Estimating population served by sewage treatment works from readily available GIS data

Temporal drivers of tryptophan-like fluorescent dissolved organic matter along a river continuum

Tryptophan-like fluorescence (TLF) is used to indicate anthropogenic inputs of dissolved organic matter (DOM), typically from wastewater, in rivers. We hypothesised that other sources of DOM, such as groundwater and planktonic microbial biomass can also be important drivers of riverine TLF dynamics. We sampled 19 contrasting sites of the River Thames, UK, and its tributaries. Multivariate mixed linear models were developed for each site using 15 months of weekly water quality observations and with predictor variables selected according to the statistical significance of their linear relationship with TLF following a stepwise procedure. The variables considered for inclusion in the models were potassium (wastewater indicator), nitrate (groundwater indicator), chlorophyll-a (phytoplankton biomass), and Total bacterial Cells Counts (TCC) by flow cytometry. The wastewater indicator was included in the model of TLF at 89 % of sites. Groundwater was included in 53 % of models, particularly those with higher baseflow indices (0.50-0.86). At these sites, groundwater acted as a negative control on TLF, diluting other potential sources. Additionally, TCC was included positively in the models of six (32 %) sites. The models on the Thames itself using TCC were more rural sites with lower sewage inputs. Phytoplankton biomass (Chlorophyll-a) was only used in two (11 %) site models, despite the seasonal phytoplankton blooms. It is also notable that, the wastewater indicator did not always have the strongest evidence for inclusion in the models. For example, there was stronger evidence for the inclusion of groundwater and TCC than wastewater in 32 % and 5 % of catchments, respectively. Our study underscores the complex interplay of wastewater, groundwater, and planktonic microbes, driving riverine TLF dynamics, with their influence determined by site characteristics.

Estimating dynamic population served by wastewater treatment plants using location-based services data

Wastewater-based epidemiology is a useful approach to estimate population-level exposure to a wide range of substances (e.g., drugs, chemicals, biological agents) by wastewater analysis. An important uncertainty in population normalized loads generated is related to the size and variability of the actual population served by wastewater treatment plants (WWTPs). Here, we built a population model using location-based services (LBS) data to estimate dynamic consumption of illicit drugs. First, the LBS data from Tencent Location Big Data and resident population were used to train a linear population model for estimating population (r² = 0.92). Then, the spatiotemporal accuracy of the population model was validated. In terms of temporal accuracy, we compared the model-based population with the time-aligned ammonia nitrogen (NH₄-N) population within the WWTP of SEG, showing a mean squared error of < 10%. In terms of spatial accuracy, we estimated the model-based population of 42 WWTPs in Dalian and compared it with the NH₄-N and design population, indicating good consistency overall (5% less than NH₄-N and 4% less than design). Furthermore, methamphetamine consumption and prevalence based on the model were calculated with an average of 111 mg/day/1000 inhabitants and 0.24%, respectively, and dynamically displayed on a visualization system for real-time monitoring. Our study provided a dynamic and accurate population for estimating the population-level use of illicit drugs, much improving the temporal and spatial trend analysis of drug use. Furthermore, accurate information on drug use could be used to assess population health risks in a community.

Estimating the eco-toxicological risk of estrogens in China's rivers using a high-resolution contaminant fate model

The contamination of freshwater systems arises in many river basins due to industrialization and population growth, posing risks to ecosystems and human health. Despite these concerns, the fate and potential impact of many emerging pollutants are currently unknown, especially when the compounds are released into surface waters from populations distributed across large spatial scales. In order to address this shortcoming, a spatially-explicit contaminant fate model was developed as an extension of the global, vector-based river routing model HydroROUT. HydroROUT operates at very high spatial resolution (∼500 m), simulates river and stream chemical transport with in-stream removal, and contains links to a set of lakes and reservoirs, which act as a partial sink during the transport. The chemical fate model was applied to China and includes a consumption and release module based on county-level population demographics, considers point-source contributions from 2547 wastewater treatment plants, and accumulates contributions of rural and urban populations not connected to sewage treatment plants. As a case study, the sources and fates of the estrogens estrone (E₁), 17β-estradiol (E₂), estriol (E₃), as well as the synthetic estrogenic steroid hormone 17α-ethinylestradiol (EE₂) were modelled in Chinese surface water bodies. Preliminary validation of the results showed predictions to be within the ranges of concentrations reported in literature, with exception of EE₂. The total estrogenic mass in the entire river and lake system amounted to 370 tonnes of estrogens, with about 1.3 tonnes per year discharged to the ocean, neighboring countries or to inland sinks. Under a selected baseline scenario, eco-toxicological risk-i.e., contaminant concentrations in excess of the predicted no effect concentration (PNEC)-is found in 23.6% of all analyzed rivers of China with an average flow > 0.1 m³/s. Out of these, about 4% of rivers showed a high level of risk of 10 times or more above PNEC. Medium-to-large rivers are disproportionally affected; for example, 23.6%, 37.3%, 29.0% and 21.6% of river length are at risk in rivers of 1-10, 10-100, 100-1,000, and 1,000-10,000 m³/s of discharge, respectively, whereas no risk was predicted in the largest rivers (i.e., >10,000 m³/s) of China. Wastewater treatment plants process 22.5% of the total hormone load and thus play an important role in water quality control by reducing the risk in substantial portions of the river network, which would otherwise show elevated risk. Releases from untreated population dominate by far the overall contribution to risk.

Nutrient fluxes from domestic wastewater: A national-scale historical perspective for the UK 1800-2010

Nutrient emissions in human waste and wastewater effluent fluxes from domestic sources are quantified for the UK over the period 1800-2010 based on population data from UK Census returns. The most important drivers of change have been the introduction of the water closet (flush toilet) along with population growth, urbanization, connection to sewer, improvements in wastewater treatment and use of phosphorus in detergents. In 1800, the population of the UK was about 12 million and estimated emissions in human waste were 37kt N, 6.2kt P and 205ktorganicC/year. This would have been recycled to land with little or no sewage going directly to rivers or coastal waters. By 1900, population had increased to 35.6 million and some 145kt N were emitted in human waste but, with only the major urban areas connected to sewers, only about 19kt N were discharged in sewage effluent. With the use of phosphorus in detergents, estimated phosphorus emissions peaked at around 63.5ktP/year in the 1980s, with about 28ktP/year being discharged in sewage effluent. By 2010, population had increased to 63 million with estimated emissions of 263kt N, 43.6kt P and 1460ktorganicC/year, and an estimated effluent flux of 104kt N, 14.8kt P and 63kt organic C. Despite improvements in wastewater treatment, current levels of nutrient fluxes in sewage effluent are substantially higher than those in the early 20th century.

Risk assessment of down-the-drain chemicals at large spatial scales: Model development and application to contaminants originating from urban areas in the Saint Lawrence River Basin

Chemicals released into freshwater systems threaten ecological functioning and may put aquatic life and the health of humans at risk. We developed a new contaminant fate model (CFM) that follows simple, well-established methodologies and is unique in its cross-border, seamless hydrological and geospatial framework, including lake routing, a critical component in northern environments. We validated the model using the pharmaceutical Carbamazepine and predicted eco-toxicological risk for 15 pharmaceuticals in the Saint-Lawrence River Basin, Canada. The results indicated negligible to low environmental risk for the majority of tested chemicals, while two pharmaceuticals showed elevated risk in up to 13% of rivers affected by municipal effluents. As an integrated model, our CFM is designed for application at very large scales with the primary goal of detecting high risk zones. In regulatory frameworks, it can help screen existing or new chemicals entering the market regarding their potential impact on human and environmental health. Due to its high geospatial resolution, our CFM can also facilitate the prioritization of actions, such as identifying regions where reducing contamination sources or upgrading treatment plants is most pertinent to achieve targeted pollutant removal or to protect drinking water resources.

Comparing measured and modelled PFOS concentrations in a UK freshwater catchment and estimating emission rates

The lifecycle, sources and fate of perfluorooctane sulfonate (PFOS) continue to generate scientific and political interest, particularly since PFOS was listed by the Stockholm Convention and largely restricted in Europe. It continues to be detected in aquatic environments, with only limited studies into the on-going sources. This paper explores PFOS emissions discharged by the general population into a small catchment comprising two rivers in the UK. A sampling campaign was undertaken to improve our understanding of population-derived PFOS sources from sewage treatment plants (STPs) and in rivers. A corresponding modelling exercise allowed an emission estimate of 13μg/day/per capita to be derived for the Aire and Calder rivers. PFOS emission was linked to STP discharges bylinear regression of measured and modelled concntrations (R(2)=0.49-0.85). The model was able to accurately estimate the spatial trends of PFOS in the rivers, while predicted concentrations were within a factor of three based on per capita emission values taken from the literature. Measured PFOS concentrations in rivers suggested that emissions from STPs are partially dependent on treatment type, where plants with secondary or tertiary treatment such as activated sludge processes emit less PFOS, possibly due to increased partitioning and retention. With refinements based on the type of treatment at each STP, predictions were further improved. The total PFOS mass discharged annually via rivers from the UK has been estimated to be between 215 and 310kg, based on the per capita emission range derived in this study.

Water policy effectiveness: 30 years of change in the hypernutrified Colne estuary, England

Wastewater discharges and agricultural run-off have caused nutrient enrichment leading to eutrophication, in receiving waters worldwide. Analysis of a 30 year data set (1981-2010) for the Colne estuary, a hypernutrified estuary in the south-east of England, revealed significant reductions in nutrient concentrations in freshwater inputs and along the estuarine gradient linked to management actions. DIN concentrations decreased, mainly as a result of reduced ammonia outputs from Colchester STW and reduced nitrate loads from the catchment. Declines in phosphate concentrations occurred due to improved STW processes. There were significant declines in phytoplankton chlorophyll a over the period. Long-term trajectories of nutrient decreases were also strongly influenced by interannual patterns of rainfall and climatic signals (winter NAO). Standardised winter DIN concentrations in the Colne estuary significantly exceed the Water Framework Directive good status target, but the estuary shows no symptoms of eutrophication.

Multi-level approach for the integrated assessment of polar organic micropollutants in an international lake catchment: the example of Lake Constance

Polar organic micropollutants (MPs) can have ecotoxicological effects on aquatic ecosystems and their occurrence in drinking water is a threat to public health. An extensive exposure assessment of MPs in large river and lake catchments is a necessary but challenging proposition for researchers and regulators. To get a complete picture of MP exposure in a large catchment, we employed a novel integrated strategy including MP measurement in the international catchment of Lake Constance and mass-flux modeling. A comprehensive screening of 252 MPs in the lake water by high-resolution mass spectrometry was used to identify the most commonly present MPs for the study site. It was found that the wastewater borne MPs diclofenac, carbamazepine, sulfamethoxazole, acesulfame, sucralose, benzotriazole, and methylbenzotriazole accounted for the most frequent and prominent findings. The concentration pattern of these compounds in the catchment was calculated based on regionalized inputs from wastewater treatment plants (WWTPs) and substance specific elimination rates. In 52, 8, and 3 of the 112 investigated river locations the concentration exceeded the predicted no-effect levels for diclofenac, sulfamethoxazole and carbamazepine, respectively. By coupling the catchment and lake model the effect of future trends in usage as well as possible mitigation options were evaluated for the tributaries and the lake. The upgrade of the major WWTPs in the catchment with a postozonation step would lead to a load reduction between 32% and 52% for all substances except for sucralose (10%).

Real-time estimation of small-area populations with human biomarkers in sewage

A new approach is conceptualized for measuring small-area human populations by using biomarkers in sewage. The basis for the concept (SCIM: Sewage Chemical-Information Mining) is supported by a comprehensive examination and synthesis of data published across several disciplines, including medicine, microbiology, clinical chemistry, and environmental science. Accurate measures of human populations are fundamental to numerous disciplines, including economics, marketing, politics, sociology, public health and safety (e.g., disease management; assessment of natural hazards; disaster prevention and response), quality of life, and the environment. Knowing the size, distribution, and flow of a small-area (local) population facilitates understanding the numerous and complex linkages and interactions between humans and the environment. Examples include material-flow (substance-flow) analysis, determining the magnitude of per capita contribution of pollutant loadings to watersheds, or forecasting future impacts of local populations on the environment or a population's demands on resources. While no definitive approach exists for measuring small-area populations, census-taking is a long-established convention. No approach exists, however, for gauging small-area populations in real-time, as none is able to capture population dynamics, which involve transient changes (e.g., daily influx and efflux) and lasting changes (e.g., births, deaths, change in residence). Accurate measurement of small-area populations in real time has never been possible but is essential for facilitating the design of more sustainable communities. Real-time measurement would provide communities the capability of testing what-if scenarios in design and policy decisions. After evaluation of a range of biomarkers (including the nitrogenous waste product creatinine, which has been long used in clinical chemistry as a parameter to normalize the concentrations of other urinary excretion products to account for urine dilution), the biomarker with the most potential for the SCIM concept for real-time measurement of population was determined to be coprostanol - the major sterol produced by microbial reduction of cholesterol in the colon.

The Ribble/Wyre observatory: major, minor and trace elements in rivers draining from rural headwaters to the heartlands of the NW England historic industrial base

Information on a new observatory study of the water quality of two major river basins in northwestern England (the Ribble and Wyre) is presented. It covers upland, intermediate and lowland environments of contrasting pollution history with sufficient detail to examine transitional gradients. The upland rivers drain acidic soils subjected to long-term acidic deposition. Nonetheless, the acidic runoff from the soils is largely neutralised by high alkalinity groundwaters, although the rivers retain, perhaps as colloids, elements such as Al and Fe that are mobilised under acid conditions. The lowland rivers are contaminated and have variable water quality due to variable urban/industrial point and diffuse inputs reflecting local and regional differences in historic and contemporary sources. For most determinands, pollutant concentrations are not a major cause for concern although phosphate levels remain high. Set against earlier studies for other regions, there may be a general decline in pollutant levels and this is most clearly observed for boron where effluent inputs have declined significantly due to reductions in household products that are flushed down the drain. High concentrations of sodium and chloride occurred briefly after a severe cold spell due to flushing of road salts. A major inventory for water quality within rural, urban, industrial and agricultural typologies is provided within data summary attachments for over 50 water quality determinands. Within the next year, the full dataset will be made available from the CEH website. This, with ongoing monitoring, represents a platform for water quality studies across a wide range of catchment typologies pertinent to environmental management of clean and impacted systems within the UK. The study provides a base of research "from source to sea" including extensions to the estuary and open sea for a semi-confined basin, the Irish Sea, where there are many issues of pollution inputs and contamination.

Plasma vitellogenin in male teleost fish from 43 rivers worldwide is correlated with upstream human population size

It has been previously demonstrated that vitellogenin (VTG)--a precursor egg yolk protein--is produced in male fish exposed to estrogenic compounds in wastewater treatment plant (WWTP) effluent. However, little attention has been given to examine whether any patterns of male VTG production exists across fish species on a global scale. We hypothesized that a composite measure of human population size over river discharge would best explain variations of protein levels in male fish. We compiled VTG data in 13 fish species from 43 rivers receiving municipal WWTP effluent on 3 continents. We found that human population size explained 28% of the variation in male VTG concentrations, whereas population/flow rate failed to significantly correlate with VTG. We suggest this result may be explained by the low solubility of estrogenic compounds, resulting in localized contamination near WWTP outfalls, rather than dilution by river water.

Modelling concentrations of decamethylcyclopentasiloxane in two UK rivers using LF2000-WQX

Current regulatory environmental exposure assessments for decamethylcyclopentasiloxane (D(5)), used in a range of personal care products, are based on a number of erroneous assumptions. Using an estimated D(5) flux to waste water of 11.6 mg cap(-1) d(-1), a 95.2% removal rate in Sewage Treatment Plants (STP) and a dilution factor of 10 results in modelled surface water concentrations that are up to an order of magnitude higher than concentrations observed downstream of STPs in two UK rivers. A GIS-based water quality model (LF2000-WQX) was used to predict concentrations of D(5) in two UK rivers. Assuming the STP removal rate is reasonable, a waste water flux of 2.4 mg cap(-1) d(-1) is needed in order to obtain a reasonable match between predicted and observed in-river concentrations. This flux is consistent with measured effluent concentrations. The results highlight major uncertainties in estimating chemical emission rates for volatile chemicals used in personal care products and suggest that measured concentrations in waste water are needed to refine exposure assessments.

Model-based evaluation of reduction strategies for micropollutants from wastewater treatment plants in complex river networks

A model based on graph theory was developed to efficiently evaluate the impact of the effluent from 742 wastewater treatment plants (WWTPs) on micropollutant loading throughout all river catchments in Switzerland. Model results agree well with measured loads for 12 compounds in river water samples, revealing mean predictive accuracy factors between 0.8 and 3.4. Subsequently, pollutant concentrations were predicted for river sections downstream from 543 WWTPs where hydrological information was available, and compared with recent recommendations for water quality criteria. At base flow conditions, carbamazepine concentrations (parent compound only) are ubiquitously below a water quality criterion of 0.5 microg L(-1). In contrast, the sum of diclofenac and its metabolites is expected to exceed the corresponding water quality criterion of 0.1 microg L(-1) in 224 river sections. If diclofenac cannot be eliminated atthe source, the model suggests a directed upgrade of 173 WWTPs to meet the condition that concentrations are never to exceed this water quality criterion.

A new generic approach for estimating the concentrations of down-the-drain chemicals at catchment and national scale

A new generic approach for estimating chemical concentrations in rivers at catchment and national scales is presented. Domestic chemical loads in waste water are estimated using gridded population data. River flows are estimated by combining predicted runoff with topographically derived flow direction. Regional scale exposure is characterised by two summary statistics: PEC(works), the average concentration immediately downstream of emission points, and, PEC(area), the catchment-average chemical concentration. The method was applied to boron at national (England and Wales) and catchment (Aire-Calder) scales. Predicted concentrations were within 50% of measured mean values in the Aire-Calder catchment and in agreement with results from the GREAT-ER model. The concentration grids generated provide a picture of the spatial distribution of expected chemical concentrations at various scales, and can be used to identify areas of potentially high risk.

An index directly indicates land-based pollutant load contributions of domestic wastewater to the water pollution and its application

As indices directly indicate land-based pollutant load contributions to public water pollution, pollutant load per capita flowing into the water body (PLCwb) for the drainage areas of inner city rivers in Chiba City, Chiba Prefecture, Japan, was analyzed. It was reaffirmed that PLCwb was different by the drainage area. For example, the biochemical oxygen demand (BOD) load per capita flowing into the water body (PLCwb-BOD) was calculated as 0.83 g BOD person(-1) day(-1) for population served with wastewater treatment plant (WWTP). In regards to the three types of on-site domestic wastewater treatment methods in Japan: 0.4-2.1 g BOD person(-1) day(-1) for combined jokaso (CJ), 4.5-21 g BOD person(-1) day(-1) for simple jokaso (SJ) and 4.3-19 g BOD person(-1) day(-1) for night soil treatment (NST). In regards to nutrient parameters of the three on-site treatment methods, population weighted average of PLCwb was [corrected] almost the same, however, relatively small PLCwb was [corrected] observed for CJ and SJ comparing to that for NST expecially in the drainage areas with smaller reaching ratios. [corrected] Environmental accounting housekeeping (EAH) books for domestic wastewater were prepared based on the analysis results as the application of the indices. EAH books are effective tools for water pollution mitigation in public water bodies. The results of the preliminary correlation analysis of the indices showed that high-efficiency treatment methods including WWTP, agriculture village wastewater treatment facility (AVETF) and CJ are effective in reducing pollutant load flowing into the water body, and that PLCwb have second-order equation relationships with population density of the drainage area. Judging from these characteristics and the analytical results of this study, PLCwb may be useful as an index for demonstrating the benefit of wastewater treatment in reduction of water pollution in the water body.