Treatment of aqueous systems using a chemically mod tannin

There is provided a composition comprising tannin containing hydroxyl groups which has been (a) chemically modified by reaction of at least one of said hydroxyl groups with at least one member selected from the group consisting of an esterification agent (e.g. acetic anhydride), etherification agent (e.g. dichloromethane or quaternary organic amine such as N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride) to form the corresponding ester, or ether, through said hydroxyl group, and (b) derivatized. The chemically modified tannin is derivatized by reaction with aldehyhde (e.g. formaldehyde), or aldehyde and at least one member selected from the group consisting of ammonia and organic amine containing at least one primary or secondary nitrogen (e.g. cyclohexyl amine); said derivatized tannin being water soluble or dispersable at a pH below 7 and water insoluble at a pH above 7. The chemically modified tannins are useful for the coagulation and/or detackification of solid particles suspended in the aqueous system, such as paint particles suspended in the waste water of a paint spray booth operation. Such tannins also have utility for demulsifying oil-in-water emulsions.