ENHANCED COD ELIMINATION AND COLOR STRIPP ING BY OZONE TREATMENT OF BIOLOGICALLY TREATED MILL EFFLUENTS

Laboratory trials have been conducted to reduce the residual COD and t o improve colour stripping in biologically treated effluents by means of O-3 and O-3/UV treatment with varied temperatures and pH's. For spe cific O-3 consumption rates < 3 g O-3/g eliminated GOD, COD eliminatio n rates oi up to 85 % and DOC elimination rates up to 64 % were achiev ed. Combined use of O-3 and UV as well as an O-3 treatment at pH's > 9 or at 40 degrees C were found to increase O-3 consumption levels. Dep ending on the set target, O-3 treatment gives a more or less complete colour stripping al reasonable costs. Depending on the original colour intensity and the desired results, ozone amounts of 20-80 mg consumed ozone/l waste water are normally sufficient. in effluents meeting cer tain boundary conditions in terms of COD and BOD5/COD ratios, the bioa vailability can be enhanced to allow additional biological treatment. Cost estimates have revealed that in comparison to current advanced tr eatment techniques, such as by adsorption or flocculation/precipitatio n, ozone treatment provides an economically viable alternative under c ertain conditions.