Polymeric Solutions for the Water and Wastewater Industries

We’re now moving on to pipework solutions. Pipes suffer from damage both on the external and internal diameters from both erosion and corrosion.

• Externally we may see environmental attack, which calls for a solution where a barrier is formed between the pipe and the environment.
• Internally we may see damage from erosion and chemical attack, possibly at high temperatures.

These forms of attack both lead to loss of wall thickness, which may eventually lead to live leak situations, often causing the asset to be taken offline whilst it is repaired or replaced . This downtime can be very costly, but by using an epoxy solution these costs can be avoided.

This case study was at a pumping station at Tarragona in Spain, where these water pipes were suffering from significant external corrosion. This was due to leaks occurring through the sealing systems between the pipes, and walls of the tanks.

To create a long-term repair for these issues, Belzona SuperWrap II was chosen to wrap the pipes. Then, on top, Belzona 5811 (Immersion Grade) was applied to provide a smoother finish to the repair. As well as this, the concrete tank was repaired with the mortar repair material Belzona 4131 (Magma-Screed). To complete the application, the pipes were coated in a blue polyurethane material, as this was the specification of the station.

There were several reasons Belzona materials were chosen for this application. Belzona SuperWrap II is a ISO/ASME compliant wrap solution. It also has outstanding properties and will restore the mechanical strength back to the pipes for twenty years. The application was able to take place whilst the pipe was online, without any disruption to the water supply. Consequently, more than 30 other smaller compliant repairs were carried out around the same facility with Belzona SuperWrap II.

WRAP AND PATCH REPAIRS

Belzona can use epoxy solutions to reinstate pipe integrity and reinforce the asset, using patch repairs or full circumferential wraps.

In order to protect against this happening in the future, we can carry out an internal coating of the pipe to protect against erosion and corrosion. Depending on access, this can be done by hand or for smaller diameters, by spin spray methods. Belzona coatings can provide protection against erosion, corrosion and chemical attack, even at elevated temperatures.

Next we’re going to be looking at Tanks and Clarifiers within the industry. We’ve split this into three areas which typically experience damage – tank exteriors, tank interiors and concrete.

Tank Exteriors

Sealant failure, adverse weather conditions or condensation can lead to corrosion of the tank base, tank failure and ultimately – leakage. Tank roofs are susceptible to rapid deterioration caused by the corrosive vapour of the stored media. Tank walls can also suffer from corrosion and leaking welds.

To combat tank base problems, Belzona formulated a tank base sealing system in the 1990s, which is liquid applied in conjunction with a reinforcement sheet. As a flexible membrane, the system possesses a unique breathable feature; liquid cannot permeate the membrane. However, the vapour escapes freely, allowing the underside of the tank to dry out.

Roof and wall damage can be safely repaired in-situ and on-line, eliminating the need to drain the tank.

This case study took place at a water treatment plant in the south of England. The tank was suffering from corrosion issues around the seam areas. And in two places the corrosion had resulted in holes in the tank, meaning the raw sewage was leaking out.

Whilst deciding what to do with the tank – whether to repair or replace it – the treatment plant asked Belzona to provide a solution, to keep the tank usable for the time being.

Therefore, temporary patches were installed using a Belzona system. Fast-curing materials were necessary because as all work had to be carried out in just one day, as the tank had to be put back into service at the end of the shift.

Consequently, a surface-tolerant material was used to patch over the holes before Belzona 1161 was used to bond the patches. After the application, the customer was very happy with the repairs and instead of building a new tank, chose to line the inside with a Belzona System.

Tank Interiors

Steel vessels, ranging from drum thickeners to digester tanks, are subjected to a range of harsh conditions by the water and wastewater industry.

MIC (Microbially Induced Corrosion) can occur to the substrate. Whilst the chlorides and sulphates present in wastewater sludge can similarly corrode steel vessel interiors, and these are just examples of the many forms of attack. Concrete tank interiors can be eroded by submersion in water or corroded by chloride chemical attack, leading to cracks and leaks, resulting in compromised water quality and plant efficiency.

Belzona coating solutions are designed to protect tank and vessel interiors by providing a chemical resistant internal lining. Belzona 4311 (Magma CR1) is designed to protect secondary containment areas against chemical attack, whilst Belzona 5811 (Immersion Grade) can protect surfaces subjected to constant or regular immersion in aggressive liquid environments. For the water and wastewater industry, Belzona 5812DW is approved for contact with potable water. Belzona solutions and coatings are easy to apply and cure at ambient temperatures, allowing for rapid application and a minimum of downtime. Providing a long-lasting, effective solution, they are an excellent alternative to lengthy replacement or repair works.

Another benefit of using a coating system is that it allows you to use a coated mild steel tank as opposed to the relatively high outlay for an all stainless steel tank, thereby keeping your costs down.

Concrete Damage

The wastewater treatment process and related activities expose concrete to a variety of damage mechanisms including:

• Erosion-corrosion
• Physical damage
• Chemical and microbiological attack
• Carbonation
• Freeze-thaw cycles

High relative humidity levels, the need for cold temperature curing and the requirement to keep operations running smoothly make repairs increasingly difficult.

Belzona concrete repair composites are designed to rebuild and repair damaged concrete surfaces, restoring the original profile with a simple procedure that minimises downtime and can be completed without hot work. Belzona concrete repair systems will cure in a matter of hours, achieving full mechanical hardness soon after. Specialist coating solutions can then be applied to improve resistance to the common forms of wear and corrosion, extending service life with a minimum of financial outlay

At this water treatment plant in Scotland, two clarifiers were in need of repairs. The running track on top of the wall had been experiencing impact and abrasion damage due to the arm.  The substrate was seriously damaged. However, there was only a limited shutdown window to make any repairs.

The chosen solution for this was Belzona 4131. This had three major benefits over a traditional concrete repair. Firstly, by using the Belzona material, a repair could be completed in a fraction of the time it would take to knock down the walls & rebuild them. As well as this, the material’s chemical & impact resistance prevents the original problem from re-occurring. As well as this, polymeric materials are non-porous, therefore will not allow water ingress, so freeze-thaw issues are not a problem anymore.