Coagulation-flocculation followed by catalytic ozonation processes for enhanced primary treatment during wet weather conditions.

Combined sewer overflows (CSO), generated during the wet weather flow from the combination of the inflow and stormwater runoff in sewer system, result in an overflow of untreated wastewater from sewer system, which might ultimately contain different micropollutants (MPs). In this study, a coagulation-flocculation-sedimentation (CFS) pretreated CSO spiked with MPs was treated by catalytic ozonation using carbon, iron, and peroxide-based catalysts. The catalysts were characterized and their activity on MPs removal was studied at two different ozone (O3) doses (5 and 10 mg L-1). The effect of the treatment on the spiked CSO effluent was also assessed from the acute toxicity of the effluent using Microtox®, Yeast, and Macrophage cell-line toxicity assay tests. All the carbon-based catalysts showed large surface area, which was strongly influenced by the activation technique in the preparation of the catalysts. The CFS treatment strongly reduced the turbidity (≥60%) but had marginal effect on the UV254, dissolved organic carbon (DOC), and pH. Sludge Based Carbon (SBC) showed strong adsorption capacity (≥60% removal efficiency) for all MPs studied compared to other carbon and iron-based catalysts. Ozonation alone was effective for the degradation of easily oxidizable MPs (sulfamethoxazole, mecoprop, and 2,4-dichlorophenoxyl acetic acid), achieving more than 80% degradation efficiency at 10 mg L-1 of ozone, but not effective for atrazine (≤60% degradation efficiency) at similar O3 dose. Catalytic ozonation (at 10 mg L-1 O3 dose) improved the degradation of the MPs at low catalyst dosage but higher dosage strongly inhibited their degradation. In all cases, the effluents showed negligible acute toxicity, indicating the suitability of the process for the treatment of CSO.

Can activated sludge treatments and advanced oxidation processes remove organophosphorus flame retardants?

This study aims to determine the occurrence of 10 OPFRs (including chlorinated, nonchlorinated alkyl and aryl compounds) in influent, effluent wastewaters and partitioning into sludge of 5 wastewater treatment plants (WWTP) in Catalonia (Spain). All target OPFRs were detected in the WWTPs influents, and the total concentration ranged from 3.67 µg L(-1) to 150 µg L(-1). During activated sludge treatment, most OPFRs were accumulated in the sludge at concentrations from 35.3 to 9980 ng g(-1) dw. Chlorinated compounds tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2,3-dichloropropyl) phosphate (TDCPP) were not removed by the conventional activated sludge treatment and they were released by the effluents at approximately the same inlet concentration. On the contrary, aryl compounds tris(methylphenyl) phosphate (TMPP) and 2-ethylhexyl diphenyl phosphate (EHDP) together with alkyl tris(2-ethylhexyl) phosphate (TEHP) were not detected in any of the effluents. Advanced oxidation processes (UV/H2O2 and O3) were applied to investigate the degradability of recalcitrant OPFRs in WWTP effluents. Those detected in the effluent sample (TCEP, TCIPP, TDCPP, tributyl phosphate (TNBP), tri-iso-butyl phosphate (TIBP) and tris(2-butoxyethyl) phosphate (TBOEP)) had very low direct UV-C photolysis rates. TBOEP, TNBP and TIBP were degraded by UV/H2O2 and O3. Chlorinated compounds TCEP, TDCPP and TCIPP were the most recalcitrant OPFR to the advanced oxidation processes applied. The study provides information on the partitioning and degradability pathways of OPFR within conventional activated sludge WWTPs.

Bacterial community characterization of a sequencing batch reactor treating pre-ozonized sulfamethoxazole in water.

Antibiotics are pharmaceutical compounds widely used to treat a broad range of infections. These chemicals appear to be recalcitrant compounds when released to water systems, and their presence at the effluent of wastewater treatment plants and surface waters has been widely documented. Sulfamethoxazole (SMX), a sulfonamide commonly used to treat urinary infections, is one of them. Ozonation was proved to be a suitable method to remove SMX antibiotic in water. However, it is stated that a high ozone dosage would be necessary to achieve the complete mineralization of the intermediates. In this work, ozonation is coupled with a Sequencing Batch Biofilm Reactor (SBBR) in order to completely degrade SMX and its metabolites from water solutions. Moreover, a precise description of the microbial community in the bioreactor is provided by means of traditional microscopy and molecular biology techniques. The results obtained showed high Total Organic Carbon removals at the end of the biological treatment (89% removal). Furthermore, nitrates produced during the aerobic SBBR's performance were monitored and eliminated by adding an anoxic stage, achieving an overall nitrogen removal of 86%. A bacterial community analysis of the SBBR during aerobic and aerobic-anoxic conditions was performed, targeting the bacterial 16S ribosomal ribonucleic acid (rRNA) gene. These results revealed a dominant contribution of bacteria from the Proteobacteria class, with a major contribution from the Rhizobiales and Burkholderiales orders during the bioreactor performance, counting 52% of the total population.

Role of sunlight and oxygen on the performance of photo-Fenton process at near neutral pH using organic fertilizers as iron chelates.

Nowadays, reaction mechanisms of photo-Fenton process with chelated iron are not yet clearly defined. In this study, five organic fertilizers were used as iron complexes to investigate the role of sunlight and oxygen in photo-Fenton at near neutral pH. UV absorbance and stability constant of each selected iron chelate is different, and this work demonstrates that these parameters affect the reaction mechanisms in SMX degradation. Irradiation experiments without H2O2 revealed that only EDDS-Fe and DTPA-Fe achieved SMX degradation, but different iron release. These results, together with soluble oxygen free experiments, allowed the proposal of complementary reaction mechanisms to those of the classical photo-Fenton. The proposed mechanisms start through the potential photoexcitation of the iron complex, followed by subsequent oxygen-mediated hydroxyl radical generation reactions that are different for EDDS-Fe and DTPA-Fe. Moreover, irradiation experiments using EDTA-Fe and HEDTA-Fe had negligible SMX degradation despite iron release was observed, evidencing the differences between iron chelates.

Can ozone inactivate SARS-CoV-2? A review of mechanisms and performance on viruses.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has challenged societies around the globe. Technologies based on ozone, a powerful oxidant, have been evaluated to inactivate this virus in aerosols and fomites. However, the high data diversity hinders the possibility of establishing a common ground for determining best practices for the use of these technologies. Furthermore, there is a lack of consensus regarding which are the main mechanisms of ozone virus inactivation. This critical review examined the most relevant information available regarding ozone application in gas-phase for different viruses inactivation (including recent publications dealing with SARS-CoV-2), and pointed towards envelope alteration as the main reaction pathway for enveloped viruses, such as is the case of SARS-CoV-2. It could also be concluded that gaseous ozone can be indeed an effective disinfectant, successfully inactivating viruses such us influenza A H1N1, MERS-CoV, SARS-CoV-1 or even SARS-CoV-2 in aerosols or fomites. In reviewed works, low ozone exposures, just around 0.1-0.4 mg L-1 min, achieve about 4 log10 of inactivation in aerosols, while exposures between 1 and 4 mg L-1 min may be needed to guarantee an inactivation of 3-4 log10 in different fomites. Although further studies are required, ozone is an effective candidate to be used against SARS-CoV-2 or other viruses in surfaces and indoor locations.

Experimental design applied to photo-Fenton treatment of highly methomyl-concentrated water.

This work is focused on the study of the suitability of the photo-Fenton process as a pretreatment for water highly contaminated with a methomyl commercial formulation in Advanced Greenhouses devices. Initial concentrations of reagents and pesticide were evaluated according to a central composite experimental design, with methomyl depletion and biocompatibility of the final effluent as response functions. A triad of optimal operation conditions could be determined, [Met.](0)=50 mg L(-1), [H(2)O(2)](0)=254 mg L(-1) and [Fe(2+)](0)=77 mg L(-1) for the best elimination yield and an acceptable BOD(5)/COD value, and initial concentration of methomyl can be established as the most important parameter for the performance of the treatment due to the limitations that impose on the hydrogen peroxide doses in the presence of the excipients of the commercial formulation.

Continuous versus single H2O2 addition in peroxone process: Performance improvement and modelling in wastewater effluents.

Ozonation combined with continuous addition of H2O2 was studied as potential strategy for the effective abatement of ozone-resistant micropollutants from wastewater effluents. Oxidant doses within and beyond immediate ozone demand completion were tested. Through experiments involving the continuous addition of H2O2 in a semi-continuous contactor, it was demonstrated that this new approach could lead to a 36 % reduction of the overall O3 needs for a constant H2O2/O3 molar ratio of 0.25 compared to single ozonation, representing a 28 % reduction in energy consumption. This improvement was mainly attributed to H2O2 addition during the secondary ozonation stage, where the direct ozone demand becomes less important. The OH-exposure per consumed ozone (i.e., ROHO3 concept) calculation demonstrated that higher (0.5-1) and lower (0.25) oxidant relationships work better in improving the process performance during initial and secondary stages, respectively. Moreover, continuous versus total initial addition of H2O2 were compared and the first one showed better performance, representing differences in energy costs up to 21 %. Finally, two strategies for the real-time control of the O3-recalcitrant MPs fate were tested, one based on the ROHO3 concept and the other on UVA254 monitoring. Both resulted in accurate predictions (R2 > 0.96) for different compounds, effluents and processes.

Photocatalytic degradation of sulfamethoxazole using TiO2 in simulated seawater: Evidence for direct formation of reactive halogen species and halogenated by-products.

Nowadays photoactivation mechanism of titanium dioxide nanoparticles (TiO2 NPs) and reactive species involved in saline waters is not sufficiently established. In this study, TiO2 photocatalytic process under simulated solar irradiation was evaluated in synthetic seawater and compared with deionized water, using sulfamethoxazole (SMX) as model organic compound. For a TiO2 concentration of 100 mg L-1, SMX degradation resulted two times slower in seawater than in deionized water by the determination of their pseudo-first order rate constants of 0.020 min-1 and 0.041 min-1, respectively. Selected scavenging experiments revealed no significant contribution of hydroxyl radicals (OH) on the degradation process in seawater, while these radicals contributed to circa 60% on the SMX depletion in deionized water. Instead, the involvement of reactive halogen species (RHS) as main contributors for the SMX degradation in seawater could be established. A mechanism for the RHS generation was proposed, whose initiation reactions involve halides with the TiO2 photogenerated holes, yielding chlorine and bromine radicals (Cl and Br) that may later generate other RHS. Production of RHS was further confirmed by the identification of SMX transformation products (TPs) and their evolution over time, carried out by liquid chromatography-mass spectrometry (LC-MS). SMX transformation was conducted through halogenation, dimerization and oxidation pathways, involving mainly RHS. Most of the detected transformation products accumulated over time (up to 360 min of irradiation). These findings bring concerns about the viability of photocatalytic water treatments using TiO2 NPs in saline waters, as RHS could be yielded resulting in the generation and accumulation of halogenated organic byproducts.

Performance of a sequencing batch biofilm reactor for the treatment of pre-oxidized sulfamethoxazole solutions.

A combined strategy of a photo-Fenton pretreatment followed by a Sequencing Batch Biofilm Reactor (SBBR) was evaluated for total C and N removal from a synthetic wastewater containing exclusively 200 mg L(-1) of the antibiotic Sulfamethoxazole (SMX). Photo-Fenton reaction was optimized at the minimum reagent doses in order to improve the biocompatibility of effluents with the subsequent biological reactor. Consequently, the pretreatment was performed with two different initial H(2)O(2) concentrations (300 and 400 mg L(-1)) and 10 mg L(-1) of Fe(2+). The pre-treated effluents with the antibiotic intermediates as sole carbon source were used as feed for the biological reactor. The SBBR was operated under aerobic conditions to mineralize the organic carbon, and the Hydraulic Retention Time (HRT) was optimized down to 8h reaching a removal of 75.7% of the initial Total Organic Carbon (TOC). The total denitrification of the NO(3)(-) generated along the chemical-biological treatment was achieved by means of the inclusion of a 24-h anoxic stage in the SBBR strategy. In addition, the Activated Sludge Model No. 1 (ASM1) was successfully used to complete the N balance determining the N fate in the SBBR. The characterization and the good performance of the SBBR allow presenting the assessed combination as an efficient way for the treatment of wastewaters contaminated with biorecalcitrant pharmaceuticals as the SMX.

Assessment of cationic surfactants mineralization by ozonation and photo-Fenton process.

Aqueous solutions of two important quaternary ammonium compounds--16-BAC (benzyl-dimethyl-hexadecylammonium-chloride) and 18-BAC (benzyl-dimethyl-stearylammonium-chloride)--were treated by the ozonation and photo-Fenton processes at different ozone doses and hydrogen peroxide concentrations, respectively. During the photo-Fenton experiments, two different types of lamps were used--a UV mercury vapor medium pressure lamp and a xenon lamp, which simulates solar radiation. The total organic carbon removal was monitored to follow the mineralization of the surfactants. According to the experimental results, after 90 minutes of treatment, the photo-Fenton process achieved up to 80% of mineralization when the UV lamp was used. The efficiency of the photo-Fenton with the xenon lamp was lower. The ozonation process reached, at most, 50% mineralization at the used conditions (ozone dose = 7.57 g/h).

Identification of intermediates, acute toxicity removal, and kinetics investigation to the Ametryn treatment by direct photolysis (UV254), UV254/H2O2, Fenton, and photo-Fenton processes.

This paper reports the degradation of 10 mg L-1 Ametryn solution with different advanced oxidation processes and by ultraviolet (UV254) irradiation alone with the main objective of reducing acute toxicity and increase biodegradability. The investigated factors included Fe2+ and H2O2 concentrations. The effectiveness of the UV254 and UV254/H2O2 processes were investigated using a low-pressure mercury UV lamp (254 nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365 nm). The UV254 irradiation process achieved complete degradation of Ametryn solution after 60 min. The degradation time of Ametryn was greatly improved by the addition of H2O2. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of H2O2. The kinetic constant of the reaction between Ametryn and HO● for UV254/H2O2 was 3.53 × 108 L mol-1 s-1. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10 min of reaction for various combinations of Fe2+ and H2O2 under investigation. Working with the highest concentration (150 mg L-1 H2O2 and 10 mg L-1 Fe2+), around 30 and 70% of TOC removal were reached within 120 min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of Vibrio fischeri. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.

Sulfamethoxazole abatement by means of ozonation.

Sulfamethoxazole (SMX) is a bacteriostatic antibiotic largely used for diverse types of illness. Its widely use in humans and even in animals releases unmetabolized and active metabolites that have a strong potential in terms of effect in organisms. In this work, 200 mg L(-1) solution of sulfamethoxazole was treated by ozonation at different pH. Results showed that ozonation was proved to be an efficient method to degrade sulfamethoxazole. After 15 min of ozonation (corresponding dose=0.4 g of ozone L(-1)), the complete antibiotic abatement was almost achieved with just 10% of mineralization. The biodegradability and toxicity of the ozonation intermediates were also studied. A biodegradability enhancement (increment of BOD(5)/COD ratio) from 0 to 0.28 was observed after 60 min of ozonation. The acute toxicity of the intermediates was followed by the Microtox test and the toxicity profile showed a slight acute toxicity increment in the first stage of ozonation. The pH variation had an important role in the TOC and COD removal, promoting their growth with the increment of alkalinity. The second order kinetic constants for the ozonation of the SMX in an order of magnitude of 10(5) L mol(-1)s(-1) were also determined for pH 5 and 7.

Bezafibrate removal by means of ozonation: primary intermediates, kinetics, and toxicity assessment.

Bezafibrate (BZF) is a lipid regulator largely used for the treatment of hyperlipidaemia. As a result of its wide use, unmetabolized BZF is released in the environment with potential toxic effects for aquatic living organisms. The results obtained in this work show that ozonation is an efficient method to degrade BZF: after 10 min of treatment (corresponding to a dose of 0.73 mmol L(-1) of ozone), the complete BZF abatement is achieved, starting from an initial concentration of 0.5 mmol L(-1). However, only a small part of the substrate is mineralized. Two different experimental approaches (absolute and competition method) are adopted to estimate the second-order kinetic constants for the ozone attack at pH=6.0, 7.0 and 8.0. A good agreement was observed between the two kinetic methods adopted. The identification of main intermediates, attempted by high-performance liquid chromatograph (HPLC)-MS technique, indicates that the oxidation of BZF develops through both the hydroxylation of the aromatic ring and the attack of ozone on the unchlorinated aromatic one. The assessment of by-products biodegradability and acute toxicity demonstrates that ozonation is a suitable technique to improve the biodegradability and reduce the toxicity of waters containing BZF.

Sulfamethoxazole abatement by photo-Fenton toxicity, inhibition and biodegradability assessment of intermediates.

The objective of this work was to study the abatement of 200mgL(-1) sulfamethoxazole (SMX) solution by means of photo-Fenton process. Biodegradability of the treated solutions was followed by the ratio biochemical oxygen demand at five days/chemical oxygen demand (BOD(5)/COD) and toxicity by Microtox and inhibition tests. Experiments with different initial concentration of H(2)O(2) were carried out. The initial amount of Fe(2+) and pH of the solution were set at 10mgL(-1) and 2.8 respectively. The temperature of the reactor was kept constant in all the experiments (25+/-0.8 degrees C). Photo-Fenton process is thought to be a successful treatment step to improve the biodegradability of wastewater containing SMX. The complete antibiotic removal was achieved for a H(2)O(2) dose over 300mgL(-1). Biodegradability (BOD(5)/COD) rose from zero (SMX solution) to values higher than 0.3 (treated solutions). Toxicity and inhibition tests pointed out in the same direction: oxidized intermediates for initial H(2)O(2) dose over 300mgL(-1) showed no toxicity effects on pure bacteria and no inhibition on activated sludge activity.

Biological and photochemical degradation of cytostatic drugs under laboratory conditions.

Cytostatic drugs, used in chemotherapy, have emerged as new environmental contaminants due to their recurrent presence in surface waters and genotoxic effects. Yet, their degradability and environmental fate is largely unknown. The aim of this study was to determine the degradation kinetics of 16 cytostatic drugs, prioritized according to their usage and occurrence in hospital and wastewater treatment plants (WWTP) effluents, through the following laboratory scale processes: hydrolysis, aerobic biodegradation, UV-C photolysis, UV-C/H2O2 and simulated solar radiation. Some drugs were unstable in milli-Q water (vincristine, vinblastine, daunorubicin, doxorubicin and irinotecan); others were photodegraded under UV-C light (melphalan and etoposide) but some others were found to be recalcitrant to biodegradation and/or UV-C, making necessary the use of advanced oxidation processes (AOPs) such as UV-C/H2O2 for complete elimination (cytarabine, ifosfamide and cyclophosphamide). Finally, radiation in a solar box was used to simulate the fate of cytostatic drugs in surface waters under natural radiation and complete removal was not observed for any drug. The degradation process was monitored using liquid chromatography coupled to high resolution mass spectrometry and pseudo-first order kinetic degradation constants were calculated. This study provides new data on the degradability of cytostatic compounds in water, thus contributing to the existing knowledge on their fate and risk in the environment.

High salinity effect on bioremediation of pretreated pesticide lixiviates from greenhouses.

Hydroponics culture greenhouses usually work in closed and semi-closed irrigation systems for nutrients and water-saving purposes. Photo-Fenton reaction has been revealed as an efficient way to depollute that kind of recycled effluents containing pesticides, even for high salinity concentrations. However, the inefficacy of organic matter chemical depletion imposes the use of a subsequent treatment. This work proposes the suitability of an integration of advanced oxidation process with a subsequent bioreactor to treat greenhouse lixiviates effluents at high or extremely high conductivity (salts concentration: up to 42 g L⁻¹). As a first step in this study, the performance of a series of sequencing batch reactors was monitored in order to check the biocompatibility of photo-Fenton pretreated effluents depending on their salinity content. In the second step, those same pretreated effluents were loaded to a biofiltration column filled with expanded clay. Finally, bacterial 16S rRNA gene sequencing was carried out to analyse microbial diversity of the biomass developed in the column. Results stated that the chemical-biological coupled system is effective for the treatment of water effluents containing pesticides. The integrated system is able to deplete more than 80% of the organic load, even under extremely high salinity.

Degradation kinetics and pathways of three calcium channel blockers under UV irradiation.

Calcium channel blockers (CCBs) are a group of pharmaceuticals widely prescribed to lower blood pressure and treat heart diseases. They have been frequently detected in wastewater treatment plant (WWTP) effluents and downstream river waters, thus inducing a potential risk to aquatic ecosystems. However, little is known about the behavior and fate of CCBs under UV irradiation, which has been adopted as a primary disinfection method for WWTP effluents. This study investigated the degradation kinetics and pathways of three commonly-used CCBs, including amlodipine (AML), diltiazem (DIL), and verapamil (VER), under UV (254 nm) irradiation. The chemical structures of transformation byproducts (TBPs) were first identified to assess the potential ecological hazards. On that basis, a generic solid-phase extraction method, which simultaneously used four different cartridges, was adopted to extract and enrich the TBPs. Thereafter, the photo-degradation of target CCBs was performed under UV fluences typical for WWTP effluent disinfection. The degradation of all three CCBs conformed to the pseudo-first-order kinetics, with rate constants of 0.031, 0.044 and 0.011 min(-1) for AML, DIL and VER, respectively. By comparing the MS(2) fragments and the evolution (i.e., formation or decay) trends of identified TBPs, the degradation pathways were proposed. In the WWTP effluent, although the target CCBs could be degraded, several TBPs still contained the functional pharmacophores and reached peak concentrations under UV fluences of 40-100 mJ cm(-2).

Fosetyl-Al photo-Fenton degradation and its endogenous catalyst inhibition.

Interferences from many sources can affect photo-Fenton reaction performance. Among them, catalyst inhibition can be caused by the complexation and/or precipitation of iron species by the organic matter and salts present in the reaction media. This is the case of the oxidation of effluents containing organophosphorous fosetyl-Al. The degradation of this fungicide generates phosphate anions that scavenge iron and hinder Fe(II) availability. Experimental design was applied to artificially enlighten photo-Fenton reaction, in order to evaluate fosetyl-Al degradation. The performed experiments suggested how iron inhibition takes place. The monitoring of photo-Fenton reaction over a mixture of fosetyl-Al with other two pesticides also showed the interferences caused by the presence of the fungicide on other species degradation. Solar empowered photo-Fenton was also essayed for comparison purposes. Artificial and solar light photo-Fenton reactions were revealed as effective treatments for the elimination of tested fungicide. However, the phosphate ions generated during fosetyl oxidation decreased iron availability, what hampered organic matter degradation.