Because of the unacceptably high color and chlorine demand in surface waters at some remote U. S. Air Force radar sites in Alaska, a method was sought to remove these objectionable characteristics. Carbon filters and chemical treatment have proved either ineffective or too expensive. Treatment with hypochlorite was shown to be effective and acceptable in the laboratory, where samples showing from 40 to 70 units of color were successfully treated by chlorine doses ranging from 10 to 40 mg/1. The rate of color removal was faster at the higher doses; however, the chlorine residuals persisted for longer periods of time.
A practical method was sought for removing the unacceptably high color and chlorine demand from the surface water source used at Kotzebue Air Force Site. Earlier laboratory tests of this water had indicated that treatment with 10 to 40 ppm chlorine would produce satisfactory water, with 95% color removal. Field tests were conducted at the site in 1962 and 1963. Treatment with 32 ppm chlorine reduced color from 70 cobalt units to 10-15 units in 24 days, with a final chlorine residual of 2 ppm. Treatment with 21 ppm chlorine reduced color to 20 units in 82 days, at which time the chlorine residual was zero and recoloration began. Although results of the field tests did not entirely agree with laboratory findings, the 32 ppm chlor:ine dose was found to be a satisfactory, simple and practical method of treatment. Reduction of chlorine residual to an acceptable level occurred within 24 days following treatment.