Using a two-pump sanitary lift station to clear fats, oils & greases
With the tables full, wait staff scurrying back and forth, and kitchen workers churning out appetizers and dinners, the last thing a restaurant needs is a grease blockage causing a sewage flood in the back of the house.
The risk is real. The byproduct of cooking a lot of food—and cleaning all of the dishes required for food prep and serving—is fats, oils and greases (FOG). There is a reason commercial kitchens have grease traps protecting their vents and installed below their sinks: They are greasy places.
Ultimately, much of this grease ends up going down the drain, despite the best efforts of the grease traps.
In the front of the house, patrons are having a good time, enjoying a nice meal or sharing a conversation over a few drinks. One of them excuses themselves and heads to use the restroom. Without a second thought, these patrons often flush items that are not necessarily intended to be flushed, including baby wipes, paper towels or feminine hygiene products. Even undergarments have been disposed of in restaurant toilets.
Eventually, the pipes running from the facilities in the front of the house connect with those coming from the kitchen. When the FOGs collide with the foreign materials flushed into the sewage system, a minor disaster is in the making.
In the restaurant industry, it is known as “ragging.” The material in the system attracts the FOGs, which begin to gather, build up and congeal.
With every drop of fat that gets washed down the kitchen drain, that mess gets larger. Eventually, it fills the entirety of the pipe, and could get as hard as a rock. The result is less space for the wastewater to escape the property. Eventually, the sewage backs up into the kitchen.
Nevermind the headaches that come with the cleanup; it also means costly maintenance and potentially lost revenue if the restaurant has to be shut down until the problem is addressed. It is a significant expense for both restaurant owners and, if not treated onsite, municipalities.
Ideally, regular maintenance and cleaning of grease traps will reduce the amount of grease and solid materials getting into the system. When dealing with high volumes, this often is unavoidable. However, there are preventive solutions for restaurants that will keep their pipes clear and the wastewater flowing out to the municipal main for treatment.
Working With Wings
Buffalo Wild Wings was building a new store in Queens, N.Y. Aware of the risks and associated costs of ragging, a key part of the project was ensuring an effective and fail-proof wastewater management system to prevent build-ups in its sewer line and the New York City sewer system. The system would be required to:
- Efficiently manage solids entering the plumbing system;
- Prevent FOGs from solidifying in the pipes;
- Ensure a consistent, free flow of waste effluent from the restaurant site into the public sewer system; and
- Incorporate emergency backups and fail-safes that would ensure the system remained functional in case of equipment failure.
To tackle the problem, Zoeller Engineered Products designed and installed a two-pump sanitary lift station based on its Shark Series 7011 bi-directional grinder pumps. A cast iron 2-hp pump with a corrosion-resistant, baked-on epoxy powder coating and hardened stainless steel cutter blades, it is factory-tested in conditions similar to that in which it is expected to operate.
The logic of the system is to have the main pump and auxiliary pump alternate between each cycle, and they work in tandem to maintain a brisk flow of effluent to keep the pipes clear.
The pair of pumps was placed at the bottom of a 108-in.-deep fiberglass basin with a 48-in. diameter. The duplex system was designed to prevent clogging by regularly reversing the flow of effluent. The grinders ensured that any solid materials were shredded before entering the sewage pipes, and reversing the direction of the grinders prevented foreign matter from getting coiled around the mechanism. This further prevented solid materials from getting lodged in the pipes where FOGs can gather.
The dual-pump mechanism served as the main fail-safe, ensuring that in case of a pump failure, the second is in place to keep the system operational. However, having a main and auxiliary pump also maximized alternating cycles that keep the material moving through the system at a rate of 2 to 3 ft per second (souring velocity) to prohibit the slowing, cooling and solidifying of the sewage and grease.
It also was necessary to ensure the system components were not subject to the same risk as the pipes. FOGs will build up on various pieces in the basin. One of the most susceptible is the float that monitors fluid levels to trigger when and how the pumps operate.
A float encased in grease is susceptible to malfunction, and could put the entire system at risk. For the Buffalo Wild Wings project, Zoeller incorporated a device called FOGrod. Designed specifically for use in situations where FOGs are a concern, it is a slim corrosion-resistant CPVC rod with 10 metal contacts that uses conductivity to measure water levels.
The rod is connected to a level indicator transmitter (LIT) with 12 relay outputs—one for each of the contacts and two fault relays. When the effluent in the basin covers a contact on the rod, it sends a signal to the LIT. Any of these 10 relays can be wired to start or stop the pump system, or to sound the alarm if there is an emerging problem.
Designed to resist FOG buildup, the rod ideally is placed in a space where currents are turbulent to ensure constant flow of fluid will inhibit material buildup. However, if it does become encumbered with FOGs, the rod sends an alert that it needs to be cleaned—a relatively easy process that occurs about once a month.
Accuracy and efficiency in the operation of this system is key. The pumps may shred foreign products and push wastewater out of the facility, but they need to be told when to turn on and which way to turn, and they require monitoring to ensure they are working properly. This is tasked to a 120-VDC three-phase Tulsar Canada control panel.
Housed in a NEMA 4X thermoplastic enclosure with a lockable hasp on a hinged front cover, the panel includes a high-water alarm light, motor contractor, pump disconnect switch, control panel disconnect switch, seal leak light, selector switches and pilot lights.
The automatic reversing function of the pumps is incorporated into the panel, ensuring the pump’s cutter blades and impellers rotate in either a clockwise or counter-clockwise direction. With each cycle of the pumps, the cutter blades rotate in the direction opposite of the previous cycle. The duplex configuration also is managed by the control panel, enabling each pump to operate as the lead mechanism during the alteration sequence.
The panel provides adjustable overload protection against thermal overload in the pump’s motors. Also included is a thermal cutout circuit interfaced with the pump’s motors and thermal sensors. Atop the unit is a visual high-water alarm with a red beacon and 360-degree visual check to alert of potential problems in the system. These alerts can be pump failures, FOG buildup on the components, a general power failure while water still is entering the system, or overflow or flooding risk alerts.
At the end of the day, time is money. Restaurants cannot afford to shut down their businesses and spend the money to clear a clog from their sewage pipes. They need this kind of reliable system to take that worry away.