiol. The FT-IRIS method, when combined with principal component analysis, enabled differentiation and grouping of cells exposed to varying concentrations of 17ß-estradiol. The FT-IRIS method shows potential to be used as a rapid and sensitive screening technique for the detection of biological responses to different emerging contaminants in relevant cells or tissues.

Understanding and modeling removal of anionic organic contaminants (AOCs) by anion exchange resins.

Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH.

Recent developments in heterogeneous catalyzed environmental remediation processes.

This article reports on recent developments in heterogeneous AOP processes such as photocatalysis, Fenton-like process and catalytic ozonation. The principle, mechanism, and influence of experimental conditions on the degradation of pollutants in heterogeneous catalytic ozonation and the photocatalytic process were discussed. Introducing solid catalysts substantially increased the efficiency of the ozonation process by producing hydroxyl radicals in the degradation process. The different types of catalyst, catalyst dosage, solution pH, ozone flow rate, water matrix and catalytic reusability and stability are reported on here. The list of various semiconductor materials used as photocatalysts, their light absorption properties, various light sources and surface properties such as surface area, pore size and pore volume as a factor in the photocatalytic degradation of various pollutants are discussed. The review article also discussed the pollutants degraded using these three processes.

An overview of the occurrence, impact of process parameters, and the fate of antibiotic resistance genes during anaerobic digestion processes.

Antibiotic resistance genes (ARGs) have emerged as a significant global health threat, contributing to fatalities worldwide. Wastewater treatment plants (WWTPs) and livestock farms serve as primary reservoirs for these genes due to the limited efficacy of existing treatment methods and microbial adaptation to environmental stressors. Anaerobic digestion (AD) stands as a prevalent biological treatment for managing sewage sludge and manure in these settings. Given the agricultural utility of AD digestate as biofertilizers, understanding ARGs' fate within AD processes is essential to devise effective mitigation strategies. However, understanding the impact of various factors on ARGs occurrence, dissemination, and fate remains limited. This review article explores various AD treatment parameters and correlates to various resistance mechanisms and hotspots of ARGs in the environment. It further evaluates the dissemination and occurrence of ARGs in AD feedstocks and provides a comprehensive understanding of the fate of ARGs in AD systems. This review explores the influence of key AD parameters such as feedstock properties, pretreatments, additives, and operational strategies on ARGs. Results show that properties such as high solid content and optimum co-digestion ratios can enhance ARG removal, while the presence of heavy metals, microplastics, and antibiotics could elevate ARG abundance. Also, operational enhancements, such as employing two-stage digestion, have shown promise in improving ARG removal. However, certain pretreatment methods, like thermal hydrolysis, may exhibit a rebounding effect on ARG levels. Overall, this review systematically addresses current challenges and offers future perspectives associated with the fate of ARGs in AD systems.

An interaction model for estimating in vitro estrogenic and androgenic activity of chemical mixtures.

There is a need to better understand and predict the biological activity and interaction of chemical constituents in mixtures. Many existing methods assume that the mixture components are additive, and in the case of endocrine disruption, deviation from additivity may occur and render predictions inconclusive. In this study, an alternate index, aRP, which enables the quantification of an antagonistic interaction from analytically derived concentrations of chemical constituents within a mixture that act upon the same molecular target is described. The index is calculated by measuring the degree to which the test compound modulates the activity of a standard hormone as a function of mixture proportions. The aRP was shown to be valid for additive mixtures. It theoretically estimates the product of the relative potential and the interaction index inverse for nonadditive mixtures. The aRP values were computed for agonists and antagonists of both the estrogen and androgen receptors by using yeast-based methods (YES and YAS). The resulting aRP estimates were then validated using higher order mixtures of agonists and antagonists. The use of aRP led to improved predictions compared to estimates based on the toxicity equivalent factor (TEF) approach. The aRP model yielded estimates that were statistically indistinguishable (α = 0.01) from the measured responses in 75% of the 32 mixtures tested. By the same criteria, the TEF approach successfully predicted 34% of the mixtures. Both the aRP and TEF approach correlated well with the observed responses (Pearson R = 0.98 and 0.84, respectively); however, the TEF estimates produced higher percent errors, particularly in mixtures with higher proportions of antagonists. It is suggested that the use of the aRP index allows for a better approximation of the net activity captured by the bioassays through the use of chemically derived concentrations.

Fabrication and photocatalytic properties of self-assembled in(OH)3 and In2O3 nano/micro-cubes.

This article reports a novel fabrication method for In(OH)3 from indium oxalate by hydrothermal process. Hydrothermal decomposition of indium oxalate at 180 degrees C for 10 h results in In(OH)3. The influence of hydrothermal experimental conditions such as temperature, time on the formation of indium hydroxide was investigated. The self-assembly process was strongly influenced the experimental conditions. The thermal decomposition of In(OH)3 at 400 degrees C results In2O3. The synthesized In(OH)3 and In2O3 were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), thermal analysis (TGA and DTA), diffuse reflectance spectra (DRS), and nitrogen adsorption analysis. The XRD patterns indicated the formation of well crystallized cubic phase In(OH)3 and In2O3. The FE-SEM results indicated formation of In(OH)3 and porous In2O3 nano/micro-cubes. The photocatalytic activity of the synthesized In(OH)3 was studied under UV light irradiation and results showed that the In(OH)3 photocatalyst was efficient for dye degradation. We proposed a plausible mechanism for the formation of In(OH)3, and In2O3 self-assembly.

Degradation of emerging per- and polyfluoroalkyl substances (PFAS) using an electrochemical plug flow reactor.

In recent years, shorter-chain fluorinated compounds have been manufactured as alternatives to legacy per- and polyfluoroalkyl substances (PFAS) after a global ban on some long-chain PFAS. This study is the first to investigate the degradability of emerging PFAS by an electrochemical plug flow reactor (EPFR). Ten different emerging PFAS, representing classes of fluorotelomer alcohol, perfluoroalkyl ether carboxylate, polyfluoroalkyl ethersulfonic acids, perfluoroalkyl ether/polyether carboxylates, perfluoroether sulfonate, N-alkyl perfluoroalkylsulfonamido carboxylate, fluoroalkyl phosphonic acid, and perfluoro alkane sulfonamide were investigated. The process kinetics was performed. The degradation of parent compounds increased with increasing retention time (RT). At 45.2 min of RT, the degradation of parent compounds ranged between 68%-100% with a current density of 17.2 mA/cm2. A linear increase in pseudo-first order rate constants was observed for all PFAS with increasing current density from 5.7 to 28.7 mA/cm2 (R2 > 0.91). The effect of pH, natural organic matter, and bicarbonate on the degradation, defluorination, and fluorine mass balance are reported. Alkaline pH (11) caused a decrease in degradation for all PFAS. While the presence of natural organic matter (NOM) significantly decreased the degradation and defluorination processes, the presence of bicarbonate at all studied concentrations (25, 50, and 100 mg/L) did not affect the process efficiency. The defluorination reduced to 34% from 81% with 15 mg/L NOM. The unknown/undetected fluorine fraction also increased in the presence of 15 mg/L NOM indicating the formation of NOM-PFAS complexes. Additionally, C2-C8 perfluoro carboxylic acids (PFCAs), one perfluoro sulfonic acid (PFSA), two H-PFCAs, and 4:2 fluorotelomer sulfonate (FTS) were identified as degradation byproducts in suspect screening. The electrical energy per order for PFAS ranged between 1.8 and 19.4 kWh/m3. This study demonstrates that emerging types of PFAS can potentially be degraded using an EPFR with relatively low electrical energy requirements.

A modified QuEChERS sample processing method for the determination of per- and polyfluoroalkyl substances (PFAS) in environmental biological matrices.

QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample processing methods have previously been applied to a range of compounds and matrices. This study presents a modified QuEChERS sample processing method that was validated and employed for 24 per- and polyfluoroalkyl substances (PFAS) for various biological matrices. PFAS are a group of synthetic chemicals that have attracted substantial attention as some compounds are acknowledged to be persistent, toxic, and bioaccumulative. It is crucial to determine PFAS in diverse environmental matrices. Currently, limited sample processing methods for PFAS in biological matrices are available and the majority only focus on a few compounds such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Thus, there is a demand to develop a sample processing method which is effective for many commonly tested PFAS compounds in environmental biological samples. In this study, the detailed sample processing procedures and method performance are described. The highlights of this method are: •The extraction solvent and salts were adjusted for PFAS extraction from environmental biological matrices.•The modified QuEChERS method is effective for extraction and cleanup from a variety of matrices including algae, plants, invertebrates, amphibians, and fish.

Influence of microbial weathering on the partitioning of per- and polyfluoroalkyl substances (PFAS) in biosolids.

Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chemicals that can accumulate in the environment. In water resource recovery facilities (WRRFs), some commonly detected PFAS tend to partition to and concentrate in biosolids where they can act as a source to ecological receptors and may leach to groundwater when land-applied. Although biosolids undergo some stabilization to reduce pathogens before land application, they still contain many microorganisms, contributing to the eventual decomposition of different components of the biosolids. This work demonstrates ways in which microbial weathering can influence biosolids decomposition, degrade PFAS, and impact PFAS partitioning in small-scale, controlled laboratory experiments. In the microbial weathering experiments, compound-specific PFAS biosolids-water partitioning coefficients (Kd) were demonstrated to decrease, on average, 0.4 logs over the course of the 91 day study, with the most rapid changes occurring during the first 10 days. Additionally, the highest rates of lipid, protein, and organic matter removal occurred during the same time. Among the evaluated independent variables, statistical analyses demonstrated that the most significant solids characteristics that impacted PFAS partitioning were organic matter, proteins, lipids, and molecular weight of organics. A multiple linear regression model was built to predict PFAS partitioning behavior in biosolids based on solid characteristics of the biosolids and PFAS characteristics with a R2 value of 0.7391 when plotting predicted and measured log Kd. The findings from this work reveal that microbial weathering can play a significant role in the eventual fate and transport of PFAS and their precursors from biosolids.

Bioaccumulation of per- and polyfluoroalkyl substances by freshwater benthic macroinvertebrates: Impact of species and sediment organic carbon content.

Per- and polyfluoroalkyl substances (PFAS) in aquatic environments have caused global concern due to their persistence, toxicity, and potential bioaccumulation of some compounds. As an important compartment of the aquatic ecosystem, sediment properties impact PFAS partitioning between aqueous and solid phases, but little is known about the influence of sediment organic carbon content on PFAS bioaccumulation in benthic organisms. In this study, three freshwater benthic macroinvertebrates - worms (Lumbriculus variegatus), mussels (Elliptio complanata) and snails (Physella acuta) - were exposed for 28 days to PFAS spiked synthetic sediment equilibrated with a synthetic surface water. Using microcosms, sediment organic carbon content - 2%, 5% and 8% - was manipulated to assess its impact on PFAS bioaccumulation. Worms were found to have substantially greater PFAS bioaccumulation compared to mussels and snails. The bioaccumulation factors (BAFs) and biota sediment accumulation factors (BSAFs) in worms were both one to two magnitudes higher than in mussels and snails, likely due to different habitat-specific uptake pathways and elimination capacities among species. In these experiments, increasing sediment organic carbon content decreased the bioaccumulation of PFAS to benthic macroinvertebrates. In worms, sediment organic carbon content was hypothesized to impact PFAS bioaccumulation by affecting PFAS partitioning and sediment ingestion rate. Notably, the BSAF values of 8:2 fluorotelomer sulfonic acid (FTS) were the largest among 14 PFAS for all species, suggesting that the benthic macroinvertebrates probably have different metabolic mechanisms for fluorotelomer sulfonic acids compared to fish evaluated in published literature. Understanding the impact of species and sediment organic carbon on PFAS bioaccumulation is key to developing environmental quality guidelines and evaluating potential ecological risks to higher trophic level species.

Impacts of divalent cations (Mg2+ and Ca2+) on PFAS bioaccumulation in freshwater macroinvertebrates representing different foraging modes.

Per- and polyfluoroalkyl substances (PFAS) have extensively contaminated freshwater aquatic ecosystems where they can be transported in water and partition to sediment and biota. In this paper, three freshwater benthic macroinvertebrates with different foraging modes were exposed to environmentally relevant concentrations of eight perfluoroalkyl carboxylates (PFCA), three perfluoroalkyl sulfonates (PFSA), and three fluorotelomer sulfonates (FTS) at varying divalent cation concentrations of magnesium (Mg2+) and calcium (Ca2+). Divalent cations can impact PFAS partitioning to solids, especially to sediments, at higher concentrations. Sediment dwelling worms (Lumbriculus variegatus), epibenthic grazing snails (Physella acuta), and sediment-dwelling filter-feeding bivalves (Elliptio complanata) were selected due to their unique foraging modes. Microcosms were composed of synthetic sediment, culture water, macroinvertebrates, and PFAS and consisted of a 28-day exposure period. L. variegatus had significantly higher PFAS bioaccumulation than P. acuta and E. complanata, likely due to higher levels of interactions with and ingestion of the contaminated sediment. "High Mg2+" (7.5 mM Mg2+) and "High Ca2+" (7.5 mM Ca2+) conditions generally had statistically higher bioaccumulation factors (BAF) than the "Reference Condition" (0.2 mM Ca2+ and 0.2 mM Mg2+) for PFAS with perfluorinated chain lengths greater than eight carbons. Long-chain PFAS dominated the PFAS profiles of the macroinvertebrates for all groups of compounds studied (PFCA, PFSA, and FTS). These results indicate that the study organism has the greatest impact on bioaccumulation, although divalent cation concentration had observable impacts between organisms depending on the environmental conditions. Elevated cation concentrations in the microcosms led to significantly greater bioaccumulation in the test organisms compared to the experimental reference conditions for long-chain PFAS.

Occurrence of estrogen hormones in biosolids, animal manure and mushroom compost.

The presence of natural estrogen hormones as trace concentrations in the environment has been reported by many researchers and is of growing concern due to its possible adverse effects on the ecosystem. In this study, municipal biosolids, poultry manure (PM) and cow manure (CM), and spent mushroom compost (SMC) were analyzed for the presence of seven estrogen hormones. 17α-estradiol, 17ß-estradiol, 17α-dihydroequilin, and estrone were detected in the sampled biosolids and manures at concentrations ranging from 6 to 462 ng/g of dry solids. 17α-estradiol, 17ß-estradiol, and estrone were also detected in SMC at concentrations ranging from 4 to 28 ng/g of dry solids. Desorption experiments were simulated in the laboratory using deionized water (milli-Q), and the aqueous phase was examined for the presence of estrogen hormones to determine their desorption potential. Very low desorption of 0.4% and 0.2% estrogen hormones was observed from municipal biosolids and SMC, respectively. An estimate of total estrogen contribution from different solid waste sources is reported. Animal manures (PM and CM) contribute to a significant load of estrogen hormones in the natural environment.

Effect of process conditions on the analysis of free and conjugated estrogen hormones by solid-phase extraction-gas chromatography/mass spectrometry (SPE-GC/MS).

Simultaneous analysis of 11 free estrogen hormones and five conjugated estrogens in water and municipal wastewater was studied. The analytical method was developed and tested for different types of solid-phase extraction adsorbents, eluents, sample containers and storage conditions, derivatization, and matrix effects. Varian Bond Elut C-18 solid-phase extraction adsorbent cartridge was selected based on its high recoveries for both free and conjugated estrogens. Sample storage conditions, as well as selection and pretreatment of sample container materials, can affect the trace level analysis of estrogens. Silanization of glassware is observed to provide low relative standard deviation (RSD) in the analysis and less percentage loss due to contacting with sample container materials. Light exposure during the test can significantly impact the results. The derivatized samples stored at -20°C for at least 6 days showed less than 10.5% average RSD in the analysis. The recovery efficiency in clean water varies from 72% to 101% for free estrogens and 78% to 82% for conjugated estrogens. The method detection limits (MDL) for most of the compounds range from 30 to 870 ng/L using a sample volume of 200 mL. With a sample volume of 3 L, the most sensitive compound produces a MDL of 0.03 ng/L. Dilute methanol is used to wash the loaded cartridge as a cleanup step in order to remove interfering species during analysis of wastewater samples. Using the optimized analytical methods, the concentration level of free estrogens in the influent and effluent municipal wastewaters is tested.

Disinfection of water using Pt- and Ag-doped TiO2 photocatalysts.

In this article we have reported heterogeneous photocatalytic disinfection using pristine and Ag- and Pt-doped nano TiO2 under near-UV light and solar light irradiation. Disinfection experiments were conducted in slurry reactors with Escherichia coli, artificial light and sunlight. The influence of various amounts of Pt and Ag loading (0.5% to 5%) on the E. coli inactivation was examined and results indicated that 5% Pt-TiO2 and 0.5% Ag-TiO2 showed the highest photocatalytic E. coli inactivation. The Pt- and Ag-doped photocatalysts were characterized using XPS and TEM analysis. The influence of experimental parameters such as various photocatalysts, photocatalyst concentration, reactor geometry effect, pH and temperature on the photocatalytic disinfection was studied. The experimental results show that sunlight or near-UV light with TiO2 photocatalyst strongly inactivates E. coli. The Ag-TiO2 photocatalyst was the most efficient photocatalyst tested for bactericidal activity. A plausible mechanism ofphotocatalysed E. coli inactivation is discussed. In conclusion, the doped nano TiO2 photocatalysts is a potential candidate for E. coli inactivation.

Synthesis and Characterization of High Viscosity Cationic Poly(Proline-Epichlorohydrin) Composite Polymer with Antibacterial Functionalities.

We report microbial resistance and catalytic activity of high viscosity cationic poly(proline-epichlorohydrin) composite (PRO-EPI) in the aqueous system. The PRO-EPI was prepared by a simple polycondensation, followed by FTIR, 1H NMR, SEM, DLS, viscosity, and DSC/TGA characterization. Several concentrations of the PRO-EPI were tested against Gram-negative (E. coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) microorganisms. The antimicrobial screening revealed that PRO-EPI was a potent antimicrobial agent with the least inhibitory concentrations (MICs) of 128 µg/mL against Gram-negative microorganisms. The PRO-EPI indicated no inhibitory effect against Gram-positive microorganisms. It was determined that PRO-EPI contains polymeric-quaternary ammonium compounds that inactivate the Gram-negative microorganisms by a dual mode of action and carries domains for electrostatic interaction with the microbial membrane and an intracellular target. To study the removal of toxic industrial wastewater, congo red (CR) was tested using sodium borohydride as a reducing agent. Adsorption was achieved within 20 min at a rate constant of 0.92 ks-1. UV-vis spectra showed that the removal of CR in the reaction solution was due to the breakup of the azo (-N=N-) bonds and adsorption of aromatic fragments. PRO is biodegradable and non-toxic, and PRO-EPI was found to be both antimicrobial and also acts as a catalyst for the removal of congo red dye.

Competitive sorption of Cd, Cr, Cu, Ni, Pb and Zn from stormwater runoff by five low-cost sorbents; Effects of co-contaminants, humic acid, salinity and pH.

For a comprehensive estimation of metals removal by sorbents in stormwater systems, it is essential to evaluate the impacts of co-contaminants. However, most studies consider only metals (single or multiple), which may overestimate performance. This study employed a batch method to investigate the performance of five low-cost sorbents - coconut coir fiber (CCF), blast furnace slag (BFS), waste tire crumb rubber (WTCR), biochar (BC), and iron coated biochar (FeBC) - for simultaneous removal of Cd, Cr, Cu, Ni, Pb and Zn from simulated stormwater (SSW) containing other contaminants (nutrients and polycyclic aromatic hydrocarbons). BFS and CCF demonstrated the highest sorption capacity of all metals (> 95% removal) in all systems (single and multi-contaminant). However, the presence of other contaminants in solution reduced metals removal for other sorbents, as follows (highest to lowest removal): single-metal > multi-metal > multi-contaminant solutions, and removal efficiency ranking among metals was generally Cr~Cu~Pb > Ni > Cd > Zn. Humic acid (HA) negatively affected the metal sorption, likely due to the formation of soluble HA-metal complexes; NaCl concentration did not impact removal, but alkaline pH improved removal. These findings indicate that sorbents need to be tested under realistic stormwater solution chemistry including co-contaminants to appropriately characterize performance prior to implementation.

Degradation and inactivation of chromosomal and plasmid encoded resistance genes/ARBs and the impact of different matrices on UV and UV/H2O2 based advanced oxidation process.

This study reports a structured investigation on the degradation kinetics of different types (gyrAR,tetAR, qnrSR) and conformational forms (chromosomal, plasmids) of ARGs and mobile genetic elements (intl-1, plasmids) as a function of water matrix (DI water, phosphate buffer, wastewater) with UV and UV/H2O2 treatments. Extracellular, intracellular and the free-ARGs fate were tracked to infer the impact of various parameters on the degradation efficacy of the treatment process. The degradation profile of e-ARGs (118-454 bp) showed 1-4 log reductions but did not correlate strongly to amplicon size indicating the importance of active sites distribution and/or types of ARGs for UV induced gene damage. The i-ARGs showed similar degradation rates compared to e-ARGs for UV in phosphate buffer (PBS) but showed (1.3-2 times) slower rates for i-ARGs with UV/H2O2 due to scavenging of OH radicals by the cellular components. While the ARB inactivation was effective, but ARG damage was not supplemental as i-ARGs and f-ARGs persisted. In the wastewater matrix, generation of radical species was contributing to improved degradation rates from UV/H2O2 treatment, specifically for f-ARGs resulting in significantly improved degradation (p<0.05) compared to PBS. These indicates a non-selective nature of attack from radical species generated from UV irradiation on the effluent organic matter (EfOM) than sequenced based damage to the genes from UV. For the plasmid degradation, conformational differences pertaining to the supercoiled structures and intracellular forms influenced slower (1.2-2.8 times) UV mediated gene damage rate as opposed to chromosomal ARGs. These results can be useful for better assessing UV based treatment processes for effective ARG removal.