Soon, sewers in the US may be using a treatment developed at The University of Queensland (UQ) to control odour and corrosion.
The team from UQ’s Advanced Water Management Centre developed the technology, which uses free nitrous acid to remove biofilms that adhere to the inner surfaces of sewer mains.
UniQuest, a UQ commercialisation company, and Atlanta-based provider of chemical treatments for water and wastewater applications, have negotiated an exclusive license agreement for the technology.
According to lead researchers and Advanced Water Management Centre Director, Professor Zhiguo Yuan, the technology was developed with municipal wastewater collection systems in mind.
According to Professor Yuan, corrosion and odour problems in sewers are most often caused by sulphate-reducing bacteria in sewer biofilms that produce hydrogen sulphide.
“Hydrogen sulphide is released into the atmosphere above the wastewater, causing odour problems, and is converted by sulphide-oxidising bacteria into sulphuric acid, which is corrosive to concrete sewer pipes," he explained.
Because of how extensive sewer networks are, and the various topographical elements within the networks, hot spots can arise, where sulphate becomes sulphide, accelerating corrosion and causing serious odour issues.
Currently, utilities use sewer pipe lining, sewer air ventilation with follow-on air treatment and around-the-clock chemical dosing in order to manage sulphide-related problems. While these methods are effective, they result in high operating costs.
The technology from UQ differs from existing treatments, because it is delivered intermittently, provides longer duration control, and effectively stops the production of hydrogen sulphide at its source. This makes it a lot more cost-effective.
It is not only more effective, but can also be used in sensitive environmental areas or to treat smaller lines. Water utilities who adopt the technology can make significant reductions to their maintenance costs.
This means the US is a great opportunity for the application of the technology -- the total annual cost of hydrogen sulphide corrosion in the US sewer network in 2000 was US$13.75 billion.
The first Australian field trial of the UQ technology was undertaken by UQ in 2012 in collaboration with USP and the Gold Coast City Council in 2012, followed by a second field trial in partnership with USP and Unitywater at Scarborough on Moreton Bay in 2014.
These trials led allowed the researchers to further refine the technology. USP expects to market for the UQ-developed technology in North America, Australia, China and Europe.