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 precast concrete 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 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. It is also important that manufacturers incorporate quality assurance and control programs in developing processes to ensure consistency and product reliability.
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, multipronged 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.