14 FEBRUARY 2022 WorldWide Drilling Resource® Fighting Sewer Pipe Corrosion and Fatbergs Compiled by the Editorial Staff of WorldWide Drilling Resource® The first concrete sanitary sewer pipe in the United States was installed in 1842, in the city of Mohawk, New York. Since then, concrete sewage pipes have become the backbone of sanitation systems around the world. The Mohawk pipe was still in service more than a century later, but that is an exception. Concrete sewer pipes frequently fail in as little as 10 to 20 years. Repairing failed pipes requires ripping up the ground, diverting traffic, and disrupting neighborhoods. Each year, repair and replacement costs run about $25 billion in the United States. This pipe failure is largely due to the acidic environment caused by wastewater. Ordinary concrete contains lime, which usually stays in the concrete and forms an alkaline coating protecting steel used to reinforce concrete from corrosion. Microbes in sewage pipes produce hydrogen sulfide gas, which combines with moisture to form sulfuric acid. The acid leaches lime from the concrete and corrodes the sewage pipes, resulting in reduced structural thickness. Not only does the pipe eventually fail, but the lime leached from the sewer pipe also contributes to the formation of fatbergs which clog sewer pipes. Fatbergs are congealed masses of fats, oils, and grease, combined with flushed nonbiodegradable materials like wet wipes and diapers. These fatbergs stick to the inside of pipes. One fatberg removed from Whitechapel in London in 2017, weighed over 140 tons and stretched 800 feet. Rajeev Roychand, a post-doctoral fellow in civil engineering at the Royal Melbourne Institute of Technology (RMIT), led a research team to address these issues and create a zero-cement concrete (ZCC) by replacing 70-100% of the conventional cement in concrete with a mixture of other ingredients. The team produced their new cementfree concrete largely using byproducts of the manufacturing industry, combining nano-silica with fly ash, slag, and hydrated lime. Using X-ray and thermal analyses, as well as scanning electron microscopy, they evaluated the concrete microstructure. Tests for compressive strength confirmed the ZCC surpassed strength standards required of sewage pipes. Next came the test for acid attack durability to assess corrosion resistance. Using previous research on the acidity in wastewater environments, the team found the pH varied between 7.2 (like tap water) at the bottom and 2.9 (about like grapefruit juice) at the top of the pipe. Since corrosion occurs slowly over years and it would have taken about a decade for the experiment, Roychand and his team used a much more acidic pH of .2 to accelerate the process. After two months of corrosion, the researchers determined the ZCC reduced corrosion by 96% and totally eliminated residual lime instrumental in the formation of fatbergs. The ZCC in its final form overcame all the major issues associated with conventional concrete use. Roychand said, “The world’s concrete sewage pipes have suffered durability issues for too long. Until now, there was a large research gap in developing eco-friendly material to protect sewers from corrosion and fatbergs. But we’ve created concrete that’s protective, strong, and environmental - the perfect trio.” The RMIT Team hopes further development will yield a ZCCwhich is totally resistant to acid. Fatberg at the Museum of London. WTR Sewer pipe corrosion. Irrigation by: Rain Bird Academy Training March 7-11 ~ Buffalo, NY March 7-11 ~ Salt Lake City, UT March 14-18 ~ Tuscaloosa, AL March 14-18 ~ Detroit, MI March 15-17 ~ Meridian, ID March 21-25 ~ Long Island, NY March 28-April 1 ~ Pensacola, FL phone: 800-498-1942 E-mail: training@rainbird.com More education opportunities during events can be found by clicking here online at: worldwidedrillingresource.com Education Connection
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