Sanitary Sewer Overflows Research Articles

Green First Approach for Wet Weather Programs

Many United States and Canadian cities have recently started to initiate combined sewer overflow (CSO) and sanitary sewer overflow (SSO) control projects to co…

Evaluating Alternative Binder Materials for Sewer Collection System Concrete Structures to Reduce Fat, Oil, and Grease Related Sanitary Sewer Overflows

Evaluating Alternative Binder Materials for Sewer Collection System Concrete Structures to Reduce Fat, Oil, and Grease Related Sanitary Sewer Overflows

Erratum: "Sanitary Sewer Overflows and Emergency Room Visits for Gastrointestinal Illness: Analysis of Massachusetts Data, 2006-2007".

[This corrects the article DOI: 10.1289/EHP2048.].

Sanitary Sewer Overflows and Emergency Room Visits for Gastrointestinal Illness: Analysis of Massachusetts Data, 2006-2007.

Background:Sanitary sewer overflows (SSOs) occur when untreated sewage is discharged into water sources before reaching the treatment facility, potentially contaminating the water source with gastrointestinal pathogens.Objectives:The objective of this paper is to assess associations between SSO events and rates of gastrointestinal (GI) illness in Massachusetts.Methods:A case-crossover study design was used to investigate association between SSO events and emergency room (ER) visits with a primary diagnosis of gastrointestinal (GI) illness in Massachusetts for 2006–2007. ER visits for GI were considered exposed if an SSO event occurred in the county of residence within three hazard periods, 0–4 d, 5–9 d, or 10–14 d, before the visit. A time-stratified bidirectional design was used to select control days for each ER visit on the same day of the week during the same month. Fixed effect logistic regression models were used to estimate the risk of ER visits following the SSO event.Results:During the study period, there were 270 SSO events for northeastern Massachusetts and 66,460 ER admissions with GI illness listed as the primary diagnostic code. The overall odds ratio (OR) for ER visits for GI illness was 1.09 [95% confidence interval (CI): 1.03, 1.16] in the 10–14 d period following an SSO event, with positive ORs for all age groups and for three of the four counties. The 0–4 d and 5–9 d periods following an SSO event were not associated with ER visits for GI illness overall, and associations by county or age were inconsistent.Conclusions:We demonstrated an association between SSO events and ER visits for GI illness using a case-crossover study design. In light of the aging water infrastructure in the United States and the expected increase in heavy rainfall events, our findings suggest a potential health impact associated with sewage overflows. https://doi.org/10.1289/EHP2048

Influence of fat and oil type on the yield, physico-chemical properties, and microstructure of fat, oil, and grease (FOG) deposits

Fat, oil, and grease (FOG) deposit, in the form of calcium soap, was found to cause sanitary sewer overflows due to its adhesion on pipe walls. To address this problem, laboratory-prepared calcium soaps have been used to investigate the formation mechanisms of FOG deposits. However, the fats and oils previously utilized were limited and some soap characteristics were not examined. This research attempted to probe through the properties of calcium soaps prepared from calcium chloride and the fats and oils of chicken, pork, palm olein, soybean, olive, and coconut to further understand FOG formation and stability. Results revealed that FOG deposits may occur as smooth, paste-like material or coarse, semi-solid substance depending on their exposure to excess fat/oil and calcium. The smooth soaps with more excess fat/oil demonstrated high apparent viscosity and consistency index, while the coarse soaps with large levels of calcium signified higher melting endset. Moreover, a soap microstructure showing evident networks and lesser void area displayed higher heat and rheological stability, respectively. Overall, fats and oils with higher oleic to palmitic acid ratio such as palm olein oil, olive oil, chicken fat, and pork fat produced soaps with greater yield and degree of saponification. Hence, establishments and authorities should be alert in managing and monitoring these wastes. On the other hand, soybean oil high in linoleic acid and coconut oil high in lauric acid do not pose an immediate threat to the sewer system since they only produced soaps in small quantity. However, their soaps showed high melting endset which could pose a serious effect when accumulated at large amount. On the whole, the fatty acid profile of fats and oils, the presence of excess fat/oil, and calcium content mainly dictate the appearance, melting, rheology, and microstructure of calcium soaps. Their distinct properties can be used as criteria in predicting the condition and stability of FOG deposits.

A critical review of fat, oil, and grease (FOG) in sewer collection systems: Challenges and control

ABSTRACTFat, oil, and grease (FOG) released into the sewer collection system have resulted in the production of insoluble solids, leading to FOG blockages in sanitary sewer pipes and consequently sanitary sewer overflows (SSOs). FOG-related SSOs continue to be a global challenge for municipalities responsible for maintaining the conveyance of wastewater in sanitary sewer systems. To provide a comprehensive understanding of FOG control in sewers, this paper critically reviews the scientific literature on the FOG deposit formation process, sources of components involved in FOG deposit formation, and solutions to the problems caused by FOG in sewer systems. The implications of these findings were also evaluated to provide support for pretreatment managers responsible for sewer collection system maintenance. Finally, the ongoing challenges in further understanding the FOG deposit formation process, the distribution of the sources of FOG/free fatty acids, the installation and maintenance of grease interceptors (GIs), and the recovery of energy from GI waste and FOG deposits, were also discussed to determine future research directions.

Application of a Multiobjective Genetic Algorithm to Reduce Wet Weather Sanitary Sewer Overflows and Surcharge

AbstractSanitary sewer overflow (SSO) is the discharge of wastewater from the collection network into the environment. SSOs are significant environmental and public health hazards. The EPA estimate...

Enhancing the Performance of a Multiobjective Evolutionary Algorithm for Sanitary Sewer Overflow Reduction

AbstractThe application of multiobjective evolutionary algorithms (MOEAs) to sanitary sewer overflow (SSO) optimization problems typically requires multiple runs of a simulation model and can be ve...

Impact of Short Duration Intense Rainfall Events on Sanitary Sewer Network Performance

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.

Attenuated Total Reflectance Fourier transform infrared spectroscopy for determination of Long Chain Free Fatty Acid concentration in oily wastewater using the double wavenumber extrapolation technique

Long Chain Free Fatty Acids (LCFFAs) from the hydrolysis of fat, oil and grease (FOG) are major components in the formation of insoluble saponified solids known as FOG deposits that accumulate in sewer pipes and lead to sanitary sewer overflows (SSOs). A Double Wavenumber Extrapolative Technique (DWET) was developed to simultaneously measure LCFFAs and FOG concentrations in oily wastewater suspensions. This method is based on the analysis of the Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectrum, in which the absorbance of carboxyl bond (1710cm−1) and triglyceride bond (1745cm−1) were selected as the characteristic wavenumbers for total LCFFAs and FOG, respectively. A series of experiments using pure organic samples (Oleic acid/Palmitic acid in Canola oil) were performed that showed a linear relationship between the absorption at these two wavenumbers and the total LCFFA. In addition, the DWET method was validated using GC analyses, which displayed a high degree of agreement between the two methods for simulated oily wastewater suspensions (1–35% Oleic acid in Canola oil/Peanut oil). The average determination error of the DWET approach was ~5% when the LCFFA fraction was above 10wt%, indicating that the DWET could be applied as an experimental method for the determination of both LCFFAs and FOG concentrations in oily wastewater suspensions. Potential applications of this DWET approach includes: (1) monitoring the LCFFAs and FOG concentrations in grease interceptor (GI) effluents for regulatory compliance; (2) evaluating alternative LCFFAs/FOG removal technologies; and (3) quantifying potential FOG deposit high accumulation zones in the sewer collection system.

Sanitary Sewer Overflows – A Systematic Approach to Understanding Why They Occur and How to Use All the Data Collected to Understand Your System

Sanitary Sewer Overflows – A Systematic Approach to Understanding Why They Occur and How to Use All the Data Collected to Understand Your System

Joint Depth, Duration, Frequency Analysis of Rainfall Leading to Sanitary Sewer Overflows

Joint Depth, Duration, Frequency Analysis of Rainfall Leading to Sanitary Sewer Overflows

“An Ounce of Prevention is Worth a Pound of Cure” Stopping Sanitary Sewer Overflows Before They Occur

“An Ounce of Prevention is Worth a Pound of Cure” Stopping Sanitary Sewer Overflows Before They Occur

Multiobjective Genetic Optimization Approach to Identify Pipe Segment Replacements and Inline Storages to Reduce Sanitary Sewer Overflows

Sanitary sewer overflows (SSOs) is the unintentional discharge of untreated sewage from the sanitary sewer system and pose serious risk to public health and to the environment. Rehabilitation plans to reduce SSOs involve increasing conveyance capacity and shaving peak flow using detention storages. Identifying the best location for rehabilitating the sanitary sewer network is a difficult task because of the great length of sanitary sewer systems. This study utilized single and multiobjective genetic algorithms (GAs) to design rehabilitation strategies for SSOs reduction in an existing sewer network. The Nondominated Sorting Genetic Algorithm II was linked to the EPA-SWMM to generate non-dominated sets of solutions that characterizes the tradeoffs between reduction in number of SSOs and cost (Case I), and the tradeoff between of volume of SSOs and cost (Case II). The results show that, when maximizing the reduction of number SSOs, the algorithm target first regions of the network with higher density of SSOs. When maximizing the reduction of volume of SSOs, the solutions prioritize the nodes with the largest overflow volumes. The tested approach provides a range of options to decision makers that seek to reduce or eliminate SSOs in an existing sanitary sewer system.

Adapting to Financially Challenging Times

Over the past decade, rehabilitation and replacement of water utility infrastructure have taken a back seat in the capital plans of US water utilities. Sanitary and combined sewer overflows, water resource planning, and nutrient removal are just a few of the items that dominate the top spots on our capital to‐do lists. As we wrestle to fund our growing capital needs, we are also pressed to control overall costs and keep customer rates low, which has become increasingly difficult in the face of declining per capita water sales. The inevitable result is a looming water infrastructure emergency – assets at or near the end of their useful lives, under‐funded asset management programs, and an unaware public that takes safe, reliable drinking water for granted.

Coupling a continuous watershed-scale microbial fate and transport model with a stochastic dose-response model to estimate risk of illness in an urban watershed

Within the United States, elevated levels of fecal indicator bacteria (FIB) remain the leading cause of surface water-quality impairments requiring formal remediation plans under the federal Clean Water Act's Total Maximum Daily Load (TMDL) program. The sufficiency of compliance with numerical FIB criteria as the targeted endpoint of TMDL remediation plans may be questionable given poor correlations between FIB and pathogenic microorganisms and varying degrees of risk associated with exposure to different fecal pollution sources (e.g. human vs animal). The present study linked a watershed-scale FIB fate and transport model with a dose-response model to continuously predict human health risks via quantitative microbial risk assessment (QMRA), for comparison to regulatory benchmarks. This process permitted comparison of risks associated with different fecal pollution sources in an impaired urban watershed in order to identify remediation priorities. Results indicate that total human illness risks were consistently higher than the regulatory benchmark of 36 illnesses/1000 people for the study watershed, even when the predicted FIB levels were in compliance with the Escherichia coli geometric mean standard of 126CFU/100mL. Sanitary sewer overflows were associated with the greatest risk of illness. This is of particular concern, given increasing indications that sewer leakage is ubiquitous in urban areas, yet not typically fully accounted for during TMDL development. Uncertainty analysis suggested the accuracy of risk estimates would be improved by more detailed knowledge of site-specific pathogen presence and densities. While previous applications of the QMRA process to impaired waterways have mostly focused on single storm events or hypothetical situations, the continuous modeling framework presented in this study could be integrated into long-term water quality management planning, especially the United States' TMDL program, providing greater clarity to watershed stakeholders and decision-makers.

Assessing SWMM 5 Hydrologic Parameter Benefits for Model Calibration

A 33 acre (13.2 ha) sewershed in Cincinnati, Ohio that is regulated by sanitary sewer overflow (SSO) structure 228 experiences high amounts of rain derived inf…

Arrival Analysis of Dry Weather Sanitary Sewer Overflows

This study investigates arrivals of sanitary sewer overflows collected from a municipality. The data set consists of recorded overflows from 2011 to 2014 during dry weather. Reliability analysis is conducted upon each data set. The Weibull distribution is adopted to evaluate the data sets. The results show that the arrival of dry weather SSOs cannot be simply modeled with a Poisson process that is featured with a constant arrival rate. For annual data set, 2-parameter Weibull generally has an acceptable fitting (except 2014 data). The shape parameters are close to 1 or a little greater than 1, indicating relatively constant arrival rate or slightly increased rate. For the entire data set, the 3-parameter Weibull distribution is able to fit the data well. The shape parameter is also greater than 1. Therefore, an increased SSO arrival rate is noticed for this data set. There are needs to make more efforts in maintaining the sewer system.

Impact of microbial activities and hydraulic retention time on the production and profile of long chain fatty acids in grease interceptors: a laboratory study

Fat, oil and grease (FOG) deposits are a major cause of sanitary sewer overflows (SSOs), and calcium salts of long chain fatty acids (LCFAs) have recently been identified as key components of FOG deposits in sewer systems.

Application of an Auxiliary Wastewater Treatment Facility to Solve Sanitary Sewer Overflows

Application of an Auxiliary Wastewater Treatment Facility to Solve Sanitary Sewer Overflows