TEMPORAL AND SPATIAL VARIATIONS AND DECAY RATES OF E. coli IN RIVER SEDIMENT

Abstract

Though the Serin River is used by the community as a source of drinking water, laundry and recreation, little is known about the bacterial contamination in the sediment. Therefore, in this study, the concentration of E. coli in the sediment was determined at nine stations in seven sampling trips and the decay rate of E. coli in the river sediment was determined in the laboratory. Results of E. coli count in the sediment shows high variation among the trips especially at stations near human activities. The highest and second highest mean populations were recorded in the sediment near human settlements. E. coli counts ranged from 4.0 to 7.2 log CFU/g and between consecutive trips mean rate of change of E. coli in the sediment ranged from -0.2 to 0.2log CFU/g per day. Contaminations of the tributary with animal farms varied likely due to oxidation pond discharge. Laboratory studies showed that decay rate of E. coli in the river sediments ranged from 0.223 to 0.435 d-1 and the first order decay model fitted the survival very well (R-2:: 0.972-0.995) except in the sediment with lower pH and high temperature. The high count of E. coli in the sediment could render the water unsuitable for drinking and water contact recreation as it could be resuspended during disturbances.