Chiral Inversion of 2-Arylpropionic Acid Enantiomers under Anaerobic Conditions.

This work examined the chiral inversion of 2-arylpropionic acids (2-APAs) under anaerobic conditions and the associated microbial community. The anaerobic condition was simulated by two identical anaerobic digesters. Each digester was fed with the substrate containing 11 either pure (R)- or pure (S)-2-APA enantiomers. Chiral inversion was evidenced by the concentration increase of the other enantiomer in the digestate and the changes in the enantiomeric fraction between the two enantiomers. Both digesters showed similar and poor removal of 2-APAs (≤30%, except for naproxen) and diverse chiral inversion behaviors under anaerobic conditions. Four compounds exhibited (S → R) unidirectional inversion [flurbiprofen, ketoprofen, naproxen, and 2-(4-tert-butylphenyl)propionic acid], and the remaining seven compounds showed bidirectional inversion. Several aerobic and facultative anaerobic bacterial genera (Candidatus Microthrix, Rhodococcus, Mycobacterium, Gordonia, and Sphingobium) were identified in both digesters and predicted to harbor the 2-arylpropionyl-CoA epimerase (enzyme involved in chiral inversion) encoding gene. These genera presented at low abundances, <0.5% in the digester dosed with (R)-2-APAs and <0.2% in the digester dosed with (S)-2-APAs. The low abundances of these genera explain the limited extent of chiral inversion observed in this study.

Multivariate experimental design provides insights for the optimisation of rechloramination conditions and water age to control disinfectant decay and disinfection by-product formation in treated drinking water.

The stability of drinking water disinfectant residuals is known to be influenced by multiple variables. To evaluate the effects of various influencing variables on disinfectant stability, a multivariate analysis of chloramine decay and associated disinfection by-products (DBPs) formation was investigated in a series of bench-scale experiments. Of nine water quality variables previously identified, monochloramine dose, pH, and bromide concentration were selected as key water quality variables based on previous investigations and modelling. Co-effects of these key variables on monochloramine decay and formation of 33 halogenated and nitrogen-containing DBPs were investigated using response surface experimental design. Rechloramination conditions, including monochloramine dose, pH and bromide concentration, were optimised via a 3-factorial multivariate analysis of monochloramine stability in post-treatment drinking water. Effects of influencing variables on disinfectant decay and DBP formation were assessed and graphically presented as response surfaces with minimal experiments using Doehlert matrix experimental design compared to other multivariate experimental designs. Concentrations of trihalomethanes (THMs), haloacetic acids (HAAs), and N-nitrosamines were found to increase with water age, whereas opposite phenomenon was observed in the net production of haloacetonitriles (HANs). Increasing pH was found to stabilise monochloramine but it could cause DBP speciation to shift. Furthermore, increasing bromide concentration elevated Br-DBP formation. In bromide-containing water, pH = 7.8-8.0 should be considered as higher pH increases Br-THMs formations and lower pH increases formations of Br-HAAs and Br-HANs. However, water age or pH has insignificant impacts on DBP formation after significant monochloramine decay or at low initial monochloramine dose. These findings indicate that effective combined control measures to maintain monochloramine stability should include the application of high monochloramine dose (>1.5 mg-Cl2.L-1) under conditions of moderate to high pH (pH = 7.8-8.0) and minimal bromide concentration. This study provides relevant insights to water utilities aiming to design effective disinfectant residual management strategies for controlling monochloramine decay and DBP formation.

Occurrence and risk assessment of trace organic contaminants and metals in anaerobically co-digested sludge.

Anaerobic co-digestion of sludge increases biogas production and maintains anaerobic digestion stability. However, it is unclear whether the addition of co-substrates may increase the concentration of trace organic contaminants (TrOCs) and metals, limiting potential resource recovery opportunities when applied to agricultural land. This study explored the occurrence of 20 TrOCs and 18 metals in wastewater sludge anaerobically co-digested with beverage rejects (cola, beer and juice) and food wastes. TrOCs results showed that cola reject caused an accumulation of caffeine in final digestate. Bisphenol A also significantly increased in food waste co-digestion when compared with the mono-digestion (control). No significant difference in TrOCs was observed in the juice reject co-digestion. Analysis of the metal composition revealed a significant increase in Cr and Al in juice reject co-digested sludge. While restaurant food waste increased concentrations of K and Ca, both of which may be beneficial when applied to land. All metals in this study were below the maximum permissible concentrations specified for agricultural land use in Australia. Environmental risk assessment of sludge when used as soil fertiliser, showed that caffeine, diuron, triclocarban, triclosan, Cu and Zn exhibited high risks, with the largest risk quotient (RQ) posed by caffeine. Estrone and naproxen implied medium risks, and ibuprofen implied a high risk except for the co-digestion using cola reject (RQ = 0.9, medium risk). The results emphasise the importance for wastewater utility operators to understand the impact of co-substrate selection on the quality of sludge to minimise environmental risk from the use of biosolids on agricultural land.

Chiral inversion of 2-arylpropionoic acid (2-APA) enantiomers during simulated biological wastewater treatment.

This study examined the removal and enantio­specific fate of a suite of eleven chiral 2-arylpropionic acids (2-APAs) during biological wastewater treatment simulated in a laboratory-scale membrane bioreactor (MBR). Using pure (R)- and (S)- enantiomers in the MBR influent, chiral inversion was determined through the increase in the concentration of the non-dominant enantiomer and changes in the enantiomeric fraction (EF) between the two enantiomers during the treatment process. Effective (>90%) and similar removal rates between (R)- and (S)- enantiomers were confirmed for eight 2-APAs. In this study, 2-APAs exhibited diverse and distinctive chiral inversion behaviours: two 2-APAs showed (R→S) unidirectional inversion, three 2-APAs showed (S→R) unidirectional inversion, and six 2-APAs showed bidirectional inversion. This is the first study to report chiral inversion behaviours of a comprehensive suite of 2-APAs with a variety of functional groups substituted onto the aryl ring. A decrease in effluent EF over time was observed for two 2-APAs. This study shows that chiral inversion of 2-APAs varies significantly from compound to compound, despite the high similarity in their chemical structures.

Surface modification of nanofiltration membranes to improve the removal of organic micropollutants: Linking membrane characteristics to solute transmission.

Surface modification of nanofiltration (NF) membranes has great potential to improve the removal of organic micropollutants (OMs) by NF membranes. This study used polydopamine (PDA) as a model coating to comprehensively link the changes in membrane properties with the changes in transmission of 34 OMs. The membrane characterization demonstrated that a thicker, denser, and more hydrophilic PDA coating can be achieved by increasing the PDA deposition time from 0.5 to 4 hours. Overall, the transmissions of target OMs were reduced by PDA-coated NF membranes compared to unmodified NF membranes. The neutral hydrophobic compounds showed lower transmissions for longer PDA coating (PDA4), while the neutral hydrophilic compounds tended to show lower transmissions for shorter PDA coating (PDA0.5). To explain this, competing effects provided by the PDA coatings are proposed including sealing defects, inducing cake-enhanced concentration polarization in the coating layer for neutral hydrophilic compounds, and weakened hydrophobic adsorption for neutral hydrophobic compounds. For charged compounds, PDA4 with the greatest negative charge among the PDA-coated membranes showed the lowest transmission. Depending on the molecular size and hydrophilicity of the compounds, the transmission of OMs by the PDA4 coating could be reduced by 70% with only a 26.4% decline in water permeance. The correlations and mechanistic insights provided by this work are highly useful for designing membranes with specific surface properties via surface modification to improve the removal of OMs without compromising water production.

A multivariate Bayesian network analysis of water quality factors influencing trihalomethanes formation in drinking water distribution systems.

Controlling disinfection by-products formation while ensuring effective drinking water disinfection is important for protecting public health. However, understanding and predicting disinfection by-product formation under a variety of conditions in drinking water distribution systems remains challenging as disinfection by-product formation is a multifactorial phenomenon. This study aimed to assess the application of Bayesian Network models to predict the concentration of trihalomethanes, the dominant halogenated disinfection by-product class, using various water quality parameters. Naïve Bayesian and semi-naïve Bayesian models were constructed from Sydney and South East Queensland datasets across 15 drinking water distribution systems in Australia. The targeted variable, total trihalomethanes concentration, was discretised into 3 bins (<0.1 mg L-1, 0.1 - 0.2 mg L-1 and >0.2 mg L-1). The Bayesian network structures were built using water quality parameters including concentrations of individual and total trihalomethanes, disinfectant species (free chlorine, monochloramine, dichloramine, total chlorine), nitrogen species (free ammonia, total ammonia, nitrate, nitrite), and other physical/chemical parameters (temperature, pH, dissolved organic carbon, total dissolved solids, conductivity and turbidity). Seven performance parameters, including predictive accuracy and the rates of true and false positive and negative results, were used to assess the accuracy and precision of the Bayesian network models. After evaluating the model performance, the optimum models were selected to be Bayesian network augmented naïve models. These were observed to have the highest predictive accuracies for Sydney (78%) and South East Queensland (94%). Although disinfectant residuals are among the key variables that lead to trihalomethanes formation, potential concentrations of trihalomethanes in distribution systems can be more confidently predicted, in terms of probability associated with a wider range of water quality variables, using Bayesian networks. The modelling procedure developed in this work can now be applied to develop system-specific Bayesian network models for trihalomethanes prediction in other drinking water distribution systems.

Biocatalytic metal-organic framework nanomotors for active water decontamination.

We report a biocatalytic, buoyancy-propelled metal-organic framework (MOF) nanomotor system with boosted removal efficiency for both inorganic heavy metal ions and organic per- and poly-fluoroalkyl substances (PFAS). With the motion-induced convection and increased mass transfer of the target pollutants, the nano system exhibits excellent contaminants remediation capacity in both fresh water and sea water environments.

Removal of organic matter from wastewater reverse osmosis concentrate using granular activated carbon and anion exchange resin adsorbent columns in sequence.

Reverse osmosis concentrate (ROC) generated as a waste stream during reverse osmosis treatment of reclaimed wastewater, presents significant disposal challenges. This is because it causes environmental pollution when it is disposed to lands and natural water bodies. A long-term dynamic adsorption experiment was conducted by passing ROC from a wastewater reclamation plant, firstly through a granular activated carbon (GAC) column, and subsequently through an anion exchange resin (Purolite) column, for the removal of two major ROC pollutants, namely dissolved organic carbon (DOC) and microorganic pollutants (MOP). GAC removed most of the smaller-sized low molecular weight neutrals and building block fractions as well as the hydrophobic fraction of DOC with much less removal by the subsequent Purolite column. In contrast, the humics fraction was less well removed by the GAC column; however, Purolite column removed all that was remaining of this fraction. This study demonstrated that combining adsorbents having different affinities towards a variety of DOC fractions constitute an effective method of taking advantage of their different properties and achieving larger DOC removals. Almost 100% of all 17 MOPs were removed by the GAC column, even after 2880 bed volumes of continuous use. This contrasted with the DOC fractions' removal which was much lower.

Disinfectant residual stability leading to disinfectant decay and by-product formation in drinking water distribution systems: A systematic review.

Secondary disinfectants, such as chlorine and chloramine, have been widely applied to minimise microbial risks in drinking water during distribution. Key challenges have included the maintenance of stable concentrations of disinfectant residuals and the control of disinfection by-products that may form as a consequence of residual decay processes. Many factors may influence disinfectant residual stability and the consequential formation of by-products. Thus predictions of disinfectant stability and by-product formation are multifactorial problems, complete with numerous complications of parameter co-dependence and feedback amplification of some key parameters. The aim of this review was to derive an understanding of how disinfectant residual stability in drinking water distribution systems is impacted by various influencing factors such as water quality and operational parameters. Factors known to influence disinfectant stability and by-product formation were critically reviewed. A systematic review method was applied to identify 1809 journal articles published in the two decades from January 1998 to December 2017. From the initial screening, 161 papers were selected for detailed assessment. Important factors were identified to include temperature, water age, piping material, corrosion products, pH, hydraulic condition, disinfectant residual type and dosage and microbial activity. Microbial activity is a particularly complex parameter on which to base predictions since many factors are known to influence the degree and nature of such activity. These include temperature, water age, piping material, corrosion products, nutrients, natural organic matter, hydraulic condition and disinfectant residual type and dosage. Disinfectant types and dosages were found to be among the most important factors. Many knowledge gaps and research needs still remain, including the need for a more complete understanding of the factors that influence the production of nitrogenous disinfection by-products.

Occurrence and bioconcentration of micropollutants in Silver Perch (Bidyanus bidyanus) in a reclaimed water reservoir.

This study examined the occurrence of 49 micropollutants in reclaimed water and Silver Perch (Bidyanus bidyanus) living in a reclaimed water reservoir. The numbers of micropollutants detected in reclaimed water, Silver Perch liver, and Silver Perch flesh were 20, 23, and 19, respectively. Concentrations of all micropollutants in reclaimed water, except benzotriazole, were well below the Australian Guideline for Recycled Water (AGRW) values for potable purposes. The concentration of benzotriazole in reclaimed water was 675 ±â€¯130 ng/L while the AGRW value for this compound was 7 ng/L. Not all micropollutants detected in the water phase were identified in the Silver Perch flesh and liver tissues. Likewise, not all micropollutants detected in the Silver Perch flesh and liver were identified in the reclaimed water. In general, micropollutant concentrations in the liver were higher than in the flesh. Perfluorooctane sulfonate (PFOS) was detected at a trace level in reclaimed water well below the AGRW guideline value for potable purposes, but showed a high and medium bioconcentration factor in Silver Perch liver and flesh, respectively. In addition, the risk quotient for PFOS was medium and high when considering its concentration in Silver Perch liver and flesh, respectively. Results reported here highlight the need to evaluate multiple parameters for a comprehensive risk assessment. The results also single out PFOS as a notable contaminant of concern for further investigation.

The fate of trace organic contaminants during anaerobic digestion of primary sludge: A pilot scale study.

A pilot-scale study was conducted to investigate the fate of trace organic contaminants (TrOCs) during anaerobic digestion of primary sludge. Of the 44 TrOCs monitored, 24 were detected in all primary sludge samples. Phase distribution of TrOCs was correlated well with their hydrophobicity (>67% mass in the solid phase when LogD > 1.5). The pilot-scale anaerobic digester achieved a steady performance with a specific methane yield of 0.39-0.92 L/gVSremoved and methane composition of 63-65% despite considerable variation in the primary sludge. The fate of TrOCs in the aqueous and solid phases was governed by their physicochemical properties. Biotransformation was significant (>83%) for five TrOCs with logD < 1.5 and electron donating functional groups in molecular structure. The remaining TrOCs with logD < 1.5 were persistent and thus accumulated in the aqueous phase. Most TrOCs with logD > 1.5 were poorly removed under anaerobic conditions. Sorption onto the solid phase appears to impede the biodegradation of these TrOCs.

Histopathology, vitellogenin and chemical body burden in mosquitofish (Gambusia holbrooki) sampled from six river sites receiving a gradient of stressors.

There are over 40,000 chemical compounds registered for use in Australia, and only a handful are monitored in the aquatic receiving environments. Their effects on fish species in Australia are largely unknown. Mosquitofish (Gambusia holbrooki) were sampled from six river sites in Southeast Queensland identified as at risk from a range of pollutants. The sites selected were downstream of a wastewater treatment plant discharge, a landfill, two agricultural areas, and two sites in undeveloped reaches within or downstream of protected lands (national parks). Vitellogenin analysis, histopathology of liver, kidney and gonads, morphology of the gonopodium, and chemical body burden were measured to characterize fish health. Concentrations of trace organic contaminants (TrOCs) in water were analyzed by in vitro bioassays and chemical analysis. Estrogenic, anti-estrogenic, anti-androgenic, progestagenic and anti-progestagenic activities and TrOCs were detected in multiple water samples. Several active pharmaceutical ingredients (APIs), industrial compounds, pesticides and other endocrine active compounds were detected in fish carcasses at all sites, ranging from <4-4700ng/g wet weight, including the two undeveloped sites. While vitellogenin protein was slightly increased in fish from two of the six sites, the presence of micropollutants did not cause overt sexual endocrine disruption in mosquitofish (i.e., no abnormal gonads or gonopodia). A correlation between lipid accumulation in the liver with total body burden warrants further investigation to determine if exposure to low concentrations of TrOCs can affect fish health and increase stress on organs such as the liver and kidneys via other mechanisms, including disruption of non-sexual endocrine axes involved in lipid regulation and metabolism.

Continuous transformation of chiral pharmaceuticals in enzymatic membrane bioreactors for advanced wastewater treatment.

This study demonstrates continuous enantiomeric inversion and further biotransformation of chiral profens including ibuprofen, naproxen and ketoprofen by an enzymatic membrane bioreactor (EMBR) dosed with laccase. The EMBR showed non-enantioselective transformations, with high and consistent transformation of both (R)- and (S)-ibuprofen (93 ± 6%, n = 10), but lower removals of both enantiomers of naproxen (46 ± 16%, n = 10) and ketoprofen (48 ± 17%, n = 10). Enantiomeric analysis revealed a bidirectional but uneven inversion of the profens, for example 14% inversion of (R)- to (S)- compared to 4% from (S)- to (R)-naproxen. With redox-mediator addition, the enzymatic chiral inversion of both (R)- and (S)-profens remained unchanged, although the overall conversion became enantioselective; except for (S)-naproxen, the addition of redox mediator promoted the degradation of (R)-profens only.

Assessing the potential for trace organic contaminants commonly found in Australian rivers to induce vitellogenin in the native rainbowfish (Melanotaenia fluviatilis) and the introduced mosquitofish (Gambusia holbrooki).

In Australia, trace organic contaminants (TrOCs) and endocrine active compounds (EACs) have been detected in rivers impacted by sewage effluent, urban stormwater, agricultural and industrial inputs. It is unclear whether these chemicals are at concentrations that can elicit endocrine disruption in Australian fish species. In this study, native rainbowfish (Melanotaenia fluviatilis) and introduced invasive (but prevalent) mosquitofish (Gambusia holbrooki) were exposed to the individual compounds atrazine, estrone, bisphenol A, propylparaben and pyrimethanil, and mixtures of compounds including hormones and personal care products, industrial compounds, and pesticides at environmentally relevant concentrations. Vitellogenin (Vtg) protein and liver Vtg mRNA induction were used to assess the estrogenic potential of these compounds. Vtg expression was significantly affected in both species exposed to estrone at concentrations that leave little margin for safety (p<0.001). Propylparaben caused a small but statistically significant 3× increase in Vtg protein levels (p=0.035) in rainbowfish but at a concentration 40× higher than that measured in the environment, therefore propylparaben poses a low risk of inducing endocrine disruption in fish. Mixtures of pesticides and a mixture of hormones, pharmaceuticals, industrial compounds and pesticides induced a small but statistically significant increase in plasma Vtg in rainbowfish, but did not affect mosquitofish Vtg protein or mRNA expression. These results suggest that estrogenic activity represents a low risk to fish in most Australian rivers monitored to-date except for some species of fish at the most polluted sites.

Synthetically tuneable biomimetic artificial photosynthetic reaction centres that closely resemble the natural system in purple bacteria.

Porphyrin-based photosynthetic reaction centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale. The established lifetimes are long compared to other processes in organic solar cells or other organic light harvesting systems. These rigid, synthetically flexible molecules provide the closest mimics to the natural PRC so far synthesised and present a future direction for the design of light harvesters with controllable absorption, redox, and kinetics properties.

Concentrations of levonorgestrel and ethinylestradiol in wastewater effluents: Is the progestin also cause for concern?

Synthetic hormones have been widely reported in treated sewage effluents, and consequently receiving aquatic environments. Ethinylestradiol (EE2) is a potent synthetic estrogen commonly used in conjunction with levonorgestrel in oral contraceptive pills. Both EE2 and levonorgestrel have been identified in the aquatic environment, but although there is a significant amount of literature on EE2, there is much less information on levonorgestrel. Using Australian prescription data as well as excretion and predicted wastewater removal rates, the concentrations of EE2 and levonorgestrel in Australian wastewater were calculated at 0.1 ng/L to 0.5 ng/L and 0.2 ng/L to 0.6 ng/L, respectively. Both compounds were analyzed in treated wastewater and surface water grab samples from 3 Southeast Queensland, Australia sites. The predicted no-effect concentration (PNEC) for EE2 of 0.1 ng/L was exceeded at most sites, with EE2 concentrations up to 2 ng/L in treated effluent, albeit quickly diluted to 0.1 ng/L to 0.2 ng/L in the receiving environment. A provisional PNEC for levonorgestrel of 0.1 ng/L derived in the present study was slightly lower than predicted effluent concentrations of 0.2 ng/L to 0.6 ng/L, indicating a potential risk of endocrine-related effects in exposed aquatic species. The detection limit for levonorgestrel in the present study was 2.5 ng/L, and all samples were below detection limit. The present study's results suggest that improvements in analytical capabilities for levonorgestrel are warranted to more accurately quantify the risk of this compound in the receiving environment. Environ Toxicol Chem 2016;35:1378-1385. © 2015 SETAC.

Impact of hazardous events on the removal of nutrients and trace organic contaminants by an anoxic-aerobic membrane bioreactor receiving real wastewater.

The impacts of four simulated hazardous events, namely, aeration failure, power loss, and chemical shocks (ammonia or bleach) on the performance of an anoxic-aerobic membrane bioreactor (MBR) receiving real wastewater were investigated. Hazardous events could alter pH and/or oxidation reduction potential of the mixed liquor and inhibit biomass growth, thus affecting the removal of bulk organics, nutrients and trace organic contaminants (TrOC). Chemical shocks generally exerted greater impact on MBR performance than aeration/power failure events, with ammonia shock exerting the greatest impact. Compared to total organic carbon, nutrient removal was more severely affected. Removal of the hydrophilic TrOCs that are resistant and/or occur at high concentrations in wastewater was notably affected. The MBR effectively reduced estrogenicity and toxicity from wastewater, but chemical shocks could temporarily increase the endocrine activity of the effluent. Depending on the chemical shock-dose and the membrane flux, hazardous events can exacerbate membrane fouling.

Analysis of organophosphate flame retardants and plasticisers in water by isotope dilution gas chromatography-electron ionisation tandem mass spectrometry.

The widespread use of organophosphate flame retardants (PFRs) in commercial products have led to their increased presence in the environment. In this study, a rapid and reliable analytical method was developed for the analysis of five PFRs in water using gas chromatography tandem mass spectrometry (GC-MS/MS) with electron ionisation (EI) and a run time of 13 min. The PFRs investigated were tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate (TDCP) and triphenyl phosphate (TPP). Solid phase extraction (SPE) was undertaken to extract and concentrate target analytes from aqueous matrices. All water samples were extracted from a volume of 500 mL. Isotopically labelled compounds were used to account for analytical variability and for accurate quantification by isotope dilution. Method recoveries for all compounds were above 80% in all tested water samples. Method detection limits for all target analytes ranged from 0.3 to 24 ng/L in ultrapure water, tap water, seawater, surface water, secondary effluent and swimming pool water. Validation of this method confirmed satisfactory method stability with less than 1% coefficients of variation, verifying that this approach produced good reproducibility.

Development of a predictive framework to assess the removal of trace organic chemicals by anaerobic membrane bioreactor.

This study aims to develop a predictive framework to assess the removal and fate of trace organic chemicals (TrOCs) during wastewater treatment by anaerobic membrane bioreactor (AnMBR). The fate of 27 TrOCs in both the liquid and sludge phases during AnMBR treatment was systematically investigated. The results demonstrate a relationship between hydrophobicity and specific molecular features of TrOCs and their removal efficiency. These molecular features include the presence of electron withdrawing groups (EWGs) or donating groups (EDGs), especially those containing nitrogen and sulphur. All seven hydrophobic contaminants were well removed (>70%) by AnMBR treatment. Most hydrophilic TrOCs containing EDGs were also well removed (>70%). In contrast, hydrophilic TrOCs containing EWGs were mostly poorly removed and could accumulate in the sludge phase. The removal of several nitrogen/sulphur bearing TrOCs (e.g., linuron and caffeine) by AnMBR was higher than that by aerobic treatment, possibly due to nitrogen or sulphur reducing bacteria.

Distinct enantiomeric signals of ibuprofen and naproxen in treated wastewater and sewer overflow.

Ibuprofen and naproxen are commonly used members of a class of pharmaceuticals known as 2-arylpropionic acids (2-APAs). Both are chiral chemicals and can exist as either of two (R)- and (S)-enantiomers. Enantioselective analyses of effluents from municipal wastewater treatment plants (WWTPs) and from untreated sewage overflow reveal distinctly different enantiomeric fractions for both pharmaceuticals. The (S)-enantiomers of both were dominant in untreated sewage overflow, but the relative proportions of the (R)-enantiomers were shown to be increased in WWTP effluents. (R)-naproxen was below method detection limits (<1 ng.L(-1)) in sewage overflow, but measurable at higher concentrations in WWTP effluents. Accordingly, enantiomeric fractions (EF) for naproxen were consistently 1.0 in sewage overflow, but ranged from 0.7­0.9 in WWTP effluents. Ibuprofen EF ranged from 0.6­0.8 in sewage overflow and receiving waters, and was 0.5 in two WWTP effluents. Strong evidence is provided to indicate that chiral inversion of (S)-2-APAs to produce (R)-2-APAs may occur during wastewater treatment processes. It is concluded that this characterization of the enantiomeric fractions for ibuprofen and naproxen in particular effluents could facilitate the distinction of treated and untreated sources of pharmaceutical contamination in surface waters.