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Using Technology to Keep Sewers, Pipes Clear
When non-degradable items are flushed into sewer systems and pipes, blockages create back-ups for the wastewater industry. Critical to wastewater systems, cities are using new technology to streamline the process to identify and remove these blockages.
About Fatbergs
The waste clusters, known as “fatbergs,” are a combination of fats, oil and grease that come into contact with calcium, phosphorus and sodium that then accumulate on non-degradable flushed items. They create a hard, “soap-like” material that begin to harden like concrete over time.
Non degradable items found in fatbergs can include wet wipes, sanitary pads, dental floss, food waste and diapers, among other household items. While cooking oil is a common contributor, three quarters of oils, fats and grease reportedly come from domestic sources, such as conditioners or cleaning products.
In 2020, at the start of the COVID-19 pandemic, a shortage of several household items including hand sanitizers, disinfectants and toilet paper, caused an issue for professionals in the wastewater industry as products used as substitutions and alternatives were being flushed. The state of New York reported that it spends roughly $18.8 million every year just to degrease, unclog and repair sewers and plant equipment affected by fatbergs at the time.
Cities turn to tech to keep sewers free of fatbergs https://t.co/OWWLXgBfdt pic.twitter.com/xJNEacX55t
— Engadget (@engadget) March 7, 2022
In 2021, a project in London to increase the city’s sewerage capacity and prevent overflowing sewage from spilling into the Thames River faced fatberg removal. Previously, Thames Water spent 18 million pounds (about $23.4 million) a year to clear 75,000 blockages from its systems.
“These huge, solid masses can block the sewers, causing sewage to back up through drains, plugholes and toilets,” said Anna Boyles, operations manager at Thames Water. “It can take our teams days, sometimes weeks, to remove them.” In short, they are an environmental and logistical nightmare.
In addition to being difficult to remove, they can produce offgas toxic compounds such as hydrogen sulfide, posing risks to health and safety. Forensic analyses have also reportedly show concentrations of chemicals, like bodybuilding supplements or illicit drugs, and bacteria.
“Fatbergs are rancid. The smell has been compared to festival toilets and rotten meat,” Boyles said. “Our fatberg-busting team typically wear gas masks and rubber suits and carry monitors that continually check for harmful levels of combustible gases.”
Disposal Methods, Technology
Typically, crews have used pickaxes and shovels to break up the masses, but recently newer methods and technologies have been used to expedite the process.
According to Engadget, the city of Atlanta uses “high pressure water and/or rodding equipment,” or hydrojets, to clear blockages. Capable of producing pressures in excess of 4,000 ppi with this method, interior surfaces of the pipe are blasted and then the slurry is sucked out of the main using a truck-mounted vacuum system and stored in an onboard tank for later disposal.
Before the fatbergs can be cleared, they have to be found using remotely operated cameras or by sending down crews. The Sewer Line Rapid Assessment Tool (SL-RAT) developed by Infosense Inc. uses sonar technology to look for obstructions.
The system is reportedly set up at the access points at both ends of the sewer main, then the transmitting unit blasts a series of sound waves into the pipe. The receiving unit measures the tonal differences between the two sets to determine the extent of any potential blockages.
The City of Irvins, Utah, implemented SL-RAT in 2020, reportedly minimizing a process that took weeks and 1,100 labor hours to a few days and 320 labor hours. “It’s less [noise] than the sound of a cleaning truck, and there is zero water usage,” said Ivins Public Works director Chuck Gillette last year.
Previously, the city would flush its pipe system of approximately 50 miles with a high-pressure stream of water using 6,000 gallons of water per day. “You’re cleaning every pipe. There’s a rod shoved up the pipe and the tip of the rod has jets that shoot backwards,” he said, adding that problems can occur if a sewer connection to a home wasn’t installed correctly.
Instead of having to clean out every single pipe, the sonar system found 57 out of 1,226 pipes that needed cleaning, saving thousands of gallons of water and the municipal authority’s time. A team of three people were able to analyze and clean the entire system in two to three weeks, with Gillette estimating that time would have only gotten him through 10% of the system using the old method.
In general, experts and municipal authorities recommend people only flush paper and anything else that typically gets flushed down the pipes to prevent the clogging.
Other Fatberg-Fighting Research
In October 2020, engineers from RMIT University (Melbourne, Australia) announced that they developed an eco-friendly, zero-cement concrete that can withstand corrosive acidic environments, commonly observed in sewage pipes and other types of wastewater infrastructure.
A paper on the study, "Development of zero cement composite for the protection of concrete sewage pipes from corrosion and fatbergs" has since been published in Resources, Conservation & Recycling.
In an attempt to combat build-ups of fat, oil and grease—often referred to as “fatbergs”—in sewers and pipelines, lead RMIT researcher Rajeev Roychand and his team developed a concrete that eliminates the chemical compound that promotes corrosion and fatbergs, free lime.
“The world’s concrete sewage pipes have suffered durability issues for too long,” Roychand said. “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.”
According to RMIT, the material consists of manufacturing by-products including a zero-cement composite of nano-silica, fly-ash, slag and hydrated lime. In using the industrial by-products, the end result is reported to surpass sewage strength standards set by ASTM International and is more durable than ordinary Portland cement.
“Though ordinary Portland cement is widely used in the fast-paced construction industry, it poses long term durability issues in some of its applications,” Roychand reported. “We found making concrete out of this composite blend—rather than cement—significantly improved longevity.”
Additionally, the final product is also environmentally friendly, reduces concrete corrosion by 96% and totally eliminates residual lime that is instrumental in the formation of fatbergs.
