Stormwater Sewer Systems Research Articles

Emissions of organic pollutants from traffic and roads: Priority pollutants selection and substance flow analysis

A large number of organic pollutants (OPs) emitted from vehicles and traffic-related activities exhibit environmental persistence and a tendency to bioaccumulate, and may have detrimental long-term effects on aquatic life. The aim of the study was to establish a list of significant sources of OPs occurring in road runoff, identify the OPs emitted from these sources, select a number of priority pollutants (PP), and estimate the quantity of PPs emitted in a road environment case study using substance flow analysis (SFA). The priority pollutants included in the SFA were selected from a list of approximately 1100 compounds found after comprehensive screening, including literature and database searches, expert judgments, the Ranking and Identification of Chemical Hazards method, and chemical analysis of sediments. The results showed the following priority order: polycyclic aromatic hydrocarbons (PAHs)>alkanes C20-C40>alkylphenols>phthalates>aldehydes>phenolic antioxidants>bisphenol A>oxygenated-PAHs>naphtha C5-C12>amides>amines. Among these, PAHs were chosen for a SFA, which was performed for a highway case study area in Gothenburg (Sweden). The SFA showed that the main sources of PAHs emitted in the area were vehicle exhaust gases, followed by tyre wear, motor lubricant oils, road surface wear, and brake linings. Only 2-6% of the total 5.8-29kg annually emitted PAHs/ha ended up in the stormwater sewer system. The measured PAH loads were found in much smaller amounts than the calculated loads and the outflow to stormwater contained much more of the hazardous PAHs than the total loads emitted in the catchment area.

Assessment of the degree of pollution of sediments from the rainstorm sewer system in the urbanised catchment

The study presents the results of tests aimed at determining variations in concentrations of polycyclic aromatic hydrocarbons and heavy metals (copper, cadmium, chromium, nickel, lead and zinc) in the sediments from the stormwater sewer system depending on the study period. The sediments were sampled in four periods that altogether extended over the hydrological year. They were collected from the settler chamber in the stormwater treatment plant located in the 804.6 ha urbanised catchment. The results of investigations show differences in the sediment grain size distribution. The dust-clay fraction is dominant as it constitutes up to 84% of the samples. The remaining part of the samples is composed of the mineral material, mainly of the psammite fraction grains (3–25%) and organic material (10–13%). The results concerning the content of heavy metals show that the lowest values were found for cadmium, namely 0.8 mg kg−1, and the highest for zinc −627.9 mg kg−1. As regards organic pollutants, a growing trend in total concentrations of PAHs was observed over the study period. The initial concentration in the winter period was 48.1 mg kg−1, whereas in the last sampling session it was as much as 87.8 mg kg−1, which indicates a continuous accumulation of pollutants in the material. An attempt was made to classify the sediments taking into account the Regulation of the Minister of Environment on soil and land quality standards (J. of Laws No. 165, item 1359) and geochemical classification.

Dynamics of biocide emissions from buildings in a suburban stormwater catchment – Concentrations, mass loads and emission processes

Biocides such as isothiazolinones, carbamates, triazines, phenylureas, azoles and others are used to protect the surfaces of buildings, e.g. painted or unpainted render or wood. These biocides can be mobilized from the materials if rainwater gets into contact with these buildings. Hence, these biocides will be found in rainwater runoff (stormwater) from buildings that is traditionally managed as “clean water” in stormwater sewer systems and often directly discharged into surface waters without further treatment. By means of a 9 month event-based high resolution sampling campaign the biocide emissions in a small suburban stormwater catchment were analysed and the emission dynamics throughout the single rain events were investigated. Five out of twelve of the rain events (peak events) proved significantly higher concentrations than the rest (average) for at least one compound. Highest median concentrations of 0.045 and 0.052 μg L−1 were found for terbutryn and carbendazim, while the concentrations for isoproturon, diuron, N-octylisothiazolinone, benzoisothiazolinone, cybutryn, propiconazole, tebuconazole, and mecoprop were one order of magnitude lower. However, during the peak events the concentrations reached up to 1.8 and 0.3 μg L−1 for terbutryn and carbendazim, respectively. Emissions of an averaged single family house into the stormwater sewer turned out to be 59 and 50 μg event−1 house−1 terbutryn and carbendazim, respectively. Emissions for the other biocides ranged from 0.1 to 11 μg event−1 house−1. Mass load analysis revealed that peak events contributed in single events as much to the emissions as 11 average events. However, the mass loads were highly dependent on the amounts of rainwater, i.e. the hydraulic flow in the receiving sewer pipe.The analysis of the emission dynamics showed first flush emissions only for single parameters in three events out of twelve. Generally biocides seemed to be introduced into the stormwater system rather continuously during the respective events than in the beginning of them. Mass flows during the events did correlate to driving rain, whereas mass loads neither correlated to the length or the intensity of rainfall nor the length of dry period.

Combined Effects of Mechanical Availability and Storage Capacity in Pumping Station Risk Assessment

Pump failure is defined as the inability of the pump to pump at design capacity. In an urban drainage system failing pumps may result in sewer overflow and flooding. However, the system failure may be due to an unexpected rainfall event exceeding the overall design capacity of the pumps, or to the failure of one or more pumps being the inflow to the pumping station less than the design capacity. Here we propose a model that incorporates two stochastic models for (a) the storm water discharge and (b) the complex system functioning, into a tool for the storm water sewer reliability assessment. In our schematic stormwater sewer system a pipe network with storage capacity transfers water to the pumping station, and the pumping station discharges the incoming flow to a water body at higher level thanks to the interplay of a number of pumping units. The model may be used to evaluate the reliability of different design solution in order to define the design criteria that maximize the system service and minimize the realization costs.

Retention Performance of Domestic Rain Water Harvesting Tank under Climate Change Conditions

The goal of this paper is to investigate the efficiency of domestic Rain Water Harvesting (RWH) tank to reduce the inflow discharge to stormwater sewer systems, which intends to be an option to increase urban resilience to climate change impacts. A dimensionless methodology developed based on a water balance model at daily temporal scale was applied to determine both the obtainable water saving due to the use of rain water for toilet flushing (i.e. reduce the use of portable water) and meanwhile reduce stormwater volumes discharging to sewer systems by the tank storage. The methodology and a RWH tank system was evaluated applying the daily rainfall data obtained in two met-stations of Blindern in Oslo and Rygge in Fredrikstad, South Norway. Results show, for all the considered scenarios in the two case studies that the use of the rainwater storage tank can provide significant reduction of water volume discharges to the storm water sewer, accordingly the resulting damages during the extreme events will be reduced.

Consequential Environmental and Economic Life Cycle Assessment of Green and Gray Stormwater Infrastructures for Combined Sewer Systems

A consequential life cycle assessment (LCA) is conducted to evaluate the trade-offs between water quality improvements and the incremental climate, resource, and economic costs of implementing green (bioretention basin, green roof, and permeable pavement) versus gray (municipal separate stormwater sewer systems, MS4) alternatives of stormwater infrastructure expansions against a baseline combined sewer system with combined sewer overflows in a typical Northeast US watershed for typical, dry, and wet years. Results show that bioretention basins can achieve water quality improvement goals (e.g., mitigating freshwater eutrophication) for the least climate and economic costs of 61 kg CO2 eq. and $98 per kg P eq. reduction, respectively. MS4 demonstrates the minimum life cycle fossil energy use of 42 kg oil eq. per kg P eq. reduction. When integrated with the expansion in stormwater infrastructure, implementation of advanced wastewater treatment processes can further reduce the impact of stormwater runoff on aquatic environment at a minimal environmental cost (77 kg CO2 eq. per kg P eq. reduction), which provides support and valuable insights for the further development of integrated management of stormwater and wastewater. The consideration of critical model parameters (i.e., precipitation intensity, land imperviousness, and infrastructure life expectancy) highlighted the importance and implications of varying local conditions and infrastructure characteristics on the costs and benefits of stormwater management. Of particular note is that the impact of MS4 on the local aquatic environment is highly dependent on local runoff quality indicating that a combined system of green infrastructure prior to MS4 potentially provides a more cost-effective improvement to local water quality.

QUANTITATIVE AND QUALITATIVE NUMERICAL ANALYSIS OF OPERATIONAL CONDITIONS OF STORM WATER SYSTEM

Operation of storm water systems in urbanized catchments, affected by increased size of drainaged area and its relative surface sealing, significant variability of rainfall events and increased usage of transport vehicles is connected to changes of sewage flow, pollutants concentrations and loads entering the sewage receiver. Thus, the application of numerical modeling to multi-variant analyses of storm water systems operation and its influence on the natural environment is reasonable and becomes a standard procedure nowadays. This paper presents the numerical modeling application to quantitative and qualitative analysis of storm-water sewer system in conditions of the selected urbanized area in the town of population reaching 40 000. The US EPA's (United States Environmental Protection Agency) software SWMM 5 was applied to our studies. Three different rainfall events of various time and intensity were applied to our research. The presented analysis was based on sewage flow velocity, wastewater table height in the pipelines and the load of pollutants leaving the sewerage system. The sewage flooding from several chambers was observed. Our studies reveals also the fact that the studied system is partially undersized and the observed concentration of TSS entering the receiver exceeds the maximum value allowable by the local standards. According to the lacking model calibration, our observations should be treated as the preliminary studies.

Pressure Transients due to Compression of Trapped Air in Rapidly Filling Sewer Storage Tunnels

Increasing numbers of lines of evidence indicate that entrapment of large pockets of air during the rapid filling of stormwater and combined sewer systems may …

Rapid Flood Evaluation Systems in Taiwan Metropolitan Areas

Hydrological issues in metropolises in Taiwan have become increasingly important because the storm water sewer systems of metropolises are frequently unable to meet the requirements of the existing and future metropolitan development. Typhoons or torrential rains that cause rainfall intensities that exceed the designed capacity of storm water sewers can result in serious flooding. The losses caused by flooding can be reduced if the areas at risk of flooding can be predicted and warnings can be issued to prompt disaster prevention and allow response units and residents to prepare before disasters occur. The primary purpose of this study is to integrate the quantitative precipitation forecasting technologies [1, 2] developed by the Taiwan Typhoon and Flood Research Institute to establish a rapid, stable, real-time, and automatic metropolitan area flood estimation system for predictive flooding analysis. The objects of this study are metropolitan areas in Taiwan with storm water sewer systems. The standard capacities of storm water sewer systems throughout Taiwan and the geographic information system (GIS) shape files are collected and compiled. Additionally, the potential flooding areas are divided into four levels (high, medium, low, and no flooding) and are compared with the rainfall warning values of the Water Resources Agency. The study combines the results of quantitative precipitation forecasts, establishes an information database (MySQL), processes Google Earth KML files, and designs a WEB GIS display interface to construct a system for estimating the flooding possibility (probability) in metropolitan areas during typhoons or torrential rains. This study subsequently employs the event of Typhoon Kalmaegi for flooding estimation and display; the estimation results are consistent with the flooding survey data, indicating that the estimations made by the flooding estimation system are correct.

Mechanisms for Surges in Vertical Shafts in Stormwater Tunnels

Transient analyses of filling stormwater or combined sewer systems are often conducted to determine the potential for water returning to grade through vertical…

Sediment Monitoring Bias by Automatic Sampler in Comparison with Large Volume Sampling for Parking Lot Runoff

A field study was conducted to assess biases of suspended sediment concentration (SSC) analyses (ASTM Standard D3977-97) performed on discrete samples obtained by automatic sampler in comparison with actual sediment concentrations from large volume sampling. Research results indicate that the biases attributed to the monitoring of sediment event mean concentration (EMC) and median particle size in parking lot runoff by automated samplers (nonisokinetic) were minimal. Large volume samples (∼15,000 L) of the first-flush event runoff were taken from a storm-water sewer system for eighteen storm events over two years. The intent was to obtain a complete portion of a storm to accurately determine EMCs and particle size distributions (PSDs). Concurrently, flow-weighted discrete samples were obtained by automatic samplers for the same portion of the events. Thus, characteristics of sediments from a whole-storm sample were compared with those of subsamples obtained by an automatic sampler using nonisokinetic sampling. SSCs and PSDs were compared for the two respective field sampling methods. The two methods showed a strong correlation for median sediment EMCs (R2=0.98, n=18). Biases to particle size distributions were found to be both for the large particles (>75–150 μm) and smaller fines (<25 μm). Specific sediment size fractions captured by the large volume sampling and automatic sampler were not significantly different (α=0.05) for D50, which = 58 and 46 μm, respectively.

Sewer system flow components identification using signal processing

The development of a continuous model to simulate the behaviour of sewer systems requires detailed information on each component of the flows contributing to the global discharge. In this paper authors investigate a novel method based on signal processing and long time series data implemented with a 2 min time step (flow rate, conductivity, pH and turbidity) in order to identify the dry weather components in a separated stormwater sewer system draining an industrial catchment. The wavelet analysis is applied to the recorded data to identify main components in dry weather flow after the removing of the signal noise. This paper highlights also a method to detect inflow into sewer system and shows how hydrological modelling can be used to characterise the relevant components. These techniques could be used as a basis for several applications.

Optimized operation plan for sewer sediment control

Severe operational problems of sediment deposition have frequently occurred in stormwater sewer systems in Shanghai city due to the flat topography of the area and serious illicit connections. To control sewer sediment and its subsequential problems, optimized operation plans were proposed and an innovative performance assessment method was developed. Simulation results demonstrated that, through changing the way of pump operation and installing necessary actuators in the system, the optimized operations, especially batch intermittent intercept plan, effectively improved the flow velocity in the entire system in dry-weather condition. In conclusion, the optimized operation is an innovative idea for improving the performance and solving the problem of sediment deposition in the sewer system in Shanghai, China.

Geysering in Rapidly Filling Storm-Water Tunnels

Events that are referred to as geysers have been observed in storm-water or combined sewer systems and are associated with jets of water rising through manholes to a considerable distance above the ground surface. Visual observations suggest that air may be a significant component of the jet. The mechanisms of geyser occurrence have been previously assumed to originate in inertial oscillations that force water up through vertical ventilation shafts. Recent laboratory investigations indicate that geyser formation is associated with the release of trapped air pockets through partially filled vertical shafts. Pressure data from a storm-water tunnel subject to infrequent geyser events is presented to indicate that measured piezometric heads adjacent to the ventilation shaft never increase to levels approaching the ground surface during a geyser event suggesting that air interactions must be an important part of the process. It is concluded that system design to avoid geyser formation must include the consideration of trapped air within the tunnel system.

Storm Water Runoff Mitigation Using a Green Roof

A prototype green roof was constructed and monitored in Pittsburgh, Pennsylvania, to demonstrate a way to reduce storm water runoff and combined sewer overflow (CSO) events. The large impervious surface area created by urban development in Pittsburgh creates a wet weather flow that the existing combined waste waster and storm water sewer system cannot contend with. Green or vegetated roofs can reduce the amount of storm water that reaches the sewer conveyance system by replacing an otherwise impervious roof with porous soil that retains rainwater and plants that evapotranspire resulting in reduced storm water flows to the sewer system. The prototype green roof reduced the runoff volume by up to 70% compared to a conventionally ballasted roof covering a control portion of the same building. A reduction of at least 20% was found for rainfalls of 1.5 cm (0.60 inches) or less. The green roof also reduced the flow rate of runoff throughout storms. Peak values from the green roof were between 5% and 70% lower t...

Análisis de la variabilidad espacio-temporal de la precipitación en una microcuenca urbana, Bogotá, Colombia

Los diseños de alcantarillados pluviales y combinados normalmente se realizan bajo el supuesto de que la precipitación es constante en tiempo y espacio para áreas inferiores a 1 km2. Con el fin de aportar al conocimiento de la variabilidad espacio-temporal de la precipitación en cuencas urbanas de este tipo, y de determinar su impacto en el diseño de alcantarillados y, más aún, en los caudales de escorrentía obtenidos a partir de la aplicación de modelos matemáticos rigurosamente calibrados y validados, se ha instrumentado densamente la microcuenca urbana del campus de la Universidad Nacional de Colombia, sede Bogotá. En este artículo se describen los análisis detallados del evento más importante en términos de intensidad y precipitación total.

Improved Simulation of Flow Regime Transition in Sewers: Two-Component Pressure Approach

Operational problems and system damage have been linked to the flow regime transition between free surface and pressurized flow in rapidly filling stormwater and combined sewer systems. In response, emphasis has been placed on the development of numerical models to describe hydraulic bores and other flow phenomena that may occur in these systems. Current numerical models are based on rigid column analyses, shock-fitting techniques, or shock-capturing procedures employing the Preissmann slot concept. The latter approach is appealing due to the comparative simplicity, but suffers from the inability to realistically describe subatmospheric full-pipe flows. A new modeling framework is proposed for describing the flow regime transition utilizing a shock-capturing technique that decouples the hydrostatic pressure from surcharged pressures occurring only in pressurized conditions, effectively overcoming the cited Preissmann slot limitation. This new approach exploits the identity between the unsteady incompressible flow equations for elastic pipe walls and the unsteady open-channel flow equations, and the resulting numerical implementation is straightforward with only minor modifications to standard free surface flow models required. A comparison is made between the model predictions and experimental data; good agreement is achieved.

Comparison of Overflows from Separate and Combined Sewers – Quantity and Quality

The use of separate sewerage systems to solve pollution problems associated with combined systems is examined. Overflows from combined stormwater-sewer systems have been found to be one of the major causes of receiving water pollution. Experiences in two countries which have predominantly one system or the other provided a basis for comparison. Wet weather overflow was found to be a major problem with similar quality of overflow produced for both systems. Minimising overflows was feasible, however proper and integrated control of stormwater and sewage flows, related to receiving water impacts, is indicated as the best solution. The use of separate sewerage systems to solve pollution problems may not be justified.

A STUDY OF RESIDENTIAL STORMWATER IMPOUNDMENTS: PERCEPTIONS AND POLICY IMPLICATIONS1

ABSTRACT: The traditional solution to stormwater runoff from housing developments has been stormwater sewer systems. A newer and increasingly popular solution is some sort of impoundment or “lake” within the development, which is thought to be cheaper, to provide recreation, to improve the aesthetics of the environment, and to increase property values. Little is known of the acceptability of these to public officials, developers, or potential residents, or of their policy implications. Two such developments in Mississauga, Ontario, were studied, in terms of the perceptions and opinions of a random sample of residents and of officials who had been involved in their planning and management. The areas have attracted a relatively young group, just beginning their child‐bearing years, with relatively high income and education. The lakes appear to be popular, and relatively successful, especially the one which provides more recreational opportunities, and which has had fewer maintenance problems. The major problems are visual and safety. The City, and to some extent the developers, are seen as the appropriate groups to manage and maintain the lakes. Some suggestions, based on residents' and officials' responses, are presented for future designs and policy formulation.

Design of a stormwater sewer by nonlinear programming—1

A methodology to design a stormwater sewer system using a nonlinear programming approach is developed. It is divided in five steps: (1) hydrology, (2) set up of the technological constraints, (3) optimization with the Rosen's projected gradient method with the pipe diameters considered as continuous variables, (4) standardization of the diameters, and (5) post-optimal analysis of the piezometric surface. The cost function includes the purchase and installation and the excavation costs of every pipe. It is a convex programming problem; therefore the minimum solution is an absolute minimum. A subsequent paper to appear in this journal will illustrate the complete design procedure and the effect of certain parameters on the design.