Ensuring the Well-Being of the Environment

through Grease Abatement Improvements

Miles Robinson

PUAF386

University of Maryland

August 24, 2014

Ensuring the Well-Being of the Environment through Grease Abatement Improvements

Many different factors contribute to the ever-present problem of environmental pollution.

Greenhouse gas emissions affect air quality, and pesticides and other chemicals can run off into

rivers and streams, affecting water purity. A less commonly known form of pollution is a

sanitary sewage overflow. Sanitary sewage overflows (SSOs), although often overlooked, pose a

serious threat to public health and the wellbeing of the environment. Even in low concentrations,

contaminants such as personal care products and pharmaceuticals have been shown to alter the

endocrine system of wildlife, which influences growth, development, and the natural

functionality of the body’s organs. This is no small problem either. There are approximately 3

to 10 billion gallons of untreated wastewater discharged into the environment annually (Aziz et

al., 2011). Along with this statistic, there is potential for severe human implications as well. It is

clear that something must be done about this incredibly high volume of pollution; however, we

must first understand what causes these sanitary sewage overflows.

Blockages caused by fats, oils, and grease (also known by the acronym, FOG) buildup

are the leading cause of sewer system blockages and account for nearly half of all the sewage

overflows in the United States (Gallimore et al., 2011). FOG enters the plumbing drains of food

service establishments and domestic homes via food preparation, dishwashing, equipment

cleaning, and even floor cleaning (Gallimore et al., 2011). It is imperative that FOG is removed

because it has a tendency to congeal along the inner sides of pipes and eventually block the pipe

entirely. In addition to causing sanitary sewage overflows, this build-up can back-up into the

basement of businesses or residential areas, onto streets, and flow into storm drains, streams, and

rivers, harming ecosystems (WSSC, 2013). If the FOG waste travels through the sewer system,

it can also cause costly and time-consuming problems at the wastewater treatment plant (NPCA,

2012). Considering only municipalities that report 100 or more SSOs per year, FOG blockages

account for 74% of overflows (Aziz et al., 2011). This alarmingly high percentage suggests that

current methods of preventing FOG from entering the sewer are inadequate and must be

improved.

Fats, oils, and grease discharge is regulated by municipalities and water utilities all across

the country. The Washington Suburban Sanitary Commission, the water utility in Maryland

which serves all of Prince George’s and Montgomery counties, started the Fats, Oils, and Grease

program in 1994 to comply with a Federal Consent Decree to reduce the number of sanitary

sewage overflows related to FOG blockages in the sewer through education and regulation

(WSSC, 2013). All food service establishments in the WSSC service area must install a grease

abatement system and apply for a FOG Discharge Permit to utilize the sewer system, or apply for

a Best Management Practices (BMP) Permit if the FSE has the potential to only discharge a

minimal amount of FOG into the sewer (WSSC, 2013). These practices include scraping food

from dishes into waste cans before rinsing and wiping down cooking pans before washing.

Currently, grease is kept out of the collection system through passive and mechanized

grease abatement devices (GADs), also commonly referred to as grease interceptors. All current

grease abatement devices work under the principle of gravity separation. Since grease and other

oils have a lower specific gravity than water, when a grease-laden mixture is left undisturbed, the

grease floats to the top and the solids settle at the bottom (NPCA, 2012). In a grease interceptor,

wastewater enters through the inlet and travels underneath the inlet baffle. After a sufficient

retention time (thirty minutes is recommended), solids collect at the bottom of the device, the

FOG is trapped at the top of the tank, and the remaining wastewater is allowed to pass

underneath the outlet baffle and into the sewer (see Figure 1).

Grease Interceptors - Grease Traps. (2014). Retrieved August 24, 2014, from

http://inspectapedia.com/plumbing/Grease_Interceptors.php

Figure 1. A typical passive-flow based (hydro-mechanical) grease abatement device.

There are two broad categories of grease abatement devices: flow-based and volume-

based. Flow-based units are usually smaller, indoor devices with a rated flow of 50 gallons per

minute or less (WSSC, n.d.). Within the flow-based category, there are passive-flow, or hydro-

mechanical, grease interceptors (as seen in Figure 1) and automatic grease recovery devices

(GRDs). Both units utilize a flow control device to limit the amount of wastewater entering the

interceptor. This flow control device minimizes turbulence and allows for a sufficient retention

time for FOG to separate (NPCA, 2012). Although both devices rely on gravity separation to

separate FOG from the wastewater, a GRD differs from a passive-flow unit in that it is designed

to assist the separation process by automatically removing grease using a thermostatically

controlled heater and a mechanical skimmer. The thermostatic heating device increases the

internal temperature of the unit, allowing FOG globules to float quickly to the top. The

mechanical skimming wheel then removes the top layer of FOG from the device and transports it

to a separate collection bin (see Figure 2).

Selecting & Specifying: Automatic Grease Interceptors. (2014). Retrieved August 24, 2014,

from http://www.highlandtank.com/grease-underground-selecting-and-specifying

Figure 2. In this diagram of an automatic grease removal device, a strainer basket collects solids

that have entered into the interceptor before the skimming wheel removes the FOG.

In contrast to passive-flow based GADs, volume-based grease interceptors range in

volume from 500 to 25,000 gallons in capacity. They generally have a rated flow of greater than

50 gallons per minute, or sometimes no flow restrictions at all (WSSC, n.d.). The most common

volume-based interceptors are precast concrete tanks located outside and underground. They can

be easily identified by the presence of three manholes in a straight line on the ground. A typical

concrete interceptor has three compartments separated by two sets of interior baffles. This

design lengthens the flow path of the wastewater, or effluent, to increase the amount of time,

retention time, for gravity separation to occur (see Figure 3). Studies have shown that a longer

retention time allows for a more complete separation of FOG from wastewater (Gallimore,

2011). Compared to flow-based units, volume-based interceptors have a much larger storage

capacity and thus, can hold a greater amount of FOG before cleaning is required.

WSSC FOG Program Expectations of Food Service Establishments. (n.d.). Retrieved August 24,

2014, from http://www.wsscwater.com/file/Communications/NewsRelease/

FOG%20Interceptor%20Cleaning%20tips%20proposed%20video%20ppt.pdf

Figure 3. In a volume-based interceptor, FOG and solids separate from the wastewater in three

different chambers before the water exits into the sewer.

Grease abatement devices are currently sized by the amount of FOG the respective FSE

has the potential to produce (WSSC, 2013). The interceptor must be large enough to allow for

sufficient FOG storage between cleaning (NPCA, 2012). For example, a small coffee shop

likely only needs a flow-based unit, while a large steakhouse requires a volume-based

interceptor. The grease output of the FSE also determines the clean-out period of the interceptor.

Flow-based GADs can be cleaned by the FSE itself or by a professional contractor. In Prince

George’s and Montgomery counties, volume-based GADs require professional cleaning by a

WSSC permitted grease disposal contractor. WSSC recommends passive-flow based

interceptors to be cleaned daily while volume-based interceptors should be cleaned out monthly

(WSSC, 2013).

The biggest shortcoming to this process is that many food service establishments do not

maintain their grease interceptors. With everything owners have to consider while running a

restaurant, grease abatement just isn’t a priority. Many jurisdictions require interceptors to be

“pumped-out” when the FOG accumulation reaches 25% of the unit capacity (NPCA, 2012). If

this 25% rule is not upheld, FOG will still be discharged into the sewer system. When you

couple that with the fact that many people living in residential areas are simply not aware that

pouring animal fats such as bacon grease down the sink drain detriments the sewer system, the

high amount of sewage overflows that have been reported are not surprising. Therefore, in order

to prevent sewage overflows and protect our environment, we must improve current methods of

grease abatement technologies and regulations, and also increase awareness about fats, oils, and

grease through education of food service establishments and outreach to the general public.

Each type of grease interceptor has its own respective drawbacks. While it may be

unrealistic to design a perfect grease abatement device, it is important to limit these

shortcomings as much as possible. The most important factors to consider in a grease interceptor

are durability and grease removal efficiency. As previously stated, lackluster grease interceptor

maintenance among FSEs creates a need to design longer lasting interceptors. Failure to

maintain a precast concrete grease interceptor can lead to corrosion and shorten the lifetime of

the interceptor (NPCA, 2012). A concrete interceptor will corrode if there is a high

concentration of sugar, yeast, or food particles that have gone septic from sitting in the

interceptor too long. (NPCA, 2012). In a 2012 study, data was collected from external, volume-

based grease interceptors at 24 different food service establishments (Aziz et al., 2012). After

testing, it was found that the retention time of the wastewater in the interceptor was significantly

longer than the recommended thirty minutes. The retention time exceeded thirty minutes by 2 to

5 times on average. Low pH levels and dissolved oxygen levels were also found (Aziz et al.,

2012). In these conditions, not only will the interceptor begin to deteriorate and allow FOG to

pass through, it will also allow acidic substances to seep into the ground, polluting the soil.

A viable solution to this dilemma is to invest in grease abatement devices that are made

of fiberglass and other corrosion-resistant materials. The Proceptor™ fiberglass grease

interceptor was designed by Green Turtle as an alternative to precast concrete and light metal

interceptors, as these materials may rust and corrode over time with long exposure to acidic

wastewater (Green Turtle, 2012). Proceptor™ grease interceptors are guaranteed to last for

thirty years without any structural defects. A concrete or light metal grease interceptor may

begin to deteriorate after only one year and may even collapse altogether after twelve years of

continued use. Proceptor™ interceptors have the potential to last 3-5 times of these standard

units because they are made of non-porous fiberglass which will not corrode, rust, or allow

pollutants to seep into the ground (Green Turtle, 2012). As a result, even if a fiberglass

interceptor is not maintained, it will still last much longer than a concrete interceptor that is left

unmaintained. From an efficiency standpoint, Proceptor™ interceptors provide superior

performance with an elliptical design and a parented distribution tee inlet. This inlet and overall

shape of the interceptor provide non-turbulent, laminar flow to allow for maximum separation

efficiency (Green Turtle, 2012).

Proceptor™. (2012). Retrieved August 24, 2014, from http://www.greenturtletech.com/infohub/

proceptor/Proceptor_Booklet-Brochure_2012.pdf

Figure 4. The GreenTurtle® Proceptor™ features a T-shaped inlet that slows down the effluent

flow by redirecting it around the sides of the interceptor.

Grease interceptors must not only be durable, but they must also be as efficient as

possible to prevent the maximum amount of FOG from entering the sewer and causing sewage

backups. The interior design of an effective grease abatement device (GAD) allows for

sufficient retention time for separation, features a large capacity to hold the maximum amount of

FOG and solid residuals, and provides a non-turbulent environment to aid separation.

To determine these characteristics, the Plumbing and Drainage Institute (PDI) evaluates

grease interceptor performance using a standardized test that involves the use heated animal fat

as a test medium for rating performance. Lard-laden water is heated and passed through the GAD

at a specified flow rate and the efficiency is determined by measuring the amount of grease that

bypasses the GAD (Aziz et al, 2011). However, this PDI test possesses a major flaw. By using

heated lard, these tests do not consider many of the factors that may affect gravity separation.

Restaurants and home-owners use a wide variety of detergents, sanitizers, and vegetable oils.

The mixing of these various substances significantly affects the separation efficiency in an

interceptor (Aziz et al, 2011). In short, this test does not accurately simulate a real-world

situation.

A study conducted in 2011 used a more accurate method for testing grease interceptor

performance. This study compared a 10-gpm (gallons per minute) passive-flow grease

interceptor (30 second retention time), a 25-gpm automatic grease recovery device (1 minute

retention time), and a WSSC designed 27 gallon (equivalent to a 1600 gallon full-sized) volume-

based grease interceptor model (30 minute retention time). FOG removal efficiency was tested

under multiple parameters including emulsion strength (how well the effluent is mixed; i.e.

weak, medium, strong), different influent liquid temperatures, and two different flow rates.

Generally, the volume-based model achieved approximately 80% FOG removal and the flow-

based units removed less than 50% under the tested conditions. Under weak emulsion levels, the

flow-based achieved nearly 80% FOG removal. (Gallimore et al., 2011)

These results suggest that emulsion strength significantly affects FOG removal

efficiency. However, we cannot control emulsion levels in FSEs, but we can control the

retention time. Therefore, multiple chambers separated by baffles are extremely important in

lengthening the retention time for FOG to separate from the wastewater. Another study

compared the interceptor performance with regards to different flow rates and retention times. It

was found that, by increasing the retention time by a factor of three, the grease removal

efficiency of the interceptor increased by 12% (Aziz et al, 2011). Through this experimentation,

it is clear that volume-based interceptors are more efficient than flow-based devices because of

their much longer retention times. Also, given their capacity, volume-based interceptors are able

to hold much more FOG than flow-based GADs.

Another important factor to consider is the turbulence of the flow inside the interceptor.

This flow characteristic is heavily dependent upon the inlet baffle design. Standard grease

interceptors have inlets that create turbulent conditions by allowing wastewater to enter directly

into the unit, disturbing the still wastewater and FOG that are already present in the tank. This

disturbance fosters a tendency for wastewater and FOG to mix together instead of separating.

Conversely, an efficient inlet design can significantly reduce turbulence and enhance FOG

removal efficiency of the interceptor. A recent study found that a distributive-style inlet

increases FOG removal efficiency by 5-7% (Aziz et al., 2011). This design is most effective

because it slows down the wastewater flowing into the interceptor by allowing a wider area for

the wastewater to travel through. This claim is further proved through fluid dynamics. At a

constant flow rate (controlled by the flow-control device in a grease interceptor), the larger the

cross-sectional area the fluid travels through, the slower the velocity of the fluid will be. Since a

distributive-style inlet increases the cross-sectional area, the wastewater travels slower, thus

reducing turbulence and unwanted mixing inside the interceptor.

After considering the evidence available, the ideal grease interceptor is made of

fiberglass or other corrosion-resistant materials, contains multiple compartments separated by

baffles to increase retention time, and features a distributive-style inlet configuration. Yet, the

only way to ensure that this type of GAD is prevalent is to enforce regulations requiring FSEs to

install grease interceptors with these characteristics. A nationwide mandate that all new GADs

that are installed must be of this type would go a long way in keeping FOG out of the wastewater

collection system and preventing it from contaminating the environment.

However, for maximum FOG removal efficiency, even the most ideal grease interceptor

is insufficient. The technology in a grease abatement device is the last line of defense against

FOG discharge. Human awareness about FOG practices must increase significantly in order to

avoid FOG blockages in the sewer and prevent sanitary sewage overflows.

A study was conducted in 2012 to test the chemical makeup of nine different FOG

buildups at different location in the sewer over a 14-month period (Williams, 2012). The study

found that the water that came in contact with these deposits tended to have high levels of oil in

them additionally contributing to the accumulation. This likely means that the nearby FSEs were

exhibiting poor FOG management practices in their kitchens, because oil-laden water was being

discharged into the sewer even after bypassing the grease interceptor.

In addition to the grease interceptor, best management practices (BMPs) should always

be used in the kitchen. BMPs include dry-wiping pans prior to dishwashing, using detergents

that promote oil and water separation, recycling waste cooking oils, and not allowing corrosive

agents to drain into the grease interceptor (NPCA, 2012). FOG disposal must become the

responsibility of the producer, not the grease interceptor manufacturer or the regulating

municipality.

To put the problem of awareness in perspective, eight WSSC FOG Investigators must

inspect approximately 4000 food service establishments in Prince George’s and Montgomery

counties and enforce regulations (WSSC, n.d.). For each routine inspection of a food service

establishment, a WSSC FOG investigator must verify that the grease abatement device is

operational and maintained, take photographs, and check for grease buildup in the sewer. If the

FSE is noncompliant, the investigator must return for a follow-up inspection (WSSC, n.d.). It is

difficult to constantly monitor all the FSEs due to the sheer amount and the lengthy inspection

checklist. The most common and significant violation by FSEs is failure to maintain the

interceptor. This is due in part by unfamiliarity with the WSSC FOG Program and unfamiliarity

with the maintenance needs of a grease interceptor (WSSC, n.d). In order to increase awareness

about FOG, food service establishments and people cooking in residential areas must be

educated beyond the yearly routine inspection by a FOG investigator. They simply cannot be

trusted to dispose of waste grease properly if they do not know how to dispose of waste grease

properly.

Once people are educated about the dangers of discharging FOG into the sewer system,

they will understand how it detriments the environment and become more conscious of following

best management practices to keep FOG out of the sewer. With this consciousness, food service

establishments will also better maintain their grease abatement devices and FOG-related sanitary

sewage overflows will become a thing of the past.

Annotated Bibliography

Aziz, T. N., Holt, L. M., Keener, K. M., Groninger, J. W., & Ducoste, J. J. (2011). Performance

of Grease Abatement Devices for Removal of Fat, Oil, and Grease. Journal of

Environmental Engineering, 137(1), 84-92. doi:10.1061/(ASCE)EE.1943-7870.0000295

Sanitary sewage overflows can release bacteria and other pathogens into the environment,

harming ecosystems and public health. Contaminants such as personal care products and pharmaceuticals

have been shown to alter the endocrine system of wildlife. There are approximately 3-10 billion gallons

of untreated wastewater discharged annually as a result of these sanitary sewage overflows (SSOs).

Almost half of these overflows are the result of blockages due to build-up of fats, oil, and grease.

Considering only municipalities that report 100 or more SSOs per year, FOG blockages account for 74%

of overflows. These high statistics suggest that current means of preventing FOG from entering the sewer

are inadequate and must be improved.

Currently, grease is kept out of the collection system through passive and mechanized grease

abatement devices. The purpose of this study is to determine whether the internal geometry of current

grease abatement devices can be altered to increase grease removal efficiency, instead of replacing

current models entirely. The tests were conducted using and oil and water emulsion as wastewater.

The Plumbing and Drainage Institute (PDI) specifies a testing procedure for the smaller, in

kitchen grease abatement devices. Testing involves the use heated animal fat as a test medium for rating

performance. Lard-laden water is heated and passed through a GAD at a specified flow rate and the

efficiency is determined by measuring the amount of grease in skimming tank after bypassing the GAD.

The end result is a GAD rating in pounds of FOG for a given flow specified. By using heated lard and

quantifying only the skimmable grease, these tests do not consider many of the factors that may affect the

FOG recoverability through continuous flow gravity separation. Restaurants and home-owners use a

wide variety of detergents, sanitizers, and vegetable oils. These factors can influence emulsification

characteristics of FOG discharges, and thus influence separation efficiency.

Experiments were conducted using 5 different internal geometries and two different retention

times, 20-minute and 1 hour. The highest FOG removal performance (90%) occurred with the standard

configuration at a 1-hour retention time. This tripling of the retention time from the standard 20-min

configuration resulted in a 12% increase in performance. Simple modifications of the standard layout

with either the flared configuration or the short inlet configuration indicated an improvement in

performance. The flared configuration yielded 83% FOG removal while the short inlet configuration

yielded 85% FOG removal. The two inverted tee configurations gave substantially different results. The

dual piped design displayed results very close to the standard configuration at 1-h HRT (87%) while the

inverted tee, no baffle configuration indicated the poorest performance (69%). This performance

difference suggests an interaction with the distributive inlet and the baffle wall that needs further

investigation. Extending the retention time to 1 hour for the inverted tee, dual pipe configuration and the

flared configuration resulted in poorer separation performance with this arrangement. These results

suggest a strong dependence on the mid baffle wall for the distributive style inlet.

(Aziz et al., 2011)

Aziz, T. N., Holt, L. M., Keener, K. M., Groninger, J. W., & Ducoste, J. J. (2012). Field

Characterization of External Grease Abatement Devices. Water Environment Research

(10614303), 84(3), 237-246. doi:10.2175/106143012X13347678384161

This study collected data from external (volume-based) grease interceptors at 24 different

food service establishments at 15-minute intervals over a 24-hour period. The data collected

included volumetric flow-rate, FOG and sludge profile, and the chemical characteristics inside

each interceptor. After testing, it was found that the retention time of the wastewater in the

interceptor was significantly longer than the recommended thirty minutes. The retention time

exceeded thirty minutes by 2 to 5 times on average. Low pH levels and dissolved oxygen levels

were also found. This suggests the occurrence of anaerobic microbial processes such as

corrosion. It was also found that submerged inlets may allow solids to pass through the first

compartment and enter into the next two compartments. Distributive-style inlets were found to

be the most effective in trapping solids in the first chamber.

(Aziz et al., 2012)

Fog In The Home. (n.d.). Retrieved August 23, 2014, from

http://ceasethegreasentx.com/FOG.asp

When poured down the drain, fats, oils, and grease (FOG) can clog pipes in homes and in

the sewer. As a result, wastewater can back up in the sewer and pollute the environment. These

backups can cause wastewater to flow into storm drains, which creates a human health hazard

and causes damage to the environment and aquatic life.

The North Texas Grease Abatement Council provides several practices to effectively

prevent these backups in residential areas and restaurants. Before dishwashing, wipe down all

pans and utensils and prewash the dishes in cold water. This will keep food scraps out of the

pipes. Needless to say, do not pour grease and cooking oil down the drain. Instead, it should

either be reused or disposed of at a household hazardous waste collection station or

Environmental Collection Center (ECC). The Environmental Collection Centers in North Texas

collect used cooking oil and convert it into bio-diesel fuel, essentially turning a waste item into a

useful commodity.

(North Texas Grease Abatement Council, n.d.)

Gallimore, E., Aziz, T. N., Movahed, Z., & Ducost, J. (2011). Assessment of Internal and

External Grease Interceptor Performance for Removal of Food-Based Fats, Oil, and

Grease from Food Service Establishments. Water Environment Research (10614303),

83(9/10), 882-892. doi:10.2175/106143011X12989211840972

Fats, oils, and grease (FOG) are the leading cause of sewer system blockages and account

for nearly half of all the sewage overflows in the United States. FOG enters the plumbing drains

of food service establishments and homes via dishwashing, equipment cleaning, and floor

cleaning. Grease abatement devices, also known as grease interceptors, prevent FOG from

entering the sewer system. All current grease interceptors work under the principle of gravity

separation, in which the fats, oils, and grease rise to the surface since they are less dense than

water, allowing water to pass underneath and into the wastewater collection system. The grease

is essentially trapped in the interceptor. There are two types of grease interceptors: flow-based

and volume-based. Flow-based grease interceptors (FGIs) are smaller units and are usually

located underneath sink fixtures. FGIs are either defined as passive-flow (PFGIs) or mechanical-

flow devices (MFGIs). What separates these apart is the presence of an electric skimmer in

MFGIs that aids in FOG removal and cleaning. Retention-based interceptors (RGIs) are large

units normally located outside and underground. Their size allows more time for FOG to

separate from the wastewater before entering the sewer system.

In this study, the grease removal efficiency was compared between flow-based grease

interceptors and retention-based (or volume-based) interceptors. FOG removal efficiency was

tested under multiple parameters including emulsion strength (how well the effluent is mixed;

i.e. weak, medium, strong), different influent liquid temperatures, and two different flow rates.

Generally, the RGI achieved approximately 80% FOG removal and the FGIs removed less than

50% under the tested conditions. The FOG removal efficiency decreased with increased

temperature because of increased breakage of FOG globules at the elevated temperature; the

smaller the FOG particle size, the longer it takes to separate from the wastewater. Under weak

emulsion levels, the FGIs achieved nearly 80% FOG removal. These results suggest that

emulsion strength significantly affects FOG removal efficiency of FGIs and should be

considered in future manufacturer testing protocol.

(Gallimore et al., 2011)

Montefrio, M., Xinwen, T., & Obbard, J. (2010). Recovery and pre-treatment of fats, oil and

grease from grease interceptors for biodiesel production. Applied Energy, 87(10), 3155-

3161. doi:10.1016/j.apenergy.2010.04.011

Domestic and commercial food service establishments generate large volumes of

wastewater that contains significant amounts of fats, oils and grease. The National Renewable

Energy Laboratory conducted a study that revealed that metropolitan areas in the United States

generate an average of 6 kilograms of grease interceptor FOG per person every year. The

primary reason for removing FOG from wastewater is to prevent sewer backups, but FOG can

also be recycled and reused as an additive for animal feed, soap, cosmetics, and compost.

However, one of the most promising uses for FOG is converting it to biofuel.

The major opposition to biofuel production is that it poses several environmental threats.

According to a recent study, most biofuel produced today “is derived from crops grown on land

converted from rainforests, peatlands, savannas, and grasslands” (Montefrio, 2010). The major

advantage of biodiesel derived from FOG is that it does not require land use conversion in order

to be produced. Hence, converting FOG to biofuel not only offsets the carbon impact of fossil

fuels, but it also helps to prevent deforestation and land degradation. As shown in this study,

biofuel production from FOG is very complex and expensive. Grease interceptor FOG has a

high moisture content and contains too many food residuals to be converted to biofuel

efficiently.

(Montefrio et al., 2010)

Operation and Maintenance for Precast Concrete Grease Interceptors. (2012).

Retrieved August 23, 2014, from http://precast.org/wp-content/uploads/2012/10/

Grease_OM_Manual.pdf

There are over 900,000 food service establishments in North America and they must all

be treated with grease abatement systems in order to prevent large quantities of grease from

discharging into the sewer, causing blockages downstream, and creating costly and time-

consuming problems at wastewater treatment plants. Raw sewage that backs up into residential

areas or commercial businesses may also cause unnecessary health problems. Grease

interceptors are necessary in complying with EPA requirements. The greatest amount of FOG

discharge comes from food service establishments that do not have grease abatement or do not

maintain their grease abatement.

Volume-based grease interceptors have different compartments and contain baffles to

control the flow of wastewater, minimize turbulence, and allow sufficient time for gravity

separation. Grease has a lower specific gravity than water, so when a grease-laden mixture is left

undisturbed, the grease will rise to the surface and the sediment will settle to the bottom.

According to the Uniform Plumbing Code (UPC), at least 30 minutes of retention time is

sufficient. The interceptor must also be large enough to store at least 25% of its capacity in

grease between cleaning operations.

In addition to the grease interceptor, best management practices (BMPs) should also be

used in the kitchen. BMPs include dry-wiping pans prior to dishwashing, using detergents that

promote oil and water separation, recycling waste cooking oils, and not allowing corrosive

agents to drain into the grease interceptor.

This manual applies to cleaning and maintenance of concrete volume-based grease interceptors.

The lifetime of precast concrete interceptors can be shortened if the environment inside becomes

corrosive. This can happen if there is a high concentration of sugar, yeast, or food particles that

have gone septic from sitting in the interceptor too long. When cleaning, every compartment

should be emptied entirely. The side walls and baffles should also be cleaned off. The sediment

at the bottom should also be vacuumed out.

(National Precast Concrete Association, 2012) (NPCA, 2012)

Partnering to Protect Clean Water. (2013, May 31). Retrieved August 23, 2014, from

http://www.wsscwater.com/home/jsp/content/food-industry.faces

The WSSC Fats, Oils, and Grease (FOG) Program began an initiative in May 2007 to

issue permits to all 9,107 food service establishments listed on the County Health Department

License list for both Prince George’s and Montgomery counties. The FOG program complies

with a Federal Consent Decree to reduce and eventually eliminate sanitary sewage overflows, as

40-% of all preventable sewage overflows in the United States are FOG related. All food service

establishments in the WSSC service area must install a grease abatement system and apply for a

FOG Discharge Permit to utilize the sewer system, or apply for a Best Management Practices

(BMP) Permit if the FSE has the potential to only discharge a minimal amount of FOG into the

sewer. These practices include scraping food from dishes into waste cans before rinsing and

wiping down cooking pans before washing.

Sanitary sewer lines are designed with diameter sufficient to carry normal waste through

them. When fats, oils, and grease are discharged into the system, they cool and accumulate on

the sidewalls of these pipes. Over time, this accumulation causes blockages in the sewer,

backups onto private property, and overflows through manholes. These overflows can even flow

into storm drains that lead to the Chesapeake Bay. Properly installed grease interceptors are the

best protection against FOG discharges. These interceptors must be installed by WSSC-licensed

master plumbers. Small, manual grease traps should be cleaned on a daily basis. Automatic

grease recovery devices have mechanical components, timers, and sensors, which should be

maintained frequently. Outside, volume-based grease interceptors must be cleaned out by a

WSSC permitted grease disposal contractor. If grease abatement is not installed and properly

maintained, WSSC may issue fines up to $1,000. Businesses that are found to be responsible for

sewer blockages may also be billed for property damage and restoration costs for affected homes

and businesses.

Waste fryer grease is different from the FOG captured by grease interceptors. This

grease is a reusable commodity that should be disposed of in a grease rendering barrel to be

recycled.

(WSSC, 2013)

Proceptor™. (2012). Retrieved August 24, 2014, from

http://www.greenturtletech.com/infohub/proceptor/Proceptor_Booklet-

Brochure_2012.pdf

The Proceptor™ grease interceptor was designed by Green Turtle as an alternative to

precast concrete and light metal interceptors, as these materials may rust and corrode over time

with long exposure to acidic wastewater. Proceptor™ grease interceptors are guaranteed to last

for thirty years without any structural defects. A concrete or light metal grease interceptor may

begin to deteriorate after only one year and may even collapse altogether after twelve years of

continued use. Proceptor™ interceptors have the potential to last 3-5 times of these standard

units because they are made of non-porous fiberglass which will not corrode, rust, or allow

pollutants to seep into the ground.

From a FOG separation standpoint, Proceptor™ interceptors provide superior

performance with an elliptical design and a parented distribution tee inlet. This inlet and overall

shape of the interceptor provide non-turbulent, laminar flow to allow for maximum separation

efficiency. Proceptor™ interceptors range in size from small, 50-gallon flow-based units to

3,000-gallon volume-based interceptors.

(Green Turtle, 2012)

WSSC FOG Program Expectations of Food Service Establishments. (n.d.). Retrieved August 24,

2014, from http://www.wsscwater.com/file/Communications/NewsRelease/

FOG%20Interceptor%20Cleaning%20tips%20proposed%20video%20ppt.pdf

Eight WSSC FOG Investigators must inspect approximately 4000 food service

establishments in Prince George’s and Montgomery counties and enforce regulations. For each

routine inspection of a food service establishment, a WSSC FOG investigator must verify that

the grease abatement device is operational and maintained, take photographs, and check for

grease buildup in the sewer. If the FSE is noncompliant, the investigator must return for a

follow-up inspection. It is difficult to constantly monitor all the FSEs due to the sheer amount

and the lengthy inspection checklist. The most common and significant violation by FSEs is

failure to maintain the interceptor. This is due in part by unfamiliarity with the WSSC FOG

Program and unfamiliarity with the maintenance needs of a grease interceptor. Often times,

when FSEs have an automatic grease removal device, they assume that no maintenance needs to

be done. However, this is simply not true. GRDs still require manual cleaning of the residuals

caught. In order to increase awareness about FOG, FSEs must be educated beyond the yearly

routine inspection by a FOG investigator.

(WSSC, n.d.)

Williams, J. B., Clarkson, C. C., Mant, C. C., Drinkwater, A. A., & May, E. E. (2012).

Fat, oil and grease deposits in sewers: Characterisation of deposits and formation

mechanisms. Water Research, 46(19), 6319-6328. doi:10.1016/j.watres.2012.09.002

Fats, oils, and grease (FOG) deposits in sewer pipes are often portrayed as the result of

FOG cooling and accumulating on the inner walls of the pipe. This study characterized the

chemical makeup of nine FOG buildups at different locations in the sewer over a 14-month

period. These locations were picked because they had previous problems with FOG-related

backups. The moisture content ranged from 15 to 95%. Water that came in contact with these

deposits tended to have high levels of oil in them (800 mg/L), additionally contributing to the

accumulation. This likely means that there are poor FOG management practices in kitchens of

the nearby FSEs.

(Williams, 2012)