Landban.
Once a hazardous waste, always a hazardous waste. Or better put, once a listed hazardous waste, always a hazardous waste. One of the main purposes of RCRA was to get people to stop making hazardous waste. All the treatment and storage options are inferior to altering the processes so it does not make HW. But in the real world, lots of HW is generated and will be for a long time. Now for characteristic HW it is possible to make it not a HW (or "exit RCRA"). For example if the waste is corrosive because it is acid, perhaps it can be neutralized with a base such that it is no longer corrosive. If there are no other problems with the waste, it can exit RCRA and be dumped in a MSW landfill. For listed wastes, they stay HW forever. Before a listed waste can be put in any but a "certified no-migration landfill" it must be treated to certain standards. These standards are known as the "landban" or "land disposal restrictions." (Here's a brief phamphlet about the LDR.) They have been a political football, and the regulations were implemented in stages. Some stages have "technology standards," others have "treatment standards." All "liquid" waste must be treated so that it is no longer liquid before it goes in any but a no-migration landfill.
More on LDR's
The LDR's have two standards: the Treatment Standards for Hazardous Waste (TSHW)
(40 CFR 268.40), the Universal Treatment Standards (UTS) (40 CFR 268.48). Both
must be met. You can get to them from http://edocket.access.gpo.gov/cfr_2010/julqtr/pdf/40cfr268.40.pdf
or
http://edocket.access.gpo.gov/cfr_2010/julqtr/pdf/40cfr268.48.pdf
The TSHW have numbers, usually concentrations of chemicals, but sometimes technology,
for each RCRA HW, indexed by the HW designation, for example D0008 or F012.
The UTS has a concentration for each chemical in a long list.
There are two types of waste under RCRA, characteristic and listed. When the
waste goes to a TSDS facility, it must be treated according to the TSHW. If
a characteristic waste can be treated to below the TSHW limits AND it
meets the UTS, then and only then can it be sent to a subtitle D landfill (MSW).
For example, gasoline soaked soil might have the characteristic of ignitability,
D001. After the gasoline is removed from the soil, the soil might still have
some lead in it. You then check if the lead is less than the UTS for lead. If
it is, then the soil can be sent to a subtitle D landfill (or replace it on
the soil).
On the other hand, if it is a listed waste, say wastewater from electroplating sludge, F006, it can never become an non-hazardous waste, no mater how much you treat it. However you must treat it to below the TSHW, if you can. If you can get it to below the concentrations indicated in the TSHW, you may dispose of it "to the land" but it must still be in a subtitle C permitted landfill. That is a HW landfill. On the other hand, if you cannot get it below the TSHW numbers, you must disposed in a special type of Subtitle C landfill, one with a "no migration variance." Your incentives to treat the waste to below the TSHW number is that first, the law says you must try, and second, the "no migration" landfills are harder to find and much more expensive.