Saving on Energy of and Determining the Best Location of Water Treatment Plant along Rivers Depending on the Effect of Broad Crested Weir on Dissolved Oxygen Concentrations in Water

Abstract

Abstrac t—This research is concerned with studying the effect of installing a weir on dissolved oxygen (DO) concentrations in water at different water depths. The study was done using a laboratory flume to be under controlled conditions; i.e constant temperature and no pollution sources. Then a mathematical simulation part is done – using Streeter-Phelps equation- to the study to relate it to real life conditions and thus determine where is the best location to install a water treatment plant on a river. Although many studies were done on examining the effect of hydraulic structures on air entrainment in water, bubbles captures in water, rate of transfer of oxygen to the water, rarely was the direct effect of hydraulic structures on dissolved oxygen concentration values in water investigated. This study will be investigating the effect of broad crested trapezoidal weirs on the dissolved oxygen (DO) in water at different longitudinal stations along the same water streamline; as well as, at different water depths. The study was done on a flume in the hydraulics laboratory at the American University in Cairo. It was found that installing the weir increased the values of the DO in water (comparing its upstream side with the downstream side) by an average of 5.3% comparing all depths. It was also found that installing a weir on a river will result in shortening the time the DO takes to recover after a pollutant was dropped in a river by 39.5%.