Daniels Training Services

Solvent Distillation as a Means to Reclaim Spent Solvents

Solvent Distillation as a Means to Reclaim Spent Solvents

Does your company purchase virgin solvent and dispose of spent solvent off-site?  If you answered yes, you’re not alone.  The costs associated with the purchase of virgin solvent and its off-site disposal is a significant financial burden for many manufacturers.  If you haven’t before perhaps you should consider the use of on-site solvent recycling equipment such as a solvent distillation unit.  Before making such a purchase you must take into account a variety of factors such as:  safety concerns, labor needs, regulatory compliance, costs, and the effect on production.  This article will focus on US EPA regulatory requirements.

States may differ in their interpretation of these Federal regulations, so I suggest you work closely with your state environmental agency before you begin on-site solvent distillation of your spent solvent.  Read here for more information about generator on-site treatment of hazardous waste in general.

The benefits of recycling of your spent solvent through distillation include:

  • Reduced purchase costs for virgin solvent.
  • Reduced disposal costs for spent solvent.
  • Possible change in hazardous waste generator status due to reduction in amount of hazardous waste generated.

A solvent distillation unit heats a spent solvent – we’ll assume it to be a hazardous waste – to its boiling point, evaporating the solvent.  The solvent vapor passes into a condensing chamber where it is recovered in its liquid form for reuse.  Any contaminants – with a different boiling point than the solvent – collect as still bottoms.  That is a vastly over-simplified description of the solvent distillation process; what then about the regulatory compliance issues?

The solvent distillation unit itself, which is a form of treatment as defined at 40 CFR 260.10, is exempt from regulation pursuant to 40 CFR 261.6(c)(1) (RO11200).  Therefore, the operation of a solvent distillation unit itself would not subject a hazardous waste generator to the permitting requirements of the Resource Conservation and Recovery Act (RCRA).  Nor is the solvent distillation unit subject to the hazardous waste generator standards of 40 CFR 262.  However, as we’ll see, the spent solvent prior to distillation and any still bottoms removed from the unit may be subject to these requirements.

Once it has been reclaimed by the distillation process to where it may be returned to its former use (the same as if it was virgin solvent) the former spent solvent is no longer a solid waste per 40 CFR 261.3(c)(2)(i) (RO12911) and therefore, cannot be a hazardous waste.  As far as the US EPA regulations are concerned it is no different than virgin solvent unless you intend to burn it or use it in a manner that constitutes disposal.  If and when you are no longer able to reclaim the spent solvent for reuse it then becomes subject to the hazardous waste determinationrequirements of 40 CFR 262.11 and the hazardous waste generator standards of 40 CFR 262.  Care must be taken to ensure you count your hazardous waste generation properly to determine your hazardous waste generator status; keep reading to ensure you don’t double-count.

Any solvent distillation unit will generate what is called a still bottom which is the contaminants removed from the spent solvent and accumulated within the unit.  Your operations may differ, but it is safe to assume that the still bottoms from a solvent distillation unit will be a listed hazardous waste per 40 CFR 261.31 (RO12911).  Though the still bottoms may accumulate in the solvent distillation unit for a period of time, since the unit is exempt from regulation the still bottoms are considered a newly generated waste – and subject to the hazardous waste generator standards of 40 CFR 262 – when they are removed from the unit (RO11420).  As with the spent solvent, read on to make sure you count the amount of hazardous waste you have generate in a calendar month with care to determine your hazardous waste generator status.

The regulatory status of the spent solvent prior to its introduction into the solvent distillation unit depends on whether or not it is stored or accumulated prior to its reclamation.  Pursuant to 40 CFR 261.6(c)(2) if the spent solvent is recycled without prior storage it is not subject to RCRA regulations (its still bottoms are however), you need only…

  • Obtain a US EPA ID number for your site if you don’t already have one.
  • Comply with the requirements of 40 CFR 265.71 and 265.72 regarding the use of the Uniform Hazardous Waste Manifest for off-site disposal of hazardous waste.
  • Comply with the RCRA air emission standards of 40 CFR 265 Subparts AA & BB.

If the spent solvent is recycled after prior storage it is subject to the full hazardous waste generator standards of 40 CFR 262 up until the point it enters the solvent distillation unit (Faxback 12895).  This includes the on-site accumulation time limits of 90 days for an LQG and 180 or 270 days for an SQG.

One final point concerns when the spent solvent or the still bottoms are counted towards your hazardous waste generator status.  As noted in the previous paragraph, if the spent solvent is recycled without prior storage it is exempt from the requirement to count it towards your generator status, but the still bottoms generated by the process are not.  If stored prior to recycling, it gets a bit trickier.  40 CFR 261.5 – though directed in its title towards conditionally exempt small quantity generators – applies to all hazardous waste generators.  At 40 CFR 261.5(d) we find:

(d) In determining the quantity of hazardous waste generated, a generator need not include:

  1. Hazardous waste when it is removed from on-site storage; or
  2. Hazardous waste produced by on-site treatment (including reclamation) of his hazardous waste, so long as the hazardous waste that is treated was counted once; or
  3. Spent materials that are generated, reclaimed, and subsequently reused on-site, so long as such spent materials have been counted once.

The above regulations are clear that whether it’s the still bottoms generated in the reclamation process (#2 above); or the spent solvent that is reclaimed and reused (#3 above) you need only count the amount of solvent begun withand not each batch of spent solvent or still bottoms.  What the regulations do not make clear – but RO 12699 does – is that since your generator status is determined by the amount of hazardous waste you generate in a calendar month this count must be made once each month.

Research the applicable regulations, determine the cost/benefits, and be sure to speak to your state environmental agency.  Once satisfied with the above, go ahead and begin recycling your spent solvent for reuse on-site.  Contact me with any questions or to let me know how things went for you.  Better yet, come to one of my nationwide trainingevents, or let me come to your site to train all of your Hazardous Waste Personnel and DOT HazMat Employees for one flat fee of $1,749.  I look forward to hearing from you.