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In order for grease removal units to be effective, they must be properly sized, installed, and maintained in a location providing adequate retention times for settling and accumulation of fats, oils, and grease.
The EPA estimates that there are at least 40,000 sanitary sewer overflows each year. The untreated sewage from these overflows can contaminate water, causing serious water quality problems.
It can also back-up into basements, causing property damage and threatening public health.
One contributing factor to these overflows is the hundreds of pounds of fats, oils, and grease (commonly known as FOG) generated by food processing plants, cosmetic and toiletry manufacturers, food warehouses, and large commercial / institutional kitchens found in hospitals, schools, convenience stores, and restaurants.
Just as the grease from a hamburger and fries clogs our arteries, this grease, if allowed to enter a sewer system, can create many problems.
When fats, oils, and grease first enter the system, they cool and coagulate on the system piping. As grease solidifies on the interiors of pipes, sewage flow becomes restricted.
“If grease gets into the pipes, it can block the sewer pipes or lift stations, and now the sewage has no where to go and it will back up through the man ways, through the lift stations, and cause a sanitary sewer overflow—and then you’ve got raw sewage being discharged into the streams and lakes,” says Greg Aymong, vice-president of wastewater treatment systems for Highland Tank and the inventor of the Highland Tank oil/water separator.
High concentrations of fats, oils, and grease in wastewater can inhibit the biological processes used to treat domestic sewage.
Most sewer treatment plants are not designed to remove fats, oils, and grease. The EPA requires that municipal sanitary sewer authorities implement pretreatment programs to control these discharges. Most restaurants and food preparation facilities tied into a sanitary sewer system are affected by these regulations.
Different Grease Removal Systems
To help alleviate some of the fats, oils, and grease from entering the environment, many facilities install grease traps and grease interceptors. The purpose of these devices is to allow separation of solids and grease, to contain them in an onsite holding facility, and to prevent these troublesome wastes from entering the main sewer system or septic drainfield.
There are different types of grease traps/interceptors. Passive grease traps collect grease as it rises to the top of a small baffled tank when wastewater generated in the facility flows through the unit. The collected grease from these units must be removed manually. These units are usually relative small in size (typically 20–25 gallons) and must be cleaned regularly.
Automatic grease interceptors are usually inside the facility either under or in proximity to sinks and other plumbing fixtures. These systems intercept, separate, and retain grease, preventing discharge into the sanitary sewer collection system. They are equipped with an electrically powered grease-skimming device designed to automatically remove grease periodically or continuously. An automatic grease removal system is generally larger than a grease trap to allow for greater retention time for better separation and performance. Automatic units must be cleaned and maintained periodically to remove settled solids buildup and keep equipment clean; however, this is usually only occasionally compared to other manual units.
In order for grease removal units to be effective, they must be properly sized, constructed, installed, and maintained in a location providing adequate retention times for settling and accumulation of fats, oils, and grease.
Connecticut’s FOG Program
Joe Nestico knows that fats, oils, and grease in sanitary sewer pipes can cause problems. Nestico, senior environmental analyst biologist for the Connecticut Department of Environmental Protection (DEP) for nearly 34 years, first got involved mediating the FOG problem in Connecticut in 1995 when he received a phone call about blockage at a nursing home in Bristol. The hauler had nowhere to go with the 1,500-gallon greasy load he collected from the nursing home. Many municipal wastewater treatment facilities stopped accepting the grease because they did not have the ability to process it. “I made a few phone calls and got it channeled to an incinerator in Naugatuck as a one time special service to us,” Nestico says. “The chief operator there said he would help out with this one particular issue but said that the problem really needed to be solved. As a matter of fact, at that time, he would have probably lit a candle in church for me if I could solve the problem.”
As Nestico learned, this was just the tip of the iceberg in solving the fats, oils, and grease issue in Connecticut. He first conducted an inventory of how many tons of grease loads local wastewater plants were dealing with. Upon further investigation, it was found that a high percentage of SSOs were the result of grease blockages in the sewer lines. So the first order of business was finding out what to do with the tons of fats, oils and grease that were being generated.
In 1998, a pilot FOG program was set up in the city of Torrington. A large tanker was brought in for facilities to bring their greasy loads. From there, they began to learn how to manage it. Samples were taken and analyzed, and it was found that the grease could safely be disposed of through incineration. Furthering those efforts, Torrington and the Torrington Area Health District received a grant from the DEP to develop a program to reduce the volume of fats, oils, and grease discharged into sewage system. This grant allowed them to hire the firm of Wright-Pierce Engineering to help with this effort. A “fract” (short for fractionization) tank was put in place to accept fats, oils, and grease. Other regional “fract” tank sites and incinerators were set up in the cities of New Haven and Willimantic. “More than 10 million gallons of greasy loads have gone through the fract tank program here in Connecticut,” Nestico reports.
Along the way, they also discovered that the greasy loads could be used as a fuel source to burn sewage sludge. “What we started to learn was that the computer connected to the incinerator was actually shutting down the natural gas and fuel oil supplies for burning because it was running off of the grease we were feeding it,” Nestico says. “That meant we now had a beneficiary reuse of material that was a problem before but now it has the ability to solve another problem, which is the source of fuel to burn sewage sludge.”
The next step, creating the regulatory tools to develop a FOG permit proved to be more difficult. The first draft of the permit, Wastewater Associated with Food Preparation Establishments, was created in March 1999. And after probably 25 or 30 revisions, the final permit was completed in September 2005.
The Food Preparation Establishment Wastewater General Permit requires food preparation facilities to install either of two methods designed to significantly control FOG at its source. The first method is the installation of a passive 1,000-gallon minimum grease interceptor outside the facility. The second method is an automatic grease interceptor unit installed inside the facility. Either method results in the capture of the FOG before it enters the sewer system. The captured FOG is then taken to regional disposal sites where it can be further treated and potentially consumed as a fuel source in regional sewage sludge incinerators.
Food preparation facilities have until July 1, 2011, to comply with the conditions of the permit. However, newly constructed facilities, facilities that renovate, and facilities that are sold must enter into compliance as part of that process. Additionally, a municipality can require a facility or facilities to implement these changes if a sewer system area is deemed to be a FOG problem area. The permit gives municipalities the authority to exempt food preparation establishments that have small discharges with minimal FOG quantities due to the nature of the food prepared.
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Facilities Working to Keep FOG Out
Henningsen Foods, located in Omaha, NE, found itself between a rock and a hard place. The company, which has more than 100 years of food processing experience in specialty eggs, specialty dehydrated meats, poultry, and seafood products, needed to expand production and come into compliance with the local and state-mandated 100-ppm effluent quality for fats, oils, and grease. “We had a couple of settling separation tanks, but they were not sufficient to reduce our numbers below 100 parts per million,” explains Gary Lorimor, vice-president of operations for Henningsen Foods Inc.
The grease removal system on which Henningsen Foods relied seemed to be no match for the daily load of solids and fats, oils, and grease. Certain food productions at the plant sometimes generated 50%–70% fat-laden waste. Samples of effluent from these holding tanks tested 579 ppm at a daily flow rate of 9,000 gallons.
Ron Emons of Olson Associates was assigned to engineer a grease recovery system capable of bringing the plant back into compliance and expanding production needs. Emons contacted Roger Jones Associates of Atlanta, GA, to provide recommendations for proper sizing, design, and product application to deal with the site and municipal parameters. The product that was specified by Emons and recommended by Roger Jones Associates was the Highland Tank Highguard triple basin grease interceptor with diffusion and switchback baffling technology.
In September 2005, with the new grease recovery system in place, Henningsen Foods conducted a production run doubling the rate of daily flow to 18,000 gallons. A sample of the effluent tested at 87 ppm, well under the required 100 ppm. Now, more than a year later, Lorimor reports that the grease interceptor is functioning well. “We’ve had good results from it. We definitely see a vast separation in the three compartments,” he says.
Chatterly’s Restaurant
Chatterly’s is a family-owned business that serves American-contemporary cuisine in Hartford, CT. The restaurant caters to some 200 customers on any given day. The establishment lacked the means to comply with the general permit. An automatic grease interceptor designed by Lowe Engineering, was installed in the basement of the facility. “We previously had one of the old-fashioned deals,” says Paul Samele, co-owner of the restaurant. “This system seemed like a better way to get rid of the grease. They really hadn’t come up with a good system up to that point, and this seemed like a really good system for as far as cleaning and stuff like that. The old way was very difficult.”
The system has been so successful that the facility is used as a model for surrounding wastewater treatment personnel to reference a properly engineered pretreatment device and its
benefits.
Rhode Island Convention Center
The Rhode Island Convention Center situated in the heart of Providence and the retail district has been host to many prominent functions over the years. The kitchen at the convention center sometimes caters to 2,000 individuals a day. The center is also located in the Narragansett Bay Commission, noted for its strict wastewater compliance regulations, due to the proximity of sensitive wetlands and waterways.
“We had two passive grease traps that didn’t work right,” says Paul Holgate plant supervisor for the Rhode Island Convention Center. “We wanted to upgrade, and in Rhode Island they want automatic grease skimming.”
Ardente Supply was contacted to help resolve the issue of poor performance with the existing system. Ardente Supply recommended the convention center replace the existing grease traps with one Lowe Engineering automatic grease interceptor. “These things have a limit on how many gallons per minute can pass through them, and the other one, sometimes on heavy demand, would back up into the pipe. ... I wanted to increase the limit, so I had to increase the size. It was basically to improve on what we had,” Holgate says.
Driving With Their FOG Lights On
Besides Connecticut, there are many other states, communities, and municipalities with FOG programs throughout the country. Hawaii, Colorado, Texas, and Oregon, just to name a few, are all on board trying to reduce the amount of fats, oils, and grease that enter the environment. The realization has come to light, that something as seemingly innocent as dumping leftover bacon grease down the drain can definitely contribute to environmental and health issues.
Nestico sums it up best. “Something that would appear to be an innocuous material really has environmental significance. It is on the same playing field as some of the other issues. Grease blockages can cause sanitary sewer overflows with raw sewage going into people’s basements or surface waters contributing to serious health problems. Or a restaurant that has a blockage and sewage coming back into the kitchen can be a dangerous situation for people in the kitchen—or possible food contamination. It’s not a hazardous material but the end result can be the same.”
Nikki Stiles is a freelance writer based in the city of Fairmont, WV.
OW - November/December 2006 |
