Aeromarine engineering adds world-leading technology to sewage plant upgrade

Timaru-based composites engineering firm Aeromarine Industries is bringing internationally-recognised technology to one of the New Zealand’s largest wastewater treatment plant upgrades ever undertaken by a district council.

Years of environmental work by the Timaru District Council to improve the way the district’s sewage is piped and treated is reaching a conclusion as the final phase of a $60 million district-wide sewerage system makeover takes shape.

Major earthworks over a total of approximately 48 hectares on both sides of Aorangi Road at Seadown, just north of Timaru, and an extensive upgrade to the wastewater treatment plant nearby, are part of the council’s Wastewater Management Strategy. The work ensures infrastructure meets new standards required in the treatment of effluent prior to its discharge into the sea.

And with the involvement of Aeromarine, the plant is now also meeting the latest standards in composites engineering with components such as plant covers, superstructure and handrails being installed in an environment known for its corrosiveness and heavy wear and tear.

Aeromarine general manager Simon Robb says that in contrast to steel and concrete, a traditional material found extensively in council treatment stations, composite components do not corrode, taint water, suffer thermal stress or require cathodic protection.

“Nor do they have to be surveyed from time to time throughout their life. Composites can withstand even the highly acidic and sulphurous sewage environment,” Mr Robb said.

Aeromarine is working with principal contractor on the treatment plant upgrade Downer EDI, sub-contractor Rooney Earthmoving, and design consultants CH2M Beca in supplying tank and manhole covers as well as handrails and accessway fitments. Steel options were considered, but the council went for composites.

The Timaru District Council’s drainage and water manager Grant Hall said today composites provided the best option.

“The dual effect of handling wastewater and being adjacent to the coast requires a material that has the required anti-corrosion properties, while being robust for the application and providing the long service life in this harsh environment,” Mr Hall said.

“Composites are seen as providing these properties and being the best option in this case.”

Mr Robb said that not only were the composite components corrosion proof with a life in excess of 50 years requiring minimal maintenance, fibreglass covers weigh only a quarter of what comparable ductile iron or steel covers would weigh, and a tenth of the weight of concrete.

“This makes them easy to handle and transport, even on steep sites, thus providing safe installation. Composite components do not require welding when fitting or modifying them. Instead joints are adhesively bonded or laminated, the major joint lugs being incorporated during component manufacture,” he said.

Aeromarine is fielding inquiries from other councils as the changing technological environment brings composites to the fore.

“We welcome these inquiries. Sewage systems in general are expensive commodities for ratepayers and no council wants to see corrosion or wear and tear necessitating replacement components in the short to medium term.

“Composites offer strength, corrosion resistance, permanence at a comparatively low cost. And because of the lightness, installation means fewer cranes and heavy lifting gear, making worksites safer and more cost-effective,” Mr Robb said.

Composites are thermally tolerant, being able to withstand temperatures of around 110°C and even up to 200°C in special cases.

He gave an example of the durability of composites at the very site of the current upgrade where a fibreglass cover over tanks at the old milliscreen plant installed in 1985 was removed during the recent work and inspected.

“The amazing thing was that a piece of the steel used to anchor the cover was corroded and needed to be replaced. The cover itself was as good as the day we installed it, apart from a few scratches where it had been removed and replaced as part of the milliscreen’s operation.”

ENDS

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