PHYSICAL-CHEMICAL TREATMENT OF WASTE EFFLUENTS FROM CANNING OF LEAFY GREEN VEGETABLES

Abstract

Suspended soilds in waste effluents from the canning of leafy green vegetables were effectively reduced by segregation and separate physical-chemical treatment of the unit wastes. Turbidity in the dunker washer effluent from spinach was reduced by treatment with 0.04 mg of an anionic polymer per liter at pH 4.0. The most concentrated effluent (from the tumbler fillers) contained 11% of the total suspended solids load and 16% of the COD in only 1.3% of the waste water flow. Treatment with 20 mg cationic polymer per liter, 80 mg ferric sulfate per liter, and 2 mg anionic polymer per liter reduced the suspended solids concentration from 1,348 mg/l to 63 mg/l—a reduction of 95%. The tumbler filler effluent from turnip greens and diced roots was treated on a pilot-scale with 70 mg cationic polymer per liter, 80 mg calcium chloride per liter and 10 mg anionic polymer per liter to reduce the suspended solids from 1,148 to 140 mg/l The composite effluent from canning of turnip greens and diced roots was treated with polymeric flocculating agents and activated carbon in a physical-chemical treatment system. The suspended solids concentration was reduced by 92% and the COD by 19% through flocculation and settling. The clarified effluent was applied to a downpass column of activated carbon which adsorbed 89% of the COD applied.