Solvent-Contaminated waste

I have a US-based client that originates large quantities of toluene and acetone-contaminated rags used to clean equipment - several hundred pounds of them a month.  At present, those rags are then incinerated, which is both expensive and undesirable from a GHG point of view, and so the client is looking to wash and recycle the rags.  The issue of course is contaminating wastewater from the plant.  The rags do not have free liquid, and as such are legal undr EPA rules to launder, but they smell of the solvents and they would no doubt require the waste water to be tested before the wastewater treatment agency would accept the waste.  My question - what is the best way to have that testing done?  Are there in-line sensors that would detect this stuff or would it require lab tests?