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Pollution Prevention and Control Technologies for Plating Operations
Section 3 - Chemical Recovery
3.7 REVERSE OSMOSIS
3.7.8 Residuals Generation
As discussed in Section 3.7.1, RO separates the feed stream into two components: (1) the permeate which passes through the membrane and (2) the concentrate which retains the dissolved and suspended solids. In typical chemical recovery applications the permeate is used as rinse water and the concentrate is used in the bath. In typical wastewater recycle applications, the permeate is used as rinse water and the concentrate is treated on-site by the end-of-pipe treatment system. In such cases, the quantity of residuals from RO is low, and mostly restricted to used cartridge filters and RO membranes.
The experience of the respondents to the Users Survey was generally the same as described above. One respondent indicated that quantity of used filters generated was 0.3 drums per year. That same shop sent 60 to 300 gpy of unspecified "overflow" to off-site treatment (PS 089). The wastes from all other respondents were treated on-site, except for the end-of-pipe, zero discharge application (PS 233). That shop indicated that the reject stream from their RO unit (300 to 600 gpd of concentrated waste with 2.5% total dissolved solids) is hauled off-site for treatment/disposal.