The Ultracoat cure

Wastewater assets, including sewers, drainage pipes, wet wells and manholes, need to be cleaned and inspected regularly to ensure they remain in a safe and serviceable condition, reducing the risk of unplanned and costly repairs. After years of heavy use, assets can become corroded and weakened, particularly if they are not maintained, leading to failure and resulting in significant costs in carrying out emergency repairs with a real risk of environmental damage

When Anglian Water sought a solution to resolve hydrogen sulphide attack problems at several of its sewage pumping stations, it approached Ferro, a leading wastewater asset and pipeline rehabilitation specialist.

Hydrogen sulphide, identifiable to the layman through its characteristic smell reminiscent of rotten eggs, is produced as a result of anaerobic digestion, whereby the bacterial action of micro-organisms breaks down biodegradable material in the form of sewage sludge. Colourless, it is toxic and responsible for eating away at concrete structures, where sewage sludge is contained.

Problem solver

Although initially contacted to help with providing a concrete repair proposal, Ferro identified the potential for the newly introduced Ultracoat product to offer an enhanced solution. Ferro presented the Ultracoat solution to Anglian Water to show its suitability to the existing problems.

Ultracoat is a spray-applied 100% solids epoxy resin coating system. Anglian Water representatives were impressed with the potential of this solution and agreed to trial it.

Ferro Monk carried out an initial project at Edith Weston Pumping Station on Rutland Water, quickly followed by a second at Ashingdon in Essex.

Both projects were brought about through the need to provide repairs to the concrete structures of the wet wells at each site, which had been the subject of severe attack by hydrogen sulphide.

In keeping with current national environmental standards, Ultracoat is a ‘green’ product – 100% solids epoxy, with no volatile organic compounds. It has a high safety value and can be applied in confined spaces, with no risk of combustion to hazardous materials. It is also resistant to algae and bacterial growth.

A major benefit of using Ultracoat is that it can be sprayed directly on to damp surfaces quickly. Its high bond strength means it can strengthen corroded structures, and it can adhere to most surfaces, including concrete, steel, brick, fibreglass and clay. It is suitable for use in tanks, wet wells, chambers, manholes and culverts.

Ultracoat is a versatile substance which, when sprayed insitu, will take the shape of the substrate. It can tolerate high levels of hydrogen sulphide, sulphur dioxide, acids and alkali.

In use for almost 20 years, although only recently introduced in the UK, Ultracoat has a strong track record, including the rehabilitation of 45,000-plus manhole chambers to date. The product is the only coating approved by the US Navy for potable water, fuel oil and sewerage applications.

Following on from the two initial projects, Ferro carried out similar treatments to structures at Canvey Island in Essex and Spalding, Lincolnshire.

The works at Canvey had been identified through a client survey of the structure that highlighted severe degeneration of the surface of the concrete through hydrogen sulphide attack. So acute was the problem that the first layer of reinforcement was exposed and this was itself at risk of corrosion.

If left unchecked, there was a distinct probability it would have resulted in a failure of the structure in the medium term. Fortunately, the standard of design and construction of the basic structure was good and a surface repair was deemed appropriate, rather than a total reconstruction, which could have been the outcome if left without maintenance. Although a concrete repair solution was considered, using the Ultracoat sprayed epoxy system offered a more durable option.

Although all of these structures were suffering from the same severe hydrogen sulphide problem, which resulted in applying Ultracoat to the surfaces, each project was different in nature and had its own specific requirements.

Site surveys

On all projects, an initial site survey is undertaken by rehabilitation managers. This seeks to determine the characteristics of the site and if any special considerations need to be made.

The first job was to ensure that all surfaces, pipes and chambers to be coated were rigorously cleaned and prepared. Although access may have been restrictive in some cases, it did not prove problematic.

To clean the surfaces, Ferro used a combination of high-pressure water jetting, followed by acid-etching and bleaching. The 100% solids structured epoxy resin was then applied using patented mixing and spraying equipment on to the still damp surface.

Wet chambers and surfaces are notoriously difficult to deal with, but Ultracoat is ideal for use in damp environments. It bonds well and systems can be back in use within as little as two hours after application.

The works at Canvey Island consisted of the treatment of the walls and soffit of a structure around 15m long, 4m wide and some 7m deep. The whole process, including preparation and lining, was completed in little over a week.

www.ferromonk.co.uk