Abstract: Reducing the heavy metals content of an aqueous composition which includes adding lime to the composition and filtering the composition.

Abstract: An improved process and a system for waste water treatment are disclosed which are particularly suited for use in industrial plants (10) having existing drainage trench networks (108-128) through which normal plant effluents, component leakage and accidental spills ordinarily would be allowed to flow. The trench system is connected to a waste water treatment facility (FIG. 1) designed to remove impurities from the effluents and return acceptably clean water to the plant for reuse or discharge it to the environment. Because some plant effluents, component leaks and unexpected spillages can increase the concentration of impurities in the waste water to levels beyond the design limits of the waste water treatment system, a series of dams (138-144, 150-154, 162-176) are provided at locations throughout the trench network so that effluents having rather high ranges of concentration of impurities are held behind the dams.