CHARACTERIZATION OF SOLVENTS AND SOLIDS IN BOOTHWATER FROM WATERBORNEPAINT

Waterborne paint includes a number of highly water soluble solvents an d disperses readily in boothwater. The result is a compositionally com plex boothwater that in turn impacts the treatment of overspray paint, emissions of volatile organic compounds (VOC) from the paint booth, a nd water disposal. Our batch and pilot booth experiments show that wat erborne paint generally results in accumulation of organic compounds a nd dissolved solids in boothwater. The organic content is mainly contr ibuted by the paint resins and solvents, which are partially captured in boothwater. The extent of capture and retention of the individual p aint solvents depends on their properties and the processes inherent t o the paint booth operation, including air/water contact in the booth scrubber, replenishment of boothwater, and biological degradation. The resins captured in boothwater are in solubilized, dispersed, or suspe nded form and may account for as much as 80% of the so-called dissolve d solids. The remaining solids in boothwater mostly consist of inorgan ic compounds from water hardness, paint pigments, and treatment chemic als. The contribution to organic content from the treatment chemicals is found to be very small.