Defining the Mixing Zone and Dilution at Lifting Drainage Water Joints Using CORMIX Model

Background: Limited water resources with the gradual increase of water demand led to higher dependence on non-conventional water resources. The increasing pollutants in the drainage water restricted the reuse of this resource, and to maintain the quality of the fresh water, rigid laws are currently applied for mixing the drainage water with the fresh water. Such rigid laws led to hanging up the operation of many lifting stations that coasted big investment and which was lifting more than 2.0 BCM/day to the irrigation network. Mathematical models offer more flexible alternative for maintaining the water quality of the fresh water through defining the mixing zone between lifted drainage water and the receiving ambient. Cornell Mixing Zone Expert System (CORMIX) model is a mathematical simulation model, which provides the quantitative predictions for pollutants dilution. The model has three modules depending on outfall characteristics (CORMIX1, 2 and 3). CORMIX3 for surface discharge was used in this study. The model was applied to define the mixing zone between the lifted drainage water from Mehalet Rough pumping station and the fresh water in Mit Yazid canal. Two water quality (WQ) parameters were assessed; biochemical oxygen demand (BOD) and total dissolved solids (TDS). Results: The simulation results verified that the two investigated parameters met WQ standards for the Egyptian law 48/1982 at a distance of 448.36 meter and 4.46 meter respectively. As the first municipal station is 3.2 km downstream the pumping station, the lifted drainage water could be accepted regardless its low quality according to these parameters. Conclusions: The results illustrated the importance of using such model to define the suitable location for using the fresh water after mixing with point sources, and for an efficient implementation of integrated water management.