Follow along as we examine solutions to the challenge of fats, oils and grease in the country’s sewer lines and treatment plant works
Fats, oils and grease continue to plague sewer systems across the country by reducing sewer line capacity, clogging sewer lines and gumming up wastewater treatment plant works.
“FOG has been a problem in this country since Colonel George A. Waring Jr. built the first separated sewer line in Memphis, Tenn., circa 1880,” says Steve Tilson, president of Tilson & Associates, a consulting firm specializing in wastewater collection system operations and training. “Everyone’s trying to reach the goal of FOG-free sewer lines, but there is no single solution that will handle every FOG problem.”
Part of the reason is that the fats, oils and greases that make up FOG are distinct, entering the sewer system from different sources and possessing unique chemical makeups.
Related: Case Study: Best Crew for the Job “Animal fats and tallows are generally introduced from manufacturing or rendering facilities and can harden in pipes over time, limiting sewer capacity and impacting sewer component longevity,” Tilson says. “FOG can be introduced from residential users and food service establishments. No single description will cover all of the sources.”
The best strategy for reducing FOG problems remains source control, through a combination of mechanical separators, and regulatory and educational efforts.
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While community outreach and education takes many forms, the New York City Department of Environmental Protection is currently quantifying the effects of education on FOG, which was implicated in approximately 60 percent of confirmed sewer backups in the city last year.
In 2013, the DEP collaborated with the New York City Housing Authority to target one housing development with an educational program outlining the impact of FOG on sewers, and proper disposal of grease and used cooking oil.
“Grease has been identified to the public as a major bad actor,” says Jim Roberts, New York’s deputy commissioner for water and sewer operations. “By measuring levels of grease buildup in those sewers where the outreach was conducted and comparing that to grease buildup in a similar sewer without the program, we’ll be able to tell if our outreach program is working.”
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Some communities require that food service establishments and other related industries employ interceptors to separate FOG at those sources, but many do not. Few communities address the issue of high-density housing that can also be a significant source of FOG in a sewer system. Tilson recommends that communities consider changing building codes for high-density housing construction to include communal FOG interceptors to reduce costly sewer issues.
“Source control is a major component of industry best practices,” Tilson says. “Encouraging source control nips the problem before it can become a threat to property and public health. As an added value, FOG can be used for a large number of purposes, from biodiesel to industrial detergents.”
While additives such as degreasers, emulsifiers, enzymes and bacteria can temporarily break down FOG deposits, they’re only a temporary solution, says Tilson.
“They’re spot treatments that will break down FOG or liquefy it long enough to move it further down the sewer line, or into the treatment plant,” he says.
There doesn’t appear to be any one additive that will permanently dissolve FOG to a state where these elements won’t recombine and replicate the problem further down the pipe.
A FOG control study completed at California’s Orange County Sanitation District in 2006 by Environmental Engineering & Contracting Inc. compared several sewer line-applied and food service establishment-applied additives among other approaches. While a few of the treatments showed some promise in certain applications, no single treatment was rated clearly superior to a well-maintained grease interceptor or thorough cleaning followed by CCTV monitoring.
In fact, in many systems the use of enzymes, emulsifiers and grease gobbling bacteria by businesses is now illegal. “You can disrupt a sewage treatment plant by shifting its pH or introducing the wrong enzyme or bacteria,” Tilson says.
Time-honored mechanical solutions for FOG problems include jetters and rodders using a variety of attachments designed to remove FOG buildup.
Pigging — sending a scrubbing device through a force main — can also offer relief. Ice pigging, a newer technology, employs a saltwater ice slurry to scour the inside of FOG-coated force mains.
Problem behind the problem
John Shaffer, president of EEC, the company that conducted the Orange County study, has also noted that FOG problems are often the most obvious and immediate symptom of some other problem.
FOG may collect in some areas because of poor pipe cleaning and maintenance, pipe defects, pipe sags or root problems.
Tilson says, “Due to this, the only effective means of dealing with FOG in sewers is source control coupled with an effective preventive maintenance program.”