Concrete distribution and sewer networks are being corroded at an alarming rate partly because of a commonly used additive in the domestic drinking water and wastewater treatment process according to published reports in the journal Science.
In countries throughout the world from industrialized nations like Australia and the USA to developing nations like Colombia, Ghana and the Philippines, the lifespan of these concrete pipe networks is being reduced by levels upwards of 90%.
Urban societies in particular are dependent upon infrastructure support to function optimally and efficiently. Wastewater collection and water distribution networks are critical components of the modern cities of today. These systems protect public health as well as enable economic productivity of our communities and nations.
Why is this corrosion occuring?
This corrosion is occuring due to the presence of hydrogen sulfide (H2S) in these piping networks. This simple, but powerful molecular compound harnessed from organic waste and sewage is metabolized by bacteria and oxidized to create sulfuric acid. This acid has particular corroding capabilities on concrete surfaces, which is the most predominantly supplied material for large diameter piping used to create these sewer networks.
Based on study evaluation, it was determined that this corrosion process converts solid concrete into crumbling powder at a rate of up to 10mm a year or more in some worst case scenarios. This would reduce the lifespan of an ordinary collection network from 50-100 years to as little as 10-12 years.
Provided the capital cost intensive nature of building and maintaining these collection networks, it is crucial to manage this corrosion process both effectively and efficiently to ensure the longevity of these piping systems.
What is it costing us to maintain these systems?
It cost municipalities/townships and cities hundreds of millions of dollars to maintain, replace and repair their wastewater collection networks. A similar amount is spent trying to mitigate this problem with costly chemicals in the sewer networks to mask these issues with little success in many cases.
How can this corrosion problem be solved?
The first step, is to look at the water and wastewater process wholistically in an integrated way. This method, allows us to assess the sources of potential hydrogen sulfide and what can be done to minimize this contaminant. Studies revealed that there is a surprising but impressive link between wastewater management and water treatment. To reduce the generation of hydrogen sulfide, we would need to either reduce the contribution of sulfate to the wastewater network or reduce the organics in the waste. The easiest way to do this is to reduce the contribution of sulfate.