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© 2020 The Royal Society of Chemistry. In water treatment, the application of advanced oxidation processes (AOPs) which involve the generation of not only hydroxyl but also sulfate radicals has recently attracted increasing attention worldwide. To the best of our knowledge, to date, the application of ultraviolet (UV) activated persulfate and peroxymonosulfate (UV/S2O82- and UV/HSO5-) has not been comprehensively studied for chloroacetanilide herbicide degradation. In our study, this process was investigated under different conditions and compared to the more conventional UV/H2O2 process. Alachlor was investigated due to its toxic properties, and the threat it poses to aquatic environments and human health, which led to its classification as a priority pollutant by the European Water Framework Directive. The alachlor degradation kinetics of different UV-based AOPs were highly dependent on the pH and the water matrix characteristics. The UV/S2O82- and UV/H2O2 processes proved to be most effective under acidic conditions (pH 5), while the UV/HSO5- process showed the highest alachlor degradation efficacy under basic conditions (pH > 8). The groundwater matrix had a greater impact on the AOPs than the surface water. PCA analysis was applied and a predictive model of alachlor degradation by UV-based AOPs was proposed. Alachlor degradation pathways were also evaluated together with NOM transformation during the applied treatments. The obtained results indicate that the more novel UV/S2O82- and UV/HSO5- processes show significant potential for herbicide degradation during water treatment, especially when the raw water is highly loaded with hydrophobic NOM.

The characteristics of the Danube river alluvial sediment are of great importance in assessing the risk for transport of pollutants to drinking water sources. Characterization of the sediment column layers has shown that the alluvial sediment, sampled near the city of Novi Sad, is a mesoporous sandy material with certain differences in the properties of individual layers. In order to investigate the sorption mechanisms of four chlorinated phenols (CPs) on the alluvial deposit, static sorption experiments were performed at pH 4, 7 and 10. The results of sorption experiments, confirmed by principal components analysis sugest different mechanisms govern the sorption process at different pH conditions. This can be attributed to the molecular characteristics of CPs, geosorbent properties and to variations in the surface charge of the sorbent at different pH conditions.

Waterworks which utilise river bank filtration water sources often have to apply aeration and sand filtration to remove iron and manganese during the drinking water treatment process. After some time, the sand becomes saturated and the spent filter sand (SFS) must be disposed of and replaced. In order to valorize this waste stream, this paper investigates the reuse of SFS as an adsorbent for the treatment of arsenic contaminated drinking water. The arsenic removal performance of SFS is compared with two synthetic iron oxide coated sands (IOCS). The sorbents were first characterized by SEM, EDS, BET specific surface area, and point of zero charge (pHpzc) measurements, and then investigated under a variety of conditions. The surface of the SFS was revealed to be coated with iron manganese binary oxide. The Freundlich model best described the isotherm experiment data, indicating a non monolayer adsorption model for arsenic adsorption on the three IOCS investigated. As(III) and As(V) removals were negatively effected by the presence of PO43− and HA anions as they competed with the arsenic species for adsorption sites. However, given the status of SFS as a waste material, the results obtained in this paper suggest it may be successfully reused as a very economically and environmentally sustainable solution for small waterworks requiring both As(V) and As(III) removal during drinking water treatment.

© 2018, Islamic Azad University (IAU). This research evaluates the effect of ultraviolet photolysis, ozonation and ozonation/ultraviolet advanced oxidation processes on different disinfection by-product precursors, during the treatment of water with low organic matter and moderate bromide contents. After different combinations of ultraviolent fluence and ozone, the formation potentials of trihalomethanes and haloacetic acids were investigated. Bromine incorporation factors were used to give specific insight into the behaviour of brominated disinfection by-products, and inorganic bromate formation was also determined. The ozone/ultraviolet process was found to be more effective in reducing the total natural organic matter content than ozonation or ultraviolet photolysis alone. Ultraviolet photolysis was more successful removing the precursors of brominated trihalomethanes than chlorinated trihalomethanes, but slightly increased the precursors of both brominated and chlorinated haloacetic acids. During ozonation, reductions in the haloacetic acid formation potential were significantly better than those of the trihalomethanes formation potential (up to 54 and 27%, respectively). In the combined ozonation/ultraviolet process, increasing the ultraviolet fluence had a varying effect on trihalomethane and haloacetic acid precursor behaviour, depending on the ozone dose applied. Bromine incorporation after ozonation alone increased to up to 38% of the total bromide, largely as a result of bromate formation. The combined process curtailed all bromate formation, but increased the bromine incorporation up to 48% at higher ozone doses, with disinfection by-product formation shifting towards the more toxic brominated species.

© 2017 Elsevier Ltd In this study, laboratory scale experiments were conducted with the horizontal continuous-flow EC reactor as a standalone technology with the capacity of 300 L/day with iron (Fe) plate bipolar electrodes to assess its efficiency in the removal of arsenic from raw groundwater without pre- and post-treatment pH modification of groundwater. The optimum EC reactor operating conditions were determined to be current density of 1.98 A/m2, charge loading of 54 C/L, flow rate of 12 L/h. The EC reactor was able to remove 96% of arsenic from raw groundwater and met respective World Health Organization (WHO) guideline value of 10 μg As/L within the 4 h experimental runs. The Fe electrode polarity change at 30 min successfully controlled passivation of Fe electrodes and enabled a steady reactor operation with the high As removal efficiency. Residual Fe concentration in treated groundwater was in the range 0.17 ± 0.07 mg/L and met WHO guideline value for drinking water. The preliminary estimated operating cost at the optimum operating conditions was 0.0135 €/m3.

The main objective of this study was to gain more detailed knowledge of how four selected polycyclic aromatic hydrocarbons (PAHs) interact on six nondegradable types of microplastics (MPs) and one biodegradable plastic (BP) in two water matrices. The results were evaluated using the popular Freundlich and Langmuir isotherm models, as well as a new modified mathematical model. The modified mathematical model was developed to additionally elucidate the adsorption mechanism, to investigate transfer kinetics of PAHs and to predict the variation of adsorption rate and capacity as a function of time. The adsorption kinetics of selected PAHs onto MPs and biodegradable plastic were described best by the pseudo-second order kinetic model (R2 = 0.810–0.999), implying that chemisorption is possibly the adsorption mechanism. The results of the adsorption isotherm study also indicated that adsorption of PAHs on selected types of microplastics was best described by the Langmuir model, implying that adsorption of PAHs is more dominant on powdered types of MPs in both synthetic and real water matrices. On the other hand, the lowest adsorption affinity was achieved for adsorption of PAHs on polylactic acid, indicating that this type of biodegradable plastic would have significantly less impact on the transport and distribution of PAHs through environment.

© 2020 Elsevier B.V. In this work, we have investigated the stability of pindolol (PIN), a non-selective β1-blocker detected in the river and wastewater of hospitals, in water solution under solar irradiation. Further, detailed insights into the stability of PIN were obtained by the density functional theory (DFT) calculations and molecular dynamics simulations. The kinetics of PIN photocatalytic degradation and mineralization has been studied using four commercial photocatalysts ZnO and TiO2 (P25, Hombikat, and Wackherr). It was found that the major role in degradation of PIN play the reactive hydroxyl radicals. The structures of degradation intermediates were suggested by LC–ESI–MS/MS and DFT calculations. Also, DFT calculations were used to refine molecular structures of intermediates and obtain their geometries. Toxicity of PIN and its mixtures formed during photocatalytic degradation were investigated using mammalian cell lines (H-4-II-E, HT-29, and MRC-5). The H-4-II-E cell line was the most sensitive to PIN and its photodegradation mixtures. The computational results were combined with the experimental data on the amounts of degradation intermediates for determination of the intermediates that were principally responsible for the toxicity. Intermediate with two hydroxyl groups, positioned on indole ring in meta and para positions, was proposed as the one with the highest contribution to toxicity.

The presence of 48 emerging micropollutants was tested in influent and effluent from primary and secondary treatment at a municipal wastewater treatment plant (WWTP) in Serbia. Sixteen emerging micropollutants (active pharmaceutical ingredients, bisphenols, parabens and UV filters) had concentrations >LOQ (max. conc. 33.4 μg/L). The removal efficiency of primary treatment ranged from 2.0% - 96.0%. In the case of secondary treatment, except for ketoprofen (61.0%), diclofenac (62.6%) and carbamazepine (−20.0%), all other measured micropollutants had removal efficiency above 77.0%. Advanced non-oxidative lab-scale treatments were investigated. Powdered activated carbon (PAC) adsorption achieved removal efficiencies in the range 52.4–99.9%, novel coagulation with natural coagulant isolated from beans achieved removal efficiencies in range 3.2–99.9%, conventional coagulation with ferric chloride 3.12–96.4%, combined adsorption/coagulation 2.69–99.9% and combined PAC/ultrafiltration (PAC/UF) 60–99.9%. For most of the micropollutants, their removal efficiencies were similar to that reported in the literature. Novel natural coagulant showed significant potential compared to the conventional coagulant during a short episode of sub-optimal WWTP operation. When natural coagulant was applied as a part of an adsorption/coagulation hybrid process, there was no negative effect on PAC adsorption, while for conventional coagulant that was not always the case. Also, a structure property relationship (SPR) study revealed correlations between the removal efficiency of the majority of treatments applied and total polar surface area (TPSA) of the micropollutants.

Sediment represents a sink for toxic and persistent chemicals such as hexachlorobenzene (HCB) and lindane (γ-HCH). This paper investigates the possibility of reducing the risks associated with the presence of these pollutants in sediments by amending the sediment with carbon-rich materials (activated carbon (AC) and humus (HC)) to sequester the contaminants and render them biologically unavailable. The effects of the dose and contact time between the sediment and the carbon-rich amendments on the effectiveness of the detoxification are estimated. Four doses of carbon-rich amendments (0.5-10%) and four equilibration contact times (14-180 days) were investigated. Results have shown that the bioavailable fraction of γ-HCH and HCB decreased significantly in comparison to the unamended sediment. Regarding the AC amendments, almost 100% for both compounds; and for HC amendments around 95% for γ-HCH, and 75% for HCB. Aging caused further reductions in the bioavailable fraction, compared to the untreated sediment. Phytotoxicity tests showed that Zea mays accumulated significantly higher amount of γ-HCH and HCB from unamended sediment, comparing to Cucurbita pepo and Lactuca sativa. Toxicity of HC and AC amended sediment assessed by Vibrio fischeri luminescence inhibition test and by measuring Zea mays germination and biomass yield was significantly reduced in the amended sediment samples. γ-HCH and HCB accumulation in the Zea mays biomass in the unamended sediment were a significantly higher than in the all HC and AC amended sediment. Both sorbents show potential to be used as remediation agents for organically contaminated sediment, but AC exhibited the better performance.

© 2019, © 2019 Taylor & Francis Group, LLC. Granular activated carbon (GAC) was modified with Fe–Mn binary oxide to produce a novel effective hybrid adsorbent (GAC–FeMn) for simultaneous removal of As(III) and As(V) from water. After characterization (including BET, SEM/EDS and XRD analyses) of the raw and modified GAC, FTIR analysis before and after As removal showed that ligand exchange was the major mechanism for As removal on GAC–FeMn. Sorption kinetics followed pseudo-second order kinetics for both As(III) and As(V) and were not controlled by intraparticle diffusion. Batch equilibrium experiments yielded adsorption capacities for As(III) and As(V) of 2.87 and 2.30 mg/g, and demonstrated that better sorption was achieved at low pH. Of the competitive anions investigated (PO 43− , SiO 32− , CO 32− , SO 42− , NO 3− , Cl − ), phosphate had the greatest negative effect on As(III) and As(V) adsorption. Three sorption/desorption cycles were conducted in continuous column tests with a real arsenic contaminated groundwater, with subsequent TCLP leaching tests confirming the stability of the spent sorbent. In the column tests, breakthrough curves were also obtained for phosphates, which were present at a relatively high concentration (1.33 mg/L) in the investigated groundwater. The phosphates limited the effective operational bed life of GAC–FeMn for arsenic removal. Nonetheless, the maximum arsenic adsorption capacities for GAC–FeMn obtained by the Thomas model during the three sorption cycles were high, ranging from 18.8 to 29.8 mg/g, demonstrating that even under high phosphate loads, with further process improvements, GAC–FeMn may provide an excellent solution for the economic removal of arsenic from real groundwaters.

A novel technique of continuous ECF using bipolar Al electrode was attempted in this study to efficiently remove arsenic from groundwater rich in hydrophobic NOM (9.31 ± 0.52 mg C/L). The effects of several operational parameters such as, initial groundwater pH, evolution of temperature, conductivity and pH, electrode polarity time change on As and NOM removal efficiency were comprehensively examined by conducting 6 h long experimental runs. The average residual As in treated groundwater was 4.6 ± 0.4 μg/L. NOM removal according to UV254 absorbance, DOC and SUVA was 89%, 70%, 64%, respectively. The highest As and NOM removal with the optimal residual Al below 0.2 mg/L was obtained at the same groundwater pH = 5.3 ± 0.3. The change of electrode polarity at 30 min successfully prevented electrode passivation and enabled highest As removal with the optimal residual Al in treated groundwater. Specific reactor electric energy and electrode consumption for operational current density of 8.86 mA/cm2 was 3.03 kW h/m3, 0.059 kg Al/m3, respectively. Indicative reactor’s operating cost at the optimal operational conditions was estimated at 0.25 €/m3.

Natural organic matter (NOM) in raw water can contribute in many ways to the poor quality of drinking water, including the formation of disinfection byproducts such as trihalomethanes (THM) and haloacetic acids (HAA) during disinfection. This paper investigates the role of individual NOM fractions on changes in THM and HAA formation during coagulation with iron chloride (FeCl3) and a combination of polyaluminium chloride and iron chloride (FeCl3/PACl). The dissolved organic carbon (DOC) in the raw water and after coagulation was fractionated into four fractions, based on their hydrophobicity. Fractionation showed that most of the DOC (68%) in the raw water comes from the fulvic acid fraction, yielding 41% of the total THM precursors and 21% of the total HAA precursors. Both coagulants remove the humic acid fraction, but result in different changes to the reactivity of the remaining NOM fractions towards THM and HAA formation, indicating that coagulation occurs by different pathways, depending upon the type of coagulant used. In particular, significant changes in the reactivities of the hydrophilic acidic and non-acidic fractions were observed.

To improve water quality, a pilot-scale evaluation into upgrading the conventional treatment process was conducted. By following DOC content, UV254 absorbance, SUVA and by-products formation, three oxidative pre-treatments were evaluated: pre-ozonation (2.2 g O3/m3); O3/H2O2 process (2.2 g O3/m3; H2O2:O3 = 1:2) and O3/H2O2 process (2.2 g O3/m3; H2O2:O3 = 2:1). The second pre-treatment gave the best results, with a final average DOC content of 0.9 mg C/L, UV254 absorbance of 0.06 cm−1 and the lowest THMFP of 130 μg/L. UV254 absorbance can serve as a proper indicator for predicting THM and HAA formation, yielding a correlation coefficient ≥ 0.90.

Interactions between arsenic and natural organic matter (NOM) are key limiting factors during the optimisation of drinking water treatment when significant amounts of both must be removed. This work uses Response Surface Methodology (RSM) to investigate how they interact during their simultaneous removal by iron chloride coagulation, using humic acid (HA) as a model NOM substance. Using a three factor Box-Behnken experimental design, As and HA removals were modelled, as well as a combined removal response. ANOVA results showed the significance of the coagulant dose for all three responses. At high initial arsenic concentrations (200 μg/l), As removal was significantly hindered by the presence of HA. In contrast, the HA removal response was found to be largely independent of the initial As concentration, with the optimum coagulant dose increasing at increasing HA concentrations. The combined response was similar to the HA removal response, and the interactions evident are most interesting in terms of optimising treatment processes during the preparation of drinking water, highlighting the importance of utilizing RSM for such investigations. The combined response model was successfully validated with two different groundwaters used for drinking water supply in the Republic of Serbia, showing excellent agreement under similar experimental conditions.

This study utilizes a combinatorial bio/chemical approach to assess the toxicological profiles of organic pollutants in water and sediment samples from two watercourses that are under significant anthropogenic pressure-the Krivaja and Jegricka rivers in Serbia. Sample preparation by solid-phase extraction and silica-gel fractionation followed by GC/MS analysis, allowed the tentative identification of a variety of non-target contaminants, divided into non-polar, medium-polar and polar fractions. The instrumental analysis revealed slightly different toxicological profiles for the water and sediment from both rivers, and confirmed the presence of various classes of organic contaminants, from non-polar hydrocarbons, to more polar compounds such as aldehydes, ketones and phenols. Polycyclic aromatic hydrocarbons and pesticides were identified, but below toxicologically relevant concentrations. The results of bioanalyses on H4IIE and PLHC-1 cells indicated that cytotoxic potential was pronounced in Jegricka water and sediment samples, and CYP1A inducing potential was observed in both Krivaja and Jegricka sediment samples, although they did not reflect high levels of contamination. Based on the overall data, the sediments of the Krivaja and Jegricka rivers are a more toxicologically relevant matrix than the water.

In the central Banat region (Northern Serbia), groundwater is used as a drinking water source. Raw water originates from a 40–80 m and 100–150 m deep layer. It contains a high amount of natural organic matter (DOC = 9.17 ± 0.87 mg C/L) with a trihalomethanes formation potential of 448 ± 88.2 μg/L and a haloacetic acid formation potential of 174 ± 68.9 μg/L. A high amount of arsenic (86.0 ± 3.4 μg/L) is also found in this water. This study used a pilot-scale system to investigate the possibilities of combining polyaluminium chloride and ferrous-chloride to remove disinfection by-products precursors and arsenic by coagulation. Two treatment trains with different pre-treatment steps were investigated (ozone vs. H2O2/O3). For the final water polishing, filtration with granulated activated carbon (GAC) was applied. Both investigated treatment lines achieved a satisfactory chemical water quality. Simulation of disinfection conditions was performed and the contents of trihalomethanes and haloacetic acids measured, to investigate whether the chemical quality of the water remained satisfactory over a 48 hour period.

This paper presents a comparison of the efficacy of three different coagulants (polyaluminium chloride (PACl), Aluminium sulphate (Al(2)(SO(4))(3)) and ferrous chloride (FeCl(3))) for natural organic matter and arsenic (As) removal from groundwater. Coagulation efficacy was evaluated for the coagulants alone and for combinations of them (PACl/FeCl(3); Al(2)(SO(4))(3)/FeCl(3)), on the basis of changes in dissolved organic matter (DOC) and arsenic content. For single coagulants, PACl (30 mg Al/L) showed optimal efficacy for DOC removal (57%, relative to raw water). The highest arsenic reduction (< 5 microg As/L in coagulated water) was achieved when a very high 300 mg/L dose of FeCl(3) was used. However, if PACl (30 mg Al/L) and FeCl(3) (10 mg FeCl(3)/L) are combined, the efficacy of DOC removal increases compared to PACl and FeCl(3) alone under similar doses (66% decrease in DOC relative to raw water). The DOC and As contents of the coagulated water after application of these doses were 2.26 mg C/L and 9.7 microg/L, respectively, compared to 6.44 mg C/L and 60.5 microg As/L measured in the raw groundwater. The combination of Al(2)(SO(4))(3) and FeCl(3) did not show any improvement in DOC and As removal efficacy relative to using those coagulants alone.