Adapted from an article written by Alex Ding and Tony Petrucci for Environmental Science & Engineering Magazine
The sewer system has an important role in our daily lives. It transports wastewater away from our homes and businesses, treating it for safe disposal. There are two types of sewer systems: sanitary sewers and storm sewers. Sanitary sewers carry wastewater from toilets, sinks, and showers to treatment plants, while storm sewers drain rainwater and melted snow from outdoor surfaces, preventing flooding and erosion.
Combined sewer systems collect both wastewater and stormwater runoff in the same pipe. They are common in older areas, specifically North American cities with sewer systems built before the 1940s. They transport all contents to wastewater treatment plants for full treatment before discharging into water bodies.
What Is Combined Sewer Overflow (CSO)?
During heavy rainfall or snowmelt, combined sewers can become overwhelmed with stormwater. To prevent flooding, these systems are designed to occasionally overflow, releasing excess wastewater into nearby water bodies.
Unfortunately, this overflow, known as combined sewer overflow (CSO), contains a mixture of contaminated waste, chemicals, and pollutants. The sewer system also transports industrial and household pollutants during rain events. Improperly treated CSO can lead to disease and environmental contamination, as toxic substances spread through the food chain, affecting natural resources.
Why Monitoring the CSO Is Essential to Avoid Flooding
Effective monitoring of combined sewer networks is crucial for assessing overflow and water quality at CSO locations and outfalls. A robust monitoring program provides vital data for remediation projects, reducing runoff contamination from sewer overflows and eliminating costly infrastructure improvements.
How to Monitor Combined Sewer Overflow (CSO)
CSO monitoring at overflow locations can be done through flow level measurements. The overflow rate can be calculated based on the overflow structure geometry using a head-discharge relationship.
For level monitoring in wastewater applications, a non-intrusive above-flow ultrasonic sensor is preferred to avoid rigging. However, the range of level measurement is limited. To ensure good data quality and cover varying CSO levels, a redundant pressure transducer should be used in addition to the ultrasonic sensor.
CSO monitoring at downstream locations, such as outfalls, can be measured using flow meters in overflow pipes. But during heavy storms, erroneous measurements may occur due to invert below mean tide levels.
To address anticipated challenges, municipalities are developing real-time monitoring systems to optimize combined sewer systems, control water pollution, and enhance infrastructure. Integrating real-time monitoring data with accurate analytical models allows for optimizing pump scheduling, detecting leaks, and implementing an overflow contamination alarm system.
Multiple permanent monitoring locations are necessary for effective logging of occurrences throughout the combined sewer system.
Integration of Smart City Water’s Real-Time Monitoring System Software
Smart City Water’s monitoring systems enable real-time data analytics and device management. Monitoring software, usually leveraged via software as a service (SaaS), uses a centralized platform that displays sensor status and performance on a dashboard.
Flow meters in combined sewer systems require flow monitoring software to manage sensors and access real-time data. These systems are integrated with geographic information systems (GIS) to capture, store, and display monitoring network information. GIS integrated systems improve data management workflow and provide detailed descriptions.
Web-based software on the cloud offers advantages over conventional desktop computer programs by using external computing resources. Cloud computing allows users to access, manage, and deliver services on multiple networks without human involvement. These systems enhance efficiency and utilization by load balancing across various applications, offering extensive data storage and processing capabilities.
Real-time data acquisition relies on wireless communication technology such as cellular, satellite, and Bluetooth, allowing remote access and sensor reading. The data is then transferred to a hosting platform instantly.
With the sunset of the previous cellular network (3G), the latest generation of cellular communication technology (LTE-M and NB-IoT) provides advantages like lower power consumption and improved signal penetration. Wireless sensors are crucial for the Internet of Things (IoT) and are part of the Smart City vision. They collect data for analytics and facilitate smart flow monitoring in underground sewer infrastructures to track performance and identify issues.
How Can Civica Help with Combined Sewer Overflow (CSO) Analysis?
Civica Infrastructure Inc. specializes in wastewater management solutions, offering sewer inspection and flow monitoring services for clients dealing with combined sewer overflow.
Sister company Smart City Water has created cutting-edge capacity management software that has made them industry leaders. They are constantly innovating to provide specialized services to clients looking to optimize their drainage systems, including flood analysis, sanitary sewer capacity analysis, and storm sewer capacity analysis.
Contact Civica today for a consultation.
Learn more at:
Flow Monitoring in Collection System Modelling
Assessing And Creating Wastewater System Capacity in Ontario
Flow and Rainfall Monitoring – Ensuring Data Quality
City of Toronto’s Sewer Infrastructure and Sewer Capacity Assessment Guidelines
