Ladies, Keep Your Eye On Your Mister

And Other Separator Water Issues

Written by Steve Henshaw, P.G., President & CEO, EnviroForensics
As seen in the November 2010 issue of Cleaner & Launderer

Cleaning and purifying dry cleaning solvents for reuse has been around since the beginning of the dry cleaning industry.  Historically, solvents were considered inexpensive, so the degree to which they were reclaimed was considerably less than it is today.  The rule of thumb used to be a 1 to 5 loss/recovery ratio.  That means that 1 part solvent was lost for every 5 parts recycled.  Today that ratio is much, much lower with some dry cleaners telling me they lose only 1 part of perchlorotheylene (perc) for every 20 parts recycled. 

While the dry cleaning machines, now in what’s considered their 5th and 6th generation, are much better designed and considered safer for the environment, the management of separator water continues to pose environmental concerns.  Separator water is generated during the distillation and solvent recovery process.  Vapors from the distillation process are condensed into a mixture of solvent and water.  The solvent is typically recoverd from the mixture by gravity in the water separator.  The remaining water in the separator has dissolved solvents in it and if the solvent being used is perc, the separator water will more likely than not be considered a hazardous waste.

Generally speaking, separator water with a perc concentration of 0.7 parts per million (ppm) or more is considered to be a listed hazardous waste (D039 Waste Code), pursuant to 40 Code of Federal Regulations (CFR) 261.24.   As such, this water must be treated as a hazardous waste in accordance with 40 CFR Parts 262 and 268.   Separator water that is discharged to a sewer system that is operated as a Publically Owned Treatment Works or POTW is typically excluded from the hazardous waste regulations under 40 CFR 261.  However, if the sewer pipes have cracks or broken sections that allow for the sewage water, now mixed with separator water, to migrate from the sewer lines, the dry cleaning facility will have caused an illegal release of hazardous waste into the environment.

Because there is no guarantee that the sewer lines in your area don’t leak, separator water and all contact water must be managed very carefully.  Additionally, more and more wastewater and sanitation districts are now prohibiting the discharge of perc laden separator water to the POTWs.  This is true for all dry cleaners connected to the Sanitation District of Los Angeles County (SDLAC), where dry cleaners must obtain a certification of zero discharge of separator water.  

The management of separator water falls into a two main classifications:

  1. Off-Site Waste Handling;  and
  2. On-Site Evaporation to the Atmosphere.

Off-Site Waste Handling

The waste filter cartridges, muck or still bottoms, and separator water is stored for disposal as a hazardous waste off-site.  The separator water, filters and muck should be stored in drums with tight fitting lids, the drums should be labeled with the accumulation start date and identification that the material is a hazardous waste, and the drums must be picked up and transported by a licensed hazardous waste transportation company under manifest.  Finally, the waste material must be processed as a hazardous waste at a licensed treatment, storage and disposal (TSD) facility.  Disposal manifests must be kept on-site for at least two years and must be made available to regulatory inspectors upon request.

On-Site Evaporation to the Atmosphere

While the spent filter cartridges and muck must still be handled as a hazardous waste in the manner described above, the separator water can be evaporated and discharged to the atmosphere.  Evaporators or misters must vent to the outdoor air, not indoors and have no connection to the sewer or any equipment that discharges to the sewer such as boilers, cooling towers or vacuum trucks.  A well designed evaporator/mister stack should be vented as high into the outside air as feasible to minimize the potential for condensation of mist falling onto the ground and allow for effective dispersion of the vapors.  It is important not vent the evaporator/mister near a window or air intake of the facility, or an adjacent building.

The evaporators should be equipped with at least a single-stage carbon filtration system to effectively remove the largest portion of the dissolved perc solvent prior to evaporation or misting into the air outside of your shop.

Documentation should be kept to demonstrate the efficiency of the filters used on the evaporation system.  This information is typically available from the manufacturer of the evaporation system.

While misters can be effective at reducing the volume of separator water that needs to be managed, we have observed numerous setups where misters appear to be contributing to environmental contamination.  Such situations include misters where the filtration system has been clogged with surfactants, lint and other debris, resulting in a release of mist that is laden with high concentrations of solvents.  We have also observed situations where the mist condenses due to the colder outside ambient temperature or because the height of the mist discharge point is not high enough off the ground and the mist condenses on the ground.  This condensate shows up as small puddles on the ground with elevated levels of solvents that serve as a contaminant source area.  While it is unclear as to the degree that this condensate may result in significant soil and/or groundwater contamination, it is clear that caution must be taken to minimize such a potential.  For these reasons, we ask dry cleaners to pay attention to potential releases caused by misters and to all my lady dry cleaners, keep an eye on your mister.