different types of poor quality water of three different turbidity ranges (5-7, 50-54 and 93-97 ntu) were prepared by adding stream sediments, digested sludge and raw sludge to stream water different concentrations of iodine (from 1.0 to 10 mg/l) were employed to inactivate e. coli in these samples at three phs (6.0, 7.5 and 9.0) and three temperatures (5, 20 and 35 $degree$ c). the results obtained were compared with those of an arbitrarily selected standard of 1.0 mg/l chlorine. under all the conditions, for which dosages of 3.0 mg/l iodine were used in the samples containing stream sediments, a water with virtually no e. coli was obtained within a 30 min contact time. for the samples containing digested sludge, a dosage of 8.0 mg/l iodine was required to achieve the same quality water, whereas for the samples containing raw sludge, a dosage of 10 mg/l was only sufficient at the lowest investigated turbidities (5-7 ntu). disinfectant capabilities of both iodine and chlorine declined with increasing temperature, ph and turbidity. the efficiency of 1.0 mg/l chlorine was slightly better that of iodine in the samples containing stream sediments, but in the samples containing digested sludge and raw sludge the efficiency of iodine was to be found better than that of the chlorine especially at the higher temperature and ph values. correlations were obtained between percentage removal of e coli, the amount of disinfectant employed, the temperature and the quality of the water represented by ph and total oxidized carbon level. (author abstract) ref