Christoph Ort

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)).

Comparing illicit drug use in 19 European cities through sewage analysis.

The analysis of sewage for urinary biomarkers of illicit drugs is a promising and complementary approach for estimating the use of these substances in the general population. For the first time, this approach was simultaneously applied in 19 European cities, making it possible to directly compare illicit drug loads in Europe over a 1-week period. An inter-laboratory comparison study was performed to evaluate the analytical performance of the participating laboratories. Raw 24-hour composite sewage samples were collected from 19 European cities during a single week in March 2011 and analyzed for the urinary biomarkers of cocaine, amphetamine, ecstasy, methamphetamine and cannabis using in-house optimized and validated analytical methods. The load of each substance used in each city was back-calculated from the measured concentrations. The data show distinct temporal and spatial patterns in drug use across Europe. Cocaine use was higher in Western and Central Europe and lower in Northern and Eastern Europe. The extrapolated total daily use of cocaine in Europe during the study period was equivalent to 356 kg/day. High per capita ecstasy loads were observed in Dutch cities, as well as in Antwerp and London. In general, cocaine and ecstasy loads were significantly elevated during the weekend compared to weekdays. Per-capita loads of methamphetamine were highest in Helsinki and Turku, Oslo and Budweis, while the per capita loads of cannabis were similar throughout Europe. This study shows that a standardized analysis for illicit drug urinary biomarkers in sewage can be applied to estimate and compare the use of these substances at local and international scales. This approach has the potential to deliver important information on drug markets (supply indicator).

Fate and transformation of silver nanoparticles in urban wastewater systems

Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP. We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (≈ 99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.

Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis

Aims To perform wastewater analyses to assess spatial differences and temporal changes of illicit drug use in a large European population. Design Analyses of raw wastewater over a 1-week period in 2012 and 2013. Setting and Participants Catchment areas of wastewater treatment plants (WWTPs) across Europe, as follows: 2012: 25 WWTPs in 11 countries (23 cities, total population 11.50 million); 2013: 47 WWTPs in 21 countries (42 cities, total population 24.74 million). Measurements Excretion products of five illicit drugs (cocaine, amphetamine, ecstasy, methamphetamine, cannabis) were quantified in wastewater samples using methods based on liquid chromatography coupled to mass spectrometry. Findings Spatial differences were assessed and confirmed to vary greatly across European metropolitan areas. In general, results were in agreement with traditional surveillance data, where available. While temporal changes were substantial in individual cities and years (P ranging from insignificant to <10−3), overall means were relatively stable. The overall mean of methamphetamine was an exception (apparent decline in 2012), as it was influenced mainly by four cities. Conclusions Wastewater analysis performed across Europe provides complementary evidence on illicit drug consumption and generally concurs with traditional surveillance data. Wastewater analysis can measure total illicit drug use more quickly and regularly than is the current norm for national surveys, and creates estimates where such data does not exist.

Evaluation of Uncertainties Associated with the Determination of Community Drug Use through the Measurement of Sewage Drug Biomarkers

The aim of this study was to integrally address the uncertainty associated with all the steps used to estimate community drug consumption through the chemical analysis of sewage biomarkers of illicit drugs. Uncertainty has been evaluated for sampling, chemical analysis, stability of drug biomarkers in sewage, back-calculation of drug use (specific case of cocaine), and estimation of population size in a catchment using data collected from a recent Europe-wide investigation and from the available literature. The quality of sampling protocols and analytical measurements has been evaluated by analyzing standardized questionnaires collected from 19 sewage treatments plants (STPs) and the results of an interlaboratory study (ILS), respectively. Extensive reviews of the available literature have been used to evaluate stability of drug biomarkers in sewage and the uncertainty related to back-calculation of cocaine use. Different methods for estimating population size in a catchment have been compared and the variability among the collected data was very high (7-55%). A reasonable strategy to reduce uncertainty was therefore to choose the most reliable estimation case by case. In the other cases, the highest uncertainties are related to the analysis of sewage drug biomarkers (uncertainty as relative standard deviation; RSD: 6-26% from ILS) and to the back-calculation of cocaine use (uncertainty; RSD: 26%). Uncertainty can be kept below 10% in the remaining steps, if specific requirements outlined in this work are considered. For each step, a best practice protocol has been suggested and discussed to reduce and keep to a minimum the uncertainty of the entire procedure and to improve the reliability of the estimates of drug use.

Refining the estimation of illicit drug consumptions from wastewater analysis: Co-analysis of prescription pharmaceuticals and uncertainty assessment

Wastewater analysis is a promising monitoring tool to estimate illicit drug consumption at the community level. The advantage of this technique over traditional surveys and other surveillance methods has been emphasized in recent studies. However, there are methodological challenges that can affect reliability. The objectives of this study were to systematically reduce and assess uncertainties associated with sampling (through a stringent optimization of the sampling method) and the back calculation of per capita drug consumption (through a refined estimation of the number of people actively contributing to the wastewater in a given period). We applied continuous flow-proportional sampling to ensure the collection of representative raw wastewater samples. Residues of illicit drugs, opioids, prescription pharmaceuticals and one artificial sweetener were analyzed by liquid chromatography coupled with tandem mass spectrometry. A parameter estimating the number of people actively contributing to wastewater over a given period was calculated from the measured loads of prescription pharmaceuticals, their annual consumption and relative excretion data. For the calculation of substance loads in sewage, uncertainties were propagated considering five individual components: sampling, chemical analysis, flow measurements, excretion rates and the number of people contributing to the wastewater. The daily consumption per 1000 inhabitants was estimated to be almost 1000 mg for cannabis and several hundred mg for cocaine, methamphetamine and ecstasy. With the best sampling practice and current chemical analysis, we calculated the remaining uncertainty to be in the range of 20-30% (relative standard deviation, RSD) for the estimation of consumed drug masses in the catchment; RSDs for the per capita consumption were lower (14-24%), as one of the biggest uncertainty components (i.e. error in flow measurements) cancels out in the proposed method for the estimation of the number of people contributing to the daily wastewater volume. In this study, we provide methodological improvements that substantially enhance the reliability of the estimation method--a prerequisite for the application of this technique to meaningfully assess changes in drug consumption and the success of drug intervention strategies in future studies.

Occurrence and removal of N-nitrosamines in wastewater treatment plants.

The presence of nitrosamines in wastewater might pose a risk to water resources even in countries where chlorination or chloramination are hardly used for water disinfection. We studied the variation of concentrations and removal efficiencies of eight N-nitrosamines among 21 full-scale sewage treatment plants (STPs) in Switzerland and temporal variations at one of these plants. N-nitrosodimethylamine (NDMA) was the predominant compound in STP primary effluents with median concentrations in the range of 5-20 ng/L, but peak concentrations up to 1 microg/L. N-nitrosomorpholine (NMOR) was abundant in all plants at concentrations of 5-30 ng/L, other nitrosamines occurred at a lower number of plants at similar levels. From concentrations in urine samples and domestic wastewater we estimated that human excretion accounted for levels of <5 ng/L of NDMA and <1 ng/L of the other nitrosamines in municipal wastewater, additional domestic sources for <5 ng/L of NMOR. Levels above this domestic background are probably caused by industrial or commercial discharges, which results in highly variable concentrations in sewage. Aqueous removal efficiencies in activated sludge treatment were in general above 40% for NMOR and above 60% for the other nitrosamines, but could be lower if concentrations were below 8-15 ng/L in primary effluent. We hypothesize that substrate competition in the cometabolic degradation explains the occurrence of such threshold concentrations. An additional sand filtration step resulted in a further removal of nitrosamines from secondary effluents even at low concentrations. Concentrations released to surface waters were largely below 10 ng/L, suggesting a low impact on Swiss water resources and drinking water generation considering the generally high environmental dilution and possible degradation. However, local impacts in case a larger fraction of wastewater is present cannot be ruled out.

Consumption-based approach for assessing the contribution of hospitals towards the load of pharmaceutical residues in municipal wastewater

Hospitals are considered as major sources of pharmaceutical residues discharged to municipal wastewater, but recent experimental studies showed that the contribution of hospitals to the loads of selected, quantifiable pharmaceuticals in sewage treatment plant (STP) influents was limited. However such conclusions are made based on the experimental analysis of pharmaceuticals in hospital wastewater which is hindered by a number of factors such as access to suitable sampling sites, difficulties in obtaining representative samples and availability of analytical methods. Therefore, this study explores a refined and extended consumption-based approach to predict the contribution of six selected Australian hospitals to the loads of 589 pharmaceuticals in municipal wastewater. In addition, the possibility that hospital-specific substances are present at levels that may pose a risk for human health was evaluated. For 63 to 84% of the pharmaceuticals investigated, the selected hospitals are not a major point source with individual contributions likely to be less than 15% which is in line with previous experimental studies. In contrast, between 10 and 20% of the pharmaceuticals consumed in the selected hospitals are exclusively used in these hospitals. For these hospital-specific substances, 57 distinct pharmaceuticals may cause concerns for human health as concentrations predicted in hospital effluents are less than 100-fold lower than effect thresholds. However, when concentrations were predicted in the influent of the corresponding STP, only 12 compounds (including the antineoplastic vincristine, the antibiotics tazobactam and piperacillin) remain in concentration close to effect thresholds, but further decrease is expected after removal in STP, dilution in the receiving stream and drinking water treatment. The results of this study suggest that risks of human exposure to the pharmaceuticals exclusively administered in the investigated hospitals are limited and decentralised wastewater treatment at these sites would not have a substantial impact on pharmaceutical loads entering STPs, and finally the environment. Overall, our approach demonstrates a unique opportunity to screen for pharmaceuticals used in hospitals and identifying priority pollutants in hospital wastewater explicitly accounting for site-specific conditions. Being based on consumption and loads discharged by hospitals into municipal wastewater, it is not limited by 1) the big effort to obtain representative samples from sewers, 2) the availability of sensitive chemical analysis or 3) a pre-selection of consumption data (e.g. consumption volume).

JEM spotlight: Monitoring the treatment efficiency of a full scale ozonation on a sewage treatment plant with a mode-of-action based test battery.

Tertiary treatment of wastewater with ozone is a promising technique for removing residual micropollutants that remain after secondary biological treatment. We monitored the performance of a full-scale ozonation reactor on a sewage treatment plant in Switzerland with a screening battery of bioassays. Six toxicity endpoints were selected that covered non-specific toxicity, as well as selected receptor-mediated modes of action and reactive toxicity. Non-specific toxicity was assessed with two bioassays, the bioluminescence inhibition of the marine luminescent bacterium Vibrio Fischeri and the growth inhibition of the green algae Pseudokirchneriella subcapitata. Treatment efficiency was around 90% for the secondary treatment, but only 65% and 76% for the ozonation step in the two non-specific endpoints, respectively. This finding is consistent with this type of oxidation reaction because ozone only modifies the organic molecules but does not mineralize them fully leaving residual toxicity of the transformation products. In contrast, the specific receptor-mediated endpoints of inhibition of photosystem II in algae and estrogenicity were largely reduced by ozonation. While compounds inhibiting photosynthesis proved to be rather recalcitrant toward biological treatment with only 47% removal, an additional 86% removal by ozonation yielded an overall treatment efficiency in the entire treatment chain of 89%. The effect on estrogenicity, quantified with the yeast estrogen screen, was even more significant: A treatment efficiency of 95% in the secondary treatment, 86% during ozonation plus a small effect by biological sand filtration yielded an overall treatment efficiency of 99.5%. Insecticides that inhibit acetylcholinesterase were fairly resistant to degradation, but an overall treatment efficiency of 91% was achieved in two steps: 72% in biological treatment and 60% during ozonation. Finally, no significant genotoxicity was observed with the umuC test after ozonation, while the influent showed a genotoxic response when it was enriched by a factor of 15 to 60. Treatment efficiency increased with the ozone dose and remained virtually unchanged over ozone doses above 500 g ozone per kg dissolved organic carbon. The reduction of toxicity can be rationalized by the chemical oxidation processes likely to occur for each group of chemicals that are typical for a given mode of toxic action. For comparison, tertiary treatment with powdered activated carbon was also evaluated, which poses a viable alternative to ozonation with respect to removal of micropollutants.

Estimating daily and diurnal variations of illicit drug use in Hong Kong: a pilot study of using wastewater analysis in an Asian metropolitan city.

The measurement of illicit drug metabolites in raw wastewater is increasingly being adopted as an approach to objectively monitor population-level drug use, and is an effective complement to traditional epidemiological methods. As such, it has been widely applied in western countries. In this study, we utilised this approach to assess drug use patterns over nine days during April 2011 in Hong Kong. Raw wastewater samples were collected from the largest wastewater treatment plant serving a community of approximately 3.5 million people and analysed for excreted drug residues including cocaine, ketamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and key metabolites using liquid chromatography coupled with tandem mass spectrometry. The overall drug use pattern determined by wastewater analysis was consistent with that have seen amongst people coming into contact with services in relation to substance use; among our target drugs, ketamine (estimated consumption: 1400-1600 mg/day/1000 people) was the predominant drug followed by methamphetamine (180-200 mg/day/1000 people), cocaine (160-180 mg/day/1000 people) and MDMA (not detected). The levels of these drugs were relatively steady throughout the monitoring period. Analysing samples at higher temporal resolution provided data on diurnal variations of drug residue loads. Elevated ratios of cocaine to benzoylecgonine were identified unexpectedly in three samples during the evening and night, providing evidence for potential dumping events of cocaine. This study provides the first application of wastewater analysis to quantitatively evaluate daily drug use in an Asian metropolitan community. Our data reinforces the benefit of wastewater monitoring to health and law enforcement authorities for strategic planning and evaluation of drug intervention strategies.