Time-proportional Sampling Research Articles

Micropollutant concentration fluctuations in combined sewer overflows require short sampling intervals

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.

Exploring drug consumption patterns across varying levels of remoteness in Australia

Wastewater-based epidemiology (WBE) relies on representative sampling that is typically achieved with autosamplers that collect time, flow, or volume proportional samples. The expense, resources and operational know-how associated with autosampler operation means they are only typically available at major wastewater treatment plants (WWTPs). This results in a lack of data on consumption levels in regional and remote areas, or in countries that lack the financial means. The aim of this study was to estimate and investigate trends in drug consumption across varying levels of remoteness in Australia. Field-calibrated, microporous polyethylene passive samplers were deployed over 2 periods (Aug/Sept 2019 and 2020) at 43 treatment plants covering all five categories of remoteness, as per Australian Bureau of Statistics definitions (Major cities, Inner regional, Outer regional, Remote, and Very remote). The per capita consumption of cocaine, methylamphetamine, nicotine, oxycodone and MDMA were estimated. No spatial trends between remoteness and drug consumption were observed, except for cocaine, where Major cities had a 5-to-10-fold higher consumption compared to the other levels of remoteness in 2019 and 2020, respectively. Outer regional sites had the highest and lowest methylamphetamine consumption. The variance in drug use among sites was much higher in Remote (and Inner/Outer regional) sites when compared with Major cities. A significant and consistent decrease in oxycodone consumption was observed at all sites between 2019 and 2020, possibly related to regulatory changes and the COVID-19 pandemic where elective surgeries were suspended. The majority of sites experienced a decrease in cocaine and methylamphetamine consumption, possibly due to border restrictions or changes in supply and demand dynamics. This was the first extensive passive sampling study to assess drug consumption in urban, regional, and remote locations, demonstrating that passive samplers can facilitate extension of wastewater-based drug monitoring programs to sites where other representative sampling options are very difficult to implement.

Effect of water sampling strategies on the uncertainty of phosphorus load estimation in subsurface drainage discharge.

Accurate phosphorus (P) load estimation in subsurface drainage water is critical to assess the field-scale efficacy of conservation practices. The HydroCycle-PO4 instrument measures real-time total reactive P (TRP) concentration without the need for sample filtration, thereby enabling comparative evaluation of different sampling strategies. The main objective of this study was to evaluate the effects of water sampling strategies on the uncertainty of P load estimation. Hourly TRP concentration and hourly drainage discharge measurements formed the reference P load dataset. Four hypothetical water sampling strategies were evaluated: (a) time-proportional discrete sampling, (b) time-proportional composite sampling, (c) flow-proportional discrete sampling, and (d) flow-proportional composite sampling. All sampling strategies underestimated TRP load compared with the reference dataset. Total reactive P load underestimation changed from 0.2 to 51% as time-proportional discrete sampling intervals increased from 3 h to 14 d. Total reactive P load underestimation changed from 12 to 43% as the time-proportional compositing scenario increased from 1 to 7 d, each with one aliquot per day. In the case of flow-proportional discrete sampling scenario, the lowest (0.6%) and the highest (-5.1%) uncertainties were observed when 1- and 5-mm flow intervals were used. The relative error based on the results provided by the flow-proportional composite sampling ranged from 0.2% when using 1-mm flow interval to -6.7% when using 5-mm flow interval. In conclusion, the flow-proportional sampling strategies provided a more accurate estimate of cumulative P load with fewer number of samples because a greater portion of samples were taken at higher flow rates compared with time-proportional sampling strategies.

Assessing the TSS Removal Efficiency of Decentralized Stormwater Treatment Systems by Long-Term In-Situ Monitoring

Decentralized treatment of stormwater runoff from heavily polluted surface can be a good solution for effective source control. Decentralized stormwater treatment systems (DS) and test procedures to monitor their performance, have been developed in recent years. At present in Germany, only lab-based tests are officially established to determine the removal efficiency of Total Suspended Solids (TSS), and in situ monitoring is still lacking. Furthermore, the fine fraction of TSS with particle sizes less than 63 µm (TSS63) have been established as a new design parameter in Germany, because of their substitute characteristics of adsorbing pollutant substances. For research and evaluation purposes continuous data of urban stormwater runoff quantity and quality at the in- and outflow of two different DS at two different sites were collected. Turbidity is used as a surrogate for TSS. Continuous turbidity data and time proportional sampling served to obtain (i) regression coefficients and (ii) to determine the TSS removal efficiency of DS. For a wide range of events the total removal efficiency of DS1 was 29% for TSS and 19% for TSS63 and for DS2 19% for TSS and 16% for TSS63. An event-based data analysis revealed a high variability of the efficiencies and its uncertainties. Moreover, outwash of still suspended or remobilization of already deposited material was observed at individual events. At both sites TSS63 dominates urban stormwater runoff as indicated by the mean ratios of TSS63 to TSS of 0.78 at the inflows and 0.89 at the outflows of both DS. A significant shift of TSS63 ratio from inflow to outflow demonstrates that TSS63 particles were removed less efficiently than coarser particles by DS1, for DS2 data was too heterogeny. It clarifies that common sedimentation methods can only contribute to a small extent to the reduction of solid emissions if the stormwater runoff contains mainly fine-particle solids. The findings suggest that treatment of urban stormwater runoff with high TSS63 pollution requires additional techniques such as a proper filtering to retain fine particles more effective.

Effect Modeling Quantifies the Difference Between the Toxicity of Average Pesticide Concentrations and Time-Variable Exposures from Water Quality Monitoring.

Synthetic chemicals are frequently detected in water bodies, and their concentrations vary over time. Water monitoring programs typically employ either a sequence of grab samples or continuous sampling, followed by chemical analysis. Continuous time-proportional sampling yields the time-weighted average concentration, which is taken as proxy for the real, time-variable exposure. However, we do not know how much the toxicity of the average concentration differs from the toxicity of the corresponding fluctuating exposure profile. We used toxicokinetic-toxicodynamic models (invertebrates, fish) and population growth models (algae, duckweed) to calculate the margin of safety in moving time windows across measured aquatic concentration time series (7 pesticides) in 5 streams. A longer sampling period (14 d) for time-proportional sampling leads to more deviations from the real chemical stress than shorter sampling durations (3 d). The associated error is a factor of 4 or less in the margin of safety value toward underestimating and an error of factor 9 toward overestimating chemical stress in the most toxic time windows. Under- and overestimations occur with approximate equal frequency and are very small compared with the overall variation, which ranged from 0.027 to 2.4 × 1010 (margin of safety values). We conclude that continuous, time-proportional sampling for a period of 3 and 14 d for acute and chronic assessment, respectively, yields sufficiently accurate average concentrations to assess ecotoxicological effects. Environ Toxicol Chem 2020;39:2158-2168. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Impact of Combined Sewer Systems on the Quality of Urban Streams: Frequency and Duration of Elevated Micropollutant Concentrations

Water quality in urban streams is highly influenced by emissions from WWTP and from sewer systems particularly by overflows from combined systems. During storm events, this causes random fluctuations in discharge and pollutant concentrations over a wide range. The aim of this study is an appraisal of the environmental impact of micropollutant loads emitted from combined sewer systems. For this purpose, high-resolution time series of river concentrations were generated by combining a detailed calibrated model of a sewer system with measured discharge of a small natural river to a virtual urban catchment. This river base flow represents the remains of the natural hydrological system in the urban catchment. River concentrations downstream of the outlets are simulated based on mixing ratios of base flow, WWTP effluent, and CSO discharge. The results show that the standard method of time proportional sampling of rivers does not capture the risk of critical stress on aquatic organisms. The ratio between average and peak concentrations and the duration of elevated concentrations strongly depends on the source and the properties of the particular substance. The design of sampling campaigns and evaluation of data should consider these characteristics and account for their effects.

Calibration and validation of a microporous polyethylene passive sampler for quantitative estimation of illicit drug and pharmaceutical and personal care product (PPCP) concentrations in wastewater influent

Wastewater-based epidemiology (WBE), the per capita normalised measurement of drugs, chemicals or metabolites in wastewater influent, relies on sampling and quantitative analysis to evaluate temporal and spatial trends of chemical consumption. Continuous, high-resolution, flow proportional composite sampling is optimal for accurate representations of chemical mass loads, but is rarely implemented, with conventional autosamplers providing relatively low frequency time or volume proportional samples. However, due to equipment or resource constraints at many wastewater treatment plants (WWTPs), even this may not be feasible. Passive sampling may provide an alternative sampling strategy. To investigate this, samplers comprising hollow, cylindrical Microporous Polyethylene Tubes (MPTs) containing polymeric sorbent phases of Strata-X and Strata-X in agarose were simultaneously deployed in a municipal WWTP influent stream. Samplers were extracted, analysed and evaluated for a range of illicit drugs and pharmaceuticals and personal care products (PPCPs) after 4, 7, 15, 21, and 29 day deployments. The MPT samplers were calibrated against 24-hour time proportional composite grab samples that were collected in parallel. Diffusion through the MPT governed uptake, reducing or eliminating the influence of external flow rates that may fluctuate unpredictably in a WWTP environment. Calibration data for six illicit drugs and fourteen PPCPs, including methamphetamine, benzoylecgonine, MDMA, codeine and carbamazepine, demonstrated linear accumulation in the samplers (R2 ≥ 0.84). Derived sampling rates for these analytes ranged from 0.25 to 17 mL d−1 for ibuprofen and verapamil, respectively. A validation study using this sampling rate data showed the MPT could effectively quantify concentrations (≥0.1 ng mL−1) of a range of amphetamine-type stimulants, opioids and metabolites as well as nicotine, accounting for 95% of the variance in parallel composite grab sample concentrations of these compounds. The MPT sampler shows promise for providing essential monitoring data for WBE, informing future intervention and research strategies.

Occurrence of Micropollutants in Wastewater and Evaluation of Their Removal Efficiency in Treatment Trains: The Influence of the Adopted Sampling Mode

The monitoring of micropollutants in water compartments, in particular pharmaceuticals and personal care products, has become an issue of increasing concern over the last decade. Their occurrence in surface and groundwater, raw wastewater and treated effluents, along with the removal efficiency achieved by different technologies, have been the subjects of many studies published recently. The concentrations of these contaminants may vary widely over a given time period (day, week, month, or year). In this context, this paper investigates the average concentration and removal efficiency obtained by adopting four different sampling modes: grab sampling, 24-h time proportional, flow proportional and volume proportional composite sampling. This analysis is carried out by considering three ideal micropollutants presenting different concentration curves versus time (day). It compares the percentage deviations between the ideal concentration (and removal efficiencies) and the differently measured concentrations (removal efficiencies) and provides hints as to the best sampling mode to adopt when planning a monitoring campaign depending on the substances under study. It concludes that the flow proportional composite sampling mode is, in general, the approach which leads to the most reliable measurement of concentrations and removal efficiencies even though, in specific cases, the other modes can also be correctly adopted.

Not only biocidal products: Washing and cleaning agents and personal care products can act as further sources of biocidal active substances in wastewater

The emission sources of biocidal active substances in households have been under discussion since these substances have been detected frequently in municipal wastewater and receiving surface water bodies. Therefore, the goal of this study was to investigate the products responsible for the emission of these substances to wastewater.We analysed the wastewater of two streets for a set of biocidal active substances. Time-proportional sampling was conducted for one week of each season during one year in each street. The 14 substances analysed with liquid chromatography coupled with tandem mass spectrometry were 1,2-benzisothiazol-3(2H)-one (BIT), C12-benzalkonium chloride, carbendazim, 5-chloro-2-methyl-2H-isothiazol-3-one (CMIT), dichlorooctylisothiazolinone (DCOIT), N,N-diethyl-meta-toluamide (DEET), diuron, icaridine, 2-octyl-2H-isothiazol-3-one (OIT), piperonyl butoxide (PBO), triclosan, tebuconazole, terbutryn and tetramethrin. Using data available from household product inventories of the two streets, we searched the lists of ingredients for the products possibly being responsible for the emissions.Except for four substances, all substances have been detected in at least 10% of the samples. Highest concentrations were measured for C12-benzalkonium chloride with an average concentration in the daily samples of 7.7 μg/L in one of the streets. Next to C12-benzalkonium chloride, BIT, DEET and icaridine were detected in all samples in average concentrations above 1 μg/L in at least one street. The results show that washing and cleaning agents were important sources for preservatives such as BIT and OIT, while triclosan was apparently mainly emitted through personal care products. The mosquito repelling substances DEET and icaridine were found throughout the year, with highest emissions in summer and autumn.In conclusion, the results demonstrate that the sources of biocidal active substances in municipal wastewater are complex and that measures for the prevention of the emission of biocidal active substances into the aquatic environment have to be carried out under different legislations. This has to be taken into account discussing emission reduction at the source.

Proficiency testing of wastewater sampling: What did we learn?

The proficiency testing of wastewater sampling is organized by the Laboratory for Environmental Sciences and Engineering at the National Institute of Chemistry, Slovenia (NIC). Preliminary tests started in 2010 at two candidate sites to choose for a trial the most convenient one. In 2012, we organized the first collaborative field trial on wastewater sampling and such trials continued in 2013 and 2014. Between 16 and 20 sampling teams were selected from those that (1) participate in the national wastewater monitoring program and (2) perform analytical activities in laboratories. The participants used a 6-h time proportional sampling approach. They used sampling equipment with different principles of sample collection which take a series of discrete samples at fixed time intervals. Subsequent analyses involved both field and laboratory measurements. The participants, with only one exception, exhibited required technical skills for measuring field parameters (temperature and pH value). All samples taken were also analyzed at NIC. The variability between reported values of participants in the trials, expressed as CV, was found to be 8.5 %, 11.1 % and 9.5 % for chemical oxygen demand. Of all parameters, the largest variability was found for total organic carbon concentration amounting to 23.7 % and 35.7 %. Particular attention was given to separate the measurement uncertainty contributions arising from sampling and chemical analyses.

Comparison of sampling methodologies for nutrient monitoring in streams: uncertainties, costs and implications for mitigation

Abstract. Eutrophication of aquatic ecosystems caused by excess concentrations of nitrogen and phosphorus may have harmful consequences for biodiversity and poses a health risk to humans via water supplies. Reduction of nitrogen and phosphorus losses to aquatic ecosystems involves implementation of costly measures, and reliable monitoring methods are therefore essential to select appropriate mitigation strategies and to evaluate their effects. Here, we compare the performances and costs of three methodologies for the monitoring of nutrients in rivers: grab sampling; time-proportional sampling; and passive sampling using flow-proportional samplers. Assuming hourly time-proportional sampling to be the best estimate of the "true" nutrient load, our results showed that the risk of obtaining wrong total nutrient load estimates by passive samplers is high despite similar costs as the time-proportional sampling. Our conclusion is that for passive samplers to provide a reliable monitoring alternative, further development is needed. Grab sampling was the cheapest of the three methods and was more precise and accurate than passive sampling. We conclude that although monitoring employing time-proportional sampling is costly, its reliability precludes unnecessarily high implementation expenses.

Evaluation of sampling methods for monitoring effluent phosphorus for on-site wastewater treatment systems

More than 1,600 prefabricated on-site wastewater treatment plants are in operation in the Morsa watershed in Norway. As of 2010 a monitoring program on the performance of these plants is in effect. Sampling methods for wastewater treatment plants is discussed, and different methods are compared. The study includes six different plant models, of which all are prefabricated package plants. The parameters investigated were total phosphorus (Tot-P), orthophosphate (PO(4)-P) and suspended solids (SS). Diurnal curves showed no apparent repetitive variation over 24 h intervals, indicating good equalization and robust design to compensate for highly variable loadings. A comparison of grab samples and time proportional composite samples showed almost identical average values, and a paired two-tailed Student's t-test indicates no statistically significant difference between the sampling methods. The results indicate that equivalent results should be expected irrespective of sampling method, and, as composite sampling is attributed to much higher costs, it is recommended that grab sampling should be used when a large number of plants are evaluated.

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 hospital's 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.

Characterization and anaerobic biodegradability of grey water

Grey water consists of the discharges from kitchen sinks, showers, baths, washing machines and hand basins. Thorough characterization of 192 time proportional samples of grey water from 32 houses was conducted over a period of 14 months. COD concentrations were 724 ± 150 mg L − 1 , of which 34% was present as suspended COD, 25% as colloidal COD and 38% as soluble COD. The maximum anaerobic biodegradability of grey water of 70 ± 5% indicates the possibility of recovering the COD as methane. However, the low hydrolysis constant makes the application of anaerobic treatment unsuitable. Surfactants accounted for 15% of the total COD. The concentrations of anionic, cationic and noninonic surfactants were 41.1 ± 12.1 mg L − 1 , 1.7 ± 0.8 mg L − 1 and 11.3 ± 3.9 mg L − 1 , respectively. Of the trace elements which were measured were present below limits suggested for irrigation. Only boron (0.53 ± 0.19 mg L − 1 ) in a few measurements exceeded the 0.75 mg L − 1 limit established for long term irrigation.

50 Years of Environmental Monitoring at Henkel

Abstract The gradually increasing detergents consumption in Germany since 1950 resulted in higher emissions of their ingredients to the environment. The first generation of mineral oil-based surfactants, tetrapropylene benzene sulfonate (TPS), exhibited poor biodegradability and caused public environmental concerns. These prompted Henkel in 1958 to start a systematic measurement of some main detergent constituents in the river Rhine in Germany. Since then, a number of monitoring activities regarding the determination of detergent ingredients concentrations and freights in rivers and waste water treatment plants (WWTP) followed. This paper summarizes 50 years experience at Henkel in monitoring of detergent ingredients in the aquatic environment. The long-term monitoring results on the river Rhine provides an impressive record of the development of the environmental burden by surfactant emissions and of the gradual improvement of river water quality over time. The reasons for the changes are discussed. Further monitoring activities on WWTPs have shown for the first time, that domestic wastewater treatment plants (DWTP) are similarly suitable for the removal of surfactants like municipal ones. The good removal of prominent organic detergent ingredients was shown by several time-proportional sampling campaigns in municipal WWTPs. Finally the positive impact of the modernisation of a municipal WWTP on the chemical and biological water quality on a small river creek is reported over the time period of 7 years. All of the reported studies indicate a low environmental burden due to the use of detergents ingredients today. The learnings from the different activities in environmental monitoring by Henkel have contributed to a solid understanding of the fate of detergent ingredients in the environment. This in turn was the prerequisite for development of reliable exposure prediction models. Today, Henkel employs both, environmental monitoring and modeling instruments, for assessing the environmental exposure of chemicals.

Comparison of Atrazine Losses in Three Small Headwater Catchments

Understanding the processes causing herbicide transport to surface waters is crucial to determine mitigation options to reduce these losses. To this end, we investigated the atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) transport in three agricultural catchments (1.1-2.1 km2) in the watershed of Lake "Greifensee" (Switzerland). In 1999, atrazine application data were recorded for all three catchments. Time proportional samples were taken at a high temporal resolution at the catchment outlets. Extremely wet conditions caused large relative losses from the catchments, ranging between 0.6 and 3.5% of the amount applied. Most of the atrazine load was due to event-driven diffuse losses from the fields. Farmyard runoff contributed less but caused the highest concentrations (up to 31 microg L(-1)) in the brooks. The maximum concentrations due to diffuse losses varied between 1.2 and 8.2 microg L(-1) among the catchments. Despite different absolute concentration levels, the concentration time-series were very similar. It seems that the travel-times within the catchments were mainly controlled by the rainfall pattern with little influence of the catchment properties. These properties, however, caused the relative losses to vary by a factor of 6 between the catchments. This variability could be partly explained by differences in the connectivity of the fields to the brooks and by their hydrological soil properties. A comparison of the losses from the three catchments with those from the entire watershed of Lake Greifensee demonstrated that they were representative for the larger area. Hence, the study results provide a good data set to evaluate distributed models predicting herbicide losses.

Organics in wheat and rye straw pulp bleaching and combined mill effluents (II) ecotoxicological screening

Potential environmental effects of the discharge of industrial wastewater from manufacturing of bleached straw pulp have been studied. Bleached neutral sulphite straw pulping results in discharges of both black cooking and spent bleaching liquors. Time proportional samples were taken from the combined bleaching effluent and the combined mill effluent, (i) Mutagenic activity of the two samples in an Ames’ test, and (ii) acute toxicity of the combined mill effluent sample towards the photosynthetic activity of natural marine phytoplankton from the receiving waters were determined. Also, acute toxicity was determined of the slowly biodegradable or persistent organics remaining after aerobic stabilization of the sample towards (ii) photosynthetic activity of natural phytoplankton, (iii) mussels (Mytilus edulis), (iv) eels (Anguilla anguilla) and, (v) crustacean (Nitocra spinipes); and furthermore, (vi) reproduction test of the crustacean and (vii) growth inhibition test of the marine diatom (Phaeodactylum tricornutum) were performed. Mutagenicity emission factors (MEF's) and toxicity emission factors (TEF's) were calculated to classify the effluents. Combined mill effluent sample showed a mutagenic activity per t90 of one fourth the activity of a kraft pulp bleaching effluent, and the inhibition of the photosynthesis of natural phytoplankton was significant up to 2600 times dilution. After aerobic stabilization, inhibition was observed up to 400 times dilution. Other effects of the combined mill effluent sample were only significant below 40 times dilution. The bleaching effluent showed a mutagenic activity per t90 comparable to kraft bleaching effluents. Other effects were only significant below 20 times dilution.

Grab versus composite sampling: A primer for the manager and engineer

Effluent subsamples are usually aggregated into flow or time proportional samples before analysis. Although this provides information on average process conditions, that on process variability is lost by compositing. Fisher's information is defined and used to estimate the loss due to compositing. The results of simulations based on parameters derived from actual waste streams support the fact that random grabs serve as well as composite samples for monitoring purposes. These findings favor changes in regulatory practice to allow compliance to be demonstrated by grab sample averages. Reporting requirements based on moving averages are shown to be inferior to those based on averages taken over nonoverlapping time periods.