How to tell when a sewage pipe needs repair—before it bursts

June 4, 2014

The nation's sewer system is a topic most people would prefer to avoid, but its aging infrastructure is wearing out, and broken pipes leaking raw sewage into streets and living rooms are forcing the issue. To better predict which pipes need to be fixed, scientists report in the ACS journal Environmental Science & Technology that certain conditions in the pipes can clue utilities in to which ones need repair—before it's too late.

Mark T. Hernandez and colleagues note that the maintenance of U.S. wastewater collection systems costs an estimated $4.5 billion every year, much of which goes toward fixing or replacing 8,000 miles of sewers. In the future, these annual costs could top $12 billion. Part of the problem is corrosion caused by sewer gases that feed acid-generating microbes, which grown in biofilms on the inside top surface of the pipes. Although microbe communities have long been recognized as a factor in the corrosion of concrete pipes, they have not been well studied. To fill in the gaps, Hernandez's team decided to figure out what kinds of bacteria and other conditions were most closely associated with corrosion problems.

From 10 different sewer systems in major cities around the country, the scientists measured bacterial diversity, gas concentrations in the air above the wastewater and other factors. In the most worn pipes, they found markedly little variety in the kinds of bacteria present, as well as elevated levels of both hydrogen sulfide and carbon dioxide gases. The researchers concluded that wastewater utilities could economically monitor combinations of these gases in sewage pipes to figure out which sites might be at higher risk for and take the necessary steps to prevent major damage.

Explore further: Bacteria involved in sewer pipe corrosion identified

More information: "Carbon Dioxide and Hydrogen Sulfide Associations with Regional Bacterial Diversity Patterns in Microbially Induced Concrete Corrosion" Environ. Sci. Technol., Just Accepted Manuscript, DOI: 10.1021/es500763e

The microbial communities associated with deteriorating concrete corrosion fronts were characterized in 36 samples taken from wastewater collection and treatment systems in ten utilities. Bacterial communities were described using Illumina MiSeq sequencing of the V1V2 region of small subunit ribosomal RNA (SSU-rRNA) gene recovered from fresh corrosion products. Headspace gas concentrations (hydrogen sulfide, carbon dioxide, and methane), pore water pH, moisture content, and select mineralogy were tested for correlation to community outcomes and corrosion extent using pairwise linear regressions and canonical correspondence analysis. Corroding concrete was most commonly characterized by moisture contents greater than 10%, pore water pH below one, and limited richness (<10 taxa). Bacterial community composition was not correlated to geographic location when considered independently from other environmental factors. Corrosion was most severe in sites with high levels of hydrogen sulfide (>100 ppm) and carbon dioxide (>1%) gasses, conditions which also were associated with low diversity biofilms dominated by members of the acidophilic sulfur-oxidizer genus Acidithiobacillus.

Related Stories

Bacteria involved in sewer pipe corrosion identified

October 23, 2012

Microbes corrode sewer pipes from the inside, a process that can lead to spills, bad odors, disease outbreaks, and the need for costly repairs. In a first step towards reducing the corrosion, researchers have identified the ...

Robotic system to inspect underground pipes

August 17, 2012

EU-funded researchers developed a high-tech robotic imaging system for inspecting underground pipes. Commercialisation should facilitate use of corrosion-resistant materials for transport of hazardous chemicals.

Lead leaching and faucet corrosion in PVC home plumbing

June 2, 2008

Scientists in Virginia are reporting that home plumbing systems constructed with polyvinyl chloride (PVC) plastic pipes may be more susceptible to leaching of lead and copper into drinking water than other types of piping ...

Recommended for you

Heavy nitrogen molecules reveal planetary-scale tug-of-war

November 17, 2017

Nature whispers its stories in a faint molecular language, and Rice University scientist Laurence Yeung and colleagues can finally tell one of those stories this week, thanks to a one-of-a-kind instrument that allowed them ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Jun 04, 2014
Oxygenate! Flush fresh air with sewage; the oxygen will suppress H2S production. Also monitor pH; a high pH will keep the acid gases in solution. Adding a mild alkali (bicarbonate or hypochlorite) will raise the pH and discourage anaerobic bacteria.
2 / 5 (1) Jun 04, 2014
We may know they're gonna burst, but most of our cities are facing bankruptcy, thanks to our decreased population growth. So they're gonna burst anyway. No dough. Thanks, Planned Parenthood.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.