Event Duration Monitoring (EDM) in Combined Sewer Overflow (CSO) applications

Date: 12/11/20 | In: Level monitoring, wastewater management

Event Duration Monitoring (EDM) in Combined Sewer Overflow (CSO) applications has long been a priority for our water companies. They need to ensure that permitted flows are being treated at water treatment centres and that excess flows are not spilling into the environment prematurely.

Many factors add to the headache of storm overflows. These include population growth, infiltration, urban creep and dramatic changes in rainfall patterns. Failing to have the equipment in place to monitor Flows to Full Treatment (FTFT) or storm overflows will likely lead to action from the Environment Agency.

To better manage storm overflows, you must first fully understand the sewer network and get to know its capacity. After all, CSOs are there for when the sewage system is under pressure. So, if you can predict, through robust monitoring and data analysis, when there might be an issue you can do something to prevent or moderate it!

Level monitoring

Level measurement has long been the go to solution for monitoring CSOs. There are thousands of CSO monitoring installations already in place throughout the UK sewer network and many more being planned. This has led to a lot of investment in product development. The latest generation of water level sensors are more sophisticated, cost effective and reliable. Detectronic’s LIDoTT® water level sensor is MCERTS certified and was tested against the Environment Agency’s (EA) MCERTS standard for EDM monitoring making it the UK’s first battery powered MCERTS EDM monitor. When the sewer network is stressed during storm weather events or by blockages, the LIDoTT® Sensor automatically switches sensor mode from ultrasonic (level) to pressure (depth) as the water level rises. This automatic switching occurs before the water level reaches the ultrasonic deadband area. This means there is no loss of data and makes it perfect for Event Duration Monitoring.

Flows to full treatment

To effectively measure the flows to full treatment, you must monitor the flow and not just the level of your wastewater. Detectronic’s MSFM MCERTS water flow meter is a battery powered insertion monitor. It can be used in part-filled pipes and open-channels and is very versatile since it is not reliant on a flume or weir to deliver accurate flow measurement. The MSFM MCERTS will deliver guaranteed levels of accuracy and data-quality and enables water companies to further improve self-reporting.

Installing the MSFM 2.5T (MCERTS) area velocity flow meter on the inlet will record pass forward flows. Meanwhile, the LIDoTT® Sensor connected to the CSO Channel of the MSFM will accurately monitor the event duration.


Reliable flow data feeding into the DetecAnalytics AI software tool provides confidence when reporting on the Storm Overflow Assessment Framework (SOAF). We can successfully predict how a catchment will respond to changing storm events, and apply a risk based management approach to the entire network. Utilising storage potential in a network brings its own risk. But with careful planning and monitoring, in-network storage acts as an efficient means of stormwater attenuation.

To speak to a Detectronic Advisor about Event Duration Monitoring in storm overflow applications,  call +44 (0)1282 449 124 or email sales@detectronic.org