Sewer Exfiltration Research Articles

Novel drainage pipeline breakages detection based on MEMS inertial sensor: From mechanism to application

Urban water environment pollution is a global concern, in developing countries, sewage infiltration resulting from urban drainage pipelines breakage is an essential element in the urban groundwater pollution and the recurrence of black odor water bodies, it is crucial to accurately and efficiently detection and localisation of urban drainage pipelines breakage to protect the urban water resources. In this paper, a device for detecting defects in drainage pipelines was developed and assembled using microelectromechanical systems (MEMS) inertial sensors as the core components, and the improved cumulative sum (CUSUM) model was used for anomalous detection of the pitch angle of the device's movement along the course of the pipeline as a method of detecting pipeline breakage. In the laboratory simulation of drainage pipeline tests, the CUSUM peaks (0.709, 1.102, 3.038, 7.990) for the case of external water infiltration rates into the pipeline at the point of pipe breakage (2.9%, 4.6%, 5.8%, 9.2%), and for the cases of sewer exfiltration rates in the pipeline of 4.2% and 6.4% (0.760, 1.382). CFD simulations of the water flow in the laboratory pipeline show a high degree of overlap between the trend of the water surface near the point of breakage and the anomalous fluctuations in the pitch angle of the device motion in the laboratory tests. Finally, the authors tested the device on municipal drains in the city of A. The results demonstrated the reliability and high accuracy of the device. The device enables to improve the ecological quality of urban water environment by accelerating the rate of defect detection in urban drainage pipelines and reducing the detection expenses.

Proactive exfiltration severity management in sewer networks: A hyperparameter optimization for two-tiered machine learning prediction

Effective management of aging sewer pipelines requires accurate analysis of sewer pipeline exfiltration. Previous research studies have not paid attention to proposing an index to represent the exfiltration severity. To this end, this study introduces a novel Exfiltration Severity Index (ESI) by considering the frequency and severity of defects captured from Closed-Circuit Television (CCTV) reports. To address the need for a proactive tool that automates the exfiltration estimation and reduces dependence on CCTV reports, we leverage Machine Learning (ML) and Deep Learning (DL) models to predict sewer exfiltration occurrence and severity. In this regard, our proposed methodology comprises a series of steps that start by computing the ESI of pipeline segments considering the frequency, type, and severity of defects. After that, physical, environmental, and climatic factors influencing pipeline exfiltration are gathered and aggregated to build predictive models. We compare the performance of six ML models and two DL models, developed in two tiers to predict exfiltration occurrence and severity, respectively. The hyperparameters of each model are optimized using GridSearchCV to enhance prediction accuracy. Among the eight algorithms, the light gradient-boosting machine performs best, with 71% and 85% accuracy in the first and second tiers, respectively. Furthermore, our study investigates the influence of various factors on pipeline exfiltration and reveals that pipe diameter and population have the most significant impact on exfiltration occurrence and severity. Our method provides a valuable tool for managing sewer pipeline exfiltration and can be utilized to prioritize sewer network maintenance and repair efforts.

Exploration of the nitrogen contamination from sewers exfiltration to the unsaturated zone by modeling

Numerous elements, such as the degree of sewer degeneration, hydraulics, and geological conditions, influence the extent to which sewage pollutes the unsaturated zones of urban. The present study discussed the influence of sewer exfiltration on the urban unsaturated zone, using nitrogen from domestic sewage as a representative contaminant in combination with experiments, literature studies, modeling and sensitivity analysis. The study shows that soils with high sand content exhibit high permeability and strong nitrification capacity, and groundwater is more susceptible to contamination with nitrate. In contrast, the nitrogen in the clay texture or wet soils has short migration distances and a weak nitrification capacity. However, under such conditions, the accumulation of nitrogen can last for more than 10 years, and there is a possible threat of groundwater contamination due to the detection difficulty. The presence of sewer exfiltration and the damage degree of a sewer can be determined by the ammonium concentration at 1–2 m near the pipe or nitrate above the water table. The sensitivity analysis revealed that all parameters impact the nitrogen concentration in the unsaturated zone to varying degrees, four of which are the primary parameters: defect area, exfiltration flux, saturated water content and first-order response constant. In addition, changes in environmental conditions significantly influence the boundaries of the pollution plume, especially the horizontal. The research data collected in this paper will not only allow for a rigorous assessment of the study scenarios but will also provide data support for other researchers.

Spatiotemporal analysis of fluorescent dissolved organic matter to identify the impacts of failing sewer infrastructure in urban streams

Failing sewer infrastructure introduces raw wastewater into streams. We used fluorescence excitation-emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) to track hotspots of raw wastewater in low- and medium-order urban streams that do not receive wastewater effluent but are impacted by sanitary sewer overflows, septic systems, and sewer exfiltration. After analyzing 296 surface water samples from 27 sites in two watersheds over a one-year period, we proposed that the (i) area-normalized ratio of soluble microbial product-like to humic acid-like fluorescence (R4/R5 ≥ 0.85) and (ii) ratio of EEM-PARAFAC components with tryptophan-like and fulvic acid-like fluorescence (C4/C3 ≥ 1.45) could distinguish when and where untreated wastewater is introduced to urban streams. The proposed ratios were validated by co-detection of contaminants of emerging concern, such as sucralose, antibiotics, and UV filters, at concentrations as high as 1354, 108, and 212 ng L−1, respectively. Based on the aggregate data, we identified three sites in rural/suburban areas that were impacted by septic systems and ten sites in urban sections affected by sanitary sewer overflows and/or sewer exfiltration. Moreover, the ratiometric C4/C3 and R4/R5 parameters were immune to dilution effects caused by rain events. Impacts on upstream sites were mostly identified in spring and early summer, but urban hotspots occurred in almost every month. These findings confirmed the potential for EEM-PARAFAC-based wastewater indicators as a quick, easy, cost-effective, and scalable technique to screen for failing sewer infrastructure in low-order streams.

Chemical and Microbial Markers for Discriminating Sanitary Sewer Contamination in Coastal, Urban Streams

Water quality benchmarks for fecal indicator bacteria (FIB) are often exceeded in many urban streams in southern California. Possible sources of elevated stream FIB concentrations within urban areas include sanitary sewer exfiltration, sanitary sewer overflows (SSOs), illegal discharges, and human or animal fecal material on the ground surface. Teasing apart the different sources remains a challenge, especially when untreated wastewater and runoff from open defecation sites both contain human fecal material. To distinguish the various sources of microbial contamination in an urban stream, temporal trends in biological and chemical markers of anthropogenic contamination were evaluated in the San Diego River and its tributaries during storm events in two consecutive hydrologic years. Temporal trends in FIB, HF183, pepper mild mottle virus (PMMoV), caffeine, sucralose, chloride, bromide, specific ultraviolet absorbance, and fluorescence index indicated that untreated wastewater flushed from the vadose zone was the main source of microbial pollution to the San Diego River, while open defecation near homeless encampments in the river margins was not a major source. We demonstrated that the combined use of caffeine/sucralose ratios and HF183 and PMMoV holds promise for identifying sewage inputs to surface waters. These findings highlight the need for maintenance and repair of aging sewer infrastructure.

Effects of inflow, infiltration, and exfiltration on water footprint increase of a sewer system: A case study of Tehran

• Total water footprint of inflow, infiltration, and exfiltration is calculated. • Inflow and infiltration are major sources of blue water footprint in the sewer system. • Most of the water footprint in the system is due to the released untreated wastewater. • Energy consumption has a small proportion of water footprint in the sewer system. • Treating no wastewater can greatly increase the grey water footprint of the system. This study investigates the effect of inflow, infiltration, and exfiltration (I&I&E) on the water footprint increase of a sewer system. After separating the dry and wet-weather periods, inflow and infiltration are considered on a daily basis of the study period. By assuming an exfiltration rate, all components of the wastewater flow entering the sewer network and reaching the wastewater treatment plant (WWTP) are calculated. Inflow and infiltration as two freshwater resources which leave the urban area are the major sources of the blue water footprint. Sewer exfiltration is a source of groundwater pollution and causes grey water footprint. Moreover, I&I&E result in different volumes of treated and untreated wastewater arriving water bodies and more electricity consumption in the WWTP. These items have their own grey and blue water footprints that are considered as indirect effects of I&I&E. The results show an aggregate 158.674 million cubic metre per year of the blue and grey water footprint increase in the Tehran sewerage system due to the I&I&E. More than 85% of this volume consists of the grey water footprint which is mostly because of the untreated wastewater released into the environment.

Persistence of Fecal Indicators and Microbial Source Tracking Markers in Water Flushed from Riverbank Soils

Sewer overflows and exfiltration can potentially contaminate water bodies with pathogens from wastewater. Microbial source tracking (MST) methods such as the detection of the HF183 gene target of Bacteroides have been proposed to monitor human fecal pollution inputs to surface waters; however, the persistence of HF183 and other MST markers in water flushed from soils after contamination events is not well understood. In this study, the persistence and decay of two culture-based fecal indicators, Escherichia coli and enterococci, and two molecular MST markers, HF183 and pepper mild mottle virus (PMMoV), were evaluated in riverbank soils spiked with untreated sewage, which were left idle for 1, 14, 28, 60, and 121 days under dark conditions and then flushed with synthetic rainwater. All four microbial indicators were still detected in flush water 4 months after the soil was contaminated. PMMoV persisted much longer and had a slower decay rate than the other microbial indicators, and E. coli degraded most rapidly. In consecutive flushing experiments with fresh (1 day) sewage-spiked soils, HF183, E. coli, and enterococci were all detected after 20 consecutive flushes with rainwater, but PMMoV was not detected after the fifth flush. Our findings indicate that water (e.g., stormwater interflow) flushing through riverbank soils that have previously been contaminated by sewer overflows or sewer exfiltration can potentially be a source of microbial pollution to surface waters, even for several months after the contamination occurs. Results from this study also demonstrate the benefits of using multiple human-associated fecal indicators to distinguish pollution from different microbial groups in water bodies.Graphical abstract

Locating illicit discharges in storm sewers in urban areas using multi-parameter source tracking: Field validation of a toolbox composite index to prioritize high risk areas

In urban areas served by separate sewerage systems, illicit connections to the storm drain system from residences or commercial establishments are frequent whether these misconnections were made accidentally or deliberately. As a result, untreated and contaminated wastewater enters into storm sewers leading to pollution of receiving waters and non-compliance with water quality standards. Typical procedures for detecting illicit connections to the storm sewer system are time consuming and expensive, especially in a highly urbanised area. In this study, we investigated the use of human wastewater micropollutants WWMPs (caffeine, theophylline, and carbamazepine) and advanced DNA molecular markers (human specific Bacteroides HF183 and mitochondrial DNA) as anthropogenic tracers in order to assist identifying potential cross connections.Water samples from storm outfalls and storm sewer pipes in three urban subcatchments were collected in dry weather from 2013 to 2018. All samples contained various concentrations of these markers especially HF183, caffeine and theophylline, suggesting that the storm pipe system studied is widely contaminated by sanitary sewers. None of the traditional indicators or markers tested is sufficient alone to determine the origin of fecal pollution. In a highly urbanised area, the combination of at least three specific human markers was needed in order to locate the residential section with likely misconnections. The human specific Bacteroides HF183, and theophylline appeared to be the most effective markers (along with E. coli) of crossconnections, whereas carbamazepine can provide an indication of contamination through sanitary sewer exfiltration. A composite sewer cross-connection index was developed, and eight misconnected houses were identified and corrected. The index approach enables the reduction of false positives that could lead to expensive interventions to identify cross-connected households. The results show the multiparameter source tracking toolbox as an effective method to identify sewer cross connections for sustainable storm water management.

Harmonized assessment of nutrient pollution from urban systems including losses from sewer exfiltration: a case study in Germany

A growing literature indicates that untreated wastewater from leaky sewers stands among major sources of pollution to water resources of urban systems. Despite that, the quantification and allocation of sewer exfiltration are often restricted to major pipe areas where inspection data are available. In large-scale urban models, the emission from sewer exfiltration is either neglected (particularly from private sewers) or represented by simplified fixed values, and as such its contribution to the overall urban emission remains questionable. This study proposes an extended model framework which incorporates sewer exfiltration pathway in the catchment model for a better justified pollution control and management of urban systems at a nationwide scale. Nutrient emission from urban areas is quantified by means of the Modelling of Nutrient Emissions in River Systems (MONERIS) model. Exfiltration is estimated for public and private sewers of different age groups in Germany using the verified methods at local to city scales, upscaling techniques, and expert knowledge. Results of this study suggest that the average exfiltration rate is likely to be less than 0.01 L/s per km, corresponding to approximately 1 mm/m/year of wastewater discharge to groundwater. Considering the source and age factors, the highest rate of exfiltration is defined in regions with significant proportions of public sewers older than 40 years. In regions where public sewers are mostly built after 1981, the leakage from private sewers can be up two times higher than such from public sewers. Overall, sewer exfiltration accounts for 9.8% and 17.2% of nitrate and phosphate loads from urban systems emitted to the environment, which increases to 11.2% and 19.5% in the case of no remediation scenario of projected defective sewer increases due to ageing effects. Our results provide a first harmonized quantification of potential leakage losses in urban wastewater systems at the nationwide scale and reveal the importance of rehabilitation planning of ageing sewer pipes in public and private sewer systems. The proposed model framework, which incorporates important factors for urban sewer managers, will allow further targeting the important data need for validating the approach at the regional and local scales in order to support better strategies for the long-term nutrient pollution control of large urban wastewater systems.

Evaluating sewer exfiltration in groundwater by pharmaceutical tracers after the 2016 Kumamoto earthquakes, Japan

In April 2016, a series of earthquakes (M 7.3 on the Japan Meteorological Agency scale) occurred in Kumamoto, Japan causing serious damage to underground sewerage networks. In this study, we evaluated sewer exfiltration in groundwater in the Kumamoto area after the earthquakes by using multiple tracers. We used 14 pharmaceuticals, including carbamazepine and crotamiton, and anthropogenic Gd as tracers, and we measured concentrations of these tracers from September 2016 to November 2017 seasonally. The detection frequency of caffeine, carbamazepine, crotamiton, ibuprofen, and anthropogenic Gd ranged from 29% to 45%, and the concentrations of the pharmaceuticals in the groundwater were lower than those in previous studies. The median of all pharmaceutical concentrations did not decrease, whereas the median of the sum of crotamiton and carbamazepine concentrations, which are quantitative sewage markers, decreased with time. The sewer exfiltration rates in September 2016 estimated using carbamazepine, crotamiton, and anthropogenic Gd were 0.59 ± 0.27%, 0.66 ± 0.47%, and 0.11 ± 0.18% of sewage dry weather flow, respectively, indicating that the effect of the earthquakes on sewer exfiltration was small, probably because the damaged sewers were quickly repaired. This study demonstrated that a multiple-tracer approach is useful for evaluating sewer exfiltration after major earthquakes.

Acesulfame as a suitable sewer tracer on groundwater pollution: A case study before and after the 2016 Mw 7.0 Kumamoto earthquakes

On April 14th and 16th, 2016, two large-scale earthquakes (Mw 6.2 and 7.0) occurred in Kumamoto, Japan. The sewer system was seriously damaged and there were concerns about groundwater pollution by sewer exfiltration. In this study, artificial sweeteners including acesulfame (ACE) in groundwater were analyzed before and after the earthquakes to evaluate sewage pollution and its temporal variation. Before the earthquakes, ACE was detected in 31 of 49 groundwater samples analyzed, indicating that wastewater may have leaked into groundwater. Groundwater was sampled from the same locations 2, 7, 12, and 30 months after the earthquakes. The detection frequency and median concentration of ACE in groundwater increased significantly 7 months after the earthquakes, from several tens to maximumly 189 times greater than the pre-earthquake concentrations. This suggests the earthquakes caused serious damage to sewer pipes and groundwater may be polluted. However, ACE concentrations drastically decreased or remained low 30 months after the earthquakes, probably due to the recovery and restoration work of sewer infrastructure. This study shows that ACE is an excellent tracer for evaluating sewer exfiltration to groundwater. In addition, it is important to obtain data on sewage tracers under normal condition as part of preparations for large-scale earthquakes.

An integrated assessment approach to prevent risk of sewer exfiltration

Regular inspection, assessment, and rehabilitation are necessary to maintain the performance levels of sewer pipelines. The primary objective of this research is to develop a causality-based model by incorporating twenty-two sewer defects, including erosion voids. The Decision Making Trial Evaluation Laboratory (DEMATEL) was used to study the causality relationship between the defects, based on a designed questionnaire, to conclude the influencing and influenced distress. The results suggested that 59% of the sewer structural and operational defects were influencing ones. Besides, the existing state of the sewer pipelines was evaluated on a scale from 1 (Excellent) to 5 (Critical) by integrating the DEMATEL technique with the Quality Function Deployment (QFD) method. The QFD-DEMATEL model was implemented on a case study to compare the model’s classifications of the pipelines’ states with the actual ones. Based on the comparison, the average accuracy and true negative rate (TNR) of the classifications were 74% and 79% respectively. Also, the average invalidity percentage (AIP) was 41.32%, causing the validity percentage to exceed 50%. The integrated approach keeps decision-makers informed about their sewer pipelines to prioritize pipelines rehabilitation. Thus, defective sewers are reduced and so are the exfiltration cases.

Urban Water Resources Toolbox - Integrating Groundwater into Urban Water Management

Holistic but applicable approaches are urgently needed to help plan long-term, cost-effective and sustainable urban water management systems. Groundwater is a central element in the urban water cycle of all cities located on aquifers, yet it remains inadequately integrated into urban water management practices. This book describes holistic approaches for quantification and balancing of urban water and solute fluxes that have been developed by the joint Euro-Australian research project AISUWRS. The new tools comprise a chain of interconnected models that link urban water supply, urban drainage and urban groundwater resources. These include a new sewer exfiltration, model that is based on pipe asset conditions which permits flows to the environment to be estimated. The book provides details on the further processing of this information through the unsaturated zone down to aquifer, where numerical groundwater flow and transport models are applied. Concise documentation is provided on each of the models. The practicability of applying the chain of models was tested by applying it in four case study cities in Australia, Germany, Slovenia and the United Kingdom that have diverse conditions in terms of hydrogeologic setup, climate and data availability. This permitted additional validation by field investigations, including problem-oriented monitoring campaigns aimed at assessing the impact of wastewater practice on groundwater. The book provides guidance and examples of the application of multilevel piezometers, on adapted monitoring strategies, and the use for interpretation purposes of microbiological parameters, pharmaceutical residues and related marker species. The socio-economic analysis in the case study cities sometimes uncovered distinctively different problem perceptions and priorities, both in the groups of experts responsible for the water management and with the remaining stakeholders. The AISUWRS project has developed tools to foster these urgently required deliberation processes. Methodologies for formal sustainability assessment with a triple bottom line background were also elaborated and tested during the case studies. The case studies have shown that the approach is valid and constitutes an important step towards integrated urban water management This title belongs to European Water Research Series ISBN: 9781843391388 (Print) ISBN: 9781780402437 (eBook)

Wastewater compounds in urban shallow groundwater wells correspond to exfiltration probabilities of nearby sewers

Wastewater compounds are frequently detected in urban shallow groundwater. Sources include sewage or reclaimed wastewater, but origins are often unknown. In a prior study, wastewater compounds were quantified in waters sampled from shallow groundwater wells in a small coastal California city. Here, we resampled those wells and expanded sample analyses to include sewage- or reclaimed water-specific indicators, i.e. pharmaceutical and personal care product chemicals or disinfection byproducts. Also, we developed a geographic information system (GIS)-based model of sanitary sewer exfiltration probability—combining a published pipe failure model accounting for sewer pipe size, age, materials of construction, with interpolated depths to groundwater—to determine if sewer system attributes relate to wastewater compounds in urban shallow groundwater. Across the wells, groundwater samples contained varying wastewater compounds, including acesulfame, sucralose, bisphenol A, 4-tert-octylphenol, estrone and perfluorobutanesulfonic acid (PFBS). Fecal indicator bacterial concentrations and toxicological bioactivities were less than known benchmarks. However, the reclaimed water in this study was positive for all bioactivity tested. Excluding one well intruded by seawater, the similarity of groundwater to sewage, based on multiple indicators, increased with increasing sanitary sewer exfiltration probability (modeled from infrastructure within ca. 300 m of each well). In the absence of direct exfiltration or defect measurements, sewer exfiltration probabilities modeled from the collection system's physical data can indicate potential locations where urban shallow groundwater is contaminated by sewage.

A case study of urban water balancing in the partly sewered city of Nablus-East (Palestine) to study wastewater pollution loads and groundwater pollution

Untreated sewage can contribute a significant proportion of urban groundwater recharge, via on-site sanitation facilities and sewer exfiltration. In the West Bank of the Palestinian Territories 94% of sewage is discharged untreated to the ground or surface waters. This has contributed to increasing nitrate concentrations in groundwater, which is the critical water source. In this case study of a drainage catchment from the city of Nablus, a water balance indicates that sewage as a source of groundwater recharge is as much as 50% of total recharge from precipitation, and nitrogen pollutant loads by area are up to 60% as much as those from agriculture. Results suggest that 22% of total wastewater flow directly infiltrates the ground via cesspits and sewer exfiltration.

Evaluating the success of sewer reconstruction by using carbamazepine as anthropogenic marker in groundwater

The antiepileptic drug carbamazepine is a useful anthropogenic marker in groundwater to detect and quantify sewer exfiltration. In 2003 its application on a city wide scale enabled the identification of a trunk sewer in extremely bad structural status with an exfiltration (of wastewater into groundwater) rate in the adjacent area of around 5% compared to an average of approximately 1% in other parts of the city. After a reconstruction of the trunk sewer investigations were carried out again in 2008. Due to the reconstruction a decrease in exfiltration to roughly 3% could be achieved, which equals a reduction of exfiltration by about 45%. Thus carbamazepine emerged as suitable anthropogenic marker to assess sewer exfiltration and to evaluate the success of reconstruction measurements on a regional scale.

Investigation of sewer exfiltration using integral pumping tests and wastewater indicators

Leaky sewers affect urban groundwater by the exfiltration of untreated wastewater. However, the impact of sewer exfiltration on the groundwater is poorly understood. Most studies on sewer exfiltration focus on water exfiltration, but not on the impact on groundwater quality. In this paper we present a new monitoring approach to estimate mass flow rates M ex of different wastewater indicators (WWIs) from leaky sewers by applying integral pumping tests (IPTs). The problem of detecting and assessing heterogeneous concentrations in the vicinity of leaky sewers can be overcome with the IPT approach by the investigation of large groundwater volumes up- and downstream of leaky sewers. The increase in concentrations downstream of a leaky sewer section can be used to calculate M ex with a numerical groundwater model. The new monitoring approach was first applied using four IPT wells in Leipzig (Germany). Over a pumping period of five days we sampled five inorganic WWIs: B , Cl −, K +, NO 3 −, NH 4 + and three xenobiotics: bisphenol-a, caffeine and tonalide. The resulting concentration–time series indicated an influence of wastewater at one IPT well downstream of the leaky sewer. We defined ranges of M ex by implementing the uncertainty of chemical analyses. The results showed a M ex of 0–10.9 g m − 1 d − 1 . The combination of M ex with wastewater concentrations from the target sewer yielded an exfiltration rate Q ex of 28.0–63.9 L m − 1 d − 1 for the conservative ion Cl −. Most non-conservative WWIs showed reduced mass flow rates in the groundwater downstream of the leaky sewer that indicate a mass depletion during their passage from the sewer to the pumping well. Application of the IPT methodology at other field sites is possible. The IPT monitoring approach provides reliable M ex values that can help to assess the impact of leaky sewers on groundwater.

Towards a better understanding of sewer exfiltration

This paper gives a full review of the importance of sewer leakage, which has received increased attention throughout the last decades. Despite the intensive interdisciplinary research that has been invested, its magnitude is still unclear and a comprehensive solution for the assessment of sewer exfiltration does not seem to be at hand. However, given that mechanisms of exfiltration and the factors influencing its extent are similar all over the world, it seems possible to develop a generic leakage approach. Several methods for modelling sewer leakage are reviewed and the available measuring techniques are critically evaluated. Based on this evaluation, we suggest a unifying framework to facilitate focused model building. Specifically, we identify open research questions and propose to (i) standardise measurement results to enable better understanding, (ii) perform more long-term experiments under realistic field conditions, and (iii) assess the uncertainty of measurement and model results so that findings are not over-interpreted.

Sources and transport of selected organic micropollutants in urban groundwater underlying the city of Halle (Saale), Germany

In this study, we used isotopic ( δ 18O, δ 2H, δ 34S-SO 4) and chemical tracers (boron) to assess the sources and transport processes of the micropollutants carbamazepine, galaxolide, and bisphenol A in groundwater underlying the city of Halle (Saale), Germany. Their ubiquitous presence in urban groundwater results from a combination of local river water infiltration, sewer exfiltration, and urban stormwater recharge. Attenuation during transport with infiltrating river water increased from carbamazepine (0–60%) to galaxolide (60–80%) in accordance with their increasing sorption affinity and decreasing recalcitrance against biodegradation. Distinctly higher attenuation during transport was found for carbamazepine (85–100%) and galaxolide (95–100%) if micropollutants originated from sewer exfiltration. Most likely, this is related to higher contents of organic matter and higher transit times of the respective flow paths. Although attenuation undoubtedly also affects the transport of bisphenol A, quantification is limited due to additional contributions from the urban stormwater recharge. As a consequence, micropollutant loads in groundwater indicate that groundwater discharge may dominate the export of bisphenol A from urban areas.

Tracing sources of carbon in urban groundwater using δ13CTDIC ratios

Total dissolved inorganic carbon (TDIC) and its stable isotope ratio δ13CTDIC are used to trace the evolution of the carbon system of groundwater in three UK Permo-Triassic sandstone aquifers. Samples were collected from multilevel piezometers, open boreholes and sewer sampling points in the British Midlands (Nottingham, Birmingham and Doncaster) to evaluate both local and regional variations in δ13CTDIC. δ13C samples of matrix and pore water have also been analysed in each aquifer to further constrain the interpretations. Combining δ13CTDIC ratios with measurements of TDIC and pH clearly distinguishes the principal processes underlying the geochemical evolution of groundwater in Triassic sandstone aquifers, where processes can be both natural (e.g. carbonate dissolution) and anthropogenic (sewer-derived recharge). The paper shows that δ13CTDIC resolves ambiguities that arise from the interpretation of TDIC and pH measurements in isolation. Field measurements demonstrate that, under natural conditions, the carbonate system evolves similarly in each aquifer. An open-system evolution during recharge largely saturates the groundwater with carbonate depending upon its availability in the sandstone matrix. The contribution of sewer exfiltration to urban recharge is readily distinguished by lower pH and higher TDIC values without significant changes in δ13CTDIC.