Investigation of Seasonal Self-purification Variations of Karun River, Iran

Evaluation of a river self-purification capacity provides required information for a sustainable management of the river receiving pollutants. The main target of this paper is to study and predict the seasonal variation of self-purification capacity of Karun River, IRAN. Dissolved oxygen (DO), BOD, nitrate and pathogens were the main quality parameters, which were considered in this paper. To achieve this aim, a length of 113 km of the river was simulated using QUAL2Kw model and calibrated and verified using field measured data in 2010. The above mentioned datasets were used also to determine the critical periods of self-purification phenomenon, involving the model for BOD, nitrate and pathogen parameters. Furthermore, three scenarios were supposed and considered, including, 30% reduction in the waste waters flow, increasing the river monthly flow by 30% and finally decrement of the waste waters concentrations by 30%. The above mentioned scenarios were assumed in order to enhance the water quality of the river, during the months with no standard limits. Results indicated that, the decrease of nitrate in January and February and the decrease of BOD for all month except October up to 30 %, have had the most positive effects on river water quality. The 30% decrease of waste waters flow rate containing pathogens had the most positive effects on the river water quality.