Separate Sewer Research Articles

A multivariate analysis to explain residue errors in pathogen concentration in wastewater-based epidemiology.

With the beginning of the COVID-19 pandemic, wastewater-based epidemiology (WBE), which according to Larsen et al. (2021), describes the science of linking pathogens and chemicals found in wastewater to population-level health, received an enormous boost worldwide. The basic procedure in WBE is to analyse pathogen concentrations and to relate these measurements to cases from clinical data. This prediction of cases is subject to large errors, due to various factors such as dilution effects, decay or wastewater matrix and inhibitors. In this study we used different models to identify the most important, what we call, wastewater-based epidemiologically relevant parameters (WBERP) to describe these errors. We used linear regression and random forest regression as base models for predicting cases and random forest regression also to analyse the importance of different WBERP. Two catchments, one with a large proportion of combined sewers and one with separate sewers, served as study areas. Our results show that the most important information to be included in any model are the variants of concern (VOCs), a time-variable parameter. The performance for both catchments is improved by ~30% in terms of root mean square error when the VOCs are used as additional information. For practical applications, this is a real drawback as it means that every time a new pathogen variant becomes dominant, we need to know the specific behaviour of the variant in the wastewater and its detection in order to interpret the WBE data correctly. This limits the predictive capabilities of such systems, perhaps not in terms of dynamics but for quantitative statements. The addition of other physicochemical parameters and faecal markers only marginally improved the results. Furthermore, there were differences in the importance of the parameters between the catchments, which limits the generalisability of the conclusions. The results show that more complex wastewater matrices (high proportion of combined sewer system) influence the relationship between pathogen concentration and medical cases more than those of less complex wastewater matrices (separate sewer system).

An Analysis of Rainfall-Derived Infiltration and Inflow Using Water Level-to-Flow Conversion

During rainfall, the rise in groundwater levels, coupled with defects in pipe connections and manhole joints, increases Rainfall-Derived Infiltration and Inflow (RDII) in separate sewer systems. This results in exceedances of planned wastewater volumes and a surge in Separate Sewer Overflows (SSOs). To implement effective measures in the sewer system, it is crucial to monitor the long-term sewage flow under both dry and wet weather conditions to identify RDII sources within the sub-basins. However, because of the cost disparity between installing flow meters and water-level sensors, many municipalities opt for the latter, which is more economical but limits the accuracy of flow measurement. Therefore, this study developed a methodology to estimate flow rates based on measured water-level data, which were validated using adjacent flow measurement data. This water level-to-flow conversion method is expected to be utilized through the installation of water-level sensors owing to their ease of deployment, in addition to budgetary constraints that limit the use of flow meters. This approach enables the application of water-level data for flow estimation.

Construction of a Block-Based Water-Level Monitoring System for RDII Management in a Separate Sewer System

In a separate sewer system designed to independently discharge sewage and stormwater, operational issues such as sewage manhole overflow and overloading of the sewage treatment plant capacity can arise during rainfall events owing to Rainfall-Derived Inflow and Infiltration (RDII) into the sewage pipelines. Although various management strategies for RDII have been studied both domestically and internationally, research on monitoring systems that can precisely identify specific locations where RDII occurs remains insufficient. Therefore, this study analyzed the shortcomings of the existing water-level monitoring system using a case study of City A, which was designed as a separate sewer system. To efficiently manage RDII, we propose a methodology for establishing a block-based water-level monitoring system divided into large, middle, and small blocks, inspired by the block system concept used in water supply networks. By conducting water-level observations at the exits of the middle and small blocks, the specific locations of RDII occurrence can be identified. This approach is expected to facilitate effective and prompt countermeasures by accurately identifying the locations where RDII occurs.

The influence of winter road maintenance on the presence of chlorides in wastewater entering small treatment plants

During the appearance of the first snowfall, there is a revival of discussion on effective methods of protecting road surfaces and sidewalks against icing. In Poland and many other countries, so-called road salt, mainly sodium chloride (NaCl) with additives, is often used to lower the melting point of snow and ice. Using chemicals to protect road surfaces brings many negative side effects reported in the literature. Less frequently published research results indicate, and also alarm, that increased chloride concentrations can appear in wastewater flowing into sanitary (separate) sewers. In the case of small wastewater treatment plants, increased chloride concentrations can have a negative impact primarily on the biological processes of wastewater treatment and, after discharge from the wastewater treatment plant, on the biological life in the waters and the nearest recipient environment of the treated wastewater. The study aimed to determine the concentrations and loads of chlorides in wastewater flowing through the distribution sewer system to 4 small wastewater treatment plants located in Poland, in the Lesser Poland Province, during snowmelt and heavy rainfall in 2019–2023. The study showed a significant increase in concentrations and loads of chlorides in wastewater in February. Unit chloride load in raw sewage during snowmelt varied from 7 to 12 kg∙d–1 per 1 km length of separate sewer network. There was also a repeated, but much lower, increase in chloride con-centrations during summer and autumn precipitation. This is when the leaching of residual salt accumulated around the road surface occurred.

The impact of blue-green infrastructure on trace contaminants: A catchment-wide assessment

Blue-green infrastructure (BGI) reduce urban combined sewer overflows (CSOs) and stormwater outlets (SWOs). However, most conventional BGI are not designed to remove trace organic contaminants. Little is known about the potential of conventional BGI to improve surface water quality by reducing the discharge of trace organic contaminants. We derived wash-off loads for street runoff (6PPD-q, DPG, and HMMM), construction materials (diuron), and wastewater-derived contaminants (diclofenac) based on measurements in the combined sewer system. Subsequently, the performance of four BGI types (bioretention cells, green roofs, porous pavements, and urban wetlands) to reduce the discharge of trace organic contaminants via SWOs and CSOs was quantified with a hydrodynamic SWMM model. Moreover, the catchment-wide impact of SWOs and CSOs on surface water was assessed using risk quotients. We found that the annually discharged load can be considerably reduced by implementing BGI. Among the studied BGI types, bioretention cells are the most effective, with a load reduction of up to 80% to surface waters, mainly due to a larger suitable implementation area and a substantial stormwater infiltration. BGI implemented in the separate sewer system are more effective in reducing stormwater contaminant loads than BGI in the combined system. The assessment of the risk quotient in the surface water showed that the concentrations during SWO and CSO discharges exceed the acute environmental threshold in the surface water for 6PPD-q, DPG, diuron, and diclofenac during several events. The implementation of BGI reduced the hours of exceeded risk quotient in the surface water by 93% for bioretention cells. These findings underscore the need for a catchment-wide assessment of future BGI implementations to quantify, manage, and mitigate the impacts of urban pollution.

MODCEL-MHUS: a comprehensive multilayer hydrodynamic unified simulation for stormwater, sanitary sewer systems, and urban surface.

Numerous countries and regions have embraced implementing a separate sewer system, segregating sanitary and storm sewers into distinct systems. However, the functionality of these systems often needs to improve due to irregular interconnections, resulting in a mixed and malfunctioning system. Sewage collection is crucial for residential sanitation, but untreated collection significantly contributes to environmental degradation. Analyzing the simultaneous operation of both systems becomes vital for effective management. Using mathematical tools for precise and unified diagnosis and prognosis becomes imperative. However, municipal professionals and companies need more tools specifically designed to evaluate these systems in a unified way, mapping all the hydraulic connections observed in practice. This study proposes a unified simulation method for stormwater and sanitary sewer urban systems, addressing real-world scenarios and potential interferences. The primary goal is to develop a simulation method for both systems, considering system interconnections and urban layouts, involving hydrodynamic and water quality simulations. The practical application of this method, the Multilayer Hydrodynamic Simulation Method (MODCEL-MHUS), successfully identifies issues in urban water networks and suggests solutions, making it a valuable tool for urban water management and environmental engineering professionals.

Tunable linear feedback control of urban drainage systems using models defined purely from data.

Real-time and model-predictive control promises to make urban drainage systems (UDS) adaptive, coordinated, and dynamically optimal. Though early implementations are promising, existing control algorithms have drawbacks in computational expense, trust, system-level coordination, and labor cost. Linear feedback control has distinct advantages in computational expense, interpretation, and coordination. However, current methods for building linear feedback controllers require calibrated software models. Here we present an automated method for generating tunable linear feedback controllers that require only system response data. The controller design consists of three main steps: (1) estimating the network connectivity using tools for causal inference, (2) identifying a linear, time-invariant (LTI) dynamical system which approximates the network, and (3) designing and tuning a feedback controller based on the LTI urban drainage system approximation. The flooding safety, erosion prevention, and water treatment performance of the method are evaluated across 190 design storms on a separated sewer model. Strong results suggest that the system knowledge required for generating effective, safe, and tunable controllers for UDS is surprisingly basic. This method allows near-turnkey synthesis of controllers solely from sensor data or reduction of process-based models.

Quantitative fecal source characterization of urban municipal storm sewer system outfall ‘wet’ and ‘dry’ weather discharges

Urban areas are built environments containing substantial amounts of impervious surfaces (e.g., streets, sidewalks, roof tops). These areas often include elaborately engineered drainage networks designed to collect, transport, and discharge untreated stormwater into local surface waters. When left uncontrolled, these discharges may contain unsafe levels of fecal waste from sources such as sanitary sewage and wildlife even under dry weather conditions. This study evaluates paired measurements of host-associated genetic markers (log10 copies per reaction) indicative of human (HF183/BacR287 and HumM2), ruminant (Rum2Bac), canine (DG3), and avian (GFD) fecal sources, 12-hour cumulative precipitation (mm), four catchment land use metrics determined by global information system (GIS) mapping, and Escherichia coli (MPN/100 ml) from seven municipal separate storm sewer system outfall locations situated at the southern portion of the Anacostia River Watershed (District of Columbia, U.S.A.). A total of 231 discharge samples were collected twice per month (n = 24 sampling days) and after rain events (n = 9) over a 13-month period. Approximately 50 % of samples (n = 116) were impaired, exceeding the local E. coli single sample maximum of 2.613 log10 MPN/100 ml. Genetic quality controls indicated the absence of amplification inhibition in 97.8 % of samples, however 14.7 % (n = 34) samples showed bias in DNA recovery. Of eligible samples, quantifiable levels were observed for avian (84.1 %), human (57.4 % for HF183/BacR287 and 40 % for HumM2), canine (46.7 %), and ruminant (15.9 %) host-associated genetic markers. Potential links between paired measurements are explored with a recently developed Bayesian qPCR censored data analysis approach. Findings indicate that human, pet, and urban wildlife all contribute to storm outfall discharge water quality in the District of Columbia, but pollutant source contributions vary based on ‘wet’ and ‘dry’ conditions and catchment land use, demonstrating that genetic-based fecal source identification methods combined with GIS land use mapping can complement routine E. coli monitoring to improve stormwater management in urban areas.

Control of overflows in interception wells based on water quantity and quality in rainwater pipelines for reducing pollution to rivers

ABSTRACT The separate sewer system has led to severe river pollution because of domestic sewage infiltrations and initial rainfall pollution. Therefore, interception wells (IWs) are installed to divert sewage to the wastewater treatment plant but similarly contribute to overflow-induced river pollution on rainy days. The aim of the present study is to propose a control strategy for the regulation of IWs’ overflow based on the online monitoring data, control measures, and software simulation. The results indicate that during light rain, overflow from the IWs is minimal, requiring no control measures. However during heavy rainfall, the overflow of sewage leads to an increase in the river’s concentration of NH3-N from 0.25 to 3.04 mg/L. Finally, Simulations demonstrate a reduction in river NH3-N levels from 2.27 to 1.33 mg/L after implementation. The results indicated the substantial effectiveness of measures in mitigating the pollution originating from IWs’ overflows during rainfall events.

Design Issue Analysis and Operation Effect Evaluation of Large-Scale Storage Tank

In order to address the issue of combined sewer overflows (CSOs), W city has constructed a large-scale storage tank with a volume of 220,000 m3. The storage tank is planned for CSO control in the near term and stormwater runoff pollution control in the long term. However, the actual operation of the storage tank is unsatisfactory. This paper elucidates the design scheme and operation mode of the tank and analyzes the challenges encountered during its design and operation. A storm water management model (SWMM) model was constructed to simulate the effect of the storage tank working in a combined sewer system (CSS), a separate sewer system (SSS) and a decentralized storage situation. This study determined that during the 2022 rainy season, the actual reduction in pollutants by the storage tank was only about 60% of the designed value. As a result, the inadequate treatment capacity of the downstream wastewater treatment plant (WWTP) resulted in the water being retained in the tank for a long time, leading to unsatisfactory operation outcomes. If the storage tank works in SSS and the problem of water retention can be solved, it could reduce the total runoff volume by 30% and the total amount of pollutants by 40% during the same rainy season. At the same time, under the premise of constant total storage volume, if decentralized storage tanks were used to control runoff pollution, the reduction effect can be increased by up to 11.6% compared with that of the centralized storage.

Evaluating Sediment Removal Efficiency of Catch Basin Inserts as a Post-Construction Water Quality Tool on Roadways

Urban areas produce large amounts of stormwater runoff due to vast areas of impervious surfaces. Stormwater inlets, or catch basins, are commonly used for collecting and directing stormwater runoff away from streets and sidewalks. The conveyances used to direct flow to surface waters may be part of a municipal separate storm sewer systems (MS4s). Typically, MS4s redirect runoff without providing a means for removing harmful pollutants. These pollutants are then often discharged directly into local lakes, rivers, and streams, potentially harming native aquatic ecosystems. Post-construction stormwater practices are commonly used to treat runoff from urban areas by reducing the total runoff volume, lowering peak flow rates, and/or removing harmful pollutants from runoff. However, some post construction stormwater practices require large footprints, construction, and maintenance. Catch basin inserts (CBIs) are one type of post-construction best management practice that are installed within existing catch basins and require no additional land use while still providing a means for removing pollutants from stormwater runoff before entering the MS4. However, limited data is available to demonstrate the expected performance of various CBIs to ensure that these practices meet the pollutant removal standards set forth by the US Environmental Protection Agency (USEPA). The objective of this study was to evaluate the sediment removal capabilities of eight different proprietary CBI products for potential use as a post-construction stormwater practice for Department of Transportation projects. Results indicate that only two basket-type CBIs met the 80% sediment retention benchmark established for the study. While not surpassing the benchmark, three bag-type CBIs did achieve more than 70% sediment retention. The remaining three CBIs (one basket-type, one bag-type, and one cartridge type) fell notably short of the performance benchmark.

Assessment of rainfall-derived inflow and infiltration in sewer systems with machine learning approaches.

Rainfall-derived inflow/infiltration (RDII) modelling during heavy rainfall events is essential for sewer flow management. In this study, two machine learning algorithms, random forest (RF) and long short-term memory (LSTM), were developed for sewer flow prediction and RDII estimation based on field monitoring data. The study implemented feature engineering for extracting physically significant features in sewer flow modelling and investigated the importance of the relevant features. The results from two case studies indicated the superior capability of machine learning models in RDII estimation in the combined and separated sewer systems, and LSTM model outperformed the two models. Compared to traditional methods, machine learning models were capable of simulating the temporal variation in RDII processes and improved prediction accuracy for peak flows and RDII volumes in storm events.

High caffeine levels in old sewer system waters reveal domestic wastewater leakage

Infrastructure deterioration is a threat to developed countries, emphasizing the need for effective management techniques. In particular, the leakage of aged domestic sewer pipeline is a major health issue, yet there is a lack of markers to identify domestic leakage. We studied the pollution in urban waters resulting from domestic sewage leakage into storm drainages. We monitored caffeine, fragrance substances and polycyclic aromatic hydrocarbons (PAHs) in the storm discharge points in five urban districts having separate sewer systems aged from 10 to over 40 years. Results show that caffeine and fragrance concentrations tended to increase with sewer system age. For instance, caffeine concentrations in the areas of sewer systems over 40 years old were at least two orders of magnitude higher than in 10-year-old sewer systems, and were as high as 1–10% of domestic sewage, strongly suggesting the leakage of domestic sewer pipelines. PAHs exhibited consistent patterns across the districts. Overall, we observe that sewer leaking processes can be distinguished by analyzing the levels of organic pollutants.

Implications of the transition towards water-wise approaches in urban areas: Elucidating the risk from micropollutants release

The transition towards circular and sustainable urban water systems, embracing a water-wise city approach, results in highly interconnected systems, introducing complexities in managing water quality due to the intricate interplay of pollutant sources, pathways, and receptors in urban environments. This study focuses on assessing the impact of transitioning to a water-wise city approach on water quality. The analysis employs an integrated model-based approach to evaluate the release of micropollutants (PFOA, PFOS, pyrene) in the urban water system, considering potential future changes. We considered Milan (Italy) as a case study and explored sustainable urban water management strategies related to the hydraulic reconnection of canals, including (i) the use of groundwater for energy purposes, (ii) the establishment of a separate stormwater sewer system, and (iii) the indirect reuse of reclaimed water for crop irrigation. Acute and chronic environmental risks were assessed at various locations of the recipients, under different water management and climate change scenarios. Uncertainties on projections related to rainfall and runoff concentrations were also considered. The model accurately predicted average micropollutants concentrations in the current situation. PFOA and PFOS exhibit chronic, but not acute risks in all scenarios; high removal efficiency is required to reduce the risk at acceptable levels. Pyrene poses higher risks for increasing separation fractions of the sewer system, with further increase for climate change, but concentration uncertainty has more influence than precipitation uncertainty on the risk extent. This study provides a water management framework, identifying critical sources and locations under current, future, and climate change scenarios.

Effects of thermal disposal of oil-water residues on operation heating plant boiler

Industrial zones are often the source of specifically polluted waters, depending on type of industry. These waters are usually not in the limits for outtake into public sewers and it is necessary to dispose them externally or build-up technologies for their pre-treatment. The article is about the real case of an industrial. A separate sewage network is built for oily water. Solid impurities are separated from the oily water and oily water is treated by evaporation technology. The evaporator produces two types of products - condensate and concentrate. Condensate is a water with high organic content, and it is necessary to purified it by a chemical treatment plant in next step. Evaporator technology remove from water the most of metal content and significantly decrease organic and water content in concentrate. Concentrate is oily stream with lower water content. Water content in concentrate decreased in next technology steps to ca. 40-50 %. The final product is certificated technological fuel, and its final elimination is in the heating plant fluidized bed boiler. The article is detailed focused on the influence of concentrate combustion. A local temperature increases around 10-15 °C extending across the combustion chamber was confirmed. There was also an increase in HF concentration in flue gas. CO concentrations were higher in the first moments of combustion, but the control system responded by increasing the combustion air supply, and CO concentrations were finally lower at the level of 3 mg·m-3. During combustion, there was no provable increase in concentrations of NOX or other substances, and the co-combustion did not have a significant effect on the operation of the boiler, so this way was evaluated like technically and economically effective.

Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.

Development of an Optimal RTK Calculation Program Using Genetic Algorithm

Rising levels of underground water and inappropriate pipe alignment during rainy weather have led to a rise in rainfall-derived infiltration and inflow (RDII), increasing incidences of separate sewer overflows (SSOs) and reducing the efficiency of sewage treatment systems. RTK analysis based on measured RDII data of the target area through computer modeling is essential when maintaining sewer pipes in order to address this RDII problem. In the Sanitary Sewer Overflow Analysis and Planning (SSOAP) program used for RTK analysis, calculating RTK using a trial and error method is a bit challenging. Accordingly, this study introduces a program to calculate the optimal RTK at the measurement point using a genetic algorithm. In ROP, accuracy was added to the RDII prediction mechanism by incorporating error rates based on time intervals into the evaluation factors of SSOAP, namely rainfall inflow rate and peak flow error rate. The error rate for the SSOAP program and ROP was validated as 2.66%.

Municipal wastewater monitoring revealed the predominance of blaGES genes with diverse variants among carbapenemase-producing organisms: high occurrence and persistence of Aeromonas caviae harboring the new blaGES variant blaGES-48.

We characterized carbapenemase-producing organism (CPO) detected in municipal wastewater to better understand the epidemiology of CPOs in the community. In total, 36 samples were collected at six sampling sites every other month from December 2020 to October 2021. CPOs were not recovered from influent taken from inlet A receiving separated sewer line, treated effluents, and river water samples upstream and downstream of the effluent outlet. By contrast, 75 CPOs were detected in all influent samples taken from inlets B and C receiving combined sewer lines collecting both domestic/industrial wastewater and rainwater runoff. Aeromonas caviae was the dominant species (25/75, 33.3%), and the other 11 Aeromonas spp. together accounted for 48% of CPOs. The remaining 39 Enterobacterales strains mainly comprised 17 Klebsiella spp. and 10 Raoultella spp. CPOs carrying blaGES carbapenemase genes were overwhelmingly dominant, accounting for 72 of 75 isolates, including two isolates harboring both blaGES-24 and blaIMP-1 (96%), followed by three blaIMPs-positive isolates, where those carbapenemase genes were mainly carried in diverse class 1 integrons. Among blaGES variants, including six new variants (blaGES-47, blaGES-48, blaGES-49, blaGES-50, blaGES-51, and blaGES-54), blaGES-5 was detected in 28 CPOs, with Aeromonas spp. accounting for 53.6% of these organisms. Quantitative analysis revealed that the repeated detection of blaGES-48-positive A. caviae ST1056 from both inlets B and C ranked the total number of this bacterial clone highest in the wastewater influent. In summary, our study revealed the high prevalence and persistence of diverse blaGES carbapenemase genes among CPOs isolated from influent inlets connected to combined sewer systems.IMPORTANCEThe emergence and spread of carbapenemase-producing organisms (CPOs) represent a global health threat because they are associated with limited treatment options and poor clinical outcomes. Wastewater is considered a hotspot for the evolution and dissemination of antimicrobial resistance. Thus, analyses of municipal wastewater are critical for understanding the circulation of these CPOs and carbapenemase genes in local communities, which remains scarcely known in Japan. This study resulted in several key observations: (i) the vast majority of blaGES genes, including six new blaGES variants, and less frequent blaIMP genes were carbapenemase genes encountered exclusively in wastewater influent; (ii) the most dominant CPO species were Aeromonas spp., in which a remarkable diversity of new sequence types was observed; and (iii) CPOs were detected from combined sewer wastewater, but not from separate sewer wastewater, suggesting that the load of CPOs from unrecognized environmental sources could greatly contribute to their detection in influent wastewater.

Inter-event and intra-event dynamics of microplastic emissions in an urban river during rainfall episodes

Urban rivers represent the major conduits for land-sourced microplastics in the global oceans, yet the real-time dynamics of their emissions in rivers during rainfall (and runoff) events are poorly understood. Herein, we report the results of high-frequency sampling of microplastic particles (MPs) and fibers (MPFs) in the surface water of an urban river in Japan over the course of three rainfall events (i.e., light, moderate, and heavy rainfalls). The event mean concentrations (EMCs) of MPs amounted to 35,000 items/m3, 929,000 items/m3, and 331,000 items/m3; and the corresponding total loads were 0.5 kg, 19.8 kg, and 35.0 kg for light, moderate and heavy rainfalls, respectively. The inter-event total loads of MPs correlate well with the total rainfall, while the concentrations were linked with the number of antecedent dry days. The dynamic trends show that <2000 μm MPs displayed first flush effects during light to moderate rainfall events (>50% mass discharged with the initial 20–40% of flow). Small-sized MPs (10–40 μm) mobilized rapidly at lower rainfall intensities, whereas MPs over 2000 μm discharged immediately after the peak rainfall intensity. Moreover, <70 μm MPs depicted a surge following heavy rainfall events due to turbulent flow conditions reverting the deposited MPs into suspension. Overall, the three events increased the loads by 4–110 folds, and EMCs by 10–350 folds compared to the concentrations during dry weather while portraying a significant impact on 300–1000 μm MPs. The dynamics of MPs were correlated with those of suspended solids in river water, and the characteristics were comparable to the same of road dust sampled in Japan. Although the dynamic trends between MPs and MPFs in river water were comparable, MPFs were relatively less impacted by rain, likely due to the intervention of separate sewer systems in the study area.

A comparative study between low- and high-tech methods for the detection and mitigation of illicit connections in stormwater systems.

Illicit connections of wastewater to stormwater systems are the main drawback of separate sewer systems, as they lead to a direct discharge of untreated wastewater to the aquatic environment. Consequently, several inspection methods have been developed for detecting illicit connections. This study simultaneously applied several low- and high-tech methods for the detection of illicit connections in the same catchment (De Heuvel, the Netherlands). The methods included mesh wire screens for capturing coarse contamination, measurements of electroconductivity and temperature, sampling and quantification of Escherichia coli and extended-spectrum ß-lactamase-producing E. coli (ESBL-EC), DNA analysis via quantitative polymerase chain reaction for human-, dog-, and bird-specific fecal indicators, and distributed temperature sensing. Significant illicit connections could be identified using all methods. Nonetheless, hydraulic conditions and, predominantly, the sewage volume determine whether a misconnection can be detected by especially the low-tech methods. Using these results, the identified misconnections were repaired and biological and DNA analyses were repeated. Our results demonstrate that there were no changes in E. coli or ESBL-EC before and after mitigation, suggesting that these common markers of fecal contamination are not specific enough to evaluate the performance of mitigation efforts. However, a marked decrease in human wastewater markers (HF183) was observed.