Powerwashing and trap cleaning operations typically yield wastewater mercury concentrations in the 1 to 200 ppb range. This means that most infrastructure cleaning operations will require the wastewater to be collected and, in most instances, to be handled as a non-hazardous waste. The determination of whether a waste material is hazardous waste or non-regulated material should be made based on TCLP analytical testing. It is possible to use generator knowledge to assume a waste is a hazardous waste if it is based on accurate and available information regarding similar wastestreams. Due to potential liability, extreme care should be taken when deciding that a wastestream is not a hazardous waste without the benefit of analytical testing.
Analytical testing is the most conservative method for waste characterization.
Although this is the best method for determining if a waste is regulated, it can be very expensive when the generator has no knowledge of the waste. This means that several different analytical test would be required to ensure that all potential waste characteristics have been evaluated. The combination of generator knowledge and analytical testing are the most common procedures used for hazardous waste determination. Using generator knowledge of the waste enables a generator to eliminate a majority of analytical testing for materials that are known not to be present. If it is determined that the collected wastewater contains mercury below one ppb and that all other pollutant concentrations are below discharge limits, this waste can be discharged to the sewer only after written approval from the MWRA has been obtained.