Evaluation of a photocatalytic reactor membrane pilot system for the removal of pharmaceuticals and endocrine disrupting compounds from water

Effect of water composition on TiO2 photocatalytic removal of endocrine disrupting compounds (EDCs) and estrogenic activity from secondary effluent

The effect of inorganic ions and dissolved organic matter (DOM) on the TiO(2) photocatalytic removal of estrogenic activity from secondary effluents of municipal wastewater treatment plants was investigated. The presence of HPO(4)(2-), NH(4)(+), and HCO(3)(-) resulted in a significantly negative impact on the photocatalytic removal of estrogenic activity from synthetic water due to their strong adsorption on the surface of TiO(2). However, only a weak impact was noted during photocatalytic removal of estrogenic activity from secondary effluent with these ions added, since the presence of DOM in real wastewater played a more important role in inhibiting photocatalytic removal of estrogenic activity than inorganic ions. By investigating the effect of different DOM fractions on photocatalytic removal of estrogenic activity, polar compounds (PC) were found to cause a temporary increase in estrogenic activity during TiO(2) photocatalysis. Fluorescence spectroscopy and molecular weight (MW) analysis on secondary effluent spiked with PC during TiO(2) photocatalysis suggest that large MW organic matter (>4.5kDa) in secondary effluent, such as humic/fulvic acid, not only could play an important role in inhibiting photocatalytic removal of estrogenic activity but also is responsible for the temporary increase in estrogenic activity during the same process.

Membrane vis-LED photoreactor for simultaneous penicillin G degradation and TiO2 separation

The hybrid membrane photoreactor (MPR) combining a photoreactor irradiated with visible-light-emitting diode (vis-LED) and a cross-flow microfiltration (MF) membrane module was investigated in both closed-loop and continuous flow-through modes for the simultaneous degradation of penicillin G (PG) and separation of visible-light responsive TiO(2) particles, namely C-sensitized-N-doped TiO(2) (T300) and C-N-S tridoped TiO(2) (T0.05-450). The turbidity of permeate water was <0.2 NTU for both T300 and T0.05-450 suspensions in the MPR system operated at different transmembrane pressures (TMPs) and cross-flow velocities (CFVs), indicating effective separation of TiO(2) particles by the MF membrane. The operations at a higher TMP or lower CFV were more prone to induce TiO(2) deposition on the membrane surface without backwashing, which resulted in the membrane fouling, the loss of TiO(2) from the photoreactor and the decrease of PG photocatalytic degradation efficiency. 75% and 84% of PG were degraded in the closed-loop MPR without backwashing operated at 10 kPa and 0.15 m s(-1) after 4 h of vis-LED irradiation using 1.0 g L(-1) of T300 and T0.05-450, respectively. With backwashing of the membrane, the PG photocatalytic degradation efficiencies in the closed-loop MPR could be significantly enhanced to achieve 93% and 95% using 1.0 g L(-1) of T300 and T0.05-450, respectively, which were almost comparable to those achieved in the batch photoreactor. Due to its shorter hydraulic residence time in the photoreactor, the PG degradation efficiency in the continuous flow-through MPR with backwashing was lower than that achieved in the closed-loop MPR.

Effects of ozone and ozone/peroxide on trace organic contaminants and NDMA in drinking water and water reuse applications

An ozone and ozone/peroxide oxidation process was evaluated at pilot scale for trace organic contaminant (TOrC) mitigation and NDMA formation in both drinking water and water reuse applications. A reverse osmosis (RO) pilot was also evaluated as part of the water reuse treatment train. Ozone/peroxide showed lower electrical energy per order of removal (EEO) values for TOrCs in surface water treatment, but the addition of hydrogen peroxide increased EEO values during wastewater treatment. TOrC oxidation was correlated to changes in UV(254) absorbance and fluorescence offering a surrogate model for predicting contaminant removal. A decrease in N-nitrosodimethylamine (NDMA) formation potential (after chloramination) was observed after treatment with ozone and ozone/peroxide. However, during spiking experiments with surface water, ozone/peroxide achieved limited destruction of NDMA, while in wastewaters net direct formation of NDMA of 6-33 ng/L was observed after either ozone or ozone/peroxide treatment. Once formed during ozonation, NDMA passed through the subsequent RO membranes, which highlights the significance of the potential for direct NDMA formation during oxidation in reuse applications.

Photocatalytic treatment of high concentration carbamazepine in synthetic hospital wastewater

Effective and sustainable treatment of hospital wastewater containing high concentration of pharmaceutical compounds presents a pivotal challenge to wastewater and environmental engineers worldwide. In this study, a titanium dioxide (TiO(2)) nanofiber based wastewater treatment process was assessed as a pre-treatment system to treat and enhance the biodegradability of a representative pharmaceutical compound, 5000 μg/L of carbamazepine (CBZ), in synthetic hospital wastewater. Results showed that the stand-alone TiO(2) pre-treatment system was capable of removing 78% of CBZ, 40% of COD and 23% of PO(4) concentrations from the influent wastewater within a 4h reaction time. High performance size exclusion chromatography demonstrated that a simultaneous biodegradability enhancement of hospital wastewater was observed, whereby an apparent shift in molecular weight from higher fraction (>10-1000 kDa) to a lower fraction (<10 kDa) was induced after 0.5h of photocatalytic treatment. Eventually, it was found that the photodegradation profile for high concentration CBZ in synthetic hospital wastewater was perfectly fitted to the Langmuir-Hinshelwood kinetics model. It is anticipated that this TiO(2) pre-treatment process can be further integrated with a biological wastewater treatment process to deliver treated hospital effluent of better quality that can minimise the associated human health and environmental risks.

Bioassays as a tool for evaluating advanced oxidation processes in water and wastewater treatment

Advanced oxidation processes (AOPs) have been widely used in water and wastewater treatment for the removal of organic and inorganic contaminants as well as to improve biodegradability of industrial wastewater. Unfortunately, the partial oxidation of organic contaminants may result in the formation of intermediates more toxic than parent compounds. In order to avoid this drawback, AOPs are expected to be carefully operated and monitored, and toxicity tests have been used to evaluate whether effluent detoxification takes place. In the present work, the effect of AOPs on the toxicity of aqueous solutions of different classes of contaminants as well as actual aqueous matrices are critically reviewed. The dualism toxicity-biodegradability when AOPs are used as pre-treatment step to improve industrial wastewater biodegradability is also discussed. The main conclusions/remarks include the followings: (i) bioassays are a really useful tool to evaluate the dangerousness of AOPs as well as to set up the proper operative conditions, (ii) target organisms for bioassays should be chosen according to the final use of the treated water matrix, (iii) acute toxicity tests may be not suitable to evaluate toxicity in the presence of low/realistic concentrations of target contaminants, so studies on chronic effects should be further developed, (iv) some toxicity tests may be not useful to evaluate biodegradability potential, in this case more suitable tests should be applied (e.g., activated sludge bioassays, respirometry).

Identification of new ozonation disinfection byproducts of 17β-estradiol and estrone in water

Estrogens are a class of micro-pollutants found in water at low concentrations (in the ng L(-1) range), but often sufficient to exert estrogenic effects due to their high estrogenic potency. Disinfection of waters containing estrogens through oxidative processes has been shown to lead to the formation of disinfection byproducts, which may also be estrogenic. The present work investigates the formation of disinfection byproducts of 17β-estradiol (E2) and estrone (E1) in the treatment of water with ozone. Experiments have been carried out at two different concentrations of the estrogens in ground water (100 ng L(-1) and 100 μg L(-1)) and at varying ozone dosages (0-30 mg L(-1)). Detection of the estrogens and their disinfection byproducts in the water samples has been performed by means of ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with a triple quadrupole (QqQ) and a quadrupole-time of flight (QqTOF) instrument. Both E2 and E1 have been found to form two main byproducts, with molecular mass (MM) 288 and 278 in the case of E2, and 286 and 276 in the case of E1, following presumably the same reaction pathways. The E2 byproduct with MM 288 has been identified as 10 epsilon-17beta-dihydroxy-1,4-estradieno-3-one (DEO), in agreement with previously published results. The molecular structures and the formation pathways of the other three newly identified byproducts have been suggested. These byproducts have been found to be formed at both high and low concentrations of the estrogens and to be persistent even after application of high ozone dosages.

Photooxidation of the antidepressant drug Fluoxetine (Prozac®) in aqueous media by hybrid catalytic/ozonation processes

This article examines the oxidative disposal of Prozac(®) (also known as Fluoxetine, FXT) through several oxidative processes with and without UV irradiation: for example, TiO(2) alone, O(3) alone, and the hybrid methods comprised of O(3) + H(2)O(2) (PEROXONE process), TiO(2) + O(3) and TiO(2) + O(3) + H(2)O(2) at the laboratory scale. Results show a strong pH dependence of the adsorption of FXT on TiO(2) and the crucial role of adsorption in the whole degradation process. Photolysis of FXT is remarkable only under alkaline pH. The heterogeneous photoassisted process removes 0.11 mM FXT (initial concentration) within ca. 60 min with a concomitant 50% mineralization at pH 11 (TiO(2) loading, 0.050 g L(-1)). The presence of H(2)O(2) enhances the mineralization further to >70%. UV/ozonation leads to the elimination of FXT to a greater extent than does UV/TiO(2): i.e., 100% elimination of FXT is achieved by UV/O(3) in the first 10 min of reaction and almost 97% mineralization is attained under UV irradiation in the presence of H(2)O(2). The hybrid configuration UV + TiO(2) + O(3) + H(2)O(2) enhances removal of dissolved organic carbon (DOC) in ca. 30 min leaving, however, an important inorganic carbon (IC) content. In all cases, the presence of H(2)O(2) improves the elimination of DOC, but not without a detrimental effect on the biodegradability of FXT owing to the low organic carbon content in the final treated effluent, together with significant levels of inorganic byproducts remaining. The photoassisted TiO(2)/O(3) hybrid method may prove to be an efficient combination to enhance wastewater treatment of recalcitrant drug pollutants in aquatic environments.

Removal of estrogens through water disinfection processes and formation of by-products

Estrogens constitute a recognized group of environmental emerging contaminants which have been proven to induce estrogenic effects in aquatic organisms exposed to them. Low removal efficiency in wastewater treatment plants results in the presence of this type of contaminants in surface waters and also even in finished drinking water. This manuscript reviews the environmental occurrence of natural (estrone, estradiol and estriol) and synthetic (ethynyl estradiol) estrogens in different water matrices (waste, surface, ground and drinking water), and their removal mainly via chemical oxidative processes. Oxidative treatments have been observed to be very efficient in eliminating estrogens present in water; however, disinfection by-products (DBPs) are generated during the process. Characterization of these DBPs is essential to assess the risk that drinking water may potentially pose to human health since these DBPs may also have endocrine disrupting properties. This manuscript reviews the DBPs generated during oxidative processes identified so far in the literature and the estrogenicity generated by the characterized DBPs and/or by the applied disinfection technology.

Estrogen-related receptor gamma disruption of source water and drinking water treatment processes extracts

Environmental chemicals in drinking water can impact human health through nuclear receptors. Additionally, estrogen-related receptors (ERRs) are vulnerable to endocrine-disrupting effects. To date, however, ERR disruption of drinking water potency has not been reported. We used ERRgamma two-hybrid yeast assay to screen ERRgamma disrupting activities in a drinking water treatment plant (DWTP) located in north China and in source water from a reservoir, focusing on agonistic, antagonistic, and inverse agonistic activity to 4-hydroxytamoxifen (4-OHT). Water treatment processes in the DWTP consisted of pre-chlorination, coagulation, coal and sand filtration, activated carbon filtration, and secondary chlorination processes. Samples were extracted by solid phase extraction. Results showed that ERRgamma antagonistic activities were found in all sample extracts, but agonistic and inverse agonistic activity to 4-OHT was not found. When calibrated with the toxic equivalent of 4-OHT, antagonistic effluent effects ranged from 3.4 to 33.1 microg/L. In the treatment processes, secondary chlorination was effective in removing ERRgamma antagonists, but the coagulation process led to significantly increased ERRgamma antagonistic activity. The drinking water treatment processes removed 73.5% of ERRgamma antagonists. To our knowledge, the occurrence of ERRgamma disruption activities on source and drinking water in vitro had not been reported previously. It is vital, therefore, to increase our understanding of ERRy disrupting activities in drinking water.

Reactivity of effluent organic matter (EfOM) with hydroxyl radical as a function of molecular weight

The application of advanced oxidation processes (AOPs) for the treatment of wastewater is hindered by scavenging of the hydroxyl radical (HO*) by effluent organic matter (EfOM). This scavenging is directly proportional to the second-order reaction rate constant between EfOM and HO* (kEfOM-HO*). To understand the kinetics of this reaction as a function of the subcomponents of EfOM, four wastewater samples were fractionated by ultrafiltration into distinct apparent molecular weight (AMW) fractions (<1, <3, <5, and <10 kDa), and their kEfOM-HO* values were quantified. In general, the values for k(EfOM-HO*) decreased as the AMW increased. The values of k(EfOM-HO*) for the bulk waters varied between 6.32 and 14.1x10(8) MC(-1)s(-1) (units of per molar carbon concentration per second). In the case of the <1 kDa fraction, the values of kEfOM-HO* varied from 14.3 to 35.0x10(8) MC(-1)s(-1), or approximately 2.31(+/-0.24) times that of the corresponding bulk waters. For the <3 kDa, <5 kDa, and <10 kDa fractions, the k(EfOM-HO*) values were 1.83(+/-0.25), 1.32(+/-0.23), and 1.26(+/-0.35) times that of the bulk waters, respectively. Based on the obtained results, the variability and general magnitude of the kEfOM-HO* values were attributed to the production and reactivity of soluble microbial products (SMP), a major component of EfOM. Two samples collected at a wastewater treatment facility with different treatment variables had different kEfOM-HO* values, indicating that wastewater treatment processes will impact overall HO* scavenging by EfOM and should be considered during the implementation of AOPs.

Development of a fast liquid chromatography-tandem mass spectrometry method for the determination of endocrine-disrupting compounds in waters

A fast liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) method was developed to study five endocrine-disrupting compounds (4-n-nonylphenol, bisphenol A, estrone, 17β-estradiol and 17α-ethinylestradiol) in water. Different columns were tested; the chromatographic separation of the analytes was optimized on a Pinnacle DB biphenylic column with a water-acetonitrile gradient elution, which allowed the separation of the selected endocrine-disrupting compounds (EDCs) in less than 6 min. Quantitative analysis was performed in selected reaction monitoring (SRM) mode; two transitions were chosen for each compound, using the most abundant for quantitation. Calibration curves using bisphenol A-d (16) as internal standard were drawn, showing good correlation coefficients (0.9993-0.9998). All figures of merit of the method were satisfactory; limits of detection were in the low pg range for all analytes. The method was then applied to the determination of the analytes in real water samples: to this aim, polar organic chemical integrative samplers (POCIS) were deployed in the influent and in the effluent of a drinking water treatment plant in Liguria (Italy). The EDC level was rather low in the influent and negligible in the outlet, reflecting the expected function of the treatment plant.

Removal of natural organic matter from drinking water by advanced oxidation processes

Over the past 10-20years the amount of the natural organic matter (NOM) has been increased in raw water supplies on several areas. The presence of NOM causes many problems in drinking water treatment processes, including: (i) negative effect on water quality by colour, taste and odor problems, (ii) increased coagulant and disinfectant dose requirements (which in turn results increased sludge and potential harmful disinfection by-product formation), (iii) promoted biological growth in distribution system, and (iv) increased levels of complexed heavy metals and adsorbed organic pollutants. Thus, more efficient methods for the removal of NOM have emerged. Among these are advanced oxidation processes (AOPs). These include O(3)/H(2)O(2), O(3)/UV, UV/H(2)O(2), TiO(2)/UV, H(2)O(2)/catalyst, Fenton and photo-Fenton prosesses as well as ultrasound. In the present work, an overview of the recent research studies dealing with AOP methods for the removal of NOM and related compounds from drinking water is presented.

Degradation of pharmaceutical compound pentoxifylline in water by non-thermal plasma treatment

The decomposition of a model pharmaceutical compound, pentoxifylline, in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration, operated in pulsed regime, at atmospheric pressure and room temperature. The solution was made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gas-liquid interface. Oxygen was introduced with a flow rate of 600sccm. After 60min plasma treatment 92.5% removal of pentoxifylline was achieved and the corresponding decomposition yield was 16g/kWh. It was found that pentoxifylline degradation depended on the initial concentration of the compound, being faster for lower concentrations. Faster decomposition of pentoxifylline could be also achieved by increasing the pulse repetition rate, and implicitly the power introduced in the discharge, however, this had little effect on the decomposition yield. The degradation products were investigated by liquid chromatography-mass spectrometry technique (LC-MS). The evolution of the intermediates during plasma treatment showed a fast increase in the first 30min, followed by a slower decrease, so that these products are almost completely removed after 120min treatment time.

Recent developments in photocatalytic water treatment technology: a review

In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align with the "zero" waste scheme in the water/wastewater industry. The ability of this advanced oxidation technology has been widely demonstrated to remove persistent organic compounds and microorganisms in water. At present, the main technical barriers that impede its commercialisation remained on the post-recovery of the catalyst particles after water treatment. This paper reviews the recent R&D progresses of engineered-photocatalysts, photoreactor systems, and the process optimizations and modellings of the photooxidation processes for water treatment. A number of potential and commercial photocatalytic reactor configurations are discussed, in particular the photocatalytic membrane reactors. The effects of key photoreactor operation parameters and water quality on the photo-process performances in terms of the mineralization and disinfection are assessed. For the first time, we describe how to utilize a multi-variables optimization approach to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency. Both photomineralization and photo-disinfection kinetics and their modellings associated with the photocatalytic water treatment process are detailed. A brief discussion on the life cycle assessment for retrofitting the photocatalytic technology as an alternative waste treatment process is presented. This paper will deliver a scientific and technical overview and useful information to scientists and engineers who work in this field.

Fate and removal of estrogens in municipal wastewater

Natural and synthetic estrogens are some of the most potent endocrine disrupting compounds found in municipal wastewater. Much research has been conducted on the source and fate of estrogens in wastewater treatment plants. Sorption and biodegradation are the primary removal mechanisms for estrogens in activated sludge systems, which are widely used biological treatment techniques for municipal wastewater treatment. However, when removal of estrogens in a wastewater treatment plant is incomplete, these compounds enter the environment through wastewater discharges or waste activated sludge at concentrations that can cause endocrine-reproductive system alterations in birds, reptiles and mammals. Therefore, studies have also focused on potential advanced treatment technologies with the aim of removing the compounds before discharging wastewater effluent or disposing waste sludge. This review discusses the physiological effects of these estrogens and the degree of problems estrogens pose as they enter the wastewater stream. Thereafter, this review also analyzes their fate in wastewater treatment systems and how they may reach drinking water sources. Furthermore, this review includes a discussion on various treatment technologies being investigated and future research trends for this pressing environmental issue.

Ozone oxidation of pharmaceuticals, endocrine disruptors and pesticides during drinking water treatment

This study investigates the oxidation of pharmaceuticals, endocrine disrupting compounds and pesticides during ozonation applied in drinking water treatment. In the first step, second-order rate constants for the reactions of selected compounds with molecular ozone (k(O3)) were determined in bench-scale experiments at pH 8.10: caffeine (650+/-22M(-1)s(-1)), progesterone (601+/-9M(-1)s(-1)), medroxyprogesterone (558+/-9M(-1)s(-1)), norethindrone (2215+/-76M(-1)s(-1)) and levonorgestrel (1427+/-62M(-1)s(-1)). Compared to phenolic estrogens (estrone, 17beta-estradiol, estriol and 17alpha-ethinylestradiol), the selected progestogen endocrine disruptors reacted far slower with ozone. In the second part of the study, bench-scale experiments were conducted with surface waters spiked with 16 target compounds to assess their oxidative removal using ozone and determine if bench-scale results would accurately predict full-scale removal data. Overall, the data provided evidence that ozone is effective for removing trace organic contaminants from water with ozone doses typically applied in drinking water treatment. Ozonation removed over 80% of caffeine, pharmaceuticals and endocrine disruptors within the CT value of about 2 mg min L(-1). As expected, pesticides were found to be the most recalcitrant compounds to oxidize. Caffeine can be used as an indicator compound to gauge the efficacy of ozone treatment.

Photodegradation of pharmaceuticals and personal care products during UV and UV/H2O2 treatments

Photodegradation characteristics of pharmaceuticals and personal care products (PPCPs) and the effectiveness of H(2)O(2) addition for PPCPs photodegradation during UV treatment were examined in this study. Average k (1st order rate constant) value for all the PPCPs investigated increased by a factor of 1.3 by H(2)O(2) addition during UV treatment using biologically treated water (TW) spiked with the 30 PPCPs. Therefore, the effectiveness of H(2)O(2) addition for PPCPs removal during UV treatment in real wastewater treatment process was expected. It could be also known that H(2)O(2) addition would improve photodegradation rates of PPCPs highly resistant for UV treatment such as DEET, ethenzamide and theophylline. UV dose required for 90% degradation of each PPCP was calculated from k values obtained in UV and UV/H(2)O(2) treatment experiments using TW spiked with 30 PPCPs. For UV treatment, UV dose required for degrading each PPCP by 90% of initial concentration ranged from 38 mJ cm(-2) to 5644 mJ cm(-2), indicating that most of PPCPs will not be removed sufficiently in UV disinfection process in wastewater treatment plant. For UV/H(2)O(2) treatment, all the PPCPs except seven PPCPs including cyclophosphamide and 2-QCA were degraded by more than 90% by UV irradiation for 30 min (UV dose: 691 mJ cm(-2)), indicating that H(2)O(2) addition during UV treatment will be highly effective for improving the degradation of PPCPs by UV, even though much higher UV dose is still necessary comparing to for UV disinfection.

A comparison of pilot-scale photocatalysis and enhanced coagulation for disinfection byproduct mitigation

This study evaluated pilot-scale photocatalysis and enhanced coagulation for their ability to remove or destroy disinfection byproduct (DBP) precursors, trihalomethane (THM) formation potential (FP), and THMs in two Arizona surface waters. Limited photocatalysis (<5 kWh/m(3)) achieved reductions in most of the DBP precursor parameters (e.g., DOC, UV(254), and bromide) but led to increased chlorine demand and THMFP. In contrast, enhanced coagulation achieved reductions in the DBP precursors and THMFP. Extended photocatalysis (<320 kWh/m(3)) decreased THMFP once the energy consumption exceeded 20 kWh/m(3). The photocatalytic energy requirements for THM destruction were considerably lower (EEO=20-60 kWh/m(3)) than when focusing on precursor destruction and THMFP. However, rechlorination increased the total THM (TTHM) concentration well beyond the raw value, thereby negating the energy benefits of this application. Enhanced coagulation achieved consistent 20-30% removals of preformed THMs. Outstanding issues need to be addressed before TiO(2) photocatalysis is considered feasible for DBP mitigation; traditional strategies, including enhanced coagulation, may be more appropriate.