The oxidation reduction potential distribution along Diyala river within Baghdad city

Abstract

The reach of the Diyala river just before its confluence with Tigris River south of the capital city Baghdad was taken as a case-study. Its aquatic physicochemical characteristics were investigated and its pollution status was assessed in this study according to ORP (oxidation reduction potential) levels and other parameters. This segment of Diyala river was exposed to multiple points of treated and raw municipal waste water discharges, represented by the outfalls and bypass of three wastewater treatment plants of Al-Rustimiyah.Diyala River's aquatic parameters represented by DO, BOD, COD, ORP, pH, and others were monitored and measured at nine stations along the river reach for a period of one year to assess seasonal variations. It was found that station two, which lies downstream the bypass of R3, was the most polluted station among all.With regard to the ORP concentrations, the river was classified as anoxic conditions during winter to anaerobic conditions during summer from station two and downstream. Furthermore, it has been reached that the strong odor observed on site especially during summer, might be attributed to the formation of acid and methane production that goes with the obtained low levels of ORP.The COD and BOD5 levels classified the river as medium to low strength untreated wastewater during summer at station two and the downstream stations respectively.The effect of temperature on DO and ORP was found to be reversed, while a positive nonlinear relation combined the DO concentrations with ORP levels.The COD/BOD ratio of the river was found to be 1.2, which indicates the presence of biodegradable matter at high concentrations.A statistical model relating DO concentration to BOD, ORP, EC and temperature was established. It was proved to be accurate.To sum up, Diyala River at the reach of interest was found heavily polluted. The need for an urgent makeover of the water body characteristics of the river via mechanically assisted methods was found necessary to restore its original usages and ensure public health safety.