Heinz Singer

Elimination of Organic Micropollutants in a Municipal Wastewater Treatment Plant Upgraded with a Full-Scale Post-Ozonation Followed by Sand Filtration

The removal efficiency for 220 micropollutants was studied at the scale of a municipal wastewater treatment plant (WWTP) upgraded with post-ozonation followed by sand filtration. During post-ozonation, compounds with activated aromatic moieties, amine functions, or double bonds such as sulfamethoxazole, diclofenac, or carbamazepine with second-order rate constants for the reaction with ozone >10(4) M(-1) s(-1) at pH 7 (fast-reacting) were eliminated to concentrations below the detection limit for an ozone dose of 0.47 g O3 g(-1) dissolved organic carbon (DOC). Compounds more resistant to oxidation by ozone such as atenolol and benzotriazole were increasingly eliminated with increasing ozone doses, resulting in >85% removal for a medium ozone dose (approximately 0.6 g O3 g(-1) DOC). Only a few micropollutants such as some X-ray contrast media and triazine herbicides with second-order rate constants <10(2) M(-1) s(-1) (slowly reacting) persisted to a large extent. With a medium ozone dose, only 11 micropollutants of 55 detected in the secondary effluent were found at >100 ng L(-1). The combination of reaction kinetics and reactor hydraulics, based on laboratory-and full-scale data, enabled a quantification of the results by model calculations. This conceptual approach allows a direct upscaling from laboratory- to full-scale systems and can be applied to other similar systems. The carcinogenic by-products N-nitrosodimethylamine (NDMA) (< or =14 ng L(-1)) and bromate (<10 microg L(-1)) were produced during ozonation, however their concentrations were below or in the range of the drinking water standards. Furthermore, it could be demonstrated that biological sand filtration is an efficient additional barrier for the elimination of biodegradable compounds formed during ozonation such as NDMA. The energy requirement for the additional post-ozonation step is about 0.035 kWh m(-3), which corresponds to 12% of a typical medium-sized nutrient removal plant (5 g DOC m(-3)).

LC-high resolution MS in environmental analysis: from target screening to the identification of unknowns

AbstractThis article provides an overview of the state-of-the-art and future trends of the application of LC–high resolution mass spectrometry to the environmental analysis of polar micropollutants. Highly resolved and accurate hybrid tandem mass spectrometry such as quadrupole/time-of-flight and linear ion trap/orbitrap technology allows for a more reliable target analysis with reference standards, a screening for suspected analytes without reference standards, and a screening for unknowns. A reliable identification requires both high resolving power and high mass spectral accuracy to increase selectivity against the matrix background and for a correct molecular formula assignment to unknown compounds. For the identification and structure elucidation of unknown compounds within a reasonable time frame and with a reasonable soundness, advanced automated software solutions as well as improved prediction systems for theoretical fragmentation patterns, retention times, and ionization behavior are needed. Figurea Plot of nominal m/z vs. mass defect of all matrix ions observed in two retention time (Rt) windows of a full-scan HRMS chromatogram at a resolution of 60,000 from a background soil extract. b Extracted ion chromatograms of the herbicide linuron spiked into a background soil extract and of a suspected transformation product of lenacil in a soil extract, both showing a different mass defect

Identifying Small Molecules via High Resolution Mass Spectrometry: Communicating Confidence

T increased availability of high resolution mass spectrometry (HR-MS) in chemical analysis has dramatically improved the detection and identification of compounds in environmental (and other) samples. This has opened up new research opportunities in environmental sciences, demonstrated by over 200 research papers per year, increasing strongly (source: SCOPUS keywords “high resolution mass spectromet”, subject “envi”). The elucidation of small molecules such as emerging pollutants and their transformation products using HR-MSbased suspect and nontarget analysis is gaining in relevance, also in other fields (e.g., metabolomics, drug discovery, forensics). However, confidence in these HR-MS-based identifications varies between studies and substances, since it is not always possible or even meaningful to synthesize each substance or confirm them via complementary methods (e.g., nuclear magnetic resonance). These varying levels of confidence are very difficult to communicate to readers concisely and accurately. In Figure 1 we propose a level system, which arose from intense discussions within our department, to ease the communication of identification confidence and form the basis of further discussions on this topic. This level system is not intended to replace guidance documents (e.g., EU Guideline 2002/657/EG), but specifically covers the new possibilities in HR-MS-based analysis. Our discussion started with the levels published by the Metabolomics Standards Initiative (MSI), as we experienced many cases that fitted “in between” their proposed levels. While Jeon et al. first refined these levels, these were tailored to the specific investigation. The levels in Figure 1 reconcile differences in the two proposals, contain additional levels pertinent to screening methods and are clarified in the text below.

Hospital wastewater treatment by membrane bioreactor: performance and efficiency for organic micropollutant elimination.

A pilot-scale membrane bioreactor (MBR) was installed and operated for one year at a Swiss hospital. It was fed an influent directly from the hospitals sanitary collection system. To study the efficiency of micropollutant elimination in raw hospital wastewater that comprises a complex matrix with micropollutant concentrations ranging from low ng/L to low mg/L, an automated online SPE-HPLC-MS/MS analytical method was developed. Among the 68 target analytes were the following: 56 pharmaceuticals (antibiotics, antimycotics, antivirals, iodinated X-ray contrast media, antiinflamatory, cytostatics, diuretics, beta blockers, anesthetics, analgesics, antiepileptics, antidepressants, and others), 10 metabolites, and 2 corrosion inhibitors. The MBR influent contained the majority of those target analytes. The micropollutant elimination efficiency was assessed through continuous flow-proportional sampling of the MBR influent and continuous time-proportional sampling of the MBR effluent. An overall load elimination of all pharmaceuticals and metabolites in the MBR was 22%, as over 80% of the load was due to persistent iodinated contrast media. No inhibition by antibacterial agents or disinfectants from the hospital was observed in the MBR. The hospital wastewater was found to be a dynamic system in which conjugates of pharmaceuticals deconjugate and biological transformation products are formed, which in some cases are pharmaceuticals themselves.

Significance of urban and agricultural land use for biocide and pesticide dynamics in surface waters

Biocides and pesticides are designed to control the occurrence of unwanted organisms. From their point of application, these substances can be mobilized and transported to surface waters posing a threat to the aquatic environment. Historically, agricultural pesticides have received substantially more attention than biocidal compounds from urban use, despite being used in similar quantities. This study aims at improving our understanding of the influence of mixed urban and agricultural land use on the overall concentration dynamics of biocides and pesticides during rain events throughout the year. A comprehensive field study was conducted in a catchment within the Swiss plateau (25 km(2)). Four surface water sampling sites represented varying combinations of urban and agricultural sources. Additionally, the urban drainage system was studied by sampling the only wastewater treatment plant (WWTP) in the catchment, a combined sewer overflow (CSO), and a storm sewer (SS). High temporal resolution sampling was carried out during rain events from March to November 2007. The results, based on more than 600 samples analyzed for 23 substances, revealed distinct and complex concentration patterns for different compounds and sources. Five types of concentration patterns can be distinguished: a) compounds that showed elevated background concentrations throughout the year (e.g. diazinon >50 ng L(-1)), indicating a constant household source; b) compounds that showed elevated concentrations driven by rain events throughout the year (e.g. diuron 100-300 ng L(-1)), indicating a constant urban outdoor source such as facades; c) compounds with seasonal peak concentrations driven by rain events from urban and agricultural areas (e.g. mecoprop 1600 ng L(-1) and atrazine 2500 ng L(-1) respectively); d) compounds that showed unpredictably sharp peaks (e.g. atrazine 10,000 ng L(-1), diazinon 2500 ng L(-1)), which were most probably due to improper handling or even disposal of products; and finally, e) compounds that were used in high amounts but were not detected in surface waters (e.g. isothiazolinones). It can be safely concluded that in catchments of mixed land use, the contributions of biocide and pesticide inputs into surface waters from urban areas are at least as important as those from agricultural areas.

High-Throughput Identification of Microbial Transformation Products of Organic Micropollutants

During wastewater treatment, many organic micropollutants undergo microbially mediated reactions resulting in the formation of transformation products (TPs). Little is known on the reaction pathways that govern these transformations or on the occurrence of microbial TPs in surface waters. Large sets of biotransformation data for organic micropollutants would be useful for assessing the exposure potential of these TPs and for enabling the development of structure-based biotransformation prediction tools. The objective of this work was to develop an efficient procedure to allow for high-throughput elucidation of TP structures for a broad and diverse set of xenobiotics undergoing microbially mediated transformation reactions. Six pharmaceuticals and six pesticides were spiked individually into batch reactors seeded with activated sludge. Samples from the reactors were separated with HPLC and analyzed by linear ion trap-orbitrap mass spectrometry. Candidate TPs were preliminarily identified with an innovative post-acquisition data processing method based on target and non-target screenings of the full-scan MS data. Structures were proposed following interpretation of MS spectra and MS/MS fragments. Previously unreported microbial TPs were identified for the pharmaceuticals bezafibrate, diazepam, levetiracetam, oseltamivir, and valsartan. A variety of previously reported and unreported TPs were identified for the pesticides. The results showed that the complementary use of the target and non-target screening methods allowed for a more comprehensive interpretation of the TPs generated than either would have provided individually.

Determination of biocides and pesticides by on-line solid phase extraction coupled with mass spectrometry and their behaviour in wastewater and surface water.

This study focused on the input of hydrophilic biocides into the aquatic environment and on the efficiency of their removal in conventional wastewater treatment by a mass flux analysis. A fully automated method consisting of on-line solid phase extraction coupled to LC-ESI-MS/MS was developed and validated for the simultaneous trace determination of different biocidal compounds (1,2-benzisothiazoline-3-one (BIT), 3-Iodo-2-propynylbutyl-carbamate (IPBC), irgarol 1051 and 2-N-octyl-4-isothiazolinone (octhilinone, OIT), carbendazim, diazinon, diuron, isoproturon, mecoprop, terbutryn and terbutylazine) and pharmaceuticals (diclofenac and sulfamethoxazole) in wastewater and surface water. In the tertiary effluent, the highest average concentrations were determined for mecoprop (1010 ng/L) which was at comparable levels as the pharmaceuticals diclofenac (690 ng/L) and sulfamethoxazole (140 ng/L) but 1-2 orders of magnitude higher than the other biocidal compounds. Average eliminations for all compounds were usually below 50%. During rain events, increased residual amounts of biocidal contaminants are discharged to receiving surface waters.

Multiresidue analysis of 88 polar organic micropollutants in ground, surface and wastewater using online mixed-bed multilayer solid-phase extraction coupled to high performance liquid chromatography–tandem mass spectrometry

An automated multiresidue method consisting of an online solid-phase extraction step coupled to a high performance liquid chromatography-tandem mass spectrometer (online-SPE-HPLC-MS/MS method) was developed for the determination of 88 polar organic micropollutants with a broad range of physicochemical properties (logD(OW) (pH 7): -4.2 to 4.2). Based on theoretical considerations, a single mixed-bed multilayer cartridge containing four different extraction materials was composed for the automated enrichment of water samples. This allowed the simultaneous analysis of pesticides, biocides, pharmaceuticals, corrosion inhibitors, many of their transformation products, and the artificial sweetener sucralose in three matrices groundwater, surface water, and wastewater. Limits of quantification (LOQs) were in the environmentally relevant concentration range of 0.1-87 ng/L for groundwater and surface water, and 1.5-206 ng/L for wastewater. The majority of the compounds could be quantified below 10 ng/L in groundwater (82%) and surface water (80%) and below 100 ng/L in wastewater (80%). Relative recoveries were largely between 80 and 120%. Intraday and inter-day precision, expressed as relative standard deviation, were generally better than 10% and 20%, respectively. 50 isotope labeled internal standards were used for quantification and accordingly, relative recoveries as well as intraday and inter-day precision were better for compounds with corresponding internal standard. The applicability of this method was shown during a sampling campaign at a riverbank filtration site for drinking water production with travel times of up to 5 days. 36 substances of all compound classes investigated could be found in concentrations between 0.1 and 600 ng/L. The results revealed the persistence of carbamazepine and sucralose in the groundwater aquifer as well as degradation of the metamizole metabolite 4-acetamidoantipyrine.

How a Complete Pesticide Screening Changes the Assessment of Surface Water Quality

A comprehensive assessment of pesticides in surface waters is challenging due to the large number of potential contaminants. Most scientific studies and routine monitoring programs include only 15-40 pesticides, which leads to error-prone interpretations. In the present study, an extensive analytical screening was carried out using liquid chromatography-high-resolution mass spectrometry, covering 86% of all polar organic pesticides sold in Switzerland and applied to agricultural or urban land (in total 249 compounds), plus 134 transformation products; each of which could be quantified in the low ng/L range. Five medium-sized rivers, containing large areas of diverse crops and urban settlements within the respective catchments, were sampled between March and July 2012. More than 100 parent compounds and 40 transformation products were detected in total, between 30 and 50 parent compounds in each two-week composite sample in concentrations up to 1500 ng/L. The sum of pesticide concentrations was above 1000 ng/L in 78% of samples. The chronic environmental quality standard was exceeded for 19 single substances; using a mixture toxicity approach, exceedances occurred over the whole measurement period in all rivers. With scenario calculations including only 30-40 frequently measured pesticides, the number of detected substances and the mixture toxicity would be underestimated on average by a factor of 2. Thus, selecting a subset of substances to assess the surface water quality may be sufficient, but a comprehensive screening yields substantially more confidence.

Alleviating the reference standard dilemma using a systematic exact mass suspect screening approach with liquid chromatography-high resolution mass spectrometry.

In this study, the efficiency of a suspect screening strategy using liquid chromatography-high resolution mass spectrometry (LC-HRMS) without the prior purchase of reference standards was systematically optimized and evaluated for assessing the exposure of rarely investigated pesticides and their transformation products (TPs) in 76 surface water samples. Water-soluble and readily ionizable (electrospray ionization) substances, 185 in total, were selected from a list of all insecticides and fungicides registered in Switzerland and their major TPs. Initially, a solid phase extraction-LC-HRMS method was established using 45 known, persistent, and high sales volume pesticides. Seventy percent of these target substances had limit of quantitation (LOQ) < 5 ng L(-1). This compound set was then used to develop and optimize a HRMS suspect screening method using only the exact mass as a priori information. Thresholds for blank subtraction, peak area, peak shape, signal-to-noise, and isotopic pattern were applied to automatically filter the initially picked peaks. The success rate was 70%; false negatives mainly resulted from low intense peaks. The optimized approach was applied to the remaining 140 substances. Nineteen additional substances were detected in environmental samples, two TPs for the first time in the environment. Sixteen substances were confirmed with reference standards purchased subsequently, while three TP standards could be obtained from industry or other laboratories. Overall, this screening approach was fast and very successful and can easily be expanded to other micropollutant classes for which reference standards are not readily accessible such as TPs of household chemicals.