Transformation of atrazine, carbamazepine, diclofenac and sulfamethoxazole by low and medium pressure UV and UV/H2O2 treatment

Sulfonamide disinfection byproducts exhibited severe toxicity to human commensal bacteria

Many antibiotic disinfection byproducts have been detected but their toxicity has not been evaluated adequately. In this report, the chlorination reaction kinetics of five common sulfamides (SAs), reaction intermediates and their toxicity were investigated. Chlorination of sulfapyridine (SPD), sulfamethazine (SMT), sulfathiazole (STZ), and sulfisoxazole (SIZ) followed the second-order kinetics, and were degraded completely within 10 min. A large number of reaction intermediates were deteced by LC-MS, among which a total of 16 intermediates were detected for the first time. Toxicity of the five SAs chlorination solutions was evaluated separately by examining their effects on the growth rate of S. salivarius K12, a commensal bacterium in the human digestive system. After 30 min chlorination, solutions of SMT, STZ and sulfadiazine (SDZ) each exhibited severe toxicity by inhibiting the bacteria growth completely, whereas the inhibition was only 50 % and 20  % by SIZ and SPD respectively. Based on the comparison between toxicity test results and mass spectra, three SA chlorination intermediates, m/z 187.2 (C10H10N4), m/z 287.2 (C9H7N3O4S2) and m/z 215 (C7H10N4O2S/C12H14N4) were proposed to be the primary toxicants in the chlorination products. Our study demonstrated the power of combined approach of chemical analysis and toxicity testing in identifying toxic disinfection byproducts, and highlighted the ne ed for more research on the toxicity evaluation and risk assessment of antibiotic disinfection byproducts.

Multiple barriers as an efficient treatment for removing pesticides aiming direct potable reuse: A pilot scale study

Water reuse for potable purposes can represent a realistic source supply of drinking water in areas with water scarcity. Therefore, combining conventional wastewater treatment technologies with advanced technologies is necessary to remove contaminants and obtain high-quality and safe water. In this study, the pesticides and degradation products, atrazine (ATZ), hydroxyatrazine (ATZOH), deethylatrazine (DEA), deisopropylatrazine (DIA), simazine (SMZ), ametryn (AMT), diuron (DIU), 2,4-D, fipronil (FIP), fipronil sulfide (FIP-SF) and fipronil sulfone (FIP-SN) were evaluated in effluent after membrane bioreactor (MBR), effluent after advanced treatment by multiple barriers (MBR, reverse osmosis, UV/H2O2 and activated carbon), in tap water collected in the urban region of Campinas and in the Atibaia River (water supply source from city of Campinas). The pesticide concentrations in the Atibaia River and the post-MBR effluent ranged between 1 and 434 ng L-1 and 1 and 470 ng L-1, respectively. Therefore, the Atibaia River and the post-MBR effluent had the same magnitude pesticide concentrations. In the production of potable water reuse, after the multiple barriers processes, only fipronil (1 ng L-1) and atrazine (3 ng L-1) were quantified in some of the samples. In tap water from Campinas, atrazine, ATZOH, DEA, diuron, and 2,4-D were quantified in concentrations ranging between 3 and 425 ng L-1. Therefore, when comparing drinking water obtained from conventional treatment with potable water reuse, according to the pesticides studied, it is possible to conclude that the advanced treatment used on a pilot scale is promising for use in a potable water reuse plant. However, studies involving more microbiological and chemical parameters should be conducted to classify potable water reuse as drinking water.

Rapid Inactivation of Fungal Spores in Drinking Water by Far-UVC Photolysis of Free Chlorine

Effective and affordable disinfection technology is one key to achieving Sustainable Development Goal 6. In this work, we develop a process by integrating Far-UVC irradiation at 222 nm with free chlorine (UV222/chlorine) for rapid inactivation of the chlorine-resistant and opportunistic Aspergillus niger spores in drinking water. The UV222/chlorine process achieves a 5.0-log inactivation of the A. niger spores at a chlorine dosage of 3.0 mg L-1 and a UV fluence of 30 mJ cm-2 in deionized water, tap water, and surface water. The inactivation rate constant of the spores by the UV222/chlorine process is 0.55 min-1, which is 4.6-fold, 5.5-fold, and 1.8-fold, respectively, higher than those of the UV222 alone, chlorination alone, and the conventional UV254/chlorine process under comparable conditions. The more efficient inactivation by the UV222/chlorine process is mainly attributed to the enhanced generation of reactive chlorine species (e.g., 6.7 × 10-15 M of Cl•) instead of hydroxyl radicals from UV222 photolysis of chlorine, which is verified through both experiments and a kinetic model. We further demonstrate that UV222 photolysis damages the membrane integrity and benefits the penetration of chlorine and radicals into cells for inactivation. The merits of the UV222/chlorine process over the UV254/chlorine process also include the more effective inhibition of the photoreactivation of the spores after disinfection and the lower formation of chlorinated disinfection byproducts and toxicity.

Efficient degradation and detoxification of antibiotic Fosfomycin by UV irradiation in the presence of persulfate

Fosfomycin (FOS) as a widely used antibiotic has been found in abundance throughout the environment, but little effort has been devoted to its treatment. In this study, we systemically looked into the degradation of FOS by ultraviolet-activated persulfate (UV/PS) in aqueous solutions. Our findings demonstrated that FOS can be degraded efficiently under the UV/PS, e.g., >90 % of FOS was degraded with 19,200 mJ cm-2 of UV irradiance and 20 μM of PS. HO was the dominant radical responsible for FOS degradation. FOS degradation increased as PS dosage increased, and higher degradation efficiency was observed at neutral pH. Natural water constitutes either promoted (e.g., Cu2+, Fe3+, and SO42-) or inhibited (e.g., humic acid, HCO3-, and CO32-) FOS degradation to varying degrees. Hydroxyl substitution, CP bond cleavage, and coupling reactions were the major degradation pathways for FOS degradation. Finally, the toxicity evaluation revealed that FOS was toxic to E. coli and S. aureus, but the toxicity of the intermediate products of FOS to E. coli and S. aureus rapidly decreased over time after UV/PS treatment. Therefore, these findings provided a fundamental understanding of the transformation process of FOS and supplied useful information for the environmental elimination of FOS contamination and its toxicity.

Effects of wavelength on the treatment of contaminants of emerging concern by UV-assisted homogeneous advanced oxidation/reduction processes

Pollutants of emerging concern in aqueous environments present a significant threat to both the aquatic ecosystem and human health due to their rapid transfer. Among the various treatment approaches to remove those pollutants, UV-assisted advanced oxidation/reduction processes are considered competent and cost-effective. The treatment effectiveness is highly dependent on the wavelength of the UV irradiation used. This article systematically discusses the wavelength dependency of direct photolysis, UV/peroxides, UV/chlor(am)ine, UV/ClO2, UV/natural organic matter, UV/nitrate, and UV/sulfite on the transformation of contaminants. Altering wavelengths affects the photolysis of target pollutants, photo-decay of the oxidant/reductant, and quantum yields of reactive species generated in the processes, which significantly impact the degradation rates and formation of disinfection byproducts. In general, the degradation of contaminants is most efficient when using wavelengths that closely match the highest molar absorption coefficients of the target pollutants or the oxidizing/reducing agents, and the contribution of pollutant absorption is generally more significant. By matching the wavelength with the peak absorbance of target compounds and oxidants/reductants, researchers and engineers have the potential to optimize the UV wavelengths used in UV-AO/RPs to effectively remove pollutants and control the formation of disinfection byproducts.

The influence of bromide and iodide ions on the sulfamethoxazole (SMX) halogenation during chlorination

Disinfection by-products (DBPs) were produced during the chlorination process, posing a threat to drinking water safety and human health. In the presence of bromide and iodide ions, brominated and iodinated DBPs will be generated, which might be more toxic than the parent compound. However, there are few studies on brominated and iodinated DBPs of antibiotics. Therefore, in this study, the fates of sulfamethoxazole (SMX) during chlorination in different systems (Blank; SMX + NaClO; SMX+ NaClO+ Br^-; SMX+ NaClO+I^-; SMX+ NaClO+ Br^- + I^-) were investigated. In different systems, all the reaction followed a pseudo-first-order kinetics, while the reaction rates of NaClO with SMX were different, the reaction rates were in order of SMX + NaClO + Br^- + I^- > SMX + NaClO + Br^- > SMX + NaClO + I^- > SMX + NaClO. When Br^- and I^- existed simultaneously, the reaction rate was the fastest. Iodide played an important role in oxidation and promoted the chlorination of SMX. SMX mainly underwent S-C cleavage, S-N hydrolysis, desulfonation, and substitution reactions. Nine disinfection by-products, including three reported for the first time, were identified using a non-targeted approach, and degradation pathways were proposed. Furthermore, EPI Suite software was applied to predict the environmental accumulation potential and environmental persistence of the degradation products. The results indicated that SMX and degradation products had little environmental accumulative potential and environmental persistence.

Mesocosm constructed wetlands to remove micropollutants from wastewater treatment plant effluent: Effect of matrices and pre-treatments

The contamination of the aquatic environment by micropollutants (MPs) brings risks for the ecosystem and human health. Constructed wetlands (CWs) were an eco-friendly technology to remove MPs from wastewater treatment plant effluent. In this study, the removal of MPs was evaluated in seven vertical flow mesocosm CWs with different configurations, including different support matrices (sand and a combination of bark-biochar), light pre-treatments (UVC and sunlight) or bioaugmentation in support matrices (activated sludge). The CWs with bark-biochar as support matrix significantly enhanced the removal of irbesartan and carbamazepine (>40 %), compared to the CW filled with the conventional support matrix sand. UVC irradiation as pre-treatment was more efficient in removing MPs than sunlight irradiation. After UVC pre-treatment, less MPs accumulated in the plants in the subsequent CW unit compared to the CW unit without any pre-treatment. Moreover, in the UVC combined CW system, less sulfamethoxazole, furosemide, mecoprop and diclofenac were accumulated in the plants (<0.5 μg) than other MPs (>3 μg). The addition of 0.5 % activated sludge combined with the aeration of influent did not improve MP removal in the CW. Considering the application, a bark-biochar based CW combined with UVC pre-treatment will result in more MP removal than a conventional sand CW.

Removal of pharmaceuticals by advanced treatment methods

The removal of endocrine disrupting compounds (EDCs) remains a big challenge in water treatment in terms of public health. The aim of the study was evaluating the performance of nano TiO2, ozone, and UV system for removal of EDCs. In this study, the efficiency of the nano TiO₂ to degrade target EDCs under catalytic and photocatalytic ozonation was examined at different operational conditions. The maximum removal of target pollutant was obtained with pH 6.8; ozone concentration 10 mg/L; catalyst dosage 0.050 g/L and the duration time of the photocatalytic performances was 10 min showing the most treatment conditions respectively. In addition, the surface reaction mechanism of endocrine disrupting compound removal by catalytic and photocatalytic ozonation was investigated. The results showed that the catalyst can significantly enhance the removal of target compound. The 99.0%, 88.3% and 51.8% removal rates were obtained at photocatalytic ozonation, catalytic ozonation and sole ozonation, respectively. These results indicated that the Ozone/TiO₂/UV process was favorable for engineering applications for removal of endocrine disrupting compounds such as steroid hormone and likely similar micro pollutants.

A Multi-Criteria Decision-Making Approach to Evaluate Different UVC/H2O2 Systems in Wastewater Treatment

High azoxystrobin (AZO), difenoconazole (DFZ), and imidacloprid (IMD) pesticide removal rates in sixteen bench-scale experiments concerning tomato washing water treatment were obtained through a UVC/H2O2 advanced oxidative process. Experimental conditions ([H2O2]0) and irradiance (EUVC) were optimized for higher degradation rates (pseudo-first-order reaction). To consider both economic aspects and environmental impacts when defining the treatment technology, as well as technological requirements, this study applied a multi-criteria decision-making method (MCDM) to assess and differentiate similar UVC/H2O2 process configurations. This allowed for the identification of the cheapest experimental arrangement with the lowest associated environmental impacts, coupled to the highest degradation rate (kIMD). After consulting experts to determine the importance of the applied criteria and measuring alternative performances, experiment E7 ([H2O2]0 = 43.5 mg L−1; EUVC = 15.0 W m−2; kIMD = 0.236 s−1) was determined as meeting the three criteria in a balanced manner. Although E7′s technological performance regarding degradation rate did not achieve the best individual result, it presented the lowest impacts and costs among the analyzed series, although alternatives are sensitive to decision-maker priorities. This study considered different factors of a process displaying potential industrial applications still in the design stage to achieve a more efficient and balanced solution.

Antibiotic-metal complexes in wastewaters: fate and treatment trajectory

Unregulated usage, improper disposal, and leakage from pharmaceutical use and manufacturing sites have led to high detection levels of antibiotic residues in wastewater and surface water. The existing water treatment technologies are insufficient for removing trace antibiotics and these residual antibiotics tend to interact with co-existing metal ions and form antibiotic-metal complexes (AMCs) with altered bioactivity profile and physicochemical properties. Typically, antibiotics, including tetracyclines, fluoroquinolones, and sulphonamides, interact with heavy metals such as Fe²⁺, Co²⁺, Cu²⁺, Ni²⁺, to form AMCs which are more persistent and toxic than parent compounds. Although many studies have reported antibiotics detection, determination, distribution and risks associated with their environmental persistence, very few investigations are published on understanding the chemistry of these complexes in the wastewater and sludge matrix. This review, therefore, summarizes the structural features of both antibiotics and metals that facilitate complexation in wastewater. Further, this work critically appraises the treatment methods employed for antibiotic removal, individually and combined with metals, highlights the knowledge gaps, and delineates future perspectives for their treatment.

Effectiveness of Advanced Oxidation Processes in Wastewater Treatment: State of the Art

In recent years, many scientific studies have focused their efforts on quantifying the different types of pollutants that are not removed in wastewater treatment plants. Compounds of emerging concern (CECs) have been detected in different natural environments. The presence of these compounds in wastewater is not new, but they may have consequences in the future. These compounds reach the natural environment through various routes, such as wastewater. This review focuses on the study of tertiary treatment with advanced oxidation processes (AOPs) for the degradation of CECs. The main objective of the different existing AOPs applied to the treatment of wastewater is the degradation of pollutants that are not eliminated by means of traditional wastewater treatment.

Prospects on coupling UV/H2O2 with activated sludge or a fungal treatment for the removal of pharmaceutically active compounds in real hospital wastewater

Conventional active sludge (AS) process at municipal centralized wastewater treatment facilities may exhibit little pharmaceuticals (PhACs) removal efficiencies when treating hospital wastewater (HWW). Therefore, a dedicated efficient wastewater treatment at the source point is recommended. In this sense, advanced oxidation processes (AOPs) and fungal treatment (FG) have evidenced promising results in degrading PhACs. The coupling of the AOP based on UV/H₂O₂ treatment with biological treatment (AS or FG) treating a real non-sterile HWW, was evaluated in this work. In addition, a coagulation-flocculation pretreatment was applied to improve the efficiency of all approaches. Twenty-two PhACs were detected in raw HWW, which were effectively removed (93-95%) with the combination of any of the biological treatment followed by UV/H₂O₂ treatment. Similar removal results (94%) were obtained when placing UV/H₂O₂ treatment before FG, while a lower removal (83%) was obtained in the combination of UV/H₂O₂ followed by AS. However, the latest was the only treatment combination that achieved a decrease in the toxicity of water. Moreover, deconjugation of conjugated PhACs has been suggested for ofloxacin and lorazepam after AS treatment, and for ketoprofen after fungal treatment. Monitoring of carbamazepine and its transformation products along the treatment allowed to identify the same carbamazepine degradation pathway in UV/H₂O₂ and AS treatments, unlike fungal treatment, which followed another degradation route.

Combined Effects of Sulfamethoxazole and Erythromycin on a Freshwater Microalga, Raphidocelis subcapitata: Toxicity and Oxidative Stress

This study investigated the environmental effects of two familiar emerging contaminants, sulfamethoxazole (SMX) and erythromycin (ERY), and their mixture (10:1 w/w) using a green microalga, R. subcapitata. The cell density, pigment content, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) glutathione peroxidase (GSH-Px), and glutathione S-transferase (GST) were analyzed. The calculated EC₅₀ values of SMX, ERY, and their mixture after 96 h were 0.49, 0.044, and 0.06 mg/L, respectively. High concentrations of antibiotics lead to a decrease in chlorophyll a and total carotenoid content, affecting the ability to photosynthesize ROS scavenging capacity. This may be a factor leading to the inhibition of algal growth. When R. subcapitata was exposed to SMX and the mixture, SOD and CAT increased to resist oxidative damage, while the activities of GSH and GST decreased, suggesting that this algae’s antioxidant system was unbalanced due to oxidative stress. R. subcapitata reduced the ERY-induced ROS by increasing the activities of SOD, GSH, and GST. The difference in the contents of nonenzymatic antioxidants and enzyme antioxidants in R. subcapitata indicated the antioxidant mechanisms to SMX and ERY were not identical. This study provides insights into the oxidative stress process in R. subcapitata under different antibiotics.

Recent advances in the removal of pharmaceuticals and endocrine-disrupting compounds in the aquatic system: A case of polymer inclusion membranes

The presence of pharmaceuticals and endocrine-disrupting compounds in aquatic systems is a matter of great concern. The occurrence, fate, and potential toxicity of these compounds have triggered the interest of the scientific community. As a result of their high solubility and low volatility, they are common in aquatic systems, and wastewater treatment plants (WWTP) are the main reservoir for these contaminants. Conventional WWTPs have demonstrated an inability to remove these contaminants completely; hence, different advanced treatment processes have been explored to compensate for the lapses of the conventional system. The outcome of this study revealed the significant improvements made using advanced treatment processes to diminish the number of contaminants; however, some contaminants have proven to be refractory. Thus, there is a need to modify various advanced treatment processes or employ additional treatment processes. Polymer inclusion membranes (PIMs) are a liquid membrane technology that is highly efficient at removing contaminants from water. They have been widely studied for the removal of heavy metals and nutrients from aquatic systems; however, only a few studies have investigated the use of PIMs to remove pharmaceutically active compounds from aquatic systems. This research aims to raise awareness on the application of PIMs as a promising water treatment technology which has a great potential for the remediation of pharmaceuticals and endocrine disruptors in the aquatic system, due to its versatility, ease/low cost of preparation and high contaminant selectivity.

Impact of oxidation processes on the composition and biodegradability of soluble organic nutrients in wastewater effluents

The characteristics and bioavailability of wastewater derived organic nutrients and their susceptibility to removal technologies have implications in nutrient loading to aquatic environments and their contributions to eutrophication. Therefore, a better understanding of treatability of effluent organic nutrients is of interest for water resource recovery facilities (WRRFs) and regulators. Oxidation processes (OPs) can reduce concentrations of soluble organic nutrients and convert them into more biodegradable forms. In this study, three WRRF effluents were treated with low-pressure ultraviolet (UV) irradiation, hydrogen peroxide (H₂ O₂ ), and combined UV/H₂ O₂ . Untreated and treated effluents were subjected to nitrogen and phosphorus speciation analyses and soluble organic nitrogen (SON) biodegradability assays. The OP treatments did not change SON concentrations significantly. For two WRRFs, OP treatments decreased soluble organic phosphorus (SOP) and seemed to convert it into soluble acid hydrolyzable phosphorus (SAHP), indicating possible increases in phosphorus bioavailability. Fingerprinting and quantification of dissolved organic matter (DOM) using fluorescence spectroscopy with parallel factor analysis revealed changes in DOM pool composition in response to OPs treatments, which suggests likely organic nutrients composition changes. Based on biodegradability assessments, OP treatments likely changed the composition and biodegradability of effluent SON compounds. Combined UV/H₂ O₂ treatment seemed more effective than other OPs at oxidizing some of the organic nutrients. PRACTITIONER POINTS: Treatment of secondary or tertiary effluent with UV, H₂ O₂ , or UV/ H₂ O₂ was generally not effective at mineralizing SON and SOP, when applied at the doses used in this study. Treatment resulted in observable changes in DOM compositions, likely including SON and SOP compounds. Combined UV/H₂ O₂ treatment was more effective than UV or H₂ O₂ alone at oxidizing some DOM compounds. The BSON (bioavailable SON) assay indicated that the composition of the SON pool in the effluents was likely changed by the OP treatments. This was supported by fluorescence spectroscopy analysis.

Removal and toxicity evaluation of a diverse group of drugs from water by a cyclodextrin polymer/pulsed light system

The presence of pharmaceutical compounds (PhCs) in the effluents of wastewater treatment plants (WWTPs) is an ecological concern. The issue could be alleviated by trapping those substances by cyclodextrin (CD) polymers or photolyzing them by pulsed light (PL). Consequently, a sequential CD polymer/PL system was tested for the removal of PhCs. Firstly, a survey detected the presence of recurrent PhCs in the effluents of local WWTPs. Then, pure water was spiked with 21 PhCs, 100 μg/L each one. The three-dimensional network provides amphiphilic features to the CD polymer that reduced the pollutant concentration by 77 %. Sorption involves a plead of physical and chemical mechanisms hindering the establishment of a general removal model for all compounds. The performed simulations hint that the retention capacity mainly correlates with the computed binding energies, so that theoretical models are revealed as valuable tools for further improvements. The complementary action of PL rose the elimination to 91 %. The polymer can be reused at least 10 times for ibuprofen (model compound) removal, and was able to eliminate the ecotoxicity of an ibuprofen solution. Therefore, this novel sequential CD polymer/PL process seems to be an efficient alternative to eliminate PhCs from wastewater.

Kinetics and reaction mechanism of photochemical degradation of diclofenac by UV-activated peroxymonosulfate

Diclofenac (DCF) is a common non-steroidal anti-inflammatory drug, which is frequently detected in different environmental media such as surface water, groundwater, domestic sewage, and sediment. In this study, UV-activated peroxymonosulfate (PMS) was used to degrade DCF by generating active radicals (i.e., SO₄˙⁻ and HO˙) with strong oxidizing properties. The effects of PMS dosage, pH, initial DCF concentration and common water constituents on the removal of DCF as well as its degradation mechanism in UV/PMS system were investigated. Compared to UV alone and PMS alone systems, DCF was removed more efficiently in the UV/PMS system at pH 7.0 due to the contribution of SO₄˙⁻ and HO˙, and its degradation followed the pseudo-first order kinetic model. As the dosage of PMS or solution pH increased, the degradation efficiency of DCF was gradually enhanced. The highest DCF degradation was obtained at pH 11.0 in this study, because the molar absorption coefficient of PMS increased with increasing pH at 254 nm resulting in generation of more reactive radicals at high pH. Removal efficiency of DCF was decreased significantly with the increase in its initial concentration due to the insufficient concentration of radicals. The presence of HCO₃⁻ and NO₃⁻ could promote the degradation of DCF because of the role of carbonate radicals and extra HO˙ formed, respectively, while NOM inhibited DCF degradation due to its competition with DCF for reactive radicals. No obvious influence on DCF degradation was observed in the UV/PMS system with the addition of Cl⁻ and SO₄²⁻. The degradation of DCF by UV/PMS in real waters was slightly suppressed compared with its removal in ultrapure water. Seven transformation products were detected using UPLC-QTOF/MS, and the potential degradation mechanism of DCF was thus proposed showing six reaction pathways including hydroxylation, decarboxylation, dechlorination–cyclization, formylation, dehydrogenation and dechlorination–hydrogenation.

Compared to UV alone and PMS alone systems, diclofenac was removed more efficiently in UV/PMS system at pH 7.0 due to the contribution of SO₄˙⁻ and HO˙ and its degradation followed the pseudo-first order kinetic model.

Impact of Inorganic Ions and Organic Matter on the Removal of Trace Organic Contaminants by Combined Direct Contact Membrane Distillation-UV Photolysis

This study investigated the degradation of five trace organic contaminants (TrOCs) by integrated direct contact membrane distillation (DCMD) and UV photolysis. Specifically, the influence of inorganic ions including halide, nitrate, and carbonate on the performance of the DCMD–UV process was evaluated. TrOC degradation improved in the presence of different concentrations (1–100 mM) of fluoride ion and chloride ion (1 mM). With a few exceptions, a major negative impact of iodide ion was observed on the removal of the investigated TrOCs. Of particular interest, nitrate ion significantly improved TrOC degradation, while bicarbonate ion exerted variable influence—from promoting to inhibiting impact—on TrOC degradation. The performance of DCMD–UV photolysis was also studied for TrOC degradation in the presence of natural organic matter, humic acid. Results indicated that at a concentration of 1 mg/L, humic acid improved the degradation of the phenolic contaminants (bisphenol A and oxybenzone) while it inhibited the degradation of the non-phenolic contaminants (sulfamethoxazole, carbamazepine, and diclofenac). Overall, our study reports the varying impact of different inorganic and organic ions present in natural water on the degradation of TrOCs by integrated DCMD–UV photolysis: the nature and extent of the impact of the ions depend on the type of TrOCs and the concentration of the interfering ions.

A critical review on advanced oxidation processes for the removal of trace organic contaminants: A voyage from individual to integrated processes

Advanced oxidation processes (AOPs), such as photolysis, photocatalysis, ozonation, Fenton process, anodic oxidation, sonolysis, and wet air oxidation, have been investigated extensively for the removal of a wide range of trace organic contaminants (TrOCs). A standalone AOP may not achieve complete removal of a broad group of TrOCs. When combined, AOPs produce more hydroxyl radicals, thus performing better degradation of the TrOCs. A number of studies have reported significant improvement in TrOC degradation efficiency by using a combination of AOPs. This review briefly discusses the individual AOPs and their limitations towards the degradation of TrOCs containing different functional groups. It also classifies integrated AOPs and comprehensively explains their effectiveness for the degradation of a wide range of TrOCs. Integrated AOPs are categorized as UV irradiation based AOPs, ozonation/Fenton process-based AOPs, and electrochemical AOPs. Under appropriate conditions, combined AOPs not only initiate degradation but may also lead to complete mineralization. Various factors can affect the efficiency of integrated processes including water chemistry, the molecular structure of TrCOs, and ions co-occurring in water. For example, the presence of organic ions (e.g., humic acid and fulvic acid) and inorganic ions (e.g., halide, carbonate, and nitrate ions) in water can have a significant impact. In general, these ions either convert to high redox potential radicals upon collision with other reactive species and increase the reaction rates, or may act as radical scavengers and decrease the process efficiency.

A chemical, microbiological and (eco)toxicological scheme to understand the efficiency of UV-C/H2O2 oxidation on antibiotic-related microcontaminants in treated urban wastewater

An assessment comprising chemical, microbiological and (eco)toxicological parameters of antibiotic-related microcontaminants, during the application of UV-C/H₂O₂ oxidation in secondary-treated urban wastewater, is presented. The process was investigated at bench scale under different oxidant doses (0-50 mg L^-1) with regard to its capacity to degrade a mixture of antibiotics (i.e. ampicillin, clarithromycin, erythromycin, ofloxacin, sulfamethoxazole, tetracycline and trimethoprim) with an initial individual concentration of 100 μg L^-1. The process was optimized with respect to the oxidant dose. Under the optimum conditions, the inactivation of selected bacteria and antibiotic resistant bacteria (ARB) (i.e. faecal coliforms, Enterococcus spp., Pseudomonasaeruginosa and total heterotrophs), and the reduction of the abundance of selected antibiotic resistance genes (ARGs) (e.g. bla_OXA, qnrS, sul1, tetM) were investigated. Also, phytotoxicity against three plant species, ecotoxicity against Daphnia magna, genotoxicity, oxidative stress and cytotoxicity were assessed. Apart from chemical actinometry, computational fluid dynamics (CFD) modelling was applied to estimate the fluence rate. For the given wastewater quality and photoreactor type used, 40 mg L^-1 H₂O₂ were required for the complete degradation of the studied antibiotics after 18.9 J cm^-2. Total bacteria and ARB inactivation was observed at UV doses <1.5 J cm^-2 with no bacterial regrowth being observed after 24 h. The abundance of most ARGs was reduced at 16 J cm^-2. The process produced a final effluent with lower phytotoxicity compared to the untreated wastewater. The toxicity against Daphnia magna was shown to increase during the chemical oxidation. Although genotoxicity and oxidative stress fluctuated during the treatment, the latter led to the removal of these effects. Overall, it was made apparent from the high UV fluence required, that the particular reactor although extensively used in similar studies, it does not utilize efficiently the incident radiation and thus, seems not to be suitable for this kind of studies.

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.

Degradation of pharmaceutical mixtures in aqueous solutions using UV/peracetic acid process: Kinetics, degradation pathways and comparison with UV/H2O2

This paper presents an evaluation of UV/PAA process for degradation of four pharmaceuticals venlafaxine (VEN), sulfamethoxazole (SFX), fluoxetine (FLU) and carbamazepine (CBZ) with comparison to UV/H₂O₂ process. The effectiveness of combining PAA and H₂O₂ at various proportions while irradiating with UVC were also evaluated. UVC/PAA (λ = 254 nm) was effective in degrading all four pharmaceuticals and followed pseudo first-order kinetics. Increasing PAA dosage or UVC intensity resulted in a linear increase in pseudo-first order rate coefficient. Both PAA in dark conditions and UVA/PAA (λ = 360 nm) were marginally effective to degrade SFX and ineffective to degrade VEN, CBZ and FLU; indicating the need for UVC irradiation for activation of PAA. For similar oxidant dosages of 50 mg/L UVC/H₂O₂ was found to be faster than UV/PAA for VEN, CBZ and FLU by 55%, 75% and 33%, respectively. Under similar conditions, SFX was degraded 24% faster by UV/PAA. Increase in the proportion of H₂O₂ to PAA in UVC/PAA/H₂O₂ improved kinetics of degradation compared to PAA alone. Tests on TOC were conducted to determine the amount of acetic acid that is released to water when treatment by UVC/PAA is conducted. Results demonstrated that 70% of PAA by mass was ultimately converted to acetic acid and remained in the treated solutions. Hydroxyl radical attack is hypothesized to be the main mechanism of degradation by UV/PAA as degradation intermediates identified for all the target pharmaceuticals coincided with by-products identified during UV/H₂O₂ process.

Degradation kinetics and mechanism of diclofenac by UV/peracetic acid

In this work, the degradation kinetics and mechanism of diclofenac (DCF) by UV/peracetic acid (PAA) was investigated.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.

Contaminants of emerging concern removal from real wastewater by UV/free chlorine process: A comparison with solar/free chlorine and UV/H2O2 at pilot scale

The removal of contaminants of emerging concern (CECs) from urban wastewater treatment plants (UWTPs) is really important to minimize the risk for human health and environment. In this study, the homogeneous advanced oxidation process (AOP) UV-C/free chlorine (UV-C/FC) was investigated at pilot scale in the degradation of a mixture of four CECs, in different water matrices and compared to a consolidated AOP, namely UV-C/H₂O₂. As matter of fact 90% degradation of CECs was observed after 15 min (Q_UVC = 0.33 kJ L^-1) by UV-C/FC (5 mg L^-1 of FC) and 30 min (0.67 kJ L^-1) by UV-C/H₂O₂ (5 mg L^-1 of H₂O₂) in natural water. However, CECs degradation by UV-C/H₂O₂ and UV-C/FC was comparable (>82%) in wastewater samples, under the investigated conditions (60 min, 1.33 kJ L^-1). The effect of sunlight/FC process on the target CECs was also investigated (in a compound parabolic collector based reactor). Interestingly, a different behaviour was observed between the two light sources. In particular, a total removal of carbamazepine (CBZ) and imidacloprid (IMD) was observed for UV-C/FC process with 0.27 kJ L^-1 and 10 mgL^-1 of FC, while, in the sunlight/FC process (same FC dose), CBZ total removal took place quite fast (0.50 kJ L^-1), but 90% removal of IMD was observed only after 60 min (7.09 kJ L^-1). In conclusion, UV-C/FC process can be an interesting solution for tertiary treatment of urban wastewater for the removal of CECs and sunlight/FC is worthy of further investigation to evaluate its possible application in small UWTPs.

Degradation of pharmaceutical compounds in water by oxygenated electrochemical oxidation: Parametric optimization, kinetic studies and toxicity assessment

The pharmaceutical compounds sulfamethoxazole (SMX), propranolol (PRO) and carbamazepine (CBZ) are biorecalcitrant and frequently detected in waters causing negative impacts on human health and aquatic organisms. Electrochemical oxidation appears as an effective option for the removal of recalcitrant compounds and its enhancement is an important issue for the removal of emerging compounds in water. The contribution of this research lies in the comprehensive analysis of the oxygenated electro chemical oxidation of CBZ, SMX and PRO using Nb/BDD mesh anode. The effect of treatment time, current, pH and oxygen injection on the SMX, PRO and CBZ degradation was assessed using Na₂SO₄ as electrolyte, process optimization was performed, by-products were identified, kinetic and toxicity tests were carried out using different electrolytes. Finally, the process effectiveness was tested using real secondary effluent spiked with the mixture of the pharmaceutical compounds and the acute toxicity was determined. The obtained results indicated that the oxygenated electrochemical oxidation allows effective simultaneous SMX, PRO and CBZ degradation, which showed a significant dependence of treatment time, current and oxygen injection in Na₂SO₄ electrolyte. At 90 min of electrolysis the parent compounds were detected as well as eight by-products. At 150 min of treatment, further to the already determined by-products and the parent compounds, appeared phenol and p-benzoquinone. Based on the identified compounds, degradation pathways were explained as a result of two main mechanisms: transformation (hydroxylation, deamination, desulfunation) and bond rupture. The kinetic study indicated an increase of the first-order kinetic constant in the oxygenated electrochemical oxidation process using Na₂SO₄ and NaBr as electrolyte, nevertheless the constant decreased in the presence of NaCl. In the assays with secondary effluent spiked with SMX, PRO and CBZ, the oxygenation did not enhance the performance of the process, however; pharmaceuticals were degraded with a higher removal rates compared with the ones determined in the Na₂SO₄ synthetic solutions assays; the oxygenation enhanced the TOC and COD removal. The acute toxicity of spiked secondary effluent was reduced from the first few minutes of the electrochemical oxidation process.

Biocatalytic degradation/redefining "removal" fate of pharmaceutically active compounds and antibiotics in the aquatic environment

Recently, the increasing concentration and persistent appearance of antibiotics traces in the water streams are considered an issue of high concern. In this context, an array of antibiotics has been categorized as pollutants of emerging concern due to their complex and highly stable bioactivity, indiscriminate usage with ultimate release into water bodies, and notable persistence in environmental matrices. Moreover, antibiotics traces containing household sewage/drain waste and pharmaceutical wastewater effluents contain a range of bioactive/toxic organic compounds, inorganic salts, pharmaceutically-active ingredients, or a mixture of all, which possesses negative influences ranging from ecological pollution to damage biodiversity. Moreover, their uncontrolled and undesirable bioaccumulation also poses a potential threat to target and non-target organisms in the environment. Aiming to tackle this issue effectively, various detection, quantification, degradation, and redefining "removal" processes have been proposed and investigated based on physical, chemical, and biological strategies. Though both useful and side effects of antibiotics on humans and animals are usually investigated thoroughly following safety and toxicity measures, however, their direct or indirect environmental impacts are not well reviewed yet. Owing to the considerable research gap, the environmental perfectives of antibiotics traces and their effects on target and non-target populations have now become the topic of research interest. Based on literature evidence, over the past several years, numerous individual studies have been performed and published covering various aspects of antibiotics. However, a comprehensive compilation on enzyme-based degradation of antibiotics is still lacking and requires careful consideration. Hence, this review summarizes up-to-date literature on enzymes as biocatalytic systems, explicitly, free as well as immobilized forms and their effective exploitation for the degradation of various antibiotics traces and other pharmaceutically-active compounds present in the water bodies. It is further envisioned that the enzyme-based strategies, for antibiotics degradation or removal, discussed herein, will help readers for a better understanding of antibiotics persistence in the environment along with the associated risks and removal measures. In summary, the current research thrust presented in this review will additionally evoke researcher to engineer robust and sustainable processes to effectively remediate antibiotics-contaminated environmental matrices.

Influence of UV dose on the UV/H2O2 process for the degradation of carbamazepine in wastewater

This study evaluates the influence of UV dose on degradation of carbamazepine (CBZ) in wastewater under UV-C (λ = 254 nm) photolysis with and without H₂O₂. The rate of degradation of CBZ exhibited a direct dependence on the intensity of incident UV irradiation as the rate of degradation was observed to increase linearly (R² = 0.98) with UV intensity between 1.67 and 8.95 × 10¹⁷ photons/s. More than 95% of the CBZ that spiked in wastewater rapidly degraded within 4 min with a first-order rate constant of 1.2 min^-1 for an optimum H₂O₂ dose of 100 mg/L. Bench-scale continuous flow reactor experiments also showed that CBZ degraded with first-order kinetics at a rate constant of 1.02 min^-1. The kinetic parameters obtained for a continuous bench-scale reactor were in good agreement with the relationships developed through batch experiments with only a marginal deviation of ± 6.5%. The relationship between UV intensity and CBZ degradation rate obtained in this study was extrapolated to the UV disinfection unit of a wastewater treatment plant to predict possible degradation of CBZ during UV disinfection. The addition of 100 mg/L of H₂O₂ to the secondary-treated effluent entering the UV disinfection unit is predicted to achieve over 60% degradation of CBZ. Abbreviations: CBZ carbamazepine; AOPs advanced oxidation processes; UV ultraviolet radiation; UV-C ultraviolet C (λ = 254 nm) radiation; NZVI non-zerovalent iron; WWTP wastewater treatment plant; HPLC high-performance liquid chromatography.

Transformation of sulfamethazine during the chlorination disinfection process: Transformation, kinetics, and toxicology assessment

Various disinfection byproducts (DBPs) form during the process of chlorination disinfection, posing potential threats to drinking water safety and human health. Sulfamethazine (SMT), the most commonly used and frequently detected veterinary antibiotic, was investigated in detail with regard to its transformation and kinetics in reactions with free available chlorine (FAC). Using liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry, several DBPs were identified based on different confidence levels, and a variety of reaction types, including desulfonation, S-N cleavage, hydroxylation, and chlorine substitution, were proposed. The kinetic experiments indicated that the reaction rate was FAC- and pH-dependent, and SMT exhibits low reactivity toward FAC in alkaline conditions. The DBPs exhibited a much higher acute toxicity than SMT, as estimated by quantitative structure activity relationship models. More importantly, we observed that the FAC-treated SMT reaction solution might increase the genotoxic potential due to the generation of DBPs. This investigation provides substantial new details related to the transformation of SMT in the chlorination disinfection process.

Influence of solution pH on degradation of atrazine during UV and UV/H2O2 oxidation: kinetics, mechanism, and degradation pathways

The kinetics, degradation mechanism and degradation pathways of atrazine (ATZ) during sole-UV and UV/H₂O₂ processes under various pH conditions were investigated; the effects of UV irradiation time and H₂O₂ dose were also evaluated.

Mechanisms and toxicity evaluation of the degradation of sulfamethoxazole by MPUV/PMS process

In this work, a sulfate radical (SO4-)-based advanced oxidation process was applied to the degradation of sulfamethoxazole (SMX). In these experiments, a medium pressure UV (MPUV) lamp was employed to active peroxymonosulfate (PMS). It was found that 98% of SMX was removed by MPUV/PMS at a UV dose of 200 mJ cm-2 (3.95 μM SMX, 0.2 mM PMS, pH0 = 3.7). Direct MPUV photolysis played a remarkable role in SMX removal by MPUV/PMS process. As for the indirect photolysis, SO4- was the major reactive species under acidic and neutral conditions in MPUV/PMS system, while the hydroxyl radical (OH) became the predominant radical under alkaline conditions. The transformation products (TPs) of SMX that formed in the MPUV-only and MPUV/PMS experiments were identified, and the possible degradation pathways were proposed. Photoisomerization of the isoxazole ring was the major pathway of SMX during MPUV-only process. Hydroxylation/oxidation of the aniline and isoxazole ring was the predominant degradation mechanism of SMX by MPUV/PMS. Toxicity evaluation showed that MPUV/PMS was effective at reducing the antibacterial activity of SMX solutions, while MPUV-only was not. However, some TPs with equivalent or even higher antibacterial activity than SMX were formed during the initial degradation period in MPUV/PMS system. Ecotoxicity of SMX and its TPs was also hypothetically predicted via the ECOSAR program, and the results indicated that some TPs could be more toxic than SMX.

Formation of disinfection byproducts from sulfamethoxazole during sodium hypochlorite disinfection of marine culture water

The fates of the antibiotic sulfamethoxazole (SMX) in the chlorination of fresh water, simulated brackish marine culture water, and marine water were investigated. SMX was oxidized by sodium hypochlorite (NaClO) at different reaction rates in the different samples. The oxidation of SMX followed pseudo-first-order kinetics, and the rate constant was the largest in marine water (3.44 min^-1), as Br^- ions promote the oxidation reaction. Moreover, the kinds of disinfection byproducts (DBPs) were also affected by Br^- ions. Br-DBPs were found in the simulated brackish marine culture water and marine water disinfection systems. The structures of the DBPs indicated that S-C cleavage, polymerization, S-N hydrolysis, chlorine/bromine substitution, and desulfonation reactions occurred on SMX during the disinfection process. EPI (Estimation Programs Interface) Suite™ and absorbable organic halogen (AOX) analysis were used to evaluate the toxicity of the DBPs. The results suggested that DBPs in the simulated brackish marine culture water and marine water systems were more toxic than those in the fresh water system.

Potential risks from UV/H2O2 oxidation and UV photocatalysis: A review of toxic, assimilable, and sensory-unpleasant transformation products

UV based advanced oxidation processes (UV-AOPs) that efficiently eliminate organic pollutants during water treatment have been the subject of numerous investigations. Most organic pollutants are not completely mineralized during UV-AOPs but are partially oxidized into transformation products (TPs), thereby adding complexity to the treated water and posing risks to humans, ecological systems, and the environment. While the degradation kinetics and mechanisms of pollutants have been widely documented, there is little information about the risks associated with TPs. In this review, we have collated recent knowledge about the harmful TPs that are generated in UV/H₂O₂ and UV photocatalysis, two UV-AOPs that have been studied extensively. Toxic and assimilable TPs were ubiquitously observed in more than 80% of UV-AOPs of organic pollutants, of which the toxicity and assimilability levels changed with variations in the reaction conditions, such as the UV fluence and oxidant dosage. Previous studies and modeling assessments showed that toxic and assimilable TPs may be generated during hydroxylation, dealkylation, decarboxylation, and deamination. Among various reactions, TPs generated from dealkylation and decarboxylation were generally less and more toxic than the parent pollutants, respectively; TPs generated from decarboxylation and deamination were generally less and more assimilable than the parent pollutants, respectively. There is also potential concern about the sensory-unpleasant TPs generated by oxidations and subsequent metabolism of microorganisms. In this overview, we stress the need to include both the concentrations of organic pollutants and the evaluations of the risks from TPs for the quality assessments of the water treated by UV-AOPs.

Optimization of nimesulide oxidation via a UV-ABC/H2O2 treatment process: Degradation products, ecotoxicological effects, and their dependence on the water matrix

Nimesulide (Nim) degradation in ultrapure water (UW) and municipal sewage (MS) via UV-ABC/H₂O₂ was investigated. The variables included in the experimental design were time, initial Nim, and initial H₂O₂ concentrations. Resulting decreases in Nim concentration (monitored by high performance liquid chromatography (HPLC) using a photodiode array detector operating at a maximum UV absorbance of 300 nm), mineralization (from total organic carbon (TOC) measurements), and ecotoxicity (assays employing the bioindicators Daphnia similis, Artemia salina, and Allium cepa) were also studied. Degradation rates of 90% or higher were found for 15-20 min reaction times, employing combinations of [H₂O₂] = 50-150 mg L^-1 and [Nim] = 8.5-15 mg L^-1 prepared with MS. Mineralization rates of 70% and higher were attained within 60 min of reaction for [Nim] = 15 mg L^-1 prepared in MS with [H₂O₂] = 100 mg L^-1. Nim by-products were detected and possible degradation pathways proposed. Ecotoxicity evaluation using A. salina, D. similis, and A. cepa revealed that the treated samples had significantly lower toxicity. Exposure to treated samples resulted in survival rates of 79% for A. salina and over 90% for D. similis. No root growth inhibition was observed in A. cepa exposed to treated samples, whereas exposure to untreated samples inhibited root growth by 60%. Statistical analysis revealed elimination of cytotoxicity and reduction of genotoxicity against A. cepa. The results showed that the UV-ABC/H₂O₂ process can be employed as a pre- or post-treatment method to remove Nim from contaminated wastewater.

Micropollutants removal by full-scale UV-C/sulfate radical based Advanced Oxidation Processes

The high chemical stability and the low biodegradability of a vast number of micropollutants (MPs) impede their correct treatment in urban wastewater treatment plants. In most cases, the chemical oxidation is the only way to abate them. Advanced Oxidation Processes (AOPs) have been experimentally proved as efficient in the removal of different micropollutants at lab-scale. However, there is not enough information about their application at full-scale. This manuscript reports the application of three different AOPs based on the addition of homogeneous oxidants [hydrogen peroxide, peroxymonosulfate (PMS) and persulfate anions (PS)], in the UV-C tertiary treatment of Estiviel wastewater treatment plant (Toledo, Spain) previously designed and installed in the facility for disinfection. AOPs based on the photolytic decomposition of oxidants have been demonstrated as more efficient than UV-C radiation alone on the removal of 25 different MPs using low dosages (0.05-0.5 mM) and very low UV-C contact time (4-18 s). Photolysis of PMS and H₂O₂ reached similar average MPs removal in all the range of oxidant dosages, obtaining the highest efficiency with 0.5 mM and 18 s of contact time (48 and 55% respectively). Nevertheless, PMS/UV-C reached slightly higher removal than H₂O₂/UV-C at low dosages. So, these treatments are selective to degrade the target compounds, obtaining different removal efficiencies for each compound regarding the oxidizing agent, dosages and UV-C contact time. In all the cases, H₂O₂/UV-C is more efficient than PMS/UV-C, comparing the ratio cost:efficiency (€/m³·order). Even H₂O₂/UV-C treatments are more efficient than UV-C alone. Thus, the addition of 0.5 mM of H₂O₂ compensates the increased of UV-C contact time and therefore the increase of electrical consumption, that it should be need to increase the removal of MPs by UV-C treatments alone.

Direct Photolysis of Sulfamethoxazole Using Various Irradiation Sources and Wavelength Ranges-Insights from Degradation Product Analysis and Compound-Specific Stable Isotope Analysis

The environmental micropollutant sulfamethoxazole (SMX) is susceptible to phototransformation by sunlight and UV-C light which is used for water disinfection. Depending on the environmental pH conditions SMX may be present as neutral or anionic species. This study systematically investigates the phototransformation of these two relevant SMX species using four different irradiation scenarios, i.e., a low, medium, and high pressure Hg lamp and simulated sunlight. The observed phototransformation kinetics are complemented by data from compound-specific stable isotope and transformation product analysis using isotope-ratio and high-resolution mass spectrometry (HRMS). Observed phototransformation kinetics were faster for the neutral than for the anionic SMX species (from 3.4 (LP lamp) up to 6.6 (HP lamp) times). Furthermore, four phototransformation products (with m/z 189, 202, 242, and 260) were detected by HRMS that have not yet been described for direct photolysis of SMX. Isotopic fractionation occurred only if UV-B and UV-A wavelengths prevailed in the emitted irradiation and was most pronounced for the neutral species with simulated sunlight (ε_C = -4.8 ± 0.1 ‰). Phototransformation of SMX with UV-C light did not cause significant isotopic fractionation. Consequently, it was possible to differentiate sunlight and UV-C light induced phototransformation of SMX. Thus, CSIA might be implemented to trace back wastewater point sources or to assess natural attenuation of SMX by sunlight photolysis. In contrast to the wavelength range, pH-dependent speciation of SMX hardly impacted isotopic fractionation.

What happens with organic micropollutants during UV disinfection in WWTPs? A global perspective from laboratory to full-scale

The phototransformation of 18 organic micropollutants (OMPs) commonly detected in wastewater treatment plant (WWTP) effluents was examined attempting to explain their fate during UV disinfection in WWTPs. For this purpose, a lab-scale UV reactor (lamp emitting at 254nm) was used to study the influence of the operational conditions (UV dose, temperature and water matrix) on OMPs abatement and disinfection efficiency. Chemical properties of OMPs and the quality of treated effluent were identified as key factors affecting the phototransformation rate of these compounds. Sampling campaigns were carried out at the inlet and outlet of UV systems of three WWTPs, and the results evidenced that only the most photosensitive compounds, such as sulfamethoxazole and diclofenac, are eliminated. Therefore, despite UV treatment is an effective technology to phototransform OMPs, the UV doses typically applied for disinfection (10-50mJ/cm²) are not sufficient to remove them. Consequently, small modifications (increase of UV dose, use of catalysts) should be applied in WWTPs to enhance the abatement of OMPs in UV systems.

A comparison of genotoxicity change in reclaimed wastewater from different disinfection processes

Effluents before disinfection from four wastewater reclamation plants were treated with chlorine (Cl₂), ozone (O₃), chlorine dioxide (ClO₂), medium-pressure ultraviolet (MPUV) and four different combinations of the above, to evaluate the effect of disinfection processes on the genotoxicity removal by the SOS/umu test. Results showed that the genotoxicity increased after MPUV irradiation (10-100 mJ/cm²), but declined when adopting other disinfection processes. The effectiveness of genotoxicity reduction by five chemical disinfectants was identified as: O₃ > pre-ozonation with Cl₂ ≈ ClO₂ > combination of ClO₂ and Cl₂ > Cl₂. The sequential combination of MPUV, Cl₂ and O₃ reduced the genotoxicity to a level similar to the source water. The influence of differential disinfection process varied on iodinated wastewater, which is closely related to the competitive reactions between disinfectants, iodine and dissolved organic matters. The removal of genotoxic pollutants and the formation of genotoxic disinfection by-products are the two major factors that lead to the change in genotoxicity during disinfection.

Degradation kinetics and mechanism of sulfadiazine and sulfamethoxazole in an agricultural soil system with manure application

Recently, under the application of waste-water, manure and biosolids, antibiotics have been used massively in agriculture resulted in antibiotic resistance and potential environmental risks. In the present study, the removal of sulfadiazine (SDZ) and sulfamethoxazole (SMX) in an agricultural soil system was explored. All the experiments were conducted under different incubation conditions for 49days. The experimental results indicated that all the degradation processes could effectively follow a first-order kinetic model. Based on the analyses of these two antibiotics, SDZ had a higher reaction rate and a shorter DT50 value. Additionally, there were no marked differences in DT50 values at varying initial concentrations under the same conditions (p>0.05). Compared with the non-sterile soil, the degradation rates of SMX and SDZ were slower (<70%), and the associated DT50 values (>21days) were higher in the sterile soil. Because the biodegradation played a major role, it may be effective for the removal of these contaminants from the soils. The processes of SDZ and SMX degradations were slightly accelerated by applying manure (<20%). There were different accelerating effects on the removal of SDZ and SMX in soils by manure Single- and Repeated-application, which may be related to the amount of manure during the degradation processes, and different methods of adding manure could only affect the degradation rate. The major intermediate products were derived from the hydroxylation, sulfonamide SN bond cleavage and aniline moiety oxidation. Therefore, the present study inferred that possible degradation pathways of SDZ and SMX were hydroxylation of the benzene ring, oxidation of the amine group at the benzene ring, ring open and SN bond cleavage. Results revealed that more attention should be paid to the transformation products because they could be more toxic than the parent compounds.

Static and Continuous flow-through pulsed light technology for pesticide abatement in water

Perspectives concerning pulsed light (PL) technology as a novel water decontamination treatment are overviewed in this work. Degradation of atrazine, malathion, chlorpyriphos-methyl and bromopropylate in aqueous solutions at different concentrations was performed employing static and continuous flow-through PL units. Results for both PL systems were compared in terms of efficacy of pesticides degradation and derived photoproducts formed. The pesticides degradation increased with the applied total fluence for both PL systems. In general, PL induced rapid degradation of all studied compounds although some differences were observed in the rate of degradation among them. The most intense treatment in the static unit (11J/cm²) yielded degradations between 60 and 85% whereas degradations between 74 and 93% were observed after exposure to slightly lower fluences (10J/cm²) in the dynamic unit. For both PL systems bromopropylate was the most affected compound. Photodegradation products arose from chemical reactions involving structural changes like dehalogenation, desulfuration, dealkylaytion and oxidation of the alkyl chains. Although further research is needed before an efficient application in full-scale systems, PL appears as a promising technology in order to reduce the presence of pesticides residues in process or waste waters, allowing thereby recirculation of these waters with the subsequent economic and environmental advantages.

Oxidation of atrazine in aqueous media by solar- enhanced Fenton-like process involving persulfate and ferrous ion

The oxidation of s-triazines (using atrazine (ATZ) as a model compound) by a solar-enhanced Fenton-like process involving persulfate and ferrous ion was studied. A flow-through tubular photoreactor was employed for the experiments. The solar-enhanced oxidative system involving ferrous ion and persulfate (Solar/S₂O₈^2-/Fe²⁺) showed the highest ATZ degradation efficiency when compared with other treatments (unactivated S₂O₈^2-, Solar - sunlight only, S₂O₈^2-/Fe²⁺, Solar/S₂O₈^2-). Complete degradation of ATZ and 20% reduction in total organic carbon (TOC) content were observed after 30min of the treatment. The in situ generated ^•ОН and SO₄^-• radicals were shown to be involved in ATZ oxidation using the radical scavengers methanol and tert-butyl alcohol. Furthermore, iron compounds were shown to act not only as catalysts but also as photo-sensitizers, as the introduction of ferrous ion into the reaction mixture led to an increased absorbance of the solution and expansion of the absorption spectrum into the longer wavelength spectral region.

Monitoring, sources, receptors, and control measures for three European Union watch list substances of emerging concern in receiving waters - A 20year systematic review

Pollution of European receiving waters with contaminants of emerging concern (CECs), such as with 17-beta-estradiol (a natural estrogenic hormone, E2), along with pharmaceutically-active compounds diclofenac (an anti-inflammatory drug, DCL) and 17-alpha-ethynylestradiol (a synthetic estrogenic hormone, EE2)) is a ubiquitous phenomenon. These three CECs were added to the EU watch list of emerging substances to be monitoring in 2013, which was updated in 2015 to comprise 10 substances/groups of substances in the field of water policy. A systematic literature review was conducted of 3952 potentially relevant articles over period 1995 to 2015 that produced a new EU-wide database consisting of 1268 publications on DCL, E2 and EE2. European surface water concentrations of DCL are typically reported below the proposed annual average environmental quality standard (AA EQS) of 100ng/l, but that exceedances frequently occur. E2 and EE2 surface water concentrations are typically below 50ng/l and 10ng/l respectively, but these values greatly exceed the proposed AA EQS values for these compounds (0.04 and 0.035ng/l respectively). However, levels of these CECs are frequently reported to be disproportionately high in EU receiving waters, particularly in effluents at control points that require urgent attention. Overall it was found that DCL and EE2 enter European aquatic environment mainly following human consumption and excretion of therapeutic drugs, and by incomplete removal from influent at urban wastewater treatment plants (WWTPs). E2 is a natural hormone excreted by humans which also experiences incomplete removal during WWTPs treatment. Current conventional analytical chemistry methods are sufficiently sensitive for the detection and quantification of DCL but not for E2 and EE2, thus alternative, ultra-trace, time-integrated monitoring techniques such as passive sampling are needed to inform water quality for these estrogens. DCL appears resistant to conventional wastewater treatment while E2 and EE2 have high removal efficiencies that occur through biodegradation or sorption to organic matter. There is a pressing need to determine fate and behaviour of these CECs in European receiving waters such as using GIS-modelling of river basins as this will identify pressure points for informing priority decision making and alleviation strategies for upgrade of WWTPs and for hospital effluents with advanced treatment technologies. More monitoring data for these CECs in receiving waters is urgently needed for EU legislation and effective risk management.

Atrazine, triketone herbicides, and their degradation products in sediment, soil and surface water samples in Poland

The aim of this study was to monitor the sediment, soil and surface water contamination with selected popular triketone herbicides (mesotrione (MES) and sulcotrione(SUL)), atrazine (ATR) classified as a possible carcinogen and endocrine disrupting chemical, as well as their degradation products, in Silesia (Poland). Seventeen sediment samples, 24 soil samples, and 64 surface water samples collected in 2014 were studied. After solid-liquid extraction (SLE) and solid phase extraction (SPE), analytes were determined by high-performance liquid chromatography (HPLC) with diode array detection (DAD). Ten years after the withdrawal from the use, ATR was not detected in any of the collected samples; however, its degradation products are still present in 41 % of sediment, 71 % of soil, and 8 % of surface water samples. SUL was determined in 85 % of soil samples; its degradation product (2-chloro-4-(methylosulfonyl) benzoic acid (CMBA)) was present in 43 % of soil samples. In 17 % of sediment samples, CMBA was detected. Triketones were detected occasionally in surface water samples. The chemometric analysis (clustering analysis (CA), single-factor analysis of variance (ANOVA), N-Way ANOVA) was applied to find relations between selected soil and sediment parameters and herbicides concentration. In neither of the studied cases a statistically significant relationship between the concentrations of examined herbicides, their degradation products and soil parameters (organic carbon (OC), pH) was observed.