Spec Check: Disposers

Almost any kind of foodservice operation can use a commercial disposer to process food waste. By specifying disposers, operators can reduce garbage odors, which can attract insects and vermin to dumpsters, and these systems also can decrease the amount of overall waste, which will help lower hauling costs.

Because some regions have regulations that prohibit the use of disposers, operators should check with their local zoning or municipal boards before installing to confirm that these systems are suitable for use in their area. Also, some areas require food waste to pass through solid interceptors and grease traps before traveling into the sewer. Some equipment dealers and disposer manufacturers can provide the necessary information in terms of regulations and requirements.

Disposers can process most types of food waste. Even scraps that are more difficult to grind can be deposited in these systems. It’s important to note that large quantities of this type of waste can shorten the disposer blades’ service life over time. As a result, manufacturers recommend that operators not process large amounts of meat bones, shellfish and other hard organics in disposers.

An operation’s size and amount of waste will dictate the disposer size that is needed. These units are generally specified by horsepower, which ranges from ½ to 10 hp.

A common mistake foodservice operators make is specifying a disposer that is too small because they believe the waste amount will be light. In most cases, operations become more dependent on these units than anticipated. For this reason, it is advisable to specify a unit with greater horsepower in order to accommodate a large amount of waste.

Take into consideration table turns and number of seats in the operation when specifying disposers. This will help determine how much food waste the unit will eventually process.

Also, consider the factors driving the interest in adding a disposer. Some factors include:

  • Saving time with waste processing and disposing
  • Decreasing waste hauling costs
  • Minimizing odor-causing waste

These factors will impact the size and type of system that the foodservice operator should ultimately select.

Verify how many disposers the foodservice operation needs. For example, some operations will require a disposer in the pot and pan area and another in the vegetable prep area. In those instances, each disposer will operate under a different set of circumstances so they will have different sets of specifications and, as a result, the operator may need to install different sizes and types for each location.

The type of food waste that will need to be handled also will determine what disposer type is needed. High volume operations or those with waste that is tougher to grind may be best served by a disposer that includes a reversing switch, which uses both sides of the cutting blade and can double the service life of the unit.

Foodservice operators can choose from a variety of housing construction options, including aluminum, stainless steel and cast iron, which can be either coated or plated.

Also, there are different types of cutting mechanisms available. These are made of rust-resistant nickel, stainless steel or austempered heavy ductile iron. Disposers with rotor-fixed cutting teeth are the most common types on the market today. Foodservice operators can also choose from units with swivel cutting teeth or a hammermill grinder. All three types include a cutter operating at high speed inside a stationary shredder ring.

For high-volume operations, manual reverse switches can extend the life of the cutting blades, while also unjamming stuck food waste. Automatic reversing controls are available, too.

Voltage options include 115, 208, 230 and 460, with single and triple phase units available. Foodservice operators can choose from either a standard electrical wall switch or electronic controls.

Operators need to determine the type of sink configuration a disposer will be used in conjunction with. There are sink, cone and trough mounting configurations. Cone assemblies are available in 12-, 15- or 18-inch sizes.

To ensure efficient operation and help circumvent sink backups, foodservice operators need to consider the drain line size in conjunction with the disposer specified. Manufacturers may provide free site surveys to ensure the drain line can handle the disposer waste.

Foodservice operators can select a disposer system with a manual on/off switch, which is best for smaller operations or those with less food waste, or automatic controls, which automatically turn both water and energy off when the disposer is not in use, providing increased energy efficiency.

Determine if a protection device is needed to keep foreign material out of the disposer. Various screens or magnets can help prevent foreign material from getting into the system.

Disposer Alternatives
Composting, biodigesting, compactors, scrapping and pulping are other waste disposal options for municipalities that prohibit disposers.

Larger operations are more likely to justify the expense of composting and biodigesting systems. Composters biodegrade food waste, while biodigesting systems use microorganisms to break down scraps, including dairy, meat and fish scraps, bones and bread.

Pulpers also are best suited for use in larger institutions, such as universities and healthcare facilities. These systems take approximately 90 percent of the mass out of waste, which helps reduce wet waste hauling costs. Rather than food waste being sent down the drain, a pulper grinds the waste until it is pulverized. An auger brush then squeezes the water content out of the food waste. This is shot out into a receptacle and disposed of with regular waste.

Compactors consolidate food waste and are designed to produce an 85 percent reduction in its volume.

Scrapping systems are typically used in conjunction with disposers. While some systems include a disposer and use water for scrapping, others are installed in a trough application for multiple scrapping stations. Scrapping units may also use a basket instead of a disposer to collect insoluble food, while allowing solubles to wash down the drain. One system, installed in a trough application, uses a scrap basket instead of a disposer.

Disposer Do's and Don'ts
All jurisdictions monitor and control volume and contents of effluent that can be disposed of into municipal wastewater systems. The disposal of any effluent into municipal wastewater (sewer) systems is typically governed under municipal bylaws/ordinances and enforced at the local level or through a regional municipal authority, in accordance with state and federal environmental legislation. These municipal ordinances set out allowable limits of various materials and chemicals that can be present in effluent that is being disposed of into the municipal wastewater system, and that ultimately need to be processed and treated at the wastewater treatment plant.

The recommendations below are general guidelines and should not replace those provided by the manufacturer.

  • DO NOT dispose of fat, oil and grease in the disposer. Food waste containing this residue is the exception.
  • DO NOT batch feed food waste into disposers. This will block water from flushing out the waste, resulting in drain line clogs.
  • DO clear clogs by filling a 5-gallon bucket with cold water and running it through the disposer. This will help push the waste through effectively, without damaging the system.
  • DO allow cold water to run through the disposer for at least 10 to 20 seconds after food waste is disposed of to ensure small particles are pushed to the main sewer line.
  • DO NOT push plastics, silverware, straws or any other non-food items into the disposer. Doing so could cause jams and may damage the system over time.
  • DO use cold water, not hot, to flush waste. Hot water can melt fat off of food particles, which will solidify and block the drain line.
  • DO NOT regularly dispose of food waste that may create sediment, such as oyster shells, in the disposer, which can build up in the drain line.
  • DO NOT dispose of a high concentration of fibrous materials, like corn husks, in these systems. Doing so can potentially cause clogs over time.
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