The majority of liquid waste from a distillery is stillage/ spent wash: the leftover liquid after a still run, mostly water.
Wastewater districts typically have rules and regulations stating what, and how much of different materials they will accept in their system. Every locality is different, so contact your local wastewater treatment authority to find your specific rules and regulations.
BOD is Biological Oxygen Demand is “the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.” – wikipedia
The higher the BOD of a material/ liquid, the harder it is to breakdown, and the more impact it has on the wastewater plant.
Emergency Spill of High Proof Alcohol
While you probably never want to put your high proof alcohol/ your spirit/ your income down the drain, there could be an accidental spill. In fact, one of the methods we sometimes use for secondary containment (see other blogs about secondary containment) is to have it go down the drain into the sanitary sewer system. This is the safest method of containment if the liquid is on fire, because it will be put out at the trap, taken away from the building, and mixed with more water in the waste stream.
So, what would a wastewater treatment plant typically be concerned about with putting a large volume of say 90& ABV alcohol down the drain:
- Flammability of the liquid/ flash point- Most jurisdictions will have a limit to the flash point of the liquid they allow. High proof alcohol will surely exceed this limit. But, as long as the authority is reasonable and understands it is for an emergency spill only, they should accept it. Also, it depends how far you are from the wastewater treatment facility. If they are your next door neighbor, that liquid will not have a chance to be watered down. If your several miles from the facility then it will.
- BOD’s: High proof alcohol will have a high BOD content . The BOD content of 90% ethanol is 0.8 – 0.967 g O²/g substance – https://www.americanbio.com/sites/default/files/sds/AB00236.pdf
So, to figure out how many BOD we have from say 350 gallons of 90% a=ABV, the numbers would be:
350 gal x 8.345 lb/gal =2,920.75 lb
2,920.75 x 0.967 = 2,824 lbs of BOD
Some wastewater facilities might be able to handle this. Smaller facilities might hit their capacity, larger ones might not make as big of an impact. In talking with the jurisdiction, they must understand a spill like this is an accidental emergency only, and they authority should be warned it is coming to them if it does happen.
The daily wastewater is mostly spent wash/ stillage/pot ale. We can utilize figures from existing distilleries to know the average BOD of pot ale. The average pot ale for whiskey is 24.9g/ l.
24.9 gram/L * .0022 lbs./gram* 500 Gallons * 3.785 L/gal = 103 lbs BOD per day
And of course it will depend on how big of a distillery it is, this example used a 500 gallon per day waste as example. Most treatment facilities should be able to handle 100 lb of BOD a day.
Not all wastewater facilities will have a permitting process or little regulation. But, this information can be helpful to know in case they do start asking questions about what your distillery is putting down the drain!