Grease interceptors are devices designed to reduce the amount of FOG (Fats, Oil and Greases) in wastewater. Grease interceptors are used in establishments to remove excessive amounts of grease that may interfere with the proper drainage and treatment of wastewater. Most Local plumbing codes prohibit any industrial user from discharging FOG over 100 (mg/l) into the public sewer system.
The general doctrine, of most Authorities Having Jurisdiction (AHJs), is one of “user pay”--especially when it comes to solid waste. Therefore it makes sense for establishments that create FOG to be responsible for its collection and disposal and not cause unnecessary taxpayer expenditures to handle sewer blockages and grease overloads at sewer treatment plants. It is prudent for the consultant engineer to utilize a Best Management Practice (BMP) that includes adequate sizing for the grease interceptor.
Typical applications include commercial and institutional kitchens and food processing plants. The waste discharge from these facilities usually contains high temperature water, high organic loads, FOG, suspended food particles, and detergents.
New plumbing codes have eliminated the term “grease trap” from the code and now designated “Hydromechanical” Grease interceptor and “Gravity” Grease interceptor as the two types of grease interceptors. Park® manufactures both units, but the GreaseTrooper® Gravity Grease Interceptor is by far the design of choice by engineers and city officials.
| Hydromechanical Grease Interceptors|| Gravity Grease Interceptors|
| || |
|Hydromechanical Grease Interceptors incorporate air entrapment, the buoyancy of grease in the water and hydromechanical separations with interior baffling for FOG separation. Hydromechanical units incorporate a flow-control device that controls velocity as it enters the interceptor. |
These are typically smaller interceptors installed indoors in the floor or under-the-sink. Due to health concerns, some major cities have prohibited the installation of this interceptor within food preparation areas.
Hydromechanical units are sized by determining flow-through rate (gpm) at peak demand for each fixture draining into the unit.
Check with the local AHJ before specifying Hydromechanical units to determine if the jurisdiction allows these type units.
|Gravity Grease Interceptors incorporate two or more compartments in series and use its inherent larger volume to maximize the pretreatment of the wastewater. By comparison, the Gravity Interceptor is more effective because of its larger volume that acts as a heat-sink. This allows for temperature differential (cool down) and more retention time of the greasy liquid to promote separation and coagulation of FOGs from the wastewater. The Gravity Interceptor also allows for solid retention from food grinders. |
These interceptors are generally located outdoors, away from the kitchen areas. This eliminates the health concerns caused by maintenance and disposal of FOGs. Gravity Interceptors allow for optimal service intervals by third party service companies and are more likely to result in easier and proper maintenance.
Gravity Grease Interceptors manufactured by Park® are available in several styles depending on the application. GreaseTrooper® Design Considerations
One of the most important features for the successful operation of the grease interceptor is the maintenance program. Regardless of the size or design, an interceptor is only as good as its maintenance program. The interceptor should be located so that it will be easily accessible for inspection, cleaning and removal of collected FOG. The interceptor should be located near the source of the wastewater for the protection of the piping system.
There should be an adequate number of manholes to permit access for cleaning all areas of the interceptor. Access manholes should be located near the inlet and the outlet. The manholes should not be less than 20" in size. All manholes should extend to grade and be suitable for traffic loading. Indoor and sensitive areas, gas-tight access covers should be specified.