Cheat Sheet: Down the drain

Do you know where your food goes after you’ve dumped it down the drain?

1: The majority of food waste can be pushed down the garbage disposal, but there are some foods that should always avoid the sink. Grease, fats or oils solidify in the drain and should go into the trash. Some vegetables are too stringy and fibrous (i.e. celery, asparagus, etc.) and can get wrapped around the unit. Coffee grinds, although it may seem like they’re easily washing away, can also get stuck in the disposal. Egg shells, pits, seeds and bones … always a no-go.

2: Contrary to popular belief, garbage disposals do not contain spinning blades. Instead, the food is forced against a stationary grinding ring by centrifugal force. The waste is chopped up into tiny particles until it is virtually a liquid. Running water from the sink pushes the food into the wastewater pipe. Food waste that does go down the drain is immediately en route to the wastewater treatment plant.

3: Wastewater treatment plants receive and treat all kinds of waste products. The first step in the process, or primary treatment, is to screen out any suspended solids and grit from the raw sewage. Floating substances (i.e. grease, soap, oils) are also removed during this time.

4: Secondary treatment involves carefully manipulating dynamics of the environment (i.e. food supply, dissolved oxygen) so that they are suitable in habiting healthy microorganism populations, which feed on the organic waste. Microorganisms, heavy particles and other solids from the waste settle out as sludge. The sludge moves on to be treated so that it is safe for the environment. It is more often being recycled and used as fertilizer. Biogas is also released and can be stored and used for energy to power the facility.

5: The final steps in the treatment process, or tertiary treatment, include nutrient removal and disinfection of the water so that it is more than 99% free of impurities. The clean water is pumped into local waterways.