Sewer District Research Articles

Deep learning's fitness for purpose: A transformation problem frame's perspective

AbstractCombined sewer overflows represent significant risks to human health as untreated water is discharged to the environment. Municipalities, such as the Metropolitan Sewer District of Greater Cincinnati (MSDGC), recently began collecting large amounts of water‐related data and considering the adoption of deep learning (DL) solutions like recurrent neural network (RNN) for predicting overflow events. Clearly, assessing the DL's fitness for the purpose requires a systematic understanding of the problem context. In this study, we propose a requirements engineering framework that uses the problem frames to identify and structure the stakeholder concerns, analyses the physical situations in which the high‐quality data assumptions may not hold, and derives the software testing criteria in the form of metamorphic relations that incorporate both input transformations and output comparisons. Applying our framework to MSDGC's overflow prediction problem enables a principled way to evaluate different RNN solutions in meeting the requirements.

Sensor fault detection for urban drainage systems using redundant measurements

ABSTRACT In urban drainage systems, sensors are used for process monitoring, maintenance, planning, and control. The safety, reliability and performance of the systems are therefore largely dependent on the accuracy and reliability of the sensors. Faulty sensors may lead to poor operational performances in terms of flood and pollution control. An innovative real-time sensor fault detection approach based on the statistical properties of redundant measurements is proposed herein to improve the operation and maintenance of urban drainage systems. This approach is easy to implement, does not require estimates of the process variables and can be configured to detect a large set of anomalies, including incipient failures. The Louisville and Jefferson County Metropolitan Sewer District’s urban drainage system in Kentucky, USA, illustrates the performance of the algorithm.

Greening the color line: historicizing water infrastructure redevelopment and environmental justice in the St. Louis metropolitan region

ABSTRACT In 2011 the St. Louis Metropolitan Sewer District developed a geographically bifurcated gray and green approach addressing aging sanitary and stormwater infrastructure in the region. This approach maps tightly to the region’s persistent patterns of racial segregation allocating green infrastructure to areas of North St. Louis which is majority Black and where significant disinvestment has taken place. While green infrastructure often is hailed as a more equitable way to address urban flooding, a crucial question remains as to how urban greening strategies grapple with persistent urban inequities. This article examines the relationship between geographically uneven infrastructural investments and persistent urban inequities. Drawing on six months of ethnographic and archival fieldwork on St. Louis’s wastewater redevelopment project, I argue that racial capitalism must be incorporated as a framework through which to analyze the equity dimensions of infrastructure redevelopment projects. I found that rather than contend with path dependencies of structural racism, St. Louis’s approach to wastewater redevelopment relies on geographies of racial capitalism to save costs, subjecting marginalized communities to cost-saving approaches with no measures or plans to measure benefits beyond stormwater retention.

Impacts of Storm Characteristics on Generating Sanitary Sewer Overflow (SSO) Events for an Urban Sewershed

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.

Use Risk‐Based Asset Prioritization to Develop Accurate Capital Budgets

North Charleston Sewer District (NCSD) was founded in 1972 to provide wastewater service for customers in an area approximately 60 mi2 in three different South Carolina counties, including six municipalities. The district currently has about 31,000 customers and manages approximately 480 miles of a gravity collection system, 35 miles of force mains, and 11 miles of identified lateral connections. In total, the linear asset network is 520–530 miles.

Analytics and Optimization Reduce Sewage Overflows to Protect Community Waterways in Kentucky

In partnership with Tetra Tech, the Louisville and Jefferson County Metropolitan Sewer District in Kentucky pioneered the application of software that relies on sewer-monitoring data, weather forecasting, and data analytics for system optimization. Benefits include better flow routing, optimal filling and dewatering of storage basins and tunnels, and maximization of the use of treatment capacities.

합류식 하수도 지역에 대형 건축물 설계시 정화조 및 전용오수관로의 비용편익분석 사례연구

본 연구의 목적은 합류식 하수처리구역 내에 대형 건축물을 건설하는 경우, 정화조를 설치하는 대안과 정화조를 대신하여 전용오수관로를 설치하는 대안의 경제성을 비교분석하는 것이다. 이를 위해 우리나라 대표적 대형 건축물인 롯데월드타워의 사례를 들어 두 대안 간의 비용편익분석을 수행하였다. 롯데월드타워 건물에 정화조를 설치하는 대신 에 전용오수관로를 설치할 경우, 회수기간은 6.2년, 순현재가치(NPV)는 약 61.7억 원이 발생하며, B/C비율은 1.93인 것으로 나타났다. 이러한 사례분석 결과는 향후 정화조 폐쇄에 대한 정책수립과 대형 건축물 신축 시 전용오수관로 건설에 대한 타당성을 검토할 때 적용할 수 있는 유용한 지침을 제공해 줄 것으로 보인다. 향후에는 원인자부담금과 전용오수관로 관리책임 부담여부, 악취감소에 따른 경제적 효익 등을 비용편익분석에 추가적으로 고려할 필요가 있다.

Rotate Employees to Ease Succession Planning

A water/wastewater utility's success depends on developing competent, flexible employees. The Metropolitan St. Louis Sewer District (MSD) Operations Department rotates operations supervisors, engineers, and division managers to effectively prepare them for future promotion opportunities. The result is an internal development program with greater employee retention and effortless succession planning.

Reduction of hydrogen sulfide gas in a small wastewater collection system using sodium hydroxide.

The Kennebunk Sewer District collection system experienced H2 S-induced corrosion downstream of terminus manholes for the Wells Road and Boothby Road pumping stations. An automated odor control system using sodium hydroxide (NaOH) was developed to mitigate further corrosion. System performance was quantified by recording the [H2 S] in the terminus manholes before and after NaOH treatment. Preliminary evaluation at the Wells Road facility demonstrated significant (p<0.001) reduction in the average [H2 S] between the treatment (4.8±0.3ppm) and control (67±1.5ppm). Permanent systems installed at both facilities in 2017 yielded similar positive results. The average [H2 S] in the Wells and Boothby Road terminus manholes reduced from 89.4±1.0 to 8.0±0.1ppm and from 7.9±0.2 to 0.82±0.06ppm, respectively. Thiswork demonstrates the ability of the NaOH system presented here to minimize emission of corrosive H2 S gas in small collection systems. PRACTITIONER POINTS: Biologically-produced hydrogen sulfide (H2 S) gas corrodes sewer collection system components and results in premature asset failure. Maintaining wastewater pH above 8.5 by injecting sodium hydroxide (NaOH) minimizes H2 S emission by shifting the molar distribution of sulfur species and partially inhibiting the anaerobes that produce H2 S. The practical application of this approach may be limited to small wastewater collection systems.

Watersheds in Child Mortality: The Role of Effective Water and Sewerage Infrastructure, 1880 to 1920.

We explore the first period of sustained decline in child mortality in the U.S. and provide estimates of the independent and combined effects of clean water and effective sewerage systems on under-five mortality. Our case is Massachusetts, 1880 to 1920, when authorities developed a sewerage and water district in the Boston area. We find the two interventions were complementary and together account for approximately one-third of the decline in log child mortality during the 41 years. Our findings are relevant to the developing world and suggest that a piecemeal approach to infrastructure investments is unlikely to significantly improve child health.

Application of a Hydraulic and Pneumatic Transient Model to Investigate Pavement Heaving near a Large Diameter Sewer

The sewer district serving a Midwestern United States city recently responded to an incident of pavement heaving associated with a drop structure feeding a lar…

Evidence of persistent, recurring summertime hypoxia in Green Bay, Lake Michigan

Six years (2009–2015) of temperature and dissolved oxygen profile data show hypoxic conditions are common in the bottom waters of southern Green Bay, Lake Michigan during the summer. Depleted oxygen concentrations (<5 mg L−1) affect nearly 70% of the 38 stations sampled representing an area of ~500–600 km2. Stratification typically lasts 2+ months, from late June to early September, and some stations exhibit bottom water hypoxia (<2 mg L−1) at a frequency of nearly 25% when sampled during this period. A monitoring program initiated in 1986 by the Green Bay Metropolitan Sewerage District has provided a 23 year, recreational season record (May–September) of continuous (15 min interval) in situ bottom water oxygen and temperature measurements at the Entrance Light station of the Green Bay navigational channel. The duration of the hypoxic season ranges from 2 weeks to over 3 months at this shallow 7 m offshore site. This variability likely results from a combination of thermal stratification, oxygen consumption in deeper waters of the bay, and physical forcing mechanisms that drive cool, oxygen depleted, bottom waters on a southerly trajectory across this sensor. These data suggest the duration of hypoxic conditions may have increased during the stratified season in recent years. Hypoxia in the bay would also appear to be sensitive to relatively small changes in these forces, particularly changes in organic carbon loading and the duration of stratification.

The role of municipal government agencies concerning ambient monitoring and overall management of aquatic resources

Abstract The need for quality scientific information to help managers make wise natural resource decisions is well accepted. However, the means to secure that information has historically been elusive as resources for “routine” monitoring programs are often lacking. Going forward these efforts may be more successful by identification of a consortium of area stakeholders to work together to design, implement and fund a comprehensive ambient monitoring program. This program will provide the regulatory authorities with scientifically defensible information that ensures that appropriate and realistic decisions can be made. Such programs offer many benefits (making a positive contribution to sound management of local aquatic resources, improved credibility with government agencies, demonstrating community leadership) but also come with associated costs. Balance must be achieved. An example of the NEW Water (the brand of the Green Bay Metropolitan Sewerage District) Aquatic Monitoring Program is presented. Demonstrated success for this 30+ year program might be used as a model for others. Discussion includes identification of the planning steps which are necessary to evaluate the efficacy related to development of an in-house ambient monitoring program, and a potential list of stakeholders who may be appropriate to participate in the consortium.

A Semi Risk-Based Approach for Managing Urban Drainage Systems under Extreme Rainfall

Conventional design standards for urban drainage systems are not set to deal with extreme rainfall events. As these events are becoming more frequent, there is room for proposing new planning approaches and standards that are flexible enough to cope with a wide range of rainfall events. In this paper, a semi risk-based approach is presented as a simple and practical way for the analysis and management of rainfall flooding at the precinct scale. This approach uses various rainfall events as input parameters for the analysis of the flood hazard and impacts, and categorises the flood risk in different levels, ranging from very low to very high risk. When visualised on a map, the insight into the risk levels across the precinct will enable engineers and spatial planners to identify and prioritise interventions to manage the flood risk. The approach is demonstrated for a sewer district in the city of Rotterdam, the Netherlands, using a one-dimensional (1D)/two-dimensional (2D) flood model. The risk level of this area is classified as being predominantly very low or low, with a couple of locations with high and very high risk. For these locations interventions, such as disconnection and lowering street profiles, have been proposed and analysed with the 1D/2D flood model. The interventions were shown to be effective in reducing the risk levels from very high/high risk to medium/low risk.

Combined Sewer Overflow Real-Time Modeling for Metropolitan Sewer District of Greater Cincinnati Compliance

Combined Sewer Overflow Real-Time Modeling for Metropolitan Sewer District of Greater Cincinnati Compliance

Evaluating Peracetic Acid for Wet Weather Disinfection at the Metropolitan Sewer District of Greater Cincinnati Wet Weather Facilities

Evaluating Peracetic Acid for Wet Weather Disinfection at the Metropolitan Sewer District of Greater Cincinnati Wet Weather Facilities

Combined sewer overflow events and childhood emergency department visits: A case-crossover study

In localities with combined sewer systems, combined sewer overflow (CSO) events frequently occur following high precipitation and can result in the release of untreated sewage and industrial wastewater into surface waters. We hypothesized that either direct contact with or proximity to aerosolized CSO effluent would increase the risk for childhood emergency department (ED) visits for asthma, gastrointestinal (GI) illnesses, and skin and soft tissue infections (SSTIs) in Cincinnati, OH, USA. ED visits for 2010–2014 due to GI diseases, asthma, and SSTIs were extracted from the Cincinnati Children's Hospital Medical Center electronic health records. The location and timing of CSO events were obtained from the Metropolitan Sewer District (MSD) of Greater Cincinnati. ED visits with a residential address within 500m of a CSO site were used in a case-control crossover study with two bi-directional control periods. Conditional logistic regression models were used to estimate the risk of an ED visit associated with a CSO event at lag periods of 0 to 7days. Statistically significant elevated risks for GI-related ED visits was observed two (OR: 1.16 [95% CI 1.04,1.30]) days after CSO events. CSO events were not significantly associated with asthma- or SSTI-related ED visits, but show similar trends. Our findings suggest an increased risk for GI-related ED visits following CSO events among children who reside near CSO sites.

Here comes the rain: Assessing storm hazards vulnerability in Northeast Ohio

The frequency and intensity of coastal storm events in the Great Lakes region, USA is predicted to increase in the coming decades, exposing at-risk populations to potential hazards including flooding, erosion, and combined sewer overflows. In response, applied research is needed to identify communities that are most vulnerable to storm hazards, and to support municipal officials and local residents with building capacity for resilience. This study analyzes the storm hazards vulnerability of 42 communities that are located within the Northeast Ohio Regional Sewer District (NEORSD), including the city of Cleveland and its inner and outer ring suburbs. Communities are ranked against each other for vulnerability according to a social and environmental indicator, each of which is comprised of five variables that operationalize the sociodemographic and biophysical challenges facing local populations. The indicators are combined to produce a composite Storm Hazards Vulnerability Index (SHVI). Results suggest that the most environmentally vulnerable communities are not always home to the most socially vulnerable populations. Overall storm hazards vulnerability correlates more closely with the environmental indicator than the social, especially among the most vulnerable communities.

Combined Interceptor Rehabilitation – Large-Diameter Sewer Presents Large Obstacles and Great Opportunity for North Charleston Sewer District

Combined Interceptor Rehabilitation – Large-Diameter Sewer Presents Large Obstacles and Great Opportunity for North Charleston Sewer District

Evaluating Innovative CSO Treatment Strategies at Metropolitan Sewer District of Greater Cincinnati

Evaluating Innovative CSO Treatment Strategies at Metropolitan Sewer District of Greater Cincinnati