Nanofiltration combined with ozone-based processes for the removal of antineoplastic drugs from wastewater effluents

Over the past years, there has been an increasing concern about the occurrence of antineoplastic drugs in water bodies. The incomplete removal of these pharmaceuticals from wastewaters has been confirmed by several scientists, making it urgent to find a reliable technique or a combination of techniques capable to produce clean and safe water. In this work, the combination of nanofiltration and ozone (O3)-based processes (NF + O3, NF + O3/H2O2 and NF + O3/H2O2/UVA) was studied aiming to produce clean water from wastewater treatment plant (WWTP) secondary effluents to be safely discharged into water bodies, reused in daily practices such as aquaculture activities or for recharging aquifers used as abstraction sources for drinking water production. Nanofiltration was performed in a pilot-scale unit and O3-based processes in a continuous-flow column. The peroxone process (O3/H2O2) was considered the most promising technology to be coupled to nanofiltration, all the target pharmaceuticals being removed at an extent higher than 98% from WWTP secondary effluents, with a DOC reduction up to 92%. The applicability of the clean water stream for recharging aquifers used as abstraction sources for drinking water production was supported by a risk assessment approach, regarding the final concentrations of the target pharmaceuticals. Moreover, the toxicity of the nanofiltration retentate, a polluted stream generated from the nanofiltration system, was greatly decreased after the application of the peroxone process, which evidences the positive impact on the environment of implementing a NF + O3/H2O2 process.

Treatment of refractory organics in biologically treated landfill leachate by a zero valent iron enhanced Peroxone process: Degradation efficiency and mechanism study

A zero valent iron (ZVI) enhanced Peroxone process (ZVI/Peroxone) was used to treat biologically treated landfill leachate (BTL). The treatment efficiency of the ZVI/Peroxone process was compared to single (ZVI, O₃ and H₂O₂) and dual (ZVI/H₂O₂, Fe⁰/O₃ and Peroxone) processes. The results showed that ZVI can greatly enhance the treatment capability of the Peroxone process, and the color number (CN), absorbance at 254 nm (UV₂₅₄), and total organic carbon (TOC) removal efficiencies were 98.82, 84.30 and 66.38%, respectively. In the ZVI/Peroxone process, higher O₃ and ZVI dosages improved organics removal, and H₂O₂ could promote organics removal within a certain dosage range. However, too much H₂O₂ decreased treatment efficiency. The best treatment performance by the ZVI/Peroxone process was obtained under acidic conditions. The three-dimensional excitation and emission matrix analysis showed that BTL mainly contained two fluorescent substances, which were fulvic-like substances in the ultraviolet region (Ex/Em = 235-255 nm/410-450 nm) and fulvic-like substances in the visible light region (Ex/Em = 310-360 nm/370-450 nm). Fluorescent substances could be substantially degraded by the ZVI/Peroxone process during the early stages of the reaction. An analysis of ZVI morphology and element valency changes showed that the micro Fe⁰ particles used in this study remained highly reactive during the process. The ZVI enhanced the homogenous Fenton, heterogeneous Fenton, and coagulation-flocculation effects during the Peroxone process.

Efficient removal of ibuprofen and ofloxacin pharmaceuticals using biofilm reactors for hospital wastewater treatment

Hospital wastewater is harmful to the environment and human health due to its complex chemical composition and high potency towards becoming a source of disease outbreaks. Due to these complexities, its treatment is neither efficient nor cost-effective. It is a challenging issue that requires immediate attention. This effort focuses on the treatment of hospital wastewater (HWW) by removing two selected drugs, namely ibuprofen (IBU) and ofloxacin (OFX) using individual biological treatment methods, such as moving bed biofilm reactors (MBBR) and physicochemical treatment, such as ozonation and peroxane process. The both methods are compared to find the best method overall based on effectiveness and removal efficiency. The optimal removal for ozone dosing range was nitrate (9.00% and 62.00%), biological oxygen demand (BOD) (92.00% and 64.00%), and chemical oxygen demand (COD) (96.00% and 92.00%) that required at least 10 min to reach considerable degradation. The MBBR process assured a better performance for ibuprofen removal, overall. The IBU and OFX removal was found to be 14.32-96.00% at a higher COD value and 11.33-94.00% at a lower COD value due to its biodegradation. This work strives to pave the way forward to build an HWW treatment technology using integrated MBBR processes for better efficiency and cost-effectiveness.

Degradation of triclosan by anodic oxidation/in-situ peroxone process: Kinetics, pathway and reaction mechanism

Triclosan (TCS) is an emerging contaminant that threatens the environment and human health. This study was conducted to investigate TCS abatement by a novel electro-oxidation (EO) process, which used a Ti-based nickel and antimony doped tin oxide (NATO/Ti) anode and a carbon nanotubes (CNTs) doped carbon/PTFE (CNTs-C/PTFE) gas diffusion electrode (GDE) for oxygen reduction reaction (ORR). A comparative study was also performed for TCS degradation by using a traditional EO with a nickel foam cathode, termed as HER-EO. The optimal initial TCS concentration, current density and solution pH for TCS degradation during the ORR-EO and HER-EO were investigated. Results showed that ORR-EO removed more than 98% of TCS in 10-60 min under the concentration of 5-50 mg/L. The TCS degradation followed pseudo-first-order kinetics and its main intermediates were observed during the ORR-EO and HER-EO using liquid chromatography combined mass (LC-MS). The results of FED analysis and toxicity prediction by ECOSAR software showed that less intermediates accumulated during the ORR-EO and the residues were less harmful. The ORR-EO degradation mechanism for TCS was attacking on the ether bond and the benzene ring by ^•OH. This novel ORR-EO process exhibits a great merit in the field of emerging contaminants abatement.

Removal of tetramethylammonium hydroxide (TMAH) in semiconductor wastewater using the nano-ozone H2O2 process

In this study, we used a nano-ozone bubble to enhance the efficiency of the ozone/H₂O₂ process for the degradation of tetramethylammonium hydroxide (TMAH) found in semiconductor wastewater at high levels. The nano-ozone bubble significantly increased ozone mass transfer rate compared to that of the macro-ozone bubble. The half-life of nano-ozone bubbles was 23 times longer than that of the nano-ozone bubbles. Due to the high ozone mass transfer rate and its durability, the nano-ozone bubble increased the TMAH degradation rate compared to that of the macro-ozone. The addition of H₂O₂ significantly increased the TMAH degradation rate constant by OH production during the nano-ozone bubbles/H₂O₂ process. The optimum conditions for TMAH removal was 25 °C and pH 10. Within 90 min of the nano-ozone/H₂O₂ process, TOC removal was 65 % while 80 % of nitrogen was converted into nitrate (NO₃^-) with 95 % of TMAM removal. Decreases in acute (40-fold) and chronic (2-fold) toxicity were achieved after applying the nano-ozone/H₂O₂ process to TMAH containing wastewater. However, there was no significant chronic toxicity decrease during the nano-ozone/H₂O₂ process of TMAH.

Comparison of emerging contaminant abatement by conventional ozonation, catalytic ozonation, O3/H2O2 and electro-peroxone processes

The abatement of several emerging contaminants (ECs) in groundwater by conventional ozonation and three ozone-based advanced oxidation processes (AOPs) - catalytic ozonation with manganese dioxide (MnO₂), conventional peroxone (O₃/H₂O₂), and electro-peroxone (EP) - was compared in this study. The addition of MnO₂, H₂O₂, or electro-generation of H₂O₂ during ozonation enhanced ozone transformation to hydroxyl radicals to different extent. These changes did not considerably influence the abatement of ECs with moderate to high ozone reactivities ( [Formula: see text] ), whose abatements were similar with >90 % during all four processes. In comparison, the abatements of ozone-refractory ECs (k_O3< 15 M^-1s^-1) were lower during conventional ozonation (∼40-85 % abatement), but could be enhanced by ∼10-40 % during the three ozone-based AOPs. Besides enhancing ozone-refractory EC abatement, the three AOPs, especially the O₃/H₂O₂ and EP processes, reduced considerably bromate formation compared to conventional ozonation. These results demonstrate that the EP process performs similarly as catalytic ozonation and O₃/H₂O₂ processes in terms of EC abatement and bromate control. Considering its more convenient, flexible, and safer way of operation, the EP process may provide an attractive alternative to the two more traditional AOPs for water treatment.

Synthetic fresh-cut wastewater disinfection and decontamination by ozonation at pilot scale

In this research, the capability of ozonation and peroxone treatment for the simultaneous disinfection and decontamination of wash water from the fresh-cut industry has been investigated at pilot plant scale (10 L). The removal efficiency of six organic microcontaminants (OMCs) (four of them priority substances) and the inactivation of two foodborne pathogens (Escherichia coli O157:H7 and Salmonella enteritidis) in synthetic fresh-cut wastewater (SFCWW) has been assessed. Ozonation and peroxone (O₃ with 20 mgL^-1 of H₂O₂) process has been investigated under several operational conditions: natural SFCWW pH (6.25) and basic pH (11), and two different initial ozone production (0.09 and 0.15 gO₃ L^-1 h^-1). Results showed that the highest efficiency for OMCs removal (85%) and pathogen inactivation (>5-Log) were obtained with ozonation treatment at natural pH. OMCs degradation was obtained after 120 min of treatment with an ozone dose of 27.4 mgO₃ L^-1. First order kinetic constant of each OMC degradation was obtained, and two clear different groups have been identify based on their degradation profiles, which have been correlated with their chemical structure. G₁-OMC [terbutryn > buprofezin > azoxystrobin] > G₂-OMC [imidacloprid > simazine > thiamethoxam]. As for bacterial inactivation, up to 10 min of treatment time and an ozone dose of <8.6 mgO₃ L^-1 were required to reach the detection limit (2 CFU mL^-1), showing E. coli O157:H7 a higher susceptibility to be inactivated (k: 2.79 min^-1) than S. enteritidis (k: 1.47 min^-1). Moreover, from the techno-economical and toxicological assessment of the treated water with the best operational condition, can be highlighted: i) a slight acute toxicity for V. fischeri (47 ± 2.3% of luminescence inhibition), ii) an acute toxicity for Daphnia magna (100% of immobilization) and iii) a total cost of the treatment of 1.16 € m^-3.

Removing acesulfame with the peroxone process: Transformation products, pathways and toxicity

Emerging contaminants (ECs) are receiving considerable attention because of their widespread occurrence, persistence and potential threat to the environment, wildlife and humans. Acesulfame (ACE), an extensively used artificial sweetener, is the most worrisome example of ECs. The photolysis/photocatalysis, chlorination and/or permanganate oxidation of ACE produces transformation products (TPs) that are more persistent and toxic than precursors. Thus, an alternative treatment method to treat ACE is required; oxidation by the peroxone process could be that method and was systematically investigated, as reported here. During the peroxone process, ACE degradation followed pseudo-first-order kinetics, with a rate that was significantly higher than after conventional ozonation. The hydroxyl radical was the major reactive species. Amount of hydrogen peroxide (H₂O₂) used, pH and type of water matrix showed significant influence on ACE degradation. Fifteen TPs in ultrapure water extracts, including four newly reported compounds, were identified and characterized by high resolution mass spectrometry (HR-MS) based on accurate mass measurements and MS/MS fragmentation. The reduced toxicity compared to other reported treatments of ACE was likely due to different transformation pathways and TPs generated. The peroxone process therefore appears to be one viable choice for safe removal of ACE.

Application of a ceramic membrane contacting process for ozone and peroxone treatment of micropollutant contaminated surface water

This study investigates the performance of membrane-based ozonation and peroxone processes, regarding the transformation of carbamazepine (CBZ), benzotriazole (BZT), p-chlorobenzoic acid (pCBA) and atrazine (ATZ) in natural surface waters, as well as the formation of bromates. Ozonation, performed with the use of ceramic membrane contactor, was able to diminish CBZ concentration below 0.1 μM at 0.4 mg O₃/mg DOC, i.e. presenting >90% removal rate, whereas the transformation of BZT, pCBA and ATZ was not exceeded 70%, 57% and 49%, respectively, under the same experimental conditions. The addition of H₂O₂ reduced the removal efficiency of CBZ, since up to -8% transformation values were observed at 0.1 mg O₃/mg DOC. In contrast, the transformation of ozone-resistant compounds pCBA and ATZ was slightly improved by approximately 5-10%, at 0.8 mg O₃/mg DOC. Membrane-based oxidative treatment of surface water resulted to high bromate concentrations (49 μg/L and 28 μg/L for ozone and peroxone process, respectively, at 0.8 mg O₃/mg DOC). The results obtained by using the membrane contactor were also compared with the corresponding from conventional batch experiments. These results suggest that the implementation of membrane contactors with the highest possible inner surface per volume along with the use of low ozone gas concentration are required to improve the removal of micropollutants and diminish bromate formation.

Impact of O3 or O3/H2O2 treatment via a membrane contacting system on the composition and characteristics of the natural organic matter of surface waters

The present study aims to evaluate changes in the structure-composition of natural organic matter (NOM) that occur after the application of bubbleless ozonation or peroxone treatment of surface waters. The oxidation experiments (using 0.5-2 mg O3/mg DOC, or 2:1 O₃:H₂O₂ molar ratio) were performed in a continuous mode, using a tubular ceramic membrane contactor. Fluorescence spectroscopy (emission-excitation matrix) and liquid chromatography-organic carbon detection (LC-OCD) were mainly used for the detailed DOC characterization. In brief, the application of single ozonation resulted to high reduction of humic-like peak fluorescence intensities (50-85%) and also to the formation of two new peaks in the region of protein-like components. The co-addition of H₂O₂ did not present the anticipated increase in the reduction of fluorescence intensity; however, it resulted to the further oxidation of protein-like fluorophores. LC-OCD measurements confirmed the decrease of average molecular weight of NOM during ozone treatment, due to the gradual degradation of biopolymers (14-23%) and humic substances (11-17%) towards building blocks and low molecular weight (LMW) neutrals. Advanced oxidation process (AOP) treatment by the mixture O₃/H₂O₂ resulted in the simultaneous decrease of building blocks and LMW neutral concentrations. Conventional batch ozonation and AOP experiments were conducted using ozone-saturated solutions to investigate the effect of different contacting patterns. The results revealed that the different reaction pathways followed during bubbleless and conventional batch experiments may also influence the formation of NOM oxidation intermediates.

Understanding the similarities and differences between ozone and peroxone in the degradation of naphthenic acids: Comparative performance for potential treatment

Ozonation at high doses is a costly treatment for oil sands process-affected water (OSPW) naphthenic acids (NAs) degradation. To decrease costs and limit doses, different peroxone (hydrogen peroxide/ozone; H₂O₂:O₃) processes using mild-ozone doses of 30 and 50 mg/L were investigated. The degradation efficiency of O_x-NAs (classical (O₂-NAs) + oxidized NAs) improved from 58% at 30 mg/L ozone to 59%, 63% and 76% at peroxone (1:1), 50 mg/L ozone, and peroxone (1:2), respectively. Suppressing the hydroxyl radical (•OH) pathway by adding tert-butyl alcohol did significantly reduce the degradation in all treatments, while molecular ozone contribution was around 50% and 34% for O₂-NAs and O_x-NAs, respectively. Structure reactivity toward degradation was observed with degradation increase for both O₂-NAs and O_x-NAs with increase of both carbon (n) and hydrogen deficiency/or |-Z| numbers in all treatments. However, the combined effect of n and Z showed specific insights and differences between ozone and peroxone treatments. The degradation pathway for |-Z|≥10 isomers in ozone treatments through molecular ozone was significant compared to •OH. Though peroxone (1:2) highly reduced the fluorophore organics and toxicity to Vibrio fischeri, the best oxidant utilization in the degradation of O₂-NAs (mg/L) per ozone dose (mg/L) was observed in the peroxone (1:1) (0.91) and 30 mg/L ozone treatments (0.92). At n = 9-11, peroxone (1:1) had similar or enhanced effect on the O₂-NAs degradation compared to 50 mg/L ozone. Enhancing •OH pathway through peroxone versus ozone may be an effective OSPW treatment that will allow its safe release into receiving environments with marginal cost addition.

Removal of several pesticides in a falling water film DBD reactor with activated carbon textile: Energy efficiency

Bio-recalcitrant micropollutants are often insufficiently removed by modern wastewater treatment plants to meet the future demands worldwide. Therefore, several advanced oxidation techniques, including cold plasma technology, are being investigated as effective complementary water treatment methods. In order to permit industrial implementation, energy demand of these techniques needs to be minimized. To this end, we have developed an electrical discharge reactor where water treatment by dielectric barrier discharge (DBD) is combined with adsorption on activated carbon textile and additional ozonation. The reactor consists of a DBD plasma chamber, including the adsorptive textile, and an ozonation chamber, where the DBD generated plasma gas is bubbled. In the present paper, this reactor is further characterized and optimized in terms of its energy efficiency for removal of the five pesticides α-HCH, pentachlorobenzene, alachlor, diuron and isoproturon, with initial concentrations ranging between 22 and 430 μg/L. Energy efficiency of the reactor is found to increase significantly when initial micropollutant concentration is decreased, when duty cycle is decreased and when oxygen is used as feed gas as compared to air and argon. Overall reactor performance is improved as well by making it work in single-pass operation, where water is flowing through the system only once. The results are explained with insights found in literature and practical implications are discussed. For the used operational conditions and settings, α-HCH is the most persistent pesticide in the reactor, with a minimal achieved electrical energy per order of 8 kWh/m³, while a most efficient removal of 3 kWh/m³ or lower was reached for the four other pesticides.

Ozonation of hospital raw wastewaters for cytostatic compounds removal. Kinetic modelling and economic assessment of the process

The kinetics of the ozone consumption for the pretreatment of hospital wastewater has been analysed in order to determine the reaction rate coefficients between the ozone and the readily oxidisabled organic matter and cytostatic compounds. The wastewater from a medium size hospital was treated with ozone and peroxone methodologies, varying the ozone concentration, the reaction time and the hydrogen peroxide doses. The analysis shows that there are four cytostatic compounds, i.e. irinotecan, ifosfamide, cyclophosphamide and capecitabine, detected in the wastewaters and they are completely removed with reasonably short times after the ozone treatment. Considering the reactor geometry, the gas hydrodynamics, the mass transfer of ozone from gas to liquid and the reaction of all oxidisable compounds of the wastewater it is possible to determine the chemical ozone demand, COzD, of the sample as 256mgO3L(-1) and the kinetic rate coefficient with the dissolved organic matter as 8.4M(-1)s(-1). The kinetic rate coefficient between the ozone and the cyclophosphamide is in the order of 34.7M(-1)s(-1) and higher for the other cytostatics. The direct economic cost of the treatment was evaluated considering this reaction kinetics and it is below 0.3€/m(3) under given circumstances.

Peroxone activated persulfate treatment of 1,4-dioxane in the presence of chlorinated solvent co-contaminants

1,4-dioxane is often found as a co-contaminant with chlorinated volatile organic compounds (VOCs) at solvent release sites such as landfills, solvent recycling facilities, or fire training areas. Historically, soil and groundwater samples were not routinely analyzed for 1,4-dioxane and therefore the number of known 1,4-dioxane sites is still increasing. Due to its co-occurrence with chlorinated compounds, remediation strategies are needed that simultaneously treat both 1,4-dioxane as well as chlorinated VOC co-contaminants. In this proof of concept laboratory study, the fate of 1,4-dioxane was examined during the targeted destruction of aqueous phase VOC, using a peroxone activated persulfate (PAP) chemical oxidation method. Bench-scale experiments were carried out to evaluate the treatability of 1,4-dioxane as both a single-contaminant and in the presence of trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA). Possible dependencies on oxidant concentration and reaction kinetics were studied. The oxidative destruction of 1,4-dioxane, TCE and 1,1,1-TCA in single-contaminant batch systems followed pseudo-first-order reaction kinetics and even at the most dilute oxidant concentration lasted for at least 13 days. The rate of oxidation for each contaminant increased linearly with increasing persulfate concentration over the range of oxidant concentrations tested. The rate of oxidative destruction, from most easily degraded to least, was: TCE > 1,4-dioxane > 1,1,1-TCA. Oxidation rates were up to 87% slower in a mixture of these three compounds. Although additional tests are necessary, our data suggest that PAP oxidation of 1,4-dioxane might aid in the cleanup of VOC contaminated sites.

Peroxone mineralization of chemical oxygen demand for direct potable water reuse: Kinetics and process control

Mineralization of organics in secondary effluent by the peroxone process was studied at a direct potable water reuse research treatment system serving an occupied four-bedroom, four bath university residence hall apartment. Organic concentrations were measured as chemical oxygen demand (COD) and kinetic runs were monitored at varying O3/H2O2 dosages and ratios. COD degradation could be accurately described as the parallel pseudo-1st order decay of rapidly and slowly-oxidizable fractions, and effluent COD was reduced to below the detection limit (<0.7 mg/L). At dosages ≥4.6 mg L(-1) h(-1), an O3/H2O2 mass ratio of 3.4-3.8, and initial COD <20 mg/L, a simple first order decay was indicated for both single-passed treated wastewater and recycled mineral water, and a relationship is proposed and demonstrated to estimate the pseudo-first order rate constant for design purposes. At this O3/H2O2 mass ratio, ORP and dissolved ozone were found to be useful process control indicators for monitoring COD mineralization in secondary effluent. Moreover, an average second order rate constant for OH oxidation of secondary effluent organics (measured as MCOD) was found to be 1.24 × 10(7) ± 0.64 × 10(7) M(-1) S(-1). The electric energy demand of the peroxone process is estimated at 1.73-2.49 kW h electric energy for removal of one log COD in 1 m(3) secondary effluent, comparable to the energy required for desalination of medium strength seawater. Advantages/disadvantages of the two processes for municipal wastewater reuse are discussed.

Decomposition of atrazine traces in water by combination of non-thermal electrical discharge and adsorption on nanofiber membrane

In recent decades, several types of persistent substances are detected in the aquatic environment at very low concentrations. Unfortunately, conventional water treatment processes are not able to remove these micropollutants. As such, advanced treatment methods are required to meet both current and anticipated maximally allowed concentrations. Plasma discharge in contact with water is a promising new technology, since it produces a wide spectrum of oxidizing species. In this study, a new type of reactor is tested, in which decomposition by atmospheric pulsed direct barrier discharge (pDBD) plasma is combined with micropollutant adsorption on a nanofiber polyamide membrane. Atrazine is chosen as model micropollutant with an initial concentration of 30 μg/L. While the H2O2 and O3 production in the reactor is not influenced by the presence of the membrane, there is a significant increase in atrazine decomposition when the membrane is added. With membrane, 85% atrazine removal can be obtained in comparison to only 61% removal without membrane, at the same experimental parameters. The by-products of atrazine decomposition identified by HPLC-MS are deethylatrazine and ammelide. Formation of these by-products is more pronounced when the membrane is added. These results indicate the synergetic effect of plasma discharge and pollutant adsorption, which is attractive for future applications of water treatment.