Miller Plante Inc - EPA National Pretreatment Program - Controlling Fats, Oils, and Grease Discharges from Food Service Establishments and Homes. http://yosemite.epa.gov/OA/RHC/EPAAdmin.nsf/Filings/360737AD61D13C6E8525764E0068D812/$File/CWA0820090031ATTACHMENTS.pdf

MillerPlante.net - http://en.wikipedia.org/wiki/Grease_interceptor

Miller Plante Inc - Grease traps (also known as grease interceptors, grease recovery devices and grease converters) are plumbing devices designed to intercept most greases and solids before they enter a wastewater disposal system. Common wastewater contains small amounts of oils which enter into the system and treatment facilities to form a floating scum layer. This scum layer is very slowly digested and broken down by microorganisms in the anaerobic digestion process. However, very large amounts of oil from food production in kitchens and restaurants can overwhelm the system or treatment facility, causing a release of untreated sewage into the environment. Also, high viscosity fats and cooking greases such as lard solidify when cooled, and can combine with other disposed solids to form blockages in drain pipes.

Restaurant and foodservice kitchens produce a lot of waste grease which is present in the drain lines from the various sinks dishwashers and cooking equipment such as combi ovens and commercial woks. If not removed the grease will congeal within the sewer and cause blockages and back-ups.

Miller Plante Inc - In the United States, sewers back up annually “an estimated 400, 000 times, and municipal sewer overflows on 40, 000 occasions” [1]. The EPA has determined that sewer pipe blockages are the leading cause of sewer overflows, and grease is the primary cause of sewer blockages [2]. Even if accumulated FOG does not escalate into blockages and sanitary sewer overflows, it can disrupt wastewater utility operations and increase operations and maintenance requirements” [3]

For these reasons, depending on the country, nearly all municipalities require commercial kitchen operations to fit some kind of interceptor device to collect the grease before it enters the sewer. Additionally where FOG is a concern in the local wastewater collection system communities have set up inspection programs to ensure that these grease traps and/or interceptors are being maintained on a routine basis.

The design codes for traditional traps allow for an average efficiency of as little as 85% between cleanouts for the trap to be considered adequate. This means that on average 15% of the grease in the waste water is entering the sewer line. Eventually, even with a robust cleanout regime, it is likely that there will be a sewer backup.

A traditional grease trap is not a food disposal unit. Unfinished food must be scraped into the garbage or food recycling bin. Milkshakes, gravy, sauces and food solids must be scraped off the dishes before they enter the sink or dishwasher. This does not always occur in the busy restaurant environment thus the traditional grease trap is often filled with solids which turn into sludge and dissolve into BODs/CODs. The sludge fills the trap up and reduces its efficiency thereby allowing grease to escape into the sanitary sewer system. The sludge also creates a very unpleasant odor which can often back up into the kitchen. Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) is the amount of oxygen consumed in a oxidation processes once a contaminant or chemical compound is added to a water body. BODs/CODs are considered contaminate waste water which makes it more expensive for pumping companies to dispose of.

A problem with a traditional trap is that it must be emptied either by scooping out or pumping all the contents and carting the effluent away to a specialist renderer or to a landfill. This is a very unpleasant undertaking and is, in consequence, often neglected, causing the same problems as if the trap were not there at all. When a trap is full of fat, oil, and grease, the grease has nowhere to go but down the drain and into the sanitary sewer or enter the system.

To try to maintain some degree of efficiency there has been a trend to specify larger and larger traps. Unfortunately, providing a large tank for the effluent to stand also means that food waste scraps also have time to settle to the bottom of the tank, further reducing the available volume and adding to the clean out problem. A bigger interceptor is not a better interceptor. Traditional grease traps / interceptors cannot handle the grease coming from dishwashers as the water comes in too hot and too fast. The grease from a dishwasher bypasses the trap and interceptor. A traditional grease trap / interceptor does not properly control the flow of the water to allow the grease to cool and settle.

Because it will have been in the trap for some time, grease collected in this way will have been contaminated and is unsuitable for further use. This kind of grease is referred to as brown grease. Imagine leaving a fresh chicken in your refrigerator for longer than two weeks. The rancid smell would be unbearable. There is no difference between rotten food and brown grease. Brown grease ends up in a landfill or hazardous waste site.

The essential difference between a GRD and a traditional trap or interceptor is that the GRD constantly removes the captured grease into a separate container and thus maintains its efficiency. A good GRD will have the following:

A) means of preventing the food scraps from entering the tank (a strainer basket);

B) effluent flow control to give time for the grease to cool and separate from the effluent (retention time);

C) a reliable means of separating grease from water;

D) easy and low maintenance;

E) means of regularly flushing out the fine silts which would otherwise collect in the bottom of the tank. (flush valve)

F) stainless Steel Construction (no rust or leaking)

A good GRD will take out a minimum of 98 percent of the grease from the effluent or higher. GRD's are also referred to as active grease traps or active grease recovery devices.

Properly installed in the correct kitchen environment a GRD will continuously give high levels of efficiency, ensuring the sewers remain clear with no blockages or back-ups.

A GRD stops the grease at the source. (The drain)

MillerPlante.net - Grease trap chemicals and emulsifying agents such as Septic Helper 2000 liquify the grease and push the grease further downstream. The grease problem is fixed on a temporary basis leading to bigger grease clogs and blockages in the near future. The liquefied grease will end up in the sanitary sewer. This grease will harden causing clogs and blockages. The clogs and blockages will lead to sanitary sewer overflows. Grease Trap Ordinances and sewer bylaws will result in fines to the restaurant.

In the UK certain grease trap manufacturers recommend the "combined approach" as described by London Grease Traps. This combination approach uses the mechanical efficiency of the grease trap to physically stop FOGs, along with the biological action of dosing through the direct application of biological agents into the grease trap. It can be highly effective as well as very simple to maintainain and cost effective.

Grease traps have been used since the Victorian era. They are used to reduce the amount of fats, oils and greases (FOG’s) that enter the main sewers. Effectively they are boxes within the drain run that are located between the sinks in a kitchen and the sewer system. They only have waste water flowing through them and are not served by any other drainage system such as toilets. They can be made from a number of different materials; e.g. Stainless Steel such as the Maxi-Trap design, Mild Steel, Plastics, Concrete, Cast Iron and can hold anywhere between 40 liters to 45000 liters and above. They can be located above ground, below ground, inside the kitchen or outside the building.