Our experts take a deep dive into wastewater leakage

From rainwater and sewage to wet wipes, fats, oil and grease, wastewater pipelines carry a range of pollutants.

Leakage anywhere in the network has the potential to cause a pollution event that impacts the environment, public health and a utility’s reputation, so there needs to be a sense of urgency in finding leaks in a wastewater network.

We interviewed Business Development Director for water Martin Duff and Sales and Senior Research Engineer Harry Smith, who answered some of the key questions we get asked around wastewater, including:

An image of Atmos' water experts Martin Duff (left, Business Development Director for water) and Harry Smith (right, Sales and Senior Research Engineer)

Question 1: What causes sewage pollution?

There are multiple causes of pollution. Blockages can occur in pipelines due to the buildup of things like wet wipes, fats, oils and grease, causing water to back up and exit the sewer into homes and the environment.

A common cause of sewage pollution is via combined sewer overflows (CSOs). CSOs are permitted to discharge into natural waterways during periods of high rainfall, when sewage treatment works are running at full capacity and can’t accept any more sewage. However, problems in the infrastructure can lead to CSOs spilling too early.

For example, pipelines that take treated final effluent from a sewage treatment works to be discharged into the sea can have leaks in them, causing them to fill up with sea water and creating a hydraulic back up in the system which causes the CSO to activate too early.

Rising sewer main bursts are another key area that cause pollution incidents. Rising sewer mains are pressurized pipelines carrying sewage uphill and are a notorious weak point on the wastewater network. They have a high rate of bursts and are often located near natural water resources and so can lead to damaging pollution incidents.

Question 2: Is it possible to monitor leaks in sewage pipelines?

Yes, it’s possible. There are both internal and external leak detection methods available. Given the link between sewage leaks and pollution incidents it’s important that leaks are discovered quickly, which is why internal pipeline monitoring is important.

However, sewage pipelines are typically harder to monitor due to a lack of access points to deploy and retrofit solutions. Internal pipeline monitoring typically requires a pipeline to be pressurized to function correctly, which makes it challenging in the wastewater network as it is typically gravity fed.

At Atmos we have a solution that focuses on carrying out leak detection in rising sewer mains, which are pipelines closely linked to burst events.

Question 3: How is it possible to detect leaks on a rising sewer main?

We can detect leaks on a rising sewer main by utilizing the negative pressure wave method, which involves monitoring the pressure in the rising sewer main 60 times per second. A sudden drop in pressure may indicate a new leak.

This solution typically requires instrumentation at both ends of the rising sewer main, which can be challenging as it is difficult to access the top of a rising sewer main. However, we’re able to use the high point on the rising main to reflect the negative pressure wave back down the pipe so we can pick up both negative pressure waves with a single device.

Single ended leak detection allows us to both identify a new leak as it forms as well as estimate its location along the rising main.

Question 4: What are the differences between clean water and wastewater applications when undertaking leak detection?

There is a cultural difference between leak detection in clean and wastewater networks. In clean water networks, leakage is a byproduct associated with transporting water under pressure to customers. However, reducing leakage has been a regulatory obligation in the UK for over 25 years, so leak detection is a mature concept in clean water applications.

The techniques and technologies used in clean water networks revolve around finding existing leaks, typically using acoustic techniques or external methods, but this can be a time-consuming exercise.

In wastewater applications leak detection doesn’t really exist, possibly due to the network mostly not being pressurized. Where there is positive pressure such as rising sewer mains, there are minimal access points to install leak detection equipment.

However, there needs to be a sense of urgency in finding wastewater leaks due to the environmental consequences they can have. This is the approach taken in the oil and gas industry, which has a very mature leak detection approach focused on finding new leaks as they form. Atmos is using its 30 years’ experience in the oil and gas industry to help adapt leak detection technologies that can be used in the wastewater network.

Question 5: Can a sewage leak detection system utilize existing instrumentation?

Yes, however, repeatability, resolution and data acquisition rates influence system performance.

If the existing instrumentation has any dampening or pre-filtering this can negatively affect the system. Atmos prefers to utilize analogue pressure sensors.

Question 6: How could the system be used on an intermittently pumped rising main?

We have lots of experience in the oil industry of intermittent pump activities. In wastewater networks most of the network is gravity fed, but there are intermittently pumped sections of pipeline known as rising sewer mains.

Our Atmos Wave technology (negative pressure wave) works in pressurized pipelines, including rising sewer mains which have a high rate of failure compared to the gravity fed part of the network.

Our technology understands the difference between pumps operating and bursts occurring, so an intermittently pumped rising main is within the technology’s capability. High pump noise can potentially impact the system performance, but we have a set of algorithms to manage that.

If we know where the high point is at the end of the rising sewer main we can monitor the rising main with just one instrument at the bottom of the main, as any leaks that occur along it can be reflected off the high point to provide a leak location.

Question 7: Do you see the leak detection system being a fixed monitoring solution or a portable “lift and shift” solution?

For wastewater applications it’s so important to identify and locate new leaks as soon as they form and so the only way to achieve this is to permanently monitor the network in real time, so a fixed solution is recommended.

Question 8: Can Atmos’ leak detection systems be deployed on pipelines of different sizes and materials?

As we are monitoring the internal pipeline properties, our solutions work on many different pipeline materials including metallic, plastic and concrete pipelines. Atmos’ leak detection system can also accommodate a range of diameter and material changes along the pipeline route.

Learn more about how we support the water industry

Wastewater pipelines aren’t the only part of a water utility network facing leak detection challenges.

In clean water pipelines, leakage has been accepted for many years as a necessary consequence of transporting pressurized water through pipelines, but background leaks and small new leaks can escalate into bursts, causing significant disruption.