Sanitary Sewer Overflow Reduction Optimization Using Genetic Algorithm

Short duration intense rainfall causes an increase in rainfall derived infiltration and inflow (RDII) into aging sewer networks, which leads to Sanitary Sewer Overflows (SSOs). This study presents a generalised framework for assessing and mitigating the impacts of intense rainfall on sanitary sewer networks. The first part of the proposed framework involves a detailed hydraulic modelling to evaluate the performance of the sewer network. The second part deals with the development of SSO mitigation strategies based on Water Sensitive Urban Design (WSUD) approaches. This paper also demonstrates the application of the first part of the proposed framework for a case study catchment in Melbourne, Australia. The hydraulic performance of the case study sewer network during a wet and a dry year is presented. The analysis found that for the wet year, 11 manholes had sewer overflows, whereas 53 of 57 manholes in the network of 3.2 km had surcharges. Such a study will benefit the water authorities to develop mitigation strategies for controlling SSOs in their sewer systems.

The Environmental Protection Agency (EPA) recently estimated that between 23,000 and 75,000 sanitary sewer overflows (SSOs) occur each year in the United States, resulting in releases of between three to ten billion gallons of untreated wastewater. Most SSO events are caused by sewer blockages, while most SSO volume appears to be related to events caused by wet weather and excessive inflow and infiltration. SSOs have a variety of causes, including blockages, line breaks, sewer defects that allow inflow and infiltration (I/I), lapses in sewer system operation and maintenance, inadequate sewer design and construction, power failures, and vandalism. The microbial pathogens and other pollutants present in SSOs can cause or contribute to water quality impairments and other environmental and human health problems. With limited budgets to rehabilitate and/or replace existing collection system deficiencies, it is important that municipalities and agencies prioritize segments of the collection system from most critical to least critical and develop short and long-term capital improvement plans based on this prioritization. Through a case study of an SSO evaluation conducted at a military facility in Southern California, the use of off-the-shelf GIS software was used as a tool to conduct a comprehensive risk-based SSO evaluation of a collection system. This risk based evaluation provides a cost-effective method to help municipalities and agencies identify areas within their collection system that are at greatest risk for sanitary sewer overflows, prioritize deficiencies, and then plan for short and long-term rehabilitation and/or replacement options. Conducting this evaluation will also help municipalities and agencies comply with their NPDES permits and applicable Capacity, Management, Operation, and Maintenance (CMOM) requirements and/or guidelines.

Detailed flow and rainfall measurements, accompanied by long-term simulation, were used to identify the inflow and infiltration response characteristics of the sanitary sewer collection system in Vallejo CA. This response has produced sanitary sewer overflows on numerous occasions throughout various locations in the collection system. A mix of collection system rehabilitation, capacity upgrades, storage and increased treatment capacity may be used to control future wet-weather flows to a regulatory standard. A major limitation to optimizing the design of these wet-weather controls is a relatively high uncertainty regarding the effectiveness of collection system rehabilitation to control wet-weather flows. The ability of collection system rehabilitation activities to control wet-weather flows will in turn affect the performance of all downstream controls, including conveyance, storage and treatment. If rehabilitation effectiveness is over-estimated, overall control performance will not meet design standards, and if underestimated, significant overexpenditure of resources is possible. A risk-based approach was used to identify the importance of rehabilitation effectiveness on the overall design. Probability density functions of wet-weather pollutant control for storage, treatment and rehabilitation were derived from direct observations and used to estimate the overall reliability of various mixes of design alternatives. Based on this analysis, a concentrated smallscale rehabilitation project was used to reduce the uncertainty associated with estimating the performance of rehabilitation for sanitary sewer overflow (SSO) control. The results of the rehabilitation test were used to refine the risk-based design of the SSO control plan. Actual rehabilitation costs were used to estimate a costeffectiveness relationship for this specific collection system. A process model was used to link the performance and costs of storage, treatment, conveyance and rehabilitation. This design model was formulated as a nonlinear optimization problem, and a generalized reduced gradient search algorithm was used to find the best mix of alternatives to meet various regulatory goals in a cost-effective manner. Various levels of cost and risk were then generated with this model for meeting performance expectations, aiding the design team by concentrating their efforts on an array of non-dominated solutions.

Sanitary sewer overflows (SSOs) are a major environmental issue. One of the major factors causing SSOs is the rain-derived inflow and infiltration (RDII) to a separate sanitary sewer system. If a wastewater collection system is not well maintained, cumulative system-wide RDII could easily cause the wastewater conveyance and treatment capacity to be overwhelmed, and thus lead to SSOs. Monitoring system condition is a key component in system management. The industry’s standard approaches to system monitoring include the practice of collecting and analyzing continuous rainfall and flow data at certain key locations in the system to estimate the level of RDII. However, the writer is of the opinion that the current standard analytical methodologies of the industry can be significantly improved. This paper introduces a basic regression approach with autoregressive errors to support statistical inferences with respect to the level of RDII.

The Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC (NTESS), a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration (DOE/NNSA) under contract DE-NA0003525. In 2008, a Notice of Intent (NOI) was filed for the Sandia National Laboratories, California (SNL/CA) facility to be covered under the State Water Resources Control Board (SWRCB) Order No. 2006-0003-DWQ Statewide General Waste Discharge Requirements (WDR) for Sanitary Sewer Systems (General Permit) and was issued the WDID No. 2SSO11605. The General Permit requires a proactive approach to reduce the number and frequency of sanitary sewer overflows (SSOs) within the State. Provision D.11 of the General Permit requires the development and implementation of a written Sewer System Management Plan (SSMP). This SSMP is prepared according to the mandatory elements required by Provision D.13 and D.14, as well as the schedule for a population less than 2,500 as outlined in Provision D.15.

This study explores the outcomes and impacts of sanitary sewer overflows (SSOs) and basement backups in underserved communities in Baltimore, Maryland. The larger effort is an environmental and community-driven mixed-methods project, however, the research in this manuscript focuses on the household survey portion with residents who have experienced SSOs or sewage backups. Based on the snowball sampling method applied, the resulting residents engaged are predominantly African-American individuals, females, homeowners, and residents between the ages of 50 and 69. Strikingly, 70% of respondents reported that their frequency of SSOs is between moderate to frequent. The findings reveal that SSOs are a pervasive issue affecting residents’ physical and mental health and overall quality of life. Despite residents’ perceptions that their household infrastructure is in good condition, the recurring nature of SSOs highlights systemic problems within the city’s aging sewer systems, urging a deeper understanding of the social and structural vulnerabilities involved. This research calls attention to the importance of comprehensive interventions, including effective risk communication strategies and substantial investment in infrastructure rehabilitation, to mitigate the risks posed by SSOs and promote long-term resilience in urban environments. Additionally, it emphasizes the importance of community-driven research in addressing engineering, urban planning, and public health challenges with particular support for the most affected populations.

In 1999, The Metropolitan Sewer District of Greater Cincinnati, Ohio (MSD) began negotiations with the United States Department of Justice, the United States Environmental Protection Agency, and the State of Ohio to create a program to address sanitary sewer overflows (SSO) and combined sewer overflows (CSO). The resulting document, the Consent Decree, formally outlined a process that MSD would follow and that government agencies could recognize and support. MSD had been addressing removal and reduction of SSOs and CSOs prior to the Consent Decree negotiations, but the Consent Decree defined a time frame as well for MSD. The Consent Decree required MSD to update the CSO Long Term Control Plan (LTCP). An important component of the CSO LTCP Update is the assessment of CSO control alternatives with respect to receiving water quality. As such, a field program was designed and implemented to support water quality modeling and CSO planning objectives. The field program would coincide with the water recreation season, starting in May and ending in October. The field program contained several components associated with dry and wet weather sampling and monitoring as outlined by the Consent Decree; Ohio River sampling, source characterization (CSO, SSO and Storm), and tributary sampling and continuous monitoring. This paper discusses the continuous monitoring component of the tributary sampling and monitoring program. Starting with the conceptual plan described by the Consent Decree, it outlines the process of converting a conceptual ideal into a workable field program including the installation, maintenance, data management and demobilization activities. Specific examples of unique site limitations are provided with the solutions tried and the resulting outcomes.

A pilot scale investigation was undertaken at the Allegheny County Sanitary Authority (ALCOSAN) for approximately 12 months to evaluate the feasibility of using cross-flow microfiltration for the treatment of primary sewage effluent simulating combined and sanitary sewer overflows. Ceramic membranes of various pores sizes (0.05–1.4μm) were tested to understand the impact of cross-flow velocity, transmembrane pressure, and feed suspended solids on permeate water quality and permeate flux rate. A 0.2μm membrane operated with a 1.8m∕s cross-flow velocity, a transmembrane pressure below 2.1 bar and a backpulse frequency of 60 s showed the best performance among the conditions evaluated in this study. The 0.2μm membrane consistently met water quality objectives for fecal coliforms, E Coli, enterococci, BOD5, and suspended solids independent of the feed concentration, suggesting that direct discharge to surface water may be feasible. Feed suspended solids concentration and temperature influenced membrane permeate flux. Membrane cleaning with alkaline sodium hypochlorite solution is recommended as the first step followed by nitric acid cleaning if needed.

Distribution and Fate of Escherichia coli in Lake Michigan Following Contamination with Urban Stormwater and Combined Sewer Overflows

Water Sensitive Urban Design (WSUD) Spatial Prioritisation through Global Sensitivity Analysis for Effective Urban Pluvial Flood Mitigation

There has been evidence of a relationship between death, disease, and lack of basic sanitation in the contemporary era, which is both a public health issue and a challenge for the new millennium. The poor countries in Africa, Asia, and Latin America have deficit sanitary sewage and water supply infrastructure, which leads to the proliferation of waterborne diseases in urban areas. This degree study has evaluated the cost ratio of public health and the implementation of water and sewage systems in the capital of Guinea-Bissau. Six scenarios were analyzed, including three options for the sanitary sewage system (a collective system with a collection network and a sewage collection station; an individual simplified latrine system; and a complete collective system with a collection network, a lift station, and a sewage treatment plant), and two scenario options for the water supply system (a direct capture system, and a complete system with capture, storage, and distribution). As for public health, the costs with social assistance programs, drugs, vaccines, and hospitalizations related to waterborne diseases were considered, with no distinction of sanitary sewage and water supply-related diseases. The cost ratio of 4.05 for the most efficient basic sanitation scenario was similar to the value found in literature. In other words, for every dollar invested in basic sanitation there are approximate savings of 4.3 dollars in health.

The technical, operational, legal-political, and management aspects of sanitary sewer overflows asso- ciated with non-NPDES entities were investigated. The identification of the parameters contributing to sanitary sewer overflows was focused on wet-weather conditions. Such conditions include rainfall-induced infiltration and inflow (RDII), and increased attention was given to infil- tration and inflow (I/I) sources located on private prop- erty. The study also included a reference to historical and current approaches and solutions to private-property I/I, with emphasis on local ordinances, NPDES authority, and equity of corrective actions. Telephone surveys to muni- cipalities and agencies working in the field were performed, to retrieve new information and innovating approaches. Rehabilitation of central collection systems alone can reduce I/I by an average of 30%. Although the concern is essentially legal and political when dealing with private-property owners, a comprehensive rehabili- tation effort extended on private property can reduce I/I by as much as 90%.

All You Wanted to Know About Private Service Laterals (And Then Some)!The U.S. Environmental Protection Agency (US EPA) estimates that between 23,000 and 75,000 sanitary sewer overflow (SSO) events occur per year in the U.S. (excluding basement backups) (US EPA, 2004). Regulatory authorities are increasingly requiring wastewater utilities to eliminate such overflow events. One approach to eliminating SSOs is to reduce the entry of inflow and infiltration (I/I) into...Author(s)Jane McLamarrahJaime DavidsonLaurie ChaseSourceProceedings of the Water Environment FederationSubjectSession 16: Collection System Private Property and Public Outreach EffortsDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:17L.806;1-DOI10.2175/193864711802639453Volume / Issue2011 / 17Content sourceWEFTECFirst / last page(s)806 - 810Copyright2011Word count316Subject keywordsSewer lateralslegal authoritiesprivate propertyprivate systemsSSOssource controlfundingpublic education

Sanitary sewer overflows (SSO) are becoming of increasing concern in the sewage system management to utilities and regulators. Many overflows are not easily identifiable. If undetected, they can adversely impact public health and are an environmental hazard. The number and severity of SSOs can be reduced through the proper sewerage maintenance and the detection-correction of ongoing events. A methodology is presented to locate meters to maximize the likelihood of detecting a system blockage. When a blockage occurs the discharge rates in the system are affected. If the changes are greater than one would expect due to random variability, they can be attributed to a blockage. The proposed method attempts to optimize the monitoring locations to maximize the number of blockages that can be identified by a given number of meters. The problem is solved using a set-covering approach. The approach allows the tradeoff between the number of detections and cost of gages to be easily assessed. Data from Pima County Wastewater Management's monitoring system is used as a case study. To introduce blockages and analyze system hydraulics a full hydraulic model for the sewer system is applied.

In this study, analysis of reliability of sewer network was progressed with the number of overflow nodes and overflow volume simultaneously for urban areas considering sedimentation. Reliability analysis shows that it is possible to quantify the difference in the phenomenon of the destruction of sedimentation in urban sewer system under the same design frequency. It is proposed as one of the indicators evaluated as full reliability for sewer system. To analyze detailed changes in conduit designs in urban sewer networks, tried to reduction of sedimentation in sewer networks using modified pipe slope in Bujeon-dong catchment, Busan. The various sewer designs were applied and then, the most effective improvement of reliability over 10%. Suggested reliability process can produce the quantitative evaluations about sewer systems using the results of the system simulations and use of possible the objective function for the sewer network designed with a relative evaluation.