Renovation of Dilute Process Wastewaters: Mini-Pilot Plant Evaluation of an Integrated Process System to Meet the Clean Water Act's Heavy-Metal and Organic Treatment Requirements at Oak Ridge National Laboratory

摘要

The purpose of the facility was to simulate the treatment the ORNL nonradiological wastewaters will receive in the NRWT plant. In the MPP, all wastewaters, with the exception of those not containing heavy metals (i.e., Cd, Cr, Cu, Fe, Pb, Hg, Ni, Ag, and Zn), flowed through an API-type separator. The criteria metals (except for mercury) were removed in the reactor/clarifier (R/C) as hydroxide precipitates using either calcium hydroxide (lime) and sodium carbonate (soda ash) or sodium hydroxide (caustic). Overflow from the precipitator was then treated by dual-media (sand and anthracite) filters and adjusted to a pH of 7. Wastewaters that had been pretreated by ion exchange for radionuclide removal bypassed the first four unit operations and were combined with the other wastewaters prior to air stripping. Volatile organics were removed by air stripping in a packed tower, while heavy (nonvolatile) organics and mercury were removed in three serially connected GAC columns. An ion-exchange (IX) column was operated in parallel with the R/C in order to evaluate the long-term performance of a chelating, heavy-metal-selective resin. In general, results of the MPP studies correlated well with those of the bench-scale treatability studies. The remainder of this paper details: the results of selected bench-scale treatability studies; spiking of feed streams; the MPP flowsheet and description of equipment; the results from the two MPP campaigns; and finally, the conclusions formulated by this treatability work. (ERA citation 12:012343)