October 29, 2015

Epoxy coatings in the wastewater industry

Harsh chemicals found in wastewater environments pose a range of challenges for asset owners. Significant downtime due to rehabilitation or maintenance works can also send site costs and losses through the roof.

Protective coatings of water and wastewater assets are the first points of contact between the stored liquid and the surrounding structure, and if chosen well, can significantly reduce downtime and increase the overall lifespan of the asset.


Factors facing wastewater environments

The presence of chloride and sulphuric acid within wastewater treatment facilities can cause major corrosion headaches for water industry operators and contractors.

Hydrogen sulphide gas is created by microbial degradation of organic matter in an anaerobic environment. This gas is then oxidised to sulphur dioxide when it reaches oxygen rich areas such as manholes and pump stations. From there, the gas dissolves in water and forms sulphuric acid.

Concrete installed without a protective coating can become damaged by acid within a matter of days and can be destroyed beyond repair very quickly. By applying an appropriate coating to a concrete structure, corrosion damage can be wholly avoided and hydraulic erosion mitigated.


Cleveland Bay Purification Plant

Cleveland Bay Purification plant (QLD) is Townsville’s largest wastewater treatment plant, serving an equivalent population of 108,000 and treating 25 million litres of sewage per day. The wastewater is treated by a number of processes which remove solids, organic matter and nutrients from the sewage so it can be safe to reuse or safely discharged into the environment.

In 2013 Hychem’s TL5 coating was applied to a number of facilities on-site to protect each structure from chemical corrosion. This included inlet channels, screen sewage channels, a flow distribution pit, sandfly creek bypass, primary effluent pump station, outfall pump station and thickened waste activated sludge pit.

Since first application, the site has undergone close inspection every six months to assess the effectiveness and success of the TL5 coating. The most recent inspection was held in July this year, and was attended by the coating contractor, members of the Council, engineers and Hychem.

According to Jeff Morton, Wastewater Treatment Plants Operations Engineer at Townsville City Council and present at the recent inspection, the TL5 product has effectively withstood the harsh environment.

“The works are exposed to very high levels of hydrogen sulphide, which is usually around 200 to 300 ppm.  However, on occasions the concentration has peaked at over 1000ppm.

“These levels are potentially lethal as well as damaging to the plant and equipment.

“If oxygen is available, bacteria can oxidise the sulphide to produce sulphuric acid.  This in turn will attack concrete and gradually corrode the steel reinforcement away.”

“The inspection showed that the coating was free of any defects and there was no evidence of deterioration, which was an excellent result.

Andrew Hindle from AT Edge Solutions, who applied the chemical coating, was also pleased with the TL5 results.

“It’s safe to say that the effectiveness of Hychem’s TL5 coating is excellent. It passed the most recent inspection with flying colours, not to mention every other inspection since it was first applied.”

The TL5 coating is also one of the easiest to work with and apply, said Mr Hindle.

“Hychem’s TL5 can be spray applied to an impressive thickness of up to 7mm, which means we only need to carry out one application.

“Other coatings need to be reapplied two or three times before a sufficient thickness is reached, which adds to the downtime of the facility.”

According to Hychem’s water and wastewater expert, Colin Murphy, the success of any coating system requires careful examination of all criteria and working together with key players.

“Hychem offers technical assistance at design phase right through to implementation. We work closely with design teams, consulting engineers, water authorities and project managers to ensure a high standard coating system is applied,” said Mr Murphy.

Mr Hindle agrees, stating that Hychem will always assist in any way that they can.

“Their approach sets them aside from other manufacturers I have worked with. Hychem TL5 is a product that I can always count on,” said Mr Hindle.


The Hychem TL5 advantage

Formulated to suit Australian conditions, Hychem TL5 is a high build solventless epoxy with excellent resistance to dilute sulphuric acid and excellent adhesion and impact strength. As well as this, it has been specifically designed for long-term fast-turnaround protection of water industry assets.

“The true benefit of TL5 is that it is purposely designed for the sewage and wastewater industries and has been tested for over 20 years in the harsh Australian climate,” said Mr Murphy.

“Not only can it prevent acid corrosion when installed at a new facility, it can also halt corrosion damage on an existing asset.”

The product can be applied at a minimum of 1mm and a maximum of 7mm using a wet-on-wet spray technique, or it can be trowelled where spray application is unsuitable.

Hychem TL5 coating can be coupled with Hychem  E500P and E500T as a surface filling compound applied before the coating.

The TL5 product meets Australian Standard ‘AS 4020:2005: Testing for products for use in contact with drinking water’ and can thus be used in pipelines and storage vessels for potable water. TL5 is approved by SA water and is also compliant with the requirements of Sydney Water Standard Specification 204.

Other features and benefits of Hychem TL5 are:

  • Applied by plural component spray, can be trowel applied to small difficult to access areas
  • Fast cure, early return to service
  • High acid resistance
  • High caustic resistance
  • High solvent resistance
  • Monolithic ultra high build in one application
  • High fat resistance
  • High hydrocarbon resistance
  • Good intercoat adhesion
  • Bonds to damp concrete
  • High impact strength


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