Impacts of Storm Characteristics on Generating Sanitary Sewer Overflow (SSO) Events for an Urban Sewershed
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Abstract:
Combined sewers often overflow during intensive storm activity as the capacity of the system is exceeded in response to excess stormwater inflow. Uncontrolled releases of untreated stormwater as sanitary sewer overflows (SSOs) are also possible but are far less documented, mainly due to a lack of available data, despite being a serious issue for many communities across the US. This study conducted a quantitative analysis of several key storm variables with the aim of identifying occurrence thresholds toward triggering overflows for a residential sewershed in the city of Louisville, Kentucky. Using 5-minute rainfall data and the SSO event database from the Louisville Metropolitan Sewer District (MSD), results indicated that occurrence thresholds in total storm rainfall depth (35.6 mm) and maximum storm intensity (50 mm/hr) were present which could be used to classify storms as overflow versus non-overflow events. Additionally, the majority of overflow events resulted from storms with ratios below 0.5 and could be classified as 1-year storm frequency events across all storm durations. Discriminant analysis further identified these variables as significant in grouping the storms into overflow versus non-overflow events. By analyzing the sensitivity of known SSOs within the metro sewer system to various storm characteristics and resulting stormwater inflow this research could provide stormwater planners and affected residents with better predictive and potential management capabilities for future SSO events.Keywords:
Combined sewer
Inflow
Sanitary sewer
The application of unsteady simulation to lightening urban storm waterlogged disaster involves six blocks: the main program, the database of drainage networks, the abstractions and losses block, the calculating inflow of sewer block, the drainage networks routing block and the waterlogged areas calculating block. This model can be used for simulating sewer surcharge and calculating area and water depth of waterlogged areas under storm conditions. The best design of rebuilding storm sewer system or combined sewer system can be provided by simulating existing state of built drainage pipeline. The model was used for rebuilding Shenyang drainage works last year, and the good results were obtained.
Inflow
Sanitary sewer
Combined sewer
Drainage system (geomorphology)
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Retention basin
Urban runoff
Drainage system (geomorphology)
First flush
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Combined sewers often overflow during intensive storm activity as the capacity of the system is exceeded in response to excess stormwater inflow. Uncontrolled releases of untreated stormwater as sanitary sewer overflows (SSOs) are also possible but are far less documented, mainly due to a lack of available data, despite being a serious issue for many communities across the US. This study conducted a quantitative analysis of several key storm variables with the aim of identifying occurrence thresholds toward triggering overflows for a residential sewershed in the city of Louisville, Kentucky. Using 5-minute rainfall data and the SSO event database from the Louisville Metropolitan Sewer District (MSD), results indicated that occurrence thresholds in total storm rainfall depth (35.6 mm) and maximum storm intensity (50 mm/hr) were present which could be used to classify storms as overflow versus non-overflow events. Additionally, the majority of overflow events resulted from storms with ratios below 0.5 and could be classified as 1-year storm frequency events across all storm durations. Discriminant analysis further identified these variables as significant in grouping the storms into overflow versus non-overflow events. By analyzing the sensitivity of known SSOs within the metro sewer system to various storm characteristics and resulting stormwater inflow this research could provide stormwater planners and affected residents with better predictive and potential management capabilities for future SSO events.
Combined sewer
Inflow
Sanitary sewer
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First flush
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A combination of the STORM runoff model and a two-dimensional dynamic lake type model successfully reproduced the fecal coliform levels of an urban beach on a lake in the Ottawa River. The elevated fecal coliform levels were associated with rainfall events and runoff from two large catchments upstream of the beach. Due to prevailing conditions in the lake the second largest summer storm did not produce elevated fecal coliform levels while the third and fourth largest storms did. The models predicted these events.The STORM model was calibrated on a subcatehment and supplied the runoff flow volumes and pollution levels to the dynamic lake model. The other input data for the lake model were supplied by field measurements.The models were used to assess the effectiveness of management options to improve the water quality on the beach. The most cost-effective option was identified by the model predictions. Key words: beach fecal coliform predictions, stormwater beach fecal coliforms, storm, runoff, modelling.
Indicator bacteria
Combined sewer
Urban runoff
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A major drawback of separate sewer systems is the occurrence of illicit connections: unintended sewer cross-connections that connect foul water outlets from residential or industrial premises to the storm water system and/or storm water outlets to the foul sewer system. The amount of unwanted storm water in foul sewer systems can be significant resulting in a number of detrimental effects on the performance of the wastewater system. Efficient removal of storm water inflows into foul sewers requires knowledge on the exact locations of the inflows. This paper presents a monitoring technique that can be used to localize illicit storm water inflows into foul sewer systems: Distributed Temperature Sensing (DTS). Data results from two monitoring campaigns in foul sewer systems in the Netherlands and Germany show the level of detail with which in-sewer processes can be studied. Storm water inflow can be detected as long as the temperature of this inflow differs from the in-sewer temperatures prior to the event. Also, the insewer propagation of storm water can be monitored, enabling a detailed view on advection-dispersion and mixing processes.
Sanitary sewer
Inflow
Combined sewer
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A major drawback of separate sewer systems is the occurrence of illicit connections: unintended sewer cross-connections that connect foul water outlets from residential or industrial premises to the storm water system and/or storm water outlets to the foul sewer system. The amount of unwanted storm water in foul sewer systems can be significant, resulting in a number of detrimental effects on the performance of the wastewater system. Efficient removal of storm water inflows into foul sewers requires knowledge of the exact locations of the inflows. This paper presents the use of distributed temperature sensing (DTS) monitoring data to localize illicit storm water inflows into foul sewer systems. Data results from two monitoring campaigns in foul sewer systems in the Netherlands and Germany are presented. For both areas a number of storm water inflow locations can be derived from the data. Storm water inflow can only be detected as long as the temperature of this inflow differs from the in-sewer temperatures prior to the event. Also, the in-sewer propagation of storm and wastewater can be monitored, enabling a detailed view on advection.
Sanitary sewer
Inflow
Combined sewer
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Urban stormwater samples were collected form March 2007 to April 2009 at Wangjiazhuang,a small urban catchment in Shenzhen.Six constituents(CODCr,NH3-N,TN,TP,SS,BOD5) were analysed for source apportionment of urban stormwater using the Positive Matrix Factor(PMF) analysis method.The results showed that municipal wastewater,in-sewer sediments and surface runoff were main sources of stormwater runoff.Municipal wastewater is the primary source for NH3-N and TN.CODCr,TP and BOD5 mainly come from in-sewer sediments.Surface runoff is the primary contributor of SS.PMF is well suited for source apportionment of stormwater runoff at small urban catchment which has combined sewer systems and homogeneous land use.The stability of source profiles affects PMF's results mostly.
Apportionment
Combined sewer
Sanitary sewer
Urban runoff
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The Illinois Urban Drainage Area Simulator was used to analyze the effects that (1) physical changes to storm-sewer conduits, and (2) increased runoff detention and infiltration would have on storm runoff in four urban basins in Madison, Wisconsin. The model was calibrated using monitoring data for the four basins collected over a 1-year period. A brief evaluation was made of a modified version of the model that simulates quality of urban runoff. Additional monitoring and computer analysis are necessary to calibrate the water-quality portion of the model before it can be used as a management tool in Madison. This study was done in cooperation with the Dane County Regional Planning Commission (DCRPC). Tables presenting results of various storm-water-management options are included. Some notable simulation results were that a 25 percent storm-sewer slope reduction yielded only a 3 percent peak-discharge reduction, and increasing storm-sewer roughness by increasing Manning's "n" from 0.013 to 0.0^0 decreased peak discharge about 10 to 20 percent. Detention of 10 percent of runoff throughout each basin yielded peak-discharge reductions of about 10 to 20 percent. Infiltration of all parking-lot runoff reduced peak discharges 5 to 2h percent. Peak discharges were reduced by 71 to 88 percent by substituting porous pavement for conventional pavement. Draining 90 percent of the residential rooftops onto lawns instead of driveways reduced peak discharge from 7 to 31 percent. Runoff-volume reduction was similarly reduced for the induced infiltration simulations. Storage requirements for hypothetical storm-water-treatment plants ranged from 2.6 to 29 acre-feet for the smallest and largest basins, respectively, with a treatment capacity of 25 cubic feet per second. A brief inconclusive evaluation of the water-quality subroutines of the model was made. Close agreement was noted between observed and simulated loads for nitrates, organic nitrogen, total phosphate, and total solids. Ammonia nitrogen and orthophosphate computed by the model ranged 7 to 11 times greater than the observed loads. Observed loads are doubtful because of the sparsity of water-quality data.
Combined sewer
Infiltration (HVAC)
First flush
Impervious surface
Low-impact development
Lawn
Urban runoff
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Water quality and quantity of urban storm runoff and sewage were monitored to identify the contribution of storm runoff pollution load to the receiving waters in Wuhan City from 2003 to 2005. Storm runoff from urban area carried large amount of pollutants into the receiving waters, which was an important cause of surface water quality deterioration. For the three monitored urban catchments with combined sewer system, the storm runoff produced 59.4% of the total suspended solids (TSS), 26.3% of the chemical oxygen demand (COD), 11.2% of the total nitrogen (TN), and 10.1% of the total phosphorus (TP). Adopting intercepting measure and controlling first flush pollution was the key of controlling storm runoff pollution from urban areas.
First flush
Urban runoff
Combined sewer
Total suspended solids
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