Determination of Decay Rate of Pollution in the Talar and Babolrood Rivers

Accurate estimation of pollution decay coefficient is due to its effect on the oxygen consumption of the river’s solution of important issue, in managing the quality of water resources. The main purpose of this paper is to determine the decay factor of two rivers of Iran, named Talar and Babolrood Rivers. It has been done by measuring the field and elucidating the common empirical equations in two seasons of spring and summer. The qualitative parameters including DO, BOD, pH, EC, nitrate, phosphate and temperature in Talar River were measured in 5 sections of a total length of 4 km long, and in Babolrood River in 3 sections at a total length of 2.8 km, in May and August 2018. Then the decomposition coefficient was estimated using Streeter-Phelps Analytic Model. DO and BOD values were also analyzed in both spring and summer seasons. Based on the results in both case studies, the decay rate in summer was more than spring. The decay rate in Talar River was calculated equal to 1.57 in spring and 6.11 in summer, and in Babolrood, spring was 1.2 and in the summer was 8.34 (1/ day). Also, based on the slope changes, the dissolved oxygen content in both rivers increased in spring and decreased in the summer. In Talar River the BOD was equal to 4.34, in spring and 7.44 mg per liter in summer, and in Babolrood River in spring was equal to 2.5 and in the summer equal to 3.2 mg per liter.