Wet Weather Discharges Research Articles

Monitoring (micro-)pollutants in wastewater treatment plants: Comparing discharges in wet- and dry-weather

Municipal wastewater treatment plants (WWTPs) are crucial for maintaining good quality of surface water, limiting environmental pollution. However, during wet-weather events, WWTPs become an important point-source discharge due to the activation of the bypass, which releases a mix of untreated wastewater and stormwater. This work aims to assess how the WWTP discharges (effluent and bypass) impact on the receiving surface water body during dry- and wet-weather, monitoring 78 pollutants (7 conventional pollutants, 19 heavy metals, and 52 micropollutants) in each stream (effluent during dry-weather, effluent and bypass during wet-weather), including the influent in dry-weather for comparison. The occurrence, concentration levels and variability, and environmental risk were addressed, with a specific focus on high-resolution (up to 20-min) sampling of the bypass, based on the expected relevant temporal dynamicity. A wider range of pollutants occurred in the bypass, included undetected compounds in the dry-weather influent. Besides, a greater inter-events variability in bypass concentrations was observed, but smaller intra-event variability, with only some pollutants exhibiting a distinct first-flush effect. To address the challenge of a cost-effective bypass monitoring, we explored the applicability of readily measurable water quality parameters (total suspended solids and electrical conductivity) as proxies for micropollutants. Correlations between these parameters and specific pollutant groups suggest a promising path for further investigation and broader application. The magnitude of the rain event also affected concentration levels, with event volume clearly affecting pollutants dilution. The environmental risk assessment revealed a significantly higher risk associated to bypass discharge compared to the effluent, especially for conventional pollutants, metals, and terbutryn, highlighting the urgency of improved bypass management strategies. Overall, this study highlights the contribution of wet-weather discharges from WWTPs, emphasizing the importance of high-frequency bypass monitoring to capture peak pollutant concentrations and accurately assess the environmental risk.

Embracing epistemic uncertainty: a risk evaluation method for pollutants in stormwater.

In this study, we show that pollutants of emerging concern are, by nature, prone to the emergence of epistemic uncertainty. We also show that the current uncertainty quantification methods used for pollutant modelling rely almost exclusively on parameter uncertainty, which is not adequate to tackle epistemic uncertainty affecting the model structure. We, therefore, suggest a paradigm shift in the current pollutant modelling approaches by adding a term explicitly accounting for epistemic uncertainties. In a proof-of-concept, we use this approach to investigate the impact of epistemic uncertainty in the fluctuation of pollutants during wet-weather discharge (input information) on the distribution of mass of pollutants (output distributions). We found that the range of variability negatively impacts the tail of output distributions. The fluctuation time, associated with high covariance between discharge and concentration, is a major driver for the output distributions. Adapting to different levels of epistemic uncertainty, our approach helps to identify critical unknown information in the fluctuation of pollutant concentration. Such information can be used in a risk management context and to design smart monitoring campaigns.

Contribution of different land use catchments on the microplastic pollution in detention basin sediments

The assessment of microplastic (MP) pollution in urban areas is essential considering its abundance in freshwater, particularly due to urban wet weather discharge. The precise sources of MPs must be identified to better understand its characteristics. This study examines the relationship between MP pollution in detention basin sediments and land use in the investigated catchments. The study of stormwater management infrastructure, mainly in detention basins, has enabled the quantification of MP abundance in sediments conveyed by stormwater in urban areas. Sediment sampling was conducted in ten detention basins and one combined sewer overflow (CSO) structure in the Lyon metropolitan area, France. These basins correspond to stormwater outlets of representative urban catchment areas. MP extraction involves densimetric separation and organic matter degradation. MPs were then characterized using micro-Fourier infrared spectroscopy and siMPle software. This protocol identified MPs between 50 and 500 μm in the study sites. This study highlights the high abundance in the collected sediment samples, ranging from 2,525 to 1,218,82 MP kg−1 by dry weight sediment. The MPs found have a median size around 115 μm, making them very small MPs that are mainly composed of polypropylene followed by polyethylene and polystyrene or polyethylene terephthalate. The abundance of MPs in sediments is associated with the land use type. Catchments in predominantly industrial and commercial zones were more significantly polluted with MPs compared with those in predominantly agricultural or heterogeneous zones. Finally, statistical analyses revealed links between sedimentary and urban parameters and MPs concentrations. Several recommendations are given for future research, notably concerning the analyzing of stormwater sediments to understand the sources of MP pollution.

Optimized strategies of green and grey infrastructures for integrated control objectives of runoff, waterlogging and WWDP in old storm drainages

Frequent waterlogging occurs in old high-density urban areas where the sewage is inappropriately connected to storm drainages, resulting in serious wet weather discharge pollution (WWDP). To address urban waterlogging and runoff, the optimization of green infrastructures (GIs) and grey infrastructures (GRs) has been proposed to improve rainwater management efficiency. However, most strategies neglect WWDP and fail to achieve integrated control of runoff, waterlogging, and discharge pollution. In the present study, a new optimization method was introduced to identify optimal solutions for renovating outdated storm drainage systems, considering the management of discharge pollution in wet weather. A case study in Shanghai, China was conducted to demonstrate the application of the method. The cost-benefit index (CBI) of optimized GIs (0.06) was lower than that of optimized GRs (2.78) under 22.2 mm rainfall (no runoff and WWDP), but the costs of the former were only half those of the latter. In a 5-year return period storm (no waterlogging), optimized GIs had a significantly higher CBI (2.85 times) compared to optimized GRs, costing only 44 % of the latter. When WWDP reached the control objective (COD≤70 mg/L), the optimized GIs needed to be further optimized with GRs. The CBI of optimized GI-GRs was higher than GRs by 2.50, and the cost was 58% of the latter. In areas with frequent low-intensity rainfall, optimized GIs and GRs should be selected based on local cost or benefit requirements for drainage reconstruction. In high-intensity storm-prone areas, the optimized GI-GR combination should be selected for drainage reconstruction. The proposed method can compensate for the shortcomings of existing optimization methods in controlling WWDP for the reconstruction of old storm drainages.

A stochastic approach for assessing the chronic environmental risk generated by wet-weather events from integrated urban wastewater systems

Environmental chronic risk generated by wet-weather discharges compared to final effluent was stochastically assessed, also from a climate-change perspective, stressing their growing contribution for many (micro-)pollutants.

Combined Optimization of LID Patches and the Gray Drainage System to Control Wet Weather Discharge Pollution

Low impact development (LID) has emerged as an effective management to control urban runoff. However, for storm drainage systems located in high-density old urban areas with scarce land resources and fragmented landscapes, there are difficulties in the application of LID layouts. To solve the waterlogging and wet weather discharge pollution (WWDP), based on the spatial distribution of available land resources, runoff path, ponding area, overflow nodes, and sediments in drainages, a spatial optimized layout method of LID patches combined with gray drainages was proposed and applied to a typical storm drainage system in Shanghai, China. Only 22.9% of the ground surface and 14.0% of the roof, which accounted for the study area were reconstructed to LIDs, and the optimal LID patches combined with 0.4 m storage capacity depth (SCD) could prevent discharge below 6.5 mm rainfall. The optimal LID-gray drainages increased the reduction ratios of suspended substances (SSs) in WWDP by 37–74% compared with only LID patches in 9.1–21.8 mm rainfall. The “LID patches-gray system” could effectively control WWDP in old urban areas with high frequencies of moderate and light rain. The proposed methodology can be instructive for the sustainable reconstruction of storm drainages inappropriately connected with sewage.

A decade of monitoring micropollutants in urban wet-weather flows: What did we learn?

Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the “true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered.

Urban total phosphorus loads to the St. Clair-Detroit River System

The St. Clair-Detroit River System watershed is a large, binational watershed draining into the connecting channel between lakes Huron and Erie. In addition to extensive agricultural lands, it contains large urban areas that discharge phosphorus from point source facilities, runoff of impervious surfaces, and overflows of combined sewers. To help guide actions to reduce phosphorus input to Lake Erie, we analyzed the spatial and temporal dynamics of loads from the three largest urban areas in the watershed (southeast Michigan; Windsor, Ontario; and London, Ontario), and used a previously calibrated storm water management model (SWMM) to explore options for reducing loads around metro Detroit. Point sources in these three urban areas contribute, on average, 81% of the total urban load and 19% of the Detroit River’s total phosphorus (TP) load to Lake Erie, while combined sewer overflows and runoff both contribute about 10% each to the urban load and about 2.5% each to the Detroit River’s load to Lake Erie. Most of the urban load (56%) comes from a single point source, the wastewater treatment facility in Detroit; however, TP loads from that facility have decreased by about 51% since 2008 due to improvements in wastewater treatment. Model simulations suggest that increasing pervious land area or implementing green infrastructure could help reduce combined sewer overflows in certain upper portions of the metro Detroit sewer system, but reductions were much less expressed for wet-weather discharge from the system.

Modelling engineered nanomaterials in wet-weather discharges

The impacts of the unintended release of engineered nanomaterials (ENMs) and the resulting exposure to the ecosystems are still poorly understood and intensively debated. In current mass flow models, a global transfer coefficient is used to account for ENMs discharged from sewer systems to surface waters during rain events. However, different types of sewer systems and specific ENM applications likely require a more elaborate approach to quantify ENM loads entering surface waters during rain events.Therefore, we evaluated the impact of distinguishing between different application areas of ENMs (indoor/outdoor) and different types of sewer systems (combined/separate) on the loads of selected ENMs passing through wastewater systems and reaching the surface water. We applied a dynamic mass flow analysis to eight substances (TiO2, ZnO, Ag, SiO2, FeOx, CuO, CeO2 and carbon black) for six different sewer system configurations. To estimate the runoff from streets and facades, we used a hydrological model developed for dissolved substances. For areas with separate sewer systems only and ENMs predominantly used in and released from outdoor applications (e.g. CuO, carbon black), up to ~80% of the annual loads entering the sewer systems never reach a sewage treatment plant. Those ENMs are directly discharged to surface waters via stormwater outlets. For combined sewer systems and ENMs mainly applied indoors (e.g. Ag, ZnO), the percentage of ENM bypassing sewage treatment plants remains below 2%. Although the model is setup for Switzerland and other geographical areas will show for example different rain characteristics, the relative importance of the different release pathways will broadly remain the same and the results should, therefore, be transferrable to other countries.

The importance of pollutional loads during wet weather

Wet weather discharges consist mainly of washed out surface pollution in separate sewered areas, but in combined sewered areas; resuspended pipe deposits, surface washoff and sewage, discharging via combined sewer overflows (CSOs). Of the three mentioned sources, resuspended pipe solids is dominating over the other two and may contribute as much as 50 to 90 % of the total amount of the CSO. The CSO in a normal catchment may also on an annual bases be of the same amount, or even twice as much as the effluent from the wastewater treatment plant (WWTP). If the receiving waters are vulnerable to shock loads on a daily base, it is important to be aware that the amount of CSO might, at its most adverse be up to I 00 times more than the effluent from the WWTP during a day. The annual discharge via CSOs in a catchment may easily vary with a factor of up to 8 from the driest to the wettest year, during time series of 20 to 40 years.

Microalgal whole-cell biomarkers as sensitive tools for fast toxicity and pollution monitoring of urban wet weather discharges

Urban wet weather discharge (UWWD) management is an important issue. UWWD often represents a significant source of pollution in all aquatic bodies. The occurrence of this pollution is difficult to predict due to the variability of storm events and the unknown contents of urban watershed leached out by rain. Previous studies have tried to demonstrate the ecotoxic impact of UWWD. However, most of them merely highlight the limitations of classic monospecific bioassays, given the high dilution of micropollutants or the presence of nutrients masking toxic effects. Overcoming this problem is therefore of great interest. In this study, we demonstrated the utility of a battery of biomarkers (e.g. membrane permeability, chlorophyll fluorescence, esterase and alkaline phosphatase activities) on the microalgae Chlorella vulgaris to detect the toxic effects of 7 UWWD samples after short exposures (2 and 24 h). These biomarkers are linked to microalgal life traits. Complementarily, monospecific bioassays were carried on Pseudokirchneriella subcapitata, Chlorella vulgaris, Daphnia magna and Heterocypris incongruens to compare their sensitivity to the UWWD samples. No toxic effect was detected in any of the bioassays. Yet, algal biomarkers indicated a disturbance in microalgae physiology, and particularly a perturbation of chlorophyll fluorescence, which was observed in all of the samples tested. While algal membrane permeability was affected by only one UWWD, these two enzymatic activities were stimulated or inhibited depending on the sample. Finally, this study demonstrates the sensitivity of algal biomarkers and the need to develop new, fruitful approaches to characterizing UWWD toxicity.

Assessment of 34 dissolved and particulate organic and metallic micropollutants discharged at the outlet of two contrasted urban catchments

The assessment of micropollutants in urban wet weather discharges is essential to improve the knowledge of the impact of such discharges on receiving waters. This study assessed the quality of combined sewer overflows (CSOs) in Ecully (residential catchment) and stormwater runoff in Chassieu (industrial catchment) during rain events by providing data on occurrence and total event mean concentrations (EMCt) of 34 priority substances (PS) (9 metals, 13 pesticides, 6 PAHs, 4 alkylphenols and 2 chlorobenzenes) in dissolved and particulate fractions. Over 34 substances monitored, 23 were quantified in urban wet weather discharges of both catchments. For both catchments, 9 metals and 6 PAHs monitored were always quantified, reflecting their ubiquitous presence. For other organic pollutants, only 5 pesticides were quantified and only 2 alkyphenols were measured solely in dissolved fraction. A significant site-to-site difference was observed for metals, PAHs and alkylphenols. The highest concentrations were measured in stormwater runoff in Chassieu vs. Ecully. On the contrary, the diuron concentrations were highest in CSO discharges in Ecully. Distribution of the PS between particulate and dissolved fractions provides information for urban stormwater practitioners. Most PS in urban wet weather discharges were mainly linked to particles (PAHs, Pb, Ti for example). The comparison between daily flows of wastewater treatment plants during dry weather and CSOs daily flows in Ecully showed that stormwater was the most important source of contamination for fluoranthene, benzo(b)fluoranthene and benzo(k)fluoranthene and 7 metals (As, Cr, Co, Cu, Pb, Ti and Zn) in receiving water bodies, but not for pesticides and alkylphenols.

The Rouge River Area of Concern - A multi-year, multi-level successful approach to restoration of Impaired Beneficial Uses

Citizen outcry in the 1960s led to passage of the 1972 U.S. Clean Water Act. Expansion of industrial permitting and availability of federal grants to municipalities controlled industrial waste and untreated municipal sewage entering the Rouge River. However, many sources persisted – notably wet weather discharges, stormwater runoff, and contaminated sediments. This remaining pollution led state officials to cooperatively craft the Rouge River Remedial Action Plan in 1985. This plan addressed all pollution sources, but was not substantially implemented until 1993 when the federal government, encouraged by Congressmen Dingell and Knollenberg, committed to the Rouge River National Wet Weather Demonstration Project. The federal government ultimately delivered $350 million that was matched by $700 million in local funds. Efforts have been sustained through multi-year state and federal grants, with additional funding from local communities and other stakeholders. Early focus of the Rouge Project was on untreated sewage from combined sewer overflows, but quickly expanded to address other impairments from sanitary sewer overflows, stormwater runoff, illicit connections and failing septic systems. With major sewage discharges under control, efforts shifted to remediating contaminated sediments and improving in-stream water quality and habitat. In total, over 380 projects were completed by 75 communities and agencies at a cost of over $1 billion since 1988, resulting in improved water, sediment, and biological quality. Prior to the U.S. Clean Water Act, the Rouge River nearly continuously failed to meet water quality standards. After decades of effort and investment, it now rarely violates standards. This miraculous recovery was initiated by a small handful of citizens, facilitated by local municipal leaders, and supported by the federal government. The Rouge River is a model for how a holistic, ecosystem approach to water pollution can result in cost-effective and greater and faster achievement of restoration, while meeting local needs.

Xurography-based microfluidic algal biosensor and dedicated portable measurement station for online monitoring of urban polluted samples

A critical need exists to develop rapid, in situ, and real-time tools to monitor the impact of pollution discharge toxicity on aquatic ecosystems. The present paper deals with the development of a novel, simple-to-use, low-cost, portable, and user-friendly algal biosensor. In this study, a complete and autonomous portable fluorimeter was developed to assess the A-chlorophyll fluorescence of microalgae, inserted by capillarity into low-cost and disposable xurography-based microfluidic chips. Three microalgae populations were used to develop the biosensor: Chlorella vulgaris, Pseudokirchneriella subcapitata, and Chlamydomonas reinhardtii. Biosensor feasibility and sensitivity parameters, such as algal concentration and light intensity, were optimized beforehand to calibrate the biosensor sensitivity with Diuron, a pesticide known to be very toxic for microalgae. Finally, the biosensor was employed in 10 aqueous urban polluted samples (7 urban wet-weather discharges and 3 wastewater) in order to prove its reliability, reproducibility, and performance in the detection of toxic discharges in the field.

Performance of Two Advanced Rainwater Harvesting Systems in Washington DC

Combined sewer overflows (CSOs) are a concern for many cities managing stormwater through combined sewer systems, including the District of Columbia (DC). Advanced rainwater harvesting (ARH) is an innovative approach to managing stormwater and has the potential to minimize CSOs and maximize water conservation. ARH systems use continuous monitoring and adaptive control (CMAC) technology to store or release water from a rainwater harvesting cistern. This study assessed the efficacy of ARH systems to mitigate wet weather discharges at two firehouses in DC. Continuous monitoring data was collected over a period of three years for the systems that were installed in 2012. The collected data indicates that the systems were effective at mitigating wet weather discharges, with average event harvesting rates greater than 95%. These results suggest that if implemented on a larger scale, ARH systems would be a valuable tool in effectively managing stormwater.

Total and settling velocity-fractionated pollution potential of sewer sediments in Jiaxing, China.

Sewer sediments and their associated contaminant released along with wet-weather discharges pose potential pollution risks to environment. This paper presents total characteristics of sediments collected from Jiaxing, China. Size distribution and concentrations of volatile solids (VS) and four metals (Pb, Cu, Zn, Cr) of sediment samples from seven land use categories were analyzed. Then, the sediment samples were graded five fractions according to its settling velocity through the custom-built settling velocity-grading device. Sediment mass and pollution load distribution based on settling velocity were also assessed. The results show that there are relatively high level of heavy metal load in the sediment of separated storm drainage systems in Jiaxing, especially for the catchment of residential area (RA), road of developed area (RDA), and industrial area (IA). Although grain size follows a trend of increasing along with settling velocity, the methods of settling velocity grading are meaningful for stormwater treatment facilities with precipitation. For all land use categories, the pollution concentrations of the three lower settling velocity-fractionated sediment are relatively consistent and higher than others. Combined with mass distribution, the pollution percentage of fraction with different velocities for seven land use categories were also evaluated. Based on it, the statistical conclusion of design target settling velocity to different pollution load removal rates are drawn, which is helpful to guide design of on-site precipitation separation facilities.

Influences of rainfall variables and antecedent discharge on urban effluent concentrations and loads in wet weather

For storm drainages inappropriately connected with sewage, wet weather discharge is a major factor that adversely affects receiving waters. A study of the wet weather influences of rainfall-discharge variables on storm drainages connected with sewage was conducted in the downtown Shanghai area (374 ha). Two indicators, event mean concentration (EMC) and event pollutant load per unit area (EPL), were used to describe the pollution discharge during 20 rain events. The study showed that the total rainfall and discharge volume were important factors that affect the EMCs and EPLs of the chemical oxygen demand, total phosphorus, and especially those of NH4+-N. The pollutant concentrations at the beginning of the discharge and the discharge period were also major factors that influence the EMCs of these three pollutants. Regression relationships between the rainfall-discharge variables and discharge volume/ EPLs (R2 = 0.824-0.981) were stronger than the relationships between the rainfall-discharge variables and EMCs. These regression equations can be considered reliable in the system, with a relative validation error of less than ±10% for the discharge volume, and less than ±20% for the EPLs. The results presented in this paper provide guidance for effectively controlling pollution in similar storm drainages.

Identification and assessment of ecotoxicological hazards attributable to pollutants in urban wet weather discharges.

Urbanization has led to considerable pressure on urban/suburban aquatic ecosystems. Urban Wet Weather Discharges (UWWD) during rainfall events are a major source of pollutants leached onto and into urban surfaces and sewers, which in turn affect aquatic ecosystems. We assessed the ecotoxicity of the different compounds identified in UWWD and identified the hazard represented by each of them. To this end, hazard quotient (HQ) values were calculated for each compound detected in UWWD based on their predicted no effect concentration (PNEC) values and their maximum measured effluent concentrations (MECmax) found in the dissolved part of UWWD. For the 207 compounds identified in UWWD, sufficient data existed for 165 of them to calculate their PNEC. The ecotoxicity of these compounds varied greatly. Pesticides represented a high proportion of the wide variety of hazardous compounds whose HQ values were calculated (94 HQ values), and they were among the most hazardous pollutants (HQ > 1000) transported by stormwater. The hazard of combined sewer overflows (CSO) was linked mainly to heavy metals and pharmaceutical compounds. Consequently, the monitoring of these pollutants should be a priority in the future. The hazard level of certain pollutants could have been underestimated due to their adsorption onto particles, leading to their low concentration in the dissolved phase of UWWD. Hence, an in-depth study of these pollutants will be required to clarify their effects on aquatic organisms.

Pollution characterization and source analysis of the wet weather discharges in storm drainages

Pollution characterization and source analysis of the wet weather discharges in storm drainages

Model-based screening for critical wet-weather discharges related to micropollutants from urban areas

Wet-weather discharges contribute to anthropogenic micropollutant loads entering the aquatic environment. Thousands of wet-weather discharges exist in Swiss sewer systems, and we do not have the capacity to monitor them all. We consequently propose a model-based approach designed to identify critical discharge points in order to support effective monitoring.We applied a dynamic substance flow model to four substances representing different entry routes: indoor (Triclosan, Mecoprop, Copper) as well as rainfall-mobilized (Glyphosate, Mecoprop, Copper) inputs. The accumulation on different urban land-use surfaces in dry weather and subsequent substance-specific wash-off is taken into account. For evaluation, we use a conservative screening approach to detect critical discharge points. This approach considers only local dilution generated onsite from natural, unpolluted areas, i.e. excluding upstream dilution.Despite our conservative assumptions, we find that the environmental quality standards for Glyphosate and Mecoprop are not exceeded during any 10-min time interval over a representative one-year simulation period for all 2500 Swiss municipalities. In contrast, the environmental quality standard is exceeded during at least 20% of the discharge time at 83% of all modelled discharge points for Copper and at 71% for Triclosan. For Copper, this corresponds to a total median duration of approximately 19 days per year. For Triclosan, discharged only via combined sewer overflows, this means a median duration of approximately 10 days per year. In general, stormwater outlets contribute more to the calculated effect than combined sewer overflows for rainfall-mobilized substances. We further evaluate the Urban Index (Aurban,impervious/Anatural) as a proxy for critical discharge points: catchments where Triclosan and Copper exceed the corresponding environmental quality standard often have an Urban Index >0.03.A dynamic substance flow analysis allows us to identify the most critical discharge points to be prioritized for more detailed analyses and monitoring. This forms a basis for the efficient mitigation of pollution.