Experienced inspector and engineer explains why it is critical to understand grease interceptor standards and watertightness testing protocols.
By James Baginski, P.E.
The term FOG often describes the streets of London during the early morning hours. Sorry ole’ chap, but this term has become an acronym that strikes fear in the hearts of wastewater collection system managers. Or does it?
Over the past few decades, after all our wastewater treatment plants were upgraded, the EPA (U.S. Environmental Protection Agency) began to focus on observed fats, oils and grease (FOG) discharged to public sewer systems. FOG had arguably become the No. 1 cause of costly sanitary sewer overflows that can result in adverse impact to public health and the environment. Well, that will not do. Surely municipalities require restaurants and food service establishments (FSEs) to control FOG discharges. Or do they? Do FOG-removal devices such as grease interceptors take care of this nasty problem?
The problem: misunderstanding interceptor issues
Many municipalities, in fact, did not have adequate FOG-control programs in place to ensure that properly sized grease interceptors were installed at FOG-discharging FSEs. This lack of oversight may no longer be the case now that many of our eyes have been opened – or blackened, I should say – by EPA enforcement actions for excessive FOG-caused wastewater spills. A properly designed, sized, installed and maintained grease interceptor prevents excessive FOG generated by FSEs from being discharged into our public wastewater systems. A well-designed grease interceptor will provide the necessary retention time to allow FOG to separate from, or float to the surface of, the wastewater in the tank. Interceptors adequately designed for the facility’s discharge flow rate will retain FOG for future removal and proper disposal.
Although this solution sounds simple and straightforward, problems can arise when manufacturers, specifying engineers, local inspectors, regulators and owners do not understand all of the concerns associated with installing an effective, reliable and safe grease interceptor.
Why ASTM matters to you
The purpose of ASTM (See: http://www2.astm.org/ABOUT/aboutASTM.html#_1) standards is to ensure that the products and services we use are safe and reliable. Grease interceptors must be watertight and structurally sound to withstand the loads to which they may be subjected in various FSE installation sites (Figures 1 through 3). It is also important that manufacturers incorporate quality assurance and control programs in developing processes to ensure consistency and product reliability.
To find out how much you know about ASTM Standard C 1613, “Standard Specification for Precast Concrete Grease Interceptor Tanks,” take the test on page 10. You might be surprised to discover what a great resource ASTM is for our industry.
Trouble in paradise
Even here in paradise (Hawaii, where the author works), we (Honolulu’s source control specialists or inspectors) have come across grease interceptors that are falling apart, leaking or of questionable origin. It’s reasonably safe to say that Hawaiian inspectors aren’t the only ones who have seen poor tank product quality, improper sizing or lack of routine cleaning. In these cases, here and on the mainland, it is important to address the issues by requiring the tank owner to take corrective action and even to seek the assistance of other regulatory entities; it is critical for the inspector to take the correct action before potentially unsafe conditions result in an accident, discharge to the environment or personal injury.
In recent years, Honolulu dealt with a particular contractor-turned-tank-manufacturer who began precasting his own grease interceptors for sale and installation at Oahu’s FSEs. Because of our (inspectors’) concerns about questionable product compliance with ASTM standards, we were compelled to insist that this business obtain the appropriate certification for its devices.
Designing a better mouse trap: FOG retention time
All grease removal device manufacturers strive to design a better “mouse trap.” In lieu of a national or industry-accepted performance standard for grease interceptors, municipal inspectors may wish to develop a procedure to verify tank performance. When I say “performance criteria” I am referring to the device’s retention time. All grease interceptors have the potential to short circuit, when FOG may not be adequately retained and pass through the interceptor and into the public collection system. The actual retention time of the device, therefore, can be determined only through some form of flow-based modeling applying the maximum expected discharge flow rate of the FSE in question.
Municipalities that apply flow-rate and retention-time-based grease interceptor sizing criteria (like Honolulu) can develop a simple dye test protocol to establish their own in-house performance criteria. In 1999, when Honolulu was developing its grease-interceptor sizing criteria, precast concrete interceptors were the most common type of large grease interceptor available. Honolulu, therefore, used the precast concrete grease interceptor in establishing a retention-time-based performance criterion.
Interceptor standards contribute to 90% spill reduction
In Honolulu, FOG-caused wastewater spills have been reduced by 90% since 1999. This remarkable reduction was achieved through the development and implementation of a reasonable in-house FOG-control program. Our program includes a technically based grease-interceptor sizing criteria, and a system to identify FOG problem areas in the collection system and locate the FSEs discharging excessive FOG into the collection system. Identified FSEs are required to upgrade their grease removal devices to meet our FOG-control program criteria. Other contributing factors to effective FOG control are: repair of system-operational issues (line sags), an effective line-cleaning program, and public education.
It is interesting to note that this spill reduction has been achieved by requiring only about one-third of all Honolulu FSEs to upgrade to meet the current FOG-control criteria. In both 2008 and 2009, only four FOG-caused spills were attributed to commercial dischargers within Honolulu’s 2,100 miles (3,380 km) of gravity sewer lines. We anticipate further reduction in the future.
The formula: standards, line cleaning, system repairs and education
As long as there are meats and fried foods on the menu, there will be FOG discharges to our wastewater collection systems, and those of us in the industry (producers, inspectors, specifying engineers and regulators) need to control it. Collection system cleaning programs, correcting system-operational problems and public education initiatives play a significant role in minimizing spills.
There is no silver bullet that will make FOG problems go away. However, a reasonable and methodical, multi-pronged attack of source control, system repairs, line cleaning and public education will yield the desired goal of minimizing FOG-caused wastewater spills and reducing collection system maintenance costs.
James Baginski, P.E., has 25 years of environmental engineering experience and has been with the City and County of Honolulu Department of Environmental Services since 1993. Baginski is the author of Honolulu’s FOG control program and he has served as an expert witness in FOG control program litigation. He has served as Regulatory Control Branch Manager and Assistant Chief of Collection System Maintenance.
ASTM C 1613: Take the Test!
Check Your Knowledge of the Precast Concrete Grease Interceptors
Originally called the American Society for Testing and Materials (ASTM) and currently known simply as ASTM International, this important organization was formed more than a century ago by engineers and scientists. ASTM is one of the largest voluntary standards development organizations in the world. ASTM is a trusted source of information, because its voting members include producers, users, consumers, government regulators and academia, who developed standards by consensus. ASTM’s purpose: to make products and service safer, better and more cost-effective.
To find out how much you know about existing grease interceptor standards, take the following test (answers at bottom):
- Engineers should always specify compressive strength for precast grease interceptor tanks in bid documents; minimum is 5,000 psi (35 MPa) for commercial tanks. True or False (T or F)
- Specifiers must define the depth of earth cover, live load at the surface and ground water level at the site where the tank will be installed. T or F
- Project engineers should specify the required capacity of the grease interceptor tank in gallons or liters. T or F
- Vacuum testing for interceptor watertightness is routine for precast manufacturers who comply with the specifications of ASTM C 1613. T or F
- Any special cement required for the site conditions (sulfateresisting C 150 Type II or highly sulfate-resisting cement C 150 Type V) should be called out in the owner’s bid documents. T or F
- All grease interceptors are designed to resist live traffic loading (AASHTO H-20 load rating). T or F
- Owners of food service establishments (FSEs) generally understand the requirements for a well-designed grease interceptor. T or F
- All producers of grease interceptors offer almost identical products that are manufactured in compliance with ASTM C 1613. T or F
- The best way for restaurant owners, specifying engineers, producers or inspectors to avoid structural problems with grease interceptors is to insist on product compliance with ASTM C 1613. T or F
- When interceptors are manufactured in compliance with ASTM C 1613, regulators and specifiers may be assured that minimum concrete compressive strength, reinforcement requirements, traffic-load ratings and watertightness testing criteria are met. T or F
A precast concrete grease interceptor that is manufactured in compliance with ASTM C 1613 gives assurance to inspectors, owners and specifiers that the interceptor meets current standards for minimum compressive strength, live-load ratings, proper sealing and watertightness.
Answers: 1. F ; 2. T; 3. T; 4. T; 5. T; 6. F; 7. F ; 8. F; 9. T; and 10. T.