Aging water and wastewater infrastructures are difficult and expensive to manage. But how much does the corrosion problem cost the industry? And how can water utilities better manage corrosion to reduce these costs?
In an effort to understand how water industry practices, technologies, industry skilling, and regulatory frameworks contribute to corrosion costs in the Australian mainland and Naval defense sectors, an economic impact study was undertaken by the Australasian Corrosion Association (ACA).
A subsequent 2010 report by Greg Moore, entitled “Corrosion Challenges: Urban Water Industry”, estimated the region’s total annual corrosion costs at $982M (AUD) (± 30%). Of this, $91M (AUD) was attributed to consequential disruptions such as flooding, road closures, and loss of trade. Water pipeline corrosion repairs were estimated at $118M (AUD).
Moore’s report identified a number of challenges facing the industry, particularly in corrosion management, due in part to inadequate training and improper use of corrosion technologies. The report recommended a more proactive approach to condition assessments, implementing industry-specific training, and improving how available technologies are used, such as cathodic protection, semi-structural linings, and CCTV inspection programs.
Materials and Assets Currently in Use
The initial construction of pipelines and freshwater/wastewater treatment facilities in the Australian mainland began during European colonization in the mid-1800s, and continued until after the First World War. The greatest later expansion occurred during the 1970s, when approximately 3,107 miles (5,000 kilometers) of pipeline were installed.
Today, a network of pressurized and non-pressurized pipelines comprises the largest group of assets operated by water authorities in urban areas. Piping is made from a range of materials—ductile iron, cast iron, steel, and asbestos and concrete cement—that are all susceptible to internal and external corrosion to varying degrees. Grey cast iron and asbestos cement make up a large portion of reticulation pipes, and many of these are fast approaching the time when replacement will be required.
On the wastewater side, the major urban water utilities operate 260 water treatment plants and 442 sewage treatment plants. Sewage treatment plants are exposed to a highly corrosive hydrogen sulfide gas, and many plants are located on or near the coast in harsh salt-air environments. The consequences of failure of a water treatment plant are usually not as serious as a pipeline failure, but the facilities still require ongoing maintenance and repair. The costs of sewage plant maintenance and repair are estimated at $176M (AUD).
While some drinking water supplies are only disinfected, the majority of supplies are also filtered and treated to remove impurities to ensure that the water quality meets the Australian Drinking Water Guidelines (ADWG).
Current Practices and Recommendations
The report found that “the incidence and cost of repairs and maintenance attributable to corrosion is unacceptably high”.
The Water Services Association of Australia (WSAA) monitors pressurized pipeline performance, which it reports as the number of water main breaks per 62 miles (100km) of pipe per year. Using an average, the Moore report estimated 26,700 pipeline breaks per year, with about 79% of the breaks attributable to corrosion. The additional cost of water loss from leaks and failures was estimated at $124M (AUD).
With buried pipe, the water industry has followed a reactive maintenance approach, allowing pipelines to run to failure. Individual pipe failures are often repaired until the failure rate reaches a predetermined level, at which point the entire section of pipeline is replaced. For smaller pipes, this is still considered “best practice” for the industry, but for larger critical pipelines, a more proactive approach is being adopted.
The Moore report found that current water asset management practices “leave significant opportunities for improvement”. A key recommendation is for water authorities to increase pipeline condition assessment to better predict when and where failures might occur. Currently, class conditions are always corrective rather than preventive, and lead to missed maintenance opportunities that could significantly reduce costs and repairs.
Currently in urban settings, where the consequences of failure are high, condition assessments evaluate whether pipeline replacement is required to avoid major failures.
There will always be difficulties in any proactive approach to manage buried assets where there is limited technology to carry out condition assessments. Most water utilities have active CCTV inspection programs to assess internal corrosion of non-pressure sewer pipes; and repair, rehabilitate, or replace them before major collapses occur.
While cathodic protection is broadly used, there is a need to further increase its use to mitigate external corrosion of steel mains, according to the report. As the same time, the use of CP on other metallic piping such as cast iron or ductile iron (lined or unlined), is not a viable application of this technology.
The water industry in Australia utilizes the skills of a wide range of staff to manage, operate, and design water and sewage systems, but there are very few training courses available to teach corrosion and its impact on the water industry.
While corrosion data is an important foundation in managing corrosion, interpretation of pipeline failure data is often performed by operations staff who do not have specific training in corrosion management.
Currently, most corrosion expertise rests with specialist groups in some water utilities. Recommended programs to disseminate this knowledge across the utilities would be of benefit. The report also recommends implementing accredited corrosion training courses designed specifically for water industry personnel. New courses would cover topics such as:
- Corrosion basics for the water industry
- Materials and corrosion control for use in conjunction with the Water Supply Code of Australia and the Sewerage Code of Australia
- Identification and assessment of pipeline failures in the water industry
In particular, there should also be increased training in cathodic protection technologies, especially as applied to aging steel water mains, tanks, and other structures. The ACA has begun scaling up training offerings for the water industry through seminars and corrosion management certification programs across Australia and New Zealand to answer this need.
The Corrosion Challenges report also covers the corrosion costs of the naval defense sector and includes corrosion case studies covering assets such as amphibious vessels and surface force vessels.
You can read and download the full report here.