Waste treatment process

Claim 1

A process for treating waste waters comprising the steps of sequentially: A. mixing with a waste water composition from about 500 to 5000 parts per million (based on total composition) of a dissolved, water-soluble iron salt, selected from the group consisting of ferrous sulfate, ferric sulfate, and ferric chloride, said waste water composition being selected from the group consisting of: a. water derived from clean-up of at least one water based printing ink of a flexographic type, and b. water derived from clean up of at least one starch based adhesive of a type used in corrugated paper board manufacture, and, said waste water composition containing from about 4,000 to 60,000 parts per million based on total composition of suspended solids below about 200 millimicrons in average diameter, said waste water composition comprising on a 100 weight percent total weight basis from about 1 to 6 weight percent combined non-aqueous matter with the balance thereof being water, said non-aqueous matter including contaminants selected from the group consisting of in the respective indicated minimum amounts: Contaminant Minimum amount present (parts by weight per mil- lion total composition) ______________________________________ Chrome (trivalent) ions 10. Chrome (hexavalent) ions 5.0 Copper ions 3.0 Cyanide ions 2.0 Iron ions 15.0 Lead ions 0.1 Oil (hydrocarbon) 100. Phenol 0.5 Zinc ions 2.0 ______________________________________ B. agitating the resulting mixture for a time ranging from about 20 minutes to 4 hours, C. mixing with the so-agitated mixture from about 500 to 5000 parts per million (based on total composition) of calcium hydroxide, said calcium hydroxide being comprised initially of particles not greater than about 250μ, D. agitating the resulting mixture for a time ranging from about 20 minutes to 4 hours, and E. continuously passing the resulting mixture over cylindrical outer surface portions of a horizontally rotating drum of a vacuum filter assembly, said surface portions being coated with a layer of substantially completely water-insoluble, inert, particulate material having a particle size below about 250μ while simultaneously continuously drawing aqueous portions of said resulting mixture through said surface portions and also continuously removing along a longitudinal position of said rotating drum the filter cake deposited on said outer surface portions thereof.