Reactive Waste or Not

It is very, very difficult for us to accept that this waste is “reactive.” Do you have any advice?


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Q. We are a job shop metal finishing facility with a conventional wastewater pretreatment system. Because of the mixture of our numerous processes, the aggressive cleaning we do because of very dirty and oily parts and lack of wastewater and spent waste storage capacity (and no room to add more), we have always struggled maintaining compliance with our wastewater discharge and, on top of that, had very high chemical costs. Several months ago, our chemical supplier introduced us to a new wastewater precipitant containing an organic sulfide. Within days of using it, our effluent metals, especially zinc and copper, dropped well below our permit limits and, based upon its dosage, we projected significant costs savings compared to old chemistry. Also, within weeks, we also observed a significant reduction in our filter press cake generation rate.

Now the bad news. Recently, the firm that handles our filter press cake, which is a listed hazardous waste (F006), sampled the waste and informed us that in addition to its current F006 designation, it is a “reactive” hazardous waste with code D003. Furthermore, because the current hazardous waste treatment/disposal facility is not permitted to handle “reactive” hazardous waste, they have to ship the waste more than 1,000 miles further to a facility that is able to accept it. This will increase our disposal costs by thousands per pickup and tens of thousand per year.

When we asked why it is now “reactive,” they responded the sulfide was tested “positive” by their lab. When we inquired what “positive” means, they responded free sulfide over two ppm.

Steve, we have worked diligently with our chemical supplier to make sure we do not have excessive sulfide in our wastewater. Typically, the wastewater has no or very little “rotten egg” odor, so we know we are not excessively overdosing. As an experiment, we cut the sulfide precipitant dose by only 25% and within hours our effluent visibly deteriorated so we restored the dose.

It is very, very difficult for us to accept that this waste is “reactive.” Do you have any advice? C.W.

A. Unfortunately, the hazardous waste characteristic of “reactivity” can be quite subjective. USEPA’s definition of “reactivity” under 40CFR261.23(a)) is as follows:


  1. It is normally unstable and readily undergoes violent change without detonating.
  2. It reacts violently with water.
  3. It forms potentially explosive mixtures with water.
  4. When mixed with water, it generates toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.
  5. It is a cyanide or sulfide bearing waste which, when exposed to pH conditions between 2.0 and 12.5, can generate toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.
  6. It is capable of detonation or explosive reaction if it is subjected to a strong initiating source or if heated under confinement.
  7. It is readily capable of detonation or explosive decomposition or reaction at standard temperature and pressure.
  8. It is a forbidden explosive as defined in 49 CFR Section 173.54, or meets the definition of a class/division 1.1, 1.2, or 1.3 explosive as defined in 49 CFR Section 173.50.

Because the filter press cake has significant water content, between 70–85%, it does not meet criteria 1 through 4. And because it does not detonate or is not a forbidden explosive, it does not meet criteria 6 through 8. That leave criteria 5—a sulfide bearing waste.

In 1989, USEPA published a guidance manual (Policy guidance No. 6) that established analytical methods (SW-846) and sulfide threshold concentration (500 mg/kg) in order to assist generators with the characterization of their waste material relative to the hazardous waste characteristic of reactivity. However, in 1998, USEPA rescinded the guidance manual due to errors made in its development. Currently, there is nothing in its place, and if you visit USEPA web page (www.epa.gov/epaoswer/osw/hazwaste.htm#hazwaste), it will state that there are no tests for “reactivity” available. It is quite some challenge to develop a test that exposes a waste to “pH conditions between 2.0 and 12.5” and determine whether or not it generates “toxic gases, vapor, or fumes..” that it “present a danger to human health or the environment.”

The test the lab uses is a “spot” test and is an acceptable ASTM D4978-89 method although USEPA has made it clear that there are no “reactivity” tests available. Unfortunately, many treatment/disposal sites are using it as their default test in order to protect themselves from future liability.

Based upon our communications with our state EPA, a local hazardous waste treatment/disposal facility, and a local solid waste disposal facility (aka sanitary landfill), the general consensus is the following:


  1. There is no USEPA accepted analytical method for determining reactivity. If a sample is submitted to a laboratory, a sulfide screen will be performed that will indicate “positive” (>2 mg/kg) or “negative (<2 mg/kg).”  A positive result does not necessarily mean the waste is hazardous, although a negative result is much more comforting that the waste is not hazardous
  2. Generators must use their knowledge of the process generating the waste stream and the waste stream itself and make a determination if the waste is reactive, particularly in relation to Criteria #5 above.

Bottom line is if you desire to pursue this issue and are confident that the filter press cake is not a “reactive” hazardous waste (and based upon our experience with similar waste, we tend to agree), you will need to convince the facility that accepts your waste for treatment/disposal of your determination despite of the lab’s “spot” test. This may mean that you will have to change the treatment/disposal facility. Assuming you are successful in reaching agreement with a hazardous waste treatment/disposal facility that your filter press cake does not exhibit the “reactivity” characteristic, we strongly recommend that you document your determination criteria and rationale.

If any of our readers has also encountered this same issue, we sure would invite you to respond and share your experience.



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