FOG Interceptor

Kent County Public Works

FATS, OIL AND GREASE (FOG) INTERCEPTOR AND TRAP INFORMATION

WHAT ARE THEY?

WHERE DO THEY COME FROM?

HOW DO THEY CAUSE A PROBLEM?

WHAT CAN I DO ABOUT FOG?

WHAT IS KENT COUNTY DOING ABOUT THEM?

FOG BEST MANAGEMENT PRACTICES

Frequently Asked Questions About Grease

Grease Trap and Interceptor Maintenance

WHAT ARE THEY?

Fats, oils and greases (FOG) have been defined under the Kent County Sanitary Code under the term "grease" and are defined as a material either liquid or solid, composed primarily of fat, oil and grease from animal or vegetable sources. Fats are mixtures of various triglycerides with a small percentage of monoglycerides and diglycerides. Oil is often defined as triglycerides that are liquid at room temperature. Grease is a general classification for fats, oils, waxes and soaps that have a negative effect on the wastewater treatment system. Examples of FOG include kitchen cooking grease, vegetable oil, bacon grease, etc.

WHERE DO THEY COME FROM?

FOG is generated by everyone who prepares and cooks food. Some of the industries who generate FOG include meat processors, food packagers, restaurants, food preparation businesses, cafeterias in schools, churches, prisons and hospitals, and residential homeowners. Whenever food is cooked in oils there is n need to get rid of the cooking oils and greases. The most common place to get rid of these wastes is by pouring them down the drain. This method of disposal creates significant problems as the next section will discuss.

HOW DO THEY CAUSE A PROBLEM?

As we have mentioned in a prior section some of the typical fats are triglycerides. They are the same chemicals that clog arteries in people. In a wastewater system, the water flows from the sinks and toilets through pipelines to the wastewater treatment facility. These pipelines operate just like the arteries of our body, which transport blood and wastes. They too will become clogged. When pipes become clogged, the water can no longer flow through them and it will back up into sinks, toilets, and other areas. They can also create sanitary sewer overflows (SSOs) at pump stations and other areas. These SSOs can result in serious pollution of our waterways and yards. In addition, EPA does not like them and they can result in municipalities, such as Kent County being fined. These fines must come from tax dollars, and as a result YOU are creating and paying for them. The best way to prevent these overflows is to keep the FOG out of the sewer system.

WHAT IS KENT COUNTY DOING ABOUT THEM?

Kent County is developing an fats, oil and grease (FOG) program under its Sanitary Sewer Code. This program will require all haulers of grease to be permitted and all food service facilities to have a permit for their grease traps and interceptors. A food service facility is defined under the Sanitary Code as a facility that prepares and/or packages food or beverages for sale or consumption, on and off site, with the exception of private residences and facilities that serve less than 10 meal events (breakfast, lunch or dinner) per month. Food service facilities include, but are not limited to, food courts, food manufacturers, food packagers, restaurants, grocery stores, bakeries, lounges, hospitals, hotels, nursing homes, churches, prisons, schools and all other food service facilities not listed above.

The permit program and resulting Sanitary Code will also provide design criteria to ensure that all grease traps and interceptors are properly designed. It will require that all grease traps and interceptors be maintained by monthly cleaning, at a minimum. It will also provide education to all food service facilities and residents of the County about what FOG is, what it does and how to properly dispose of FOG. You can learn more about the permitting program by clicking the link below:

Fats, Oils and Grease Permit Program

WHAT CAN I DO ABOUT FOG?

There are a variety of DO's and DON'Ts that you should observe to ensure that the minimum amount of FOG gets into the wastewater system.

Scrape excess grease in a container and dispose of it in the trash or containers specifically designated for grease.

Grease should not be placed in the wastewater system. It can clog pipes, interfere with pumps and create sanitary sewer overflows that can have a detrimental effect on the environment and public health.

Place food scraps in waste containers or garbage bags for disposal with solid wastes, or start a compost pile; promote the use of scraping ware prior to washing.

Food does not belong in the wastewater system. The best alternative is to place food scraps in a compost pile and use the composted material in your gardens or on your lawns.

Place a wastebasket in the bathroom to dispose of wastes. Disposable diapers, condoms, and personal hygiene products do not belong in the sewer system. These items cannot be handled by the wastewater system.

Promote the use of the 3 "R's" :
Reduce. Reuse and Recycle.
Using the three R's is the best way to be an environmentally friendly consumer.

DO NOT…	Basis
Discharge fats, oil, and grease in concentrations that will cause an obstruction to the flow in a sewer, or pass through or interference at a wastewater treatment facility. FOG from cooking should not be placed in the kitchen or bathroom sinks or in the toilet.	Grease can solidify and trap other solid particles to completely plug the wastewater collection system. Resulting in back ups and creating sanitary sewer overflows that can affect the environment and present serious public health problems.
Discharge grease, improperly shredded garbage, animal guts or tissues, paunch manure, bones, hide, hair, fleshings, entrails, or food scraps.	These materials in combination or alone can cause blockages and other operations and maintenance problems in the wastewater collection and treatment system.
Discharge wastewater with temperatures in excess of 140° F to any grease traps. This includes water from mechanical dishwashers that have a minimum required temperature of 160° F.	Temperatures in excess of 140° F will dissolve grease, but the grease can re-congeal and cause blockages further downstream in the sanitary sewer collection system as the water cools. Note: High temperature water, such as from a dishwasher, is discharged to the remotely-located grease interceptor, if there is one. The remote location and the high volume of the interceptor allows the water time to cool so that there is not a problem with dissolving grease and moving it further downstream. The high volume also provides dilution of the detergents in the dishwasher waste.
Discharge waste from a food waste disposal unit to any grease traps.	The food waste will greatly reduce the capacity of the grease trap for retaining grease and can cause worse problems with blockages.
Discharge caustics, acids, solvents, soaps, enzymes, or other emulsifying agents into sinks that feed grease traps and/or interceptors.	Though emulsifying agents can dissolve solidified grease, the grease can re-congeal further downstream in the sanitary sewer collection system. Caustics, acids, and solvents can have other harmful effects on the wastewater treatment system and can be a hazard to employees working in the wastewater collection system.
Discharge fats, wax, grease or oils containing substances that will become viscous between 32° F (0° C) and 150° F (65° C).	The temperatures shown are temperatures that can occur in the wastewater collection and treatment system. If these substances congeal, solidify, or become too viscous, they can cause blockages and other operations and maintenance problems.
Utilize biological agents, chemicals, or enzymes for grease remediation without permission from the sanitary agency receiving the waste.	The biological agents may disrupt the biological treatment process at the wastewater treatment plant.
Clean equipment outdoors in an area where water can flow to the gutter, storm drain, or street.	Grease and dirt will be washed off the equipment and enter the storm drain system and flow to nearby streams.
Use the toilet as a wastebasket	The wastewater system can only accept water borne materials that will not solidify at room temperatures.

FOG Best Management Practices

For the recommended best management practices for handling fats, oils and greases click on the link below:

FOG BMPs

Frequently Asked Questions About Grease

Is grease a problem?

What is a grease trap and how does it work?

What is a grease interceptor?

How do I clean my grease trap?

Can you recommend a maintenance schedule?

Do I have a grease trap?

Do I need a grease trap?

Is the grease trap I have adequate?

What if I don’t install a grease trap?

Who determines if I need a grease trap or interceptor?

How can I get in compliance?

What are the criteria for inspecting grease traps?

Is grease a problem?

In the sewage collection and treatment business, the answer is an emphatic YES! Grease is singled out for special attention because of its poor solubility in water and its tendency to separate from the liquid solution.

Large amounts of oil and grease in the wastewater cause trouble in the collection system pipes. It decreases pipe capacity and, therefore, requires that piping systems be cleaned more often and/or some piping to be replaced sooner than otherwise expected. Oil and grease also hamper effective treatment at the wastewater treatment plant.

Grease in a warm liquid may not appear harmful. But, as the liquid cools, the grease or fat congeals and causes nauseous mats on the surface of settling tanks, digesters, in the wet wells of pumping stations, and the interior of pipes and other surfaces which may cause a shutdown of wastewater treatment units.

Problems caused by wastes from restaurants and other grease-producing establishments have served as the basis for ordinances and regulations governing the discharge of grease materials to the sanitary sewer system. This type of waste has forced the requirement of the installation of preliminary treatment facilities, commonly known as grease traps or interceptors.

What is a grease trap and how does it work?

A trap is a small reservoir built into the wastewater piping a short distance from the grease producing area. Baffles in the reservoir retain the wastewater long enough for the grease to congeal and rise to the surface. The grease can then be removed and disposed properly.

What is a grease interceptor?

An interceptor is a vault with a minimum capacity of between 500 and 750 gallons that is located on the exterior of the building. The vault includes a minimum of two compartments, and flow between each compartment is through a 90° fitting designed for grease retention. The capacity of the interceptor provides adequate residence time so that the wastewater has time to cool, allowing any remaining grease not collected by the traps time to congeal and rise to the surface where it accumulates until the interceptor is cleaned.

How do I clean my grease trap?

Refer to Grease Trap and Interceptor Maintenance.

Can you recommend a maintenance schedule?

All grease interceptors should be cleaned at least once each month. Some establishments will find it necessary to clean their traps more often than twice per month. If the establishment is having to clean it too often, the owner should consider installing a larger trap or interceptor.

Do I have a grease trap?

If the establishment is uncertain whether it has a grease trap, the owner should contact the Kent County Dept. of Public Works.

Do I need a grease trap?

Any establishment that introduces grease or oil into the drainage and sewage system in quantities large enough to cause line blockages or hinder sewage treatment is required to install a grease trap or interceptor. Interceptors are usually required for high volume restaurants (full menu establishments operating 16 hrs/day and/or serving 500+ meals per day) and large commercial establishments such as hotels, hospitals, factories, or school kitchens. Grease traps are required for small volume (fast food or take-out restaurants with limited menus, minimum dishwashing, and/or minimal seating capacity) and medium volume (full menu establishments operating 8-16 hrs/day and/or serving 100-400 meals/day) establishments. Medium volume establishments may be required to install an interceptor depending upon the size of the establishment.

Is the grease trap I have adequate?

The Uniform Plumbing Code requires that no grease trap have a capacity less than 20 gallons per minute (gpm) or more than 55 gpm. The size of the trap depends upon the number of fixtures connected to it. The following table provides criteria for sizing grease traps:

Total number of fixtures connected	Required rate of flow, gpm	Grease retention capacity, lbs
1	20	40
2	25	50
3	35	70
4	50	100

The size will also depend largely upon the maintenance schedule. If a grease trap or interceptor is not maintained regularly it will not provide the necessary grease removal. The establishment should work out a specific cleaning schedule that is right for the establishment. All grease traps need to have the grease cleaned out periodically and no one likes to do the job. It is a dirty job. Running extremely hot water down the drain only moves the problem down stream. It does not go away. Catch the grease at the source! This is the most economical means to reduce all costs.

DNREC has established grease trap design capacities based upon the types of fixtures. Click on the link below to view the table.

DNREC Grease Trap Design Capacity Table

What if I don’t install a grease trap?

If the establishment uses grease and oil in food preparation, it will eventually encounter a maintenance problem with a plugged building sewer line. The blockage can create a sewer backup situation and ultimately a potential health problem in the establishment. Someone will have to pay for removing the blockage. If the problem is in the building sewer line, then the establishment has direct responsibility for paying for the maintenance. If the blockage or restriction is in the public sewer main and it can be proven that the establishment is the cause of the blockage, then the establishment may have to pay for the public sewer to be maintained. Blocking a sanitary sewer line is also a violation of the federal Clean Water Act.

Who determines if I need a grease trap or interceptor?

An approved grease trap or interceptor shall be installed according to the Uniform Plumbing Code, Delaware Plumbing Code, Delaware dept. of health, and the Kent County Sanitary Code, Chapter 180. The rules of the Health Department will also assist the establishment in determining if a grease trap or interceptor is required. The Kent County Sanitary Code prohibits the discharge of materials that can solidify and create blockages in the wastewater collection system or treatment plants. The Health Department makes periodic inspections to see that no health problems exist due to improperly maintained grease interceptors. These rules will be enforced if a problem exists.

How can I get in compliance?

The establishment should contact the Kent County Dept. of Public Works. The establishment will be asked to purchase a permit for the grease trap. This will enable the proper jurisdiction to assist the establishment in cleaning schedules and advise them of a problem showing up in the wastewater collection system. A grease interceptor permit is required regardless of whether the establishment has an existing trap or is installing a new one. These are referred to as a Food Service Facility Permit.

What are the criteria for inspecting grease traps?

All food service establishments suspected of causing problems to the collection system or treatment facilities will be inspected. The inspector will use the following criteria to inspect grease traps:

Percent of Trap Filled	Trap Condition
25	Good
25 – 50	Fair
>50	Poor

If the trap is in FAIR condition, the establishment should be advised to keep an eye on the maintenance schedule. The cleaning frequency may need to be increased. If the trap is in POOR condition, the establishment should be issued a compliance order to have it cleaned immediately. The establishment should then be required to contact the issuing authority within 30 days to verify that the grease interceptor has been properly cleaned.

Grease Trap and Interceptor Maintenance

Grease Trap Maintenance
Grease Interceptor Maintenance

Grease trap maintenance is usually performed by maintenance staff, or other employees of the establishment. Grease interceptor (GI) maintenance, which is usually performed by permitted haulers or recyclers, consists of removing the entire volume (liquids and solids) from the GI and properly disposing of the material in accordance with all Federal, State, and/or local laws. When performed properly and at the appropriate frequency, grease interceptor and trap maintenance can greatly reduce the discharge of fats, oil, and grease (FOG) into the wastewater collection system.

The required maintenance frequency for grease interceptors and traps depends greatly on the amount of FOG a facility generates as well as any best management practices (BMPs) that the establishment implements to reduce the FOG discharged into its sanitary sewer system. In many cases, an establishment that implements BMPs will realize financial benefit through a reduction in their required grease interceptor and trap maintenance frequency. Refer to Best Management Practices for examples of BMPs that FOG generating establishments should implement.

WARNING! Do not use hot water, acids, caustics, solvents, or emulsifying agents when cleaning grease traps and interceptors.

Grease Trap Maintenance

A proper maintenance procedure for a grease trap is outlined below:

Trap.gif (25736 bytes)

Step	Action
1.	Bail out any water in the trap or interceptor to facilitate cleaning. The water should be discharged to the sanitary sewer system.
2.	Remove baffles if possible.
3.	Dip the accumulated grease out of the interceptor and deposit in a watertight container.
4.	Scrape the sides, the lid, and the baffles with a putty knife to remove as much of the grease as possible, and deposit the grease into a watertight container.
5.	Contact a hauler or recycler for grease pick-up.
6.	Replace the baffle and the lid.
7.	Record the volume of grease removed on the maintenance log.

Grease Interceptor Maintenance

Grease interceptors, due to their size, will usually be cleaned by grease haulers or recyclers. Licensed septage haulers can also pump out grease interceptors and haul the waste to the treatment plant. The hauler must notify DNREC when hauling grease. There are a number of companies who are permitted to land apply the grease wastes and the Kent County Wastewater facility is expanding its permit to land apply grease wastes, as well.

A proper maintenance procedure for a grease interceptor is outlined below:

NOTE: Since the establishment is liable for the condition of their pretreatment devices, the establishment owners/representatives should witness all cleaning/maintenance activities to verify that the interceptor is being fully cleaned and properly maintained.

intercept.gif (27825 bytes)

Step	Action
1.	Contact a grease hauler or recycler for cleaning.
2.	Ensure that all flow is stopped to the interceptor by shutting the isolation valve in the inlet piping to the interceptor.
3.	Remove the lid and bail out any water in the trap or interceptor to facilitate cleaning. The water should be discharged to the sanitary sewer system.
4.	Remove baffles if possible.
5.	Dip the accumulated grease out of the interceptor and deposit in a watertight container.
6.	Pump out the settled solids and then the remaining liquids.
7.	Scrape the sides, the lid, and the baffles with a putty knife to remove as much of the grease as possible, and deposit the grease into a watertight container.
8.	Replace the baffle and the lid.
9.	Record the volume of grease removed on the maintenance log.

Grease Cleaning Maintenance Log Sheet

Much of the information on this web page is taken from the Fats, Oils and Grease Best Management Practices Manual produced by Brown and Caldwell for the Oregon Clean Water Agencies.