Recycling and recovery
Acid and caustic neutralization
Permitted treatment for corrosive streams that are not worth reclaiming.
Neutralization adjusts a corrosive waste to a pH between 2 and 12.5, at which point it no longer exhibits the D002 characteristic. It must be done in a permitted unit or under the generator treatment provisions, and dilution alone does not count as treatment.
Source: 40 CFR 261.22, and 40 CFR 268.3 on dilutionWhat makes neutralization compliant
The distinction between treatment and circumvention matters here:
- Carried out in a permitted treatment unit, or in tanks and containers under the generator provisions at 40 CFR 262.17
- Genuine chemical neutralization, not dilution with water
- The resulting stream still assessed for other characteristics and for dissolved metals
- Discharge under an NPDES permit or to a POTW under pretreatment standards
- Records kept of what was treated, how, and what the result was
Diluting a corrosive to move its pH inside the range is prohibited under 40 CFR 268.3. It is one of the clearer bright lines in RCRA.
What neutralization does not fix
Removing the corrosivity characteristic does not remove other codes. A spent acid carrying dissolved chromium is still D007 after neutralization, because the metal is still there. The sludge produced by neutralizing it concentrates that metal and is itself newly generated waste.
This surprises generators regularly. The tank is neutral, the pH strip is green, and the sludge at the bottom is a hazardous waste that now needs its own determination and its own route.
Common questions
Can I neutralize in my own tank?
Generators may treat hazardous waste in accumulation tanks and containers under 40 CFR 262.17 without a permit, provided the tank standards and accumulation limits are met. The conditions are specific and worth reading before relying on them.
Is the neutralized stream still hazardous?
Not for corrosivity, if genuinely treated. It may remain hazardous for other characteristics or listings. Test the treated stream rather than assuming the treatment cleared everything.
What about the sludge?
Neutralization sludge is newly generated waste and needs its own determination. It usually concentrates whatever metals were dissolved, so it frequently carries toxicity codes the original liquid did not.
Related services
Not sure how this applies to your site?
Send a profile, an old manifest, or photographs of the drums. A technical professional will tell you where you stand.
This page summarizes federal requirements and is not legal advice. State programs can be more stringent than the federal baseline. Verify against current federal and state regulations before acting. Last reviewed September 2026.