Little is known about the environmental behavior of fenhexamid (FEN) in aquatic ecosystems such as degradation and bioaccumulation, in spite of the fact that it is critical for a comprehensive assessment of its ecological risks. This study investigated for the first time the degradation of FEN in water-sediment systems under both aerobic and anaerobic conditions and also bioaccumulation by zebrafish (Danio rerio). Water and sediments from different natural waters including river HR and lake HL were applied to build up water-sediment microcosms in the laboratory. When FEN was introduced into the aqueous phase, it would partition from water to sediment gradually and be decomposed in sediment compartment. The dissipation half-lives of FEN in water were 43.8, 75.9, 31.3, and 37.2 days for HR-aerobic, HR-anaerobic, HL-aerobic, and HL-anaerobic microcosms, respectively. Moreover, FEN degradation rate constants of whole systems varied from 0.0045 to 0.0088 per day and the half-lives were from 78.4 to 155 days. The aerobic circumstances were demonstrated to be favor of FEN degradation. The bioconcentration factor (BCF) was 2.6–3.1 obtained from zebrafish exposure experiments at environmentally relevant concentrations. Clearly, our results indicated that FEN could be accumulated in the deeper layer of sediment owing to the anaerobic condition against FEN degradation, but FEN showed a low potential for bioaccumulation. These may aid in comprehensive understanding the fate and risk of FEN in aquatic environment.

The promotive effect of constructed wetlands (CWs) with polyculture on treatment efficiency is still a controversial problem. Additionally, there is limited information regarding the influence of temperature on CWs. In this study, the influence of vegetation type, different NH₄ ⁺-N loading rates, and environmental temperatures on performance of CWs were investigated. Results of different vegetation type indicated that removal of NH₄ ⁺-N and total phosphorus (TP) in polyculture was higher than other CWs. In polyculture, tested nutrients had removal percentages greater than 94.5%. Results of different NH₄ ⁺-N loading rates demonstrated that NH₄ ⁺-N was almost completely removed (around 99.5%) in polyculture under both NH₄ ⁺-N loading rates. Temperature could substantially influenced the performance of CWs and the removal percentages of NH₄ ⁺-N, NO₃ ⁺-N, total nitrogen (TN), and TP in all CWs tended to decrease with a decline of temperature. Especially, a sharp decline in the removal percentage of NO₃ ⁻-N of all CWs (greater than 39%) was observed at low temperature (average temperature of 8.9 °C). Overall, the polyculture also showed the best performance with the decline of temperature as compared to other CWs. This study clearly documented that polyculture was an attractive solution for the treatment of domestic sewage and polyculture systems were effective for domestic sewage treatment in CWs even at low temperature (8.9 °C).

The widespread use of unconventional drilling involving hydraulic fracturing (“fracking”) has allowed for increased oil-and-gas extraction, produced water generation, and subsequent spills of produced water in Colorado and elsewhere. Produced water contains BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene, all of which are known to induce varying levels of toxicity upon exposure. When spilled, these contaminants can migrate through the soil and contaminant groundwater. This research modeled the solute transport of BTEX and naphthalene for a range of spill sizes on contrasting soils overlying groundwater at different depths. The results showed that benzene and toluene were expected to reach human health relevant concentration in groundwater because of their high concentrations in produced water, relatively low solid/liquid partition coefficient and low EPA drinking water limits for these contaminants. Peak groundwater concentrations were higher and were reached more rapidly in coarser textured soil. Risk categories of “low,” “medium,” and “high” were established by dividing the EPA drinking water limit for each contaminant into sequential thirds and modeled scenarios were classified into such categories. A quick reference guide was created that allows the user to input specific variables about an area of interest to evaluate that site’s risk of groundwater contamination in the event of a produced water spill. A large fraction of produced water spills occur at hydraulic-fracturing well pads; thus, the results of this research suggest that the surface area selected for a hydraulic-fracturing site should exclude or require extra precaution when considering areas with shallow aquifers and coarsely textured soils.

Different from direct application of free nanoparticles (NPs) in water treatment, a composite material is used to reduce the release and potential toxic effects of NPs with maintained adsorption capacity and kinetics. Novel monolithic composites with TiO₂ NPs incorporated into the walls of macroporous cryogels were synthesized and evaluated for material characteristics and their efficiency for removal of Pb(II) from aqueous solution in batch test and continuous mode. The uniformly distributed 6% TiO₂-cryogel is shown to be optimal for minimizing TiO₂ NP losses while maximizing Pb(II) removal. Under (25.0 ± 0.1) °C with the initial Pb(II) concentration of 10 mg/l, TiO₂-cryogels exhibit excellent adsorption characteristic for Pb(II) removal with adsorption capacity up to 23.27 mg/g TiO₂, which is even a little higher than that of TiO₂ NPs (21.58 mg/g TiO₂), and the results fit well with Langmuir–Freundlich isotherm. Both adsorbents work well in higher pH range with the highest removal rate at pH 6 for TiO₂-cryogel, and the adsorption mechanism might be strong chemical interaction. Pseudo-second-order process can better describe the adsorption process rather than pseudo-first-order for both adsorbents. The external mass transfer process of Pb(II) on TiO₂ NPs is much faster than that on TiO₂-cryogel, and the ultimate equilibrium time is about the same (3 h) on both adsorbents. The synthesized composites could also withstand a continuous treatment, and the effect of competing and co-existing constituents such as Cd²⁺, SO₄²⁻ and dissolved organic matter (DOM) is almost negligible. The composite design with small particles embedded into cryogels is proved to successfully keep the adsorption activity of TiO₂ NPs and prevent them from releasing into the environment in engineering practice.

The photocatalytic degradation of a cationic dye, rhodamine 6G (Rh-6G) under UV light irradiation was carried out. Rh-6G was completely decolorized in 180 min of photo-oxidative degradation period. The extent of degradation was confirmed performing total organic carbon (TOC) analysis, and up to 90.14%, TOC removal was achieved. Several critical analytical techniques including UV-Vis spectroscopy, high-performance liquid chromatography (HPLC), and ultra-performance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC/MS) were employed to scrutinize the mechanistic insights of the dye photodegradation. The degraded N-demethylation intermediates and several small molecular products were qualitatively identified, and a tentative photodegradation pathway was proposed. Toxicological evaluation of the degradation products was carried out three types of cell lines (MTT assay) and Triticum sativum seeds. In conclusion, enhanced biodegradability accompanied by toxicity reduction confirmed the promising efficiency of photocatalysis for Rh-6G degradation and therefore could be used for the remediation of textile effluents.

A heterogeneous photo-Fenton process was applied to treat aqueous solutions of indigo blue and textile wastewater using an iron-modified clay (Mt-Fe) and a copper-modified carbon (AC-Cu) as catalysts, the UV radiation source was the sunlight collected by a compound parabolic concentrator (CPC-2D). The treatments were conducted at pH 7.0 and 6.8 for the aqueous solutions and the textile wastewater, respectively, and different hydrogen peroxide concentrations and catalyst quantities were evaluated. The concentration of UV-A radiation collected by the CPC-2D was 54.29 ± 0.71 W/m², with an applied energy of 97.36 kJ from the concentrator device. The indigo blue removal efficiencies for Mt-Fe and AC-Cu were 98% (3 h) and 99% (1.5 h), respectively, using 1.5 g of catalyst, 0.5 M of H₂O₂, and UV radiation. The color removal efficiency in the textile wastewater was 93% after 4 h of treatment using 1.5 g of AC-Cu, 0.5 M of H₂O₂, and UV radiation. The removal of dye and color was improved by using AC-Cu and UV radiation for both systems (the aqueous solutions and the textile wastewater), showing that Cu has an important catalytic activity. IR spectra showed a change after the oxidation of organic matter by heterogeneous photo-Fenton process, and the application of the UV radiation collected by CPC-2D played an important role in the heterogeneous photo-Fenton process.

This study was conducted to determine the optimal conditions for PAH degradation from highly contaminated attrition sludge (PAC) using a Fenton process or successive permanganate (KMnO₄) oxidation and Fenton processes. The following parameters were studied to optimize the Fenton oxidation process: the amounts of reactants based on the stoichiometric oxidant demand (SOD), the reactant addition protocol and number of doses, and the solid/liquid ratio (S/L). The results showed that the following conditions were optimum: TS = 30%, 7.5 times SOD, H₂O₂/Fe²⁺ ratio = 10, and added five times during 60 min, which allowed the degradation of 43% of total 27 PAHs from the PAC. Successive Fenton and KMnO₄ oxidation processes were also tested. PAH degradation using a sequential Fenton process followed by KMnO₄ oxidation (or KMnO₄ followed by Fenton) was higher than for the use of Fenton or KMnO₄ treatment alone. Up to 71% of the total 27 PAHs were degraded when using a combination of both processes. It appeared that the sequential treatment is a viable method for the significant degradation of 27 PAHs from PAC (t value > 2.77).

The occurrence of endocrine-disrupting chemicals (EDCs) in the aquatic environment has brought increasing concern due to their potential adverse impacts on ecosystems and humans. These compounds are generally present in complex water matrices, such as surface waters at trace levels (ng L⁻¹) making their analysis difficult. In this work, an analytical method for the simultaneous determination of 13 EDCs, including 5 steroid estrogens, 1 progestogen, 1 androgen, and 6 endocrine-disrupting phenols in water, was developed using solid phase extraction (SPE), derivatization, and gas chromatography-mass spectrometry (GC-MS). The method was validated by spiking the 13 EDCs to the interest matrix. The recovery was in the range of 52–71% with an average of 62%. The limits of quantification were 1 and 5–10 ng L⁻¹ for phenolic compounds and hormones, respectively. The validated method was applied to assess the contamination level of the targeted EDCs in 15 sites collected from six rivers located at the cross-border area of Northern France and Belgium. The majority of the considered compounds were detected in the sampling sites and among them, bisphenol A (BPA) was found at the highest level which can be up to 286 ng L⁻¹. However, NP was the most frequently detected, followed by BPA and PG.

Currently, there are large areas of soils contaminated with hexachlorocyclohexane (HCH) isomers which are included in the group of persistent organic pollutants. For the bioremediation of such soils, a new HCH-degrading Rhodococcus wratislaviensis strain Ch628 was isolated from long-term organochlorine contaminated soils. The strain Ch628 was able to degrade 32.3% γ-hexachlorocyclohexane (γ-HCH/lindane), 25.2% hexachlorobenzene, and 100% chlorobenzene in resting cell conditions. The strain Ch628 was bioaugmented in chronically HCH-contaminated soil. The results showed that the bioaugmentation of contaminated soil with the strain Ch628 led to HCH degradation. In the bioaugmented system, the efficiency of HCH removal at the initial concentration of about 238.7 ± 4.9 mg kg⁻¹ soil was 44.8%, while the system with indigenous microflora (without R. wratislaviensis strain Ch628) and the system with abiotic control removed 33.3 and 16.4% of this compound during the same period, respectively. Strain Ch628 could effectively degrade α-, β-, and γ-isomers of HCH (77.1, 100, and 100%, respectively) and heptachlorocyclohexane (69.9%) in the model soil systems. Moreover, the bioaugmentation with the strain Ch628 led to degradation of tri-, tetra-, and penta-chlorobenzenes, which are of HCH degradation metabolites. For the first time, it was found that the bioaugmentation with the bacterial strain Rhodococcus wratislaviensis Сh628 led to a significant reduction of the toxicity of the HCH-contaminated soil for the test organisms, such as Chlorella vulgaris Beijer and Daphnia magna Straus.

The trihalomethanes (TTHMs) and others disinfection by-products (DBPs) are formed in drinking water by the reaction of chlorine with organic precursors contained in the source water, in two consecutive and linked stages, that starts at the treatment plant and continues in second stage along the distribution system (DS) by reaction of residual chlorine with organic precursors not removed. Following this approach, this study aimed at developing a two-stage empirical model for predicting the formation of TTHMs in the water treatment plant and subsequently their evolution along the water distribution system (WDS). The aim of the two-stage model was to improve the predictive capability for a wide range of scenarios of water treatments and distribution systems. The two-stage model was developed using multiple regression analysis from a database (January 2007 to July 2012) using three different treatment processes (conventional and advanced) in the water supply system of Aljaraque area (southwest of Spain). Then, the new model was validated using a recent database from the same water supply system (January 2011 to May 2015). The validation results indicated no significant difference in the predictive and observed values of TTHM (R ² 0.874, analytical variance <17%). The new model was applied to three different supply systems with different treatment processes and different characteristics. Acceptable predictions were obtained in the three distribution systems studied, proving the adaptability of the new model to the boundary conditions. Finally the predictive capability of the new model was compared with 17 other models selected from the literature, showing satisfactory results prediction and excellent adaptability to treatment processes.