Effect of open drain hydraulic cross sections changes on the quality of water passing through it

EGYPT has a history of nearly 7000 years in practicing irrigation. Except the Nile river, every bit of the Egyptian irrigation and drainage system is human made. Since there is no equal attention to drinking water and sanitation sectors, enormous quantities of polluted water discharged into agricultural open drains system. The limited water resources and low efficiency of irrigation system forced the users at tertiary canal tail ends to irrigate from the agricultural open drains. The agricultural open drains are polluted from the raw wastewater and solid wastes from urban areas, industrial raw wastewater, agricultural drainage and accumulation of garbage, plants and dead animals.As a result of the agricultural open drains continuous flow water and their independent on the regular irrigation water rotations, there is no effective way to reduce using it. Irrigation from open drains became an irrigation sub-system posing a threat to the environment.Several studies have been carried out to control pollution in open drains. They proposed full operation of wastewater treatment plants at all cities and towns along the open drains or construction a suitable aquatic treatment system. They are all inapplicable choices because of the costs and the open drains levels.The research work in this thesis aimed to measuring the effect of self purification capacities due to the hydraulic cross sections changes in open drains. To investigate such a relation, two experimental reaches were selected at Bahr El Baqar open drain from KM 52 to KM 43.9 and El Qalyoubeia open drain from KM 26 to KM 25.650. The experimental works were divided into two stages. The first stage was done during the period (January 2000-December 2001) in Bahr El Baqar open drain experimental reach. The second stage was done during the period (June 2006-August 2006) in El Qalyoubeia open drain experimental reach.Results of the first stage showed strong correlations coefficients comprised all the studied parameters. BOD and COD removal rates are oppositely proportion to flow velocities, depths, hydraulic radiuses and discharges. BOD removal rates ranged between3.52and 0.11 1/day. COD removal rates ranged between 2.89 and 0.12 1/day. The flow depths ranged between2.62 and 2.31 m, velocities ranged between 0.53 and 0.47 m/sec, hydraulic radiuses ranged between 2.67 and 2.36 m and discharges ranged between 8010144 and 6566400 m3/day.Results of the second stage before dredging showed strong correlations coefficients comprised all the studied parameters. COD removal rates are oppositely proportion to flow velocities, depths, hydraulic radiuses and discharges. COD removal rates range between 5.28 and 2.34 1/day. The flow depths ranged between 1.68 and 1.33 m, velocities ranged between 0.52 and 0.41 m/sec, hydraulic radiuses ranged between 1.54 and 1.26 m and discharges ranged between 1592352 and 992736 m3/day.Results of the second stage after dredging showed positive correlations coefficients comprised all the studied parameters. Second stage after dredging correlations coefficients are not conclusive because these parameters ranged between weak to strong.