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Grease Traps

Introduction

Greases and fats are a necessary part of the food service industry, it is used to fry foods, as the primary ingredient for many sauces and is produced from cooking many dishes. Even many restaurants or kitchens that on the surface don’t appear to produce or utilizes fats, oils and greases have a volume of these by products to handle. When the meal is completed where do these wastes go? It is common knowledge that pouring fats, oils and grease (FOG) down the drain can lead to blockages and plumbing issues in any drains, what is less common knowledge is the small residual volumes left on pots pans and baking sheets can over times cause the same issues. Even small volumes of FOG wastes can build up over time in the plumbing and drainage of buildings until it becomes a problem that can be costly and time consuming to fix. For this reason, commercial food service kitchens utilize grease traps on drains that are used for the preparation of ingredients and washing sinks in order to capture as much of this waste fats, oils and grease before entering underground plumbing. FOG wastes are characteristically less dense than water and generally solidify at room temperature, which are characteristics that grease traps utilize to separates these wastes from the wastewater. Grease traps come in a variety of sizes depending on the fixtures they service, as they need enough internal capacity to support the volume of water that may pass through it. 

Figure -Cross section of a traditional grease trap that is utilized by a majority of commercial food service establishments.

 

Grease Traps are typically found under the sinks they service or may be found permanently installed into the floor of the kitchen area. Most grease traps are large grey plastic boxes that fill with water. Any incoming wastewater from sink or drains will mix with the room temperature water currently in the trap which forces the FOG wastes to float to the top of the trap where it can solidify and remain contained in the trap until it is removed. All grease traps have some form of baffle that forces the wastewater down to the bottom when entering and leaving the trap. These baffles then help to create a large open area for the collection of the FOG wastes.

Fats, Oils and Greases (FOG) are present in any types of food preparation and cooking on both residential and commercial scales, although whenever moving to a commercial scale the volumes of FOG wastes drastically increase with the volume of food being produced. For this reason, it is mandatory for all commercial food services to have a grease trap installed on any and all fixtures that may come into contact with FOG wastes. The distinction of Commercial food service facilities does not stop at restaurants and fast-food locations, but also includes grocery stores, assisted living facilities, bakeries and hotels that offer meals in one form or another. All of these locations will produce FOG wastes at volumes greater than a typical household and may be at risk of blockages and plumbing issues both onsite and in the city Sanitary Sewer systems.

The same characteristics that allow grease traps to remove FOG wastes from wastewater are the same characteristics that cause significant issues in plumbing and sewer lines. When FOG wastes are released into this infrastructure it will come into contact with the cold sewer walls that will cause the wastes to solidify and stick to the walls, building up over time to constrict the flow of the lines. In many cases these accumulated wastes can mix and stick to other wastes in the line such as food scraps, flushed wipes and paper towel to form what is known as a ‘Fat Burge’. These fat burges can then be dislodged from pipe walls and cause dense blockages in the line that are difficult to remove. Preventing the creation of fat burges in the first place is more cost and time efficient than trying to clean and remove them after the fact.

Guidelines

The City of Lloydminster Wastewater Bylaw (15-2021) requires that all commercial and institutional food service facilities are required to have a fats, oils and grease separator installed on all fixtures or downstream of all fixtures that may release FOG wastes. These grease traps will prevent the release of FOG wastes and protect the plumbing within the building from the excessive buildup of these wastes along the walls. The Bylaw also requires the maintenance of the grease trap in good operating condition which refers to the internal plumbing of the grease trap in order to function as intended as well as regular cleaning to ensure the trap operates efficiently. The efficiency of grease traps reduces as the interior of the trap fills up, for this reason regular maintenance is vital to keeping the grease trap as efficient as possible.

Every operator of a restaurant or food service facility that maintains a grease trap is required to keep a record of all maintenance conducted on these facilities. Records can be as simple as an invoice from the third party that completed the maintenance or an ongoing log sheet that documents the date, personnel, and maintenance that has been conducted on the grease trap. These records are necessary for businesses to maintain to show that this maintenance has been conducted in the event of grease blockages in the Sanitary systems. Showing that the due diligence has been conducted is difficult without these records as the maintenance requirements of grease traps vary drastically between different restaurants and locations.

Under the Wastewater Bylaw there is a prohibition on the use of enzymes for the maintenance of grease traps. Many enzyme products are marketed as digesting FOG wastes that are found in grease traps, which works in closed systems that are serviced by septic systems rather than city infrastructure. It has been found that in open systems enzyme begin the digestion process in the grease trap, which liquifies the FOG wastes, allowing the wastes to pass through the system into the Sanitary sewer system. When these liquified FOG wastes enter the city infrastructure they can be deposited along the walls of the sewer systems and may cause blockages and drainage issues. At high concentrations these enzyme products can make their way into the Wastewater Treatment Plant and interfere with the biological treatment processes used to treat wastewater. For these reasons the use of Enzyme products for maintaining grease traps is prohibited within the City of Lloydminster.

Maintenance

Grease traps of any size, when clean, are capable of separating and containing the majority of Fat, Oil and Grease (FOG) wastes that pass through it. As the trap isolates more and more of these FOG wastes and settled solids, the effective space for the capture of grease is reduced, along with the efficiency of the trap. The effective full capacity of any grease trap, regardless of size, is when the floating FOG wastes or settled solids depth is 25% of the total wetted depth of the trap. At this 25% depth it has been found that the efficiency of grease trap is significantly reduced and only removing ~65% of FOG wastes in the water stream. With this drastically reduced efficiency it is necessary to remove all the accumulated wastes to avoid possible plumbing issues in the future.

It is recommended that a third party contractor is utilized for the cleaning of grease traps as these businesses typically utilize vac trucks that can remove all of the wastes (including water) from the trap. These cleanings are typically more effective than those conducted by staff, as staff typically does not have an adequate disposal for the wastewater left in the trap once the FOG wastes are removed. When staff conduct cleanings of grease traps it is recommended to dispose of the FOG wastes in the Landfill dumpster, disposing of the liquid wastes in this manner is not recommended.

Preventing Discharge

Fats, Oils and Greases (FOG) wastes are considered a contaminant of concern, although not directly or immediately hazardous, the characteristics and makeup of these wastes can cause significant issues. From the point of release, either from dishwashers, sinks or drains, FOG wastes are capable of solidifying into large masses or attaching itself onto the cool walls of pipes. The accumulation of FOG wastes onto the walls of pipes can restrict the flow of water or block the line entirely. This is not specific to the city infrastructure, but can occur within the plumbing of homes and businesses which can be a costly issue to fix. Throughout the entire line from the drains to the Wastewater Treatment Plant could be affected by these wastes. Within the Wastewater Treatment Plant these wastes are nutrient rich and easily digestible by the biology used for treatment, to the point of causing difficulties in treating other more difficult to digest wastes. This can cause significant upsets and problems in the treatment process that require extra attention and energy to overcome. 

Contact Us

City of Lloydminster
4420 50 Avenue, Lloydminster
AB/SK, T9V 0W2
Phone: 780-875-6184
Fax: 780-871-8345
Email: info@lloydminster.ca

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