Laundry Wastewater Treatment and Ozone Disinfection
A commercial laundry can send tens of thousands of gallons of water a day to the drain. That water carries lint, soil, detergents, oils and microorganisms, and local sewer authorities increasingly set limits on what may be discharged. Treating it, and reusing part of it, saves money on water, sewer charges and heating.
What is in laundry wastewater
- Solids and lint from fabrics and soil
- Fats, oils and grease, especially from restaurant and industrial linen
- Surfactants and other detergent chemicals, often at high pH
- Heat: discharged water can be warm
- Bacteria and other microorganisms from soiled linen
Typical treatment steps
Treatment is built in stages. Screening and lint removal come first, followed by equalization (a tank that evens out flow and temperature). Depending on the discharge limits, the water then goes through pH adjustment, flotation or settling to remove oils and solids, and filtration. Laundries that reuse water usually add a final disinfection step so recycled rinse water does not spread odor or microbes back into clean linen.
Where ozone fits
Ozone is used both as the disinfection step and to break down color and odor-causing compounds. EPA’s fact sheet on ozone disinfection summarizes its strengths and weaknesses compared with chlorine:
| Ozone advantages | Ozone disadvantages |
|---|---|
| More effective than chlorine against viruses and bacteria | Low doses may not reliably inactivate some viruses, spores and cysts |
| Short contact time, about 10–30 minutes | More complex equipment than chlorine |
| No harmful residual to remove; it decomposes quickly | Highly reactive and corrosive; needs resistant materials |
| Generated on site, so no chemical shipping or storage | Not economical for water high in solids or organic load |
| Raises dissolved oxygen in the water | Off-gas must be destroyed; higher capital and power cost |
The last row is the key practical point: ozone works best on water that has already been cleaned of most solids and oils. Put it at the end of the treatment train, not the beginning.
Water reuse
Many commercial laundries recycle treated water from the final rinses back into the first wash steps of the next load. Combined with an ozone laundry system, this can cut both fresh-water use and the energy needed for heating. Check local regulations and your sewer authority’s discharge permit before designing a reuse system, and pilot-test ozone dose and contact time on your own water: required dose depends on what is in it.