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Here is a guide to use of garbage disposers or garbage grinders at buildings served by city or municipal sewer systems. Garbage disposal units, also called garbage grinders, food waste disposal units, or garbage disposers add to the solid load in the septic tank. A garbage grinder is a mechanical grinder which receives food scraps, typically down a kitchen sink drain, and grinds them into a water/debris slurry that can pass down the building drain. Both electric and water-powered garbage grinders are available.

While garbage grinders are a convenience for the homeowner, the added waste they place in the septic tank might mean that the septic tank needs to be pumped more often. Photo courtesy of InSinkErator™. The garbage disposal unit shown is their Evolution Septic Assist(TM) that includes an enzyme injector for use with private septic systems. However depending on local municipal ordinances regarding use of garbage disposal units in cities and towns, this unit and similar models might be found installed in homes served by municipal sewers as well.

This document is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

SEWER SYSTEMS & GARBAGE GRINDERS - Garbage Disposal Unit Effects on Public Sewer Systems

While garbage grinders can cause an added loading on conventional, residential, on-site septic systems, their use is not necessarily bad in municipal sewer systems according to some researchers, as indicated in the article abstract quoted below. Other studies of the effects of garbage disposers on municipal sewers have been conducted by various groups including the University of Wisconsin, Delft University Netherlands, and the Cooperative Research Centre, in Sydney, Australia, and the New York City Dept. of Environmental Protection

Most cities served by municipal sewers `in the U.S. permit the use of garbage disposals and some cities require their use. Using a kitchen disposer or grinder in cities served by a municipal sewer reduce the volume of organic waste which otherwise has to be hauled to a landfill. Cities in the U.S. and other countries are inconsistent in their view of the use of garbage disposers. New York City now (since 1977) permits their use on residential buildings. Austin Texas has a rebate program to convert garbage disposer use in food service businesses to a scrap bin system.

Rules for Use of Garbage Disposers in New York City

New York City, which used to prohibit the use of these devices legalized their use in 1997, out of concern for the increasing volume of garbage in the city, and in the face of inconclusive test results about their effect on the sewer system.

There has been episodic debate over the question of whether or not garbage disposals clog municipal sewer lines & systems. The New York Times reported in2009 that a New York City ban on residential disposals in effect from 1971 was lifted in 1997 after a two year test convinced the NYC DEP that in New York City residential garbage disposals were not causing a problem. In New York City restaurants are prohibited from using garbage grinders and disposal units, and co-ops and condominium boards are allowed to restrict their use as well.

According to Bolzonella et als., "The use of garbage grinders is not a usual practice in Europe, but it is in other countries around the world (e.g., North America, Japan and Australia). Sometimes, garbage grinders are accused of producing problems in sewers and wastewater treatment plants and are prohibited by environmental protection laws. In this study, the different impacts determined by the use of this technology were considered to show the positive impacts of its use.

In particular, it was shown that garbage grinders enable the disposal of household organic wastes with advantages for the wastewater treatment processes because of an increase in the carbon/nutrients ratio in the wastewater. This is particularly important for biological nutrients removal processes. Daily specific contributions for person equivalent (PE) due to organic waste disposal through garbage grinders were found to be equal to 75 gCODPE(-1) d(-1) for carbon (as COD), 2.5 gNPE(-1) d(-1) for nitrogen and 0.25 gPPE(-1) d(-1) for phosphorous, respectively.

Those determined a value of 30 for the COD/N ratio. Moreover, no problems with solids settling in sewers were noted. These results were extensively compared with literature data. The economical balance showed that the use of garbage grinders allowed a global saving of some 17 Euro year(-1) for a three people family. Important benefits are also gained from an environmental point of view (e.g., organic wastes disposal nutrients removal in wastewater treatment and increase in biogas production with energy reclamation)."

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WHAT CAN GO INTO TOILETS & DRAINS?
NEVER FLUSH INTO SEPTICS
BETTER NOT TO FLUSH
HOUSEHOLD CHEMICALS
OTHER CHEMICALS
CHLORINE IN DRINKING WATER
CHLORINE IN SEPTIC WASTEWATER
DISHWASHERS vs SEPTICS
DRUGS INTO the SEPTIC TANK?
GARBAGE DISPOSAL vs SEPTICS
  GARBAGE GRINDERS on Septics
  GARBAGE GRINDERS on Sewers
REVERSE OSMOSIS CONCENTRATE WASTE DISPOSAL
TOILET TISSUE?
TOILET TISSUE TEST
WASHING MACHINES
WATER SOFTENERS
* NO FLUSH SUMMARY LIST

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• "[The] under sink garbage grinder: a friendly technology for the environment", Bolzonella D, Pavan P, Battistoni P, Cecchi F., Department of Science and Technology, University of Verona, Strada Le Grazie 15, I-37134 Verona, Italy, Environmental Technology, 2003 Mar;24(3):349-59, abstract and article also available from the U.S. NIH at www.ncbi.nlm.nih.gov
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