The technologies available to rehabilitate sewers are continuously evolving. Here we take a closer look at epoxy sewer lining, a technique which has a number of benefits that make it well suited to rehabilitating existing sewer systems.
As Australia’s critical assets age, more and more emphasis is directed at rehabilitating and maintaining existing assets, as opposed to building new assets. Rehabilitation, rather than rebuilding, is better for the asset owner, better for the community and better for the environment.
Australia’s water utilities have asset management and rehabilitation plans in place. In addition, many also have annual targets for the inspection and maintenance of their assets.
There is a wide range of materials and technologies available for the rehabilitation of existing structures. These include epoxy liners, calcium aluminate cement (CAC) mortars, HDPE liners and others.
Epoxy liners in particular are well suited to the task of lining and relining sewer structures. Some of the key benefits they offer include:
Epoxy products have superior acid resistance, which makes them particularly useful in the sewer environment, where structures are subject to acid attack.
Because they are chemically resistant, epoxy liners are long-lasting. An epoxy liner will stay in place with minimal erosion for years and even decades. In contrast, CAC mortars, for example, will erode over time, depending on the level of hydrogen sulphide the liner is exposed to.
Epoxy liners have a smooth finish, which means they are low-friction. As matter is moved through the system, it won’t stick to the liner, which can cause blockages – a sewer asset manager’s worst nightmare!
An epoxy liner can be applied in thicknesses as small as 2-3mm. This means that valuable internal diameter doesn’t have to be handed over to rehabilitating an asset. When compared to other liners, which can have thicknesses of up to 30mm+, it’s a considerable difference.
Benefits to water authorities
According to Colin Murphy, product manager for Hychem, water authorities are starting to take notice of the benefits epoxy coatings can offer. “We have a number of clients in the water industry who have been very impressed with the performance of epoxy coatings in their systems in the long-term. “The product has an attractive price point, holds up well to the rigours of the harsh sewer environment, and can last the distance. We have clients who have reported minimal change to the lining they had installed 15-20 years ago.”
One such project was the North Drop Structure, which was relined by Melbourne Water in the 1990s.
Melbourne Water commissioned an assessment of the state of the coating in 2013. When assessed by a National Association of Corrosion Engineers-certified assessor, the coating was found to have held up considerably well in what was an extremely harsh environment.
The sewer featured a range of materials in its construction, including concrete, bricks and mortar and steel – a testament to the versatility of the coating used, Hychem TL5. The assessor noted that in the approximately 15 years since the coating had been applied, in many places, the coating remained the same as the original high build thickness applied. Where corrosion had occurred, it was as a result of acid attack.
The assessor noted the quality of the coating and the way it performed compared to other coatings in similar situations. The assessor recommended that where rehabilitation of the North Drop Structure was required, Hychem TL5 should be used again.
In 1995, Hychem TL5 was used by Tenix Australia to rehabilitate a 300 square metre section of the Geelong outfall sewer for Barwon Water. The 2.4m outfall pipe drop structure was coated in the Hychem product, and, in a highly aggressive environment, provided excellent protection to the main structure. Peter Clark, owner of epoxy sewer lining specialist Peltos, is particularly impressed with the performance of Hychem TL5 on this project. “When inspected as part of the routine maintenance cycle, the coating was in the same condition as when it was installed,” said Mr Clark. “In a high hydrogen sulphide environment, Hychem stood up the to test. Peltos has a 100 per cent success rate with this product – it never fails.”
A versatile solution
Hychem TL5 epoxy coating has proven itself in harsh and aggressive sewer environments, having been used by numerous utilities and water authorities around Australia.