Featured Research

from universities, journals, and other organizations

Fat turns into soap in sewers, contributes to overflows

Date:
April 21, 2011
Source:
North Carolina State University
Summary:
Researchers have discovered how fat, oil and grease can create hardened deposits in sewer lines: it turns into soap! The hardened deposits, which can look like stalactites, contribute to sewer overflows.

Sewer pipe. Researchers have discovered how fat, oil and grease (FOG) can create hardened deposits in sewer lines: it turns into soap.
Credit: iStockphoto/John Mroz

Researchers from North Carolina State University have discovered how fat, oil and grease (FOG) can create hardened deposits in sewer lines: it turns into soap! The hardened deposits, which can look like stalactites, contribute to sewer overflows.

"We found that FOG deposits in sewage collection systems are created by chemical reactions that turn the fatty acids from FOG into, basically, a huge lump of soap," says Dr. Joel Ducoste, a professor of civil, construction and environmental engineering at NC State and co-author of a paper describing the research. Collection systems are the pipes and pumping stations that carry wastewater from homes and businesses to sewage-treatment facilities.

These hardened FOG deposits reduce the flow of wastewater in the pipes, contributing to sewer overflows -- which can cause environmental and public-health problems and lead to costly fines and repairs.

The research team used a technique called Fourier Transform Infrared (FTIR) spectroscopy to determine what the FOG deposits were made of at the molecular level. FTIR spectroscopy shoots a sample material with infrared light at various wavelengths. Different molecular bonds vibrate in response to different wavelengths. By measuring which infrared wavelengths created vibrations in their FOG samples, researchers were able to determine each sample's molecular composition.

Using this technique, researchers confirmed that the hardened deposits were made of calcium-based fatty acid salts -- or soap.

"FOG itself cannot create these deposits," Ducoste says. "The FOG must first be broken down into its constituent parts: glycerol and free fatty acids. These free fatty acids -- specifically, saturated fatty acids -- can react with calcium in the sewage collection system to form the hardened deposits.

"Until this point we did not know how these deposits were forming -- it was just a hypothesis," Ducoste says. "Now we know what's going on with these really hard deposits."

The researchers are now focused on determining where the calcium in the collection system is coming from, and how quickly these deposits actually form. Once they've resolved those questions, Ducoste says, they will be able to create numerical models to predict where a sewage system may have "hot spots" that are particularly susceptible to these blockages.

Ultimately, Ducoste says, "if we know how -- and how quickly -- these deposits form, it may provide scientific data to support policy decisions related to preventing sewer overflows."

The research was funded by the Water Resources Research Institute and the U.S. Environmental Protection Agency.


Story Source:

The above story is based on materials provided by North Carolina State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xia He, Mahbuba Iasmin, Lisa O. Dean, Simon E. Lappi, Joel J. Ducoste, and Francis L. de los Reyes, III. Evidence for Fat, Oil, and Grease (FOG) Deposit Formation Mechanisms in Sewer Lines. Environmental Science & Technology, (in press)

Cite This Page:

North Carolina State University. "Fat turns into soap in sewers, contributes to overflows." ScienceDaily. ScienceDaily, 21 April 2011. <www.sciencedaily.com/releases/2011/04/110421104501.htm>.
North Carolina State University. (2011, April 21). Fat turns into soap in sewers, contributes to overflows. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2011/04/110421104501.htm
North Carolina State University. "Fat turns into soap in sewers, contributes to overflows." ScienceDaily. www.sciencedaily.com/releases/2011/04/110421104501.htm (accessed October 20, 2014).

Share This



More Earth & Climate News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Powerful Hurricane Gonzalo Heads to Bermuda

Raw: Powerful Hurricane Gonzalo Heads to Bermuda

AP (Oct. 17, 2014) Hurricane Gonzalo pounded Bermuda with wind and heavy surf on Friday, bearing down on the tiny British territory as a powerful Category 3 storm that could raise coastal seas as much as 10 feet. (Oct. 17) Video provided by AP
Powered by NewsLook.com
So, Kangaroos Didn't Always Hop

So, Kangaroos Didn't Always Hop

Newsy (Oct. 16, 2014) Researchers believe an extinct kangaroo species weighed 500 pounds or more and couldn't hop. Video provided by Newsy
Powered by NewsLook.com
Hurricane Gonzalo Is A Category 4 And Heading To Bermuda

Hurricane Gonzalo Is A Category 4 And Heading To Bermuda

Newsy (Oct. 16, 2014) Powerful hurricane could hit Bermuda this weekend, and even if it misses it will likely do some damage. Video provided by Newsy
Powered by NewsLook.com
The Largest Volcano In Centuries Is Spewing Toxic Gas

The Largest Volcano In Centuries Is Spewing Toxic Gas

Newsy (Oct. 16, 2014) One of the largest volcanic eruptions in centuries is occurring on Iceland. The volcano Bardarbunga is producing high levels of sulfur dioxide. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins