Experimental study of the effect of urban wastewater treatment on the process of deposition and consolidation of cohesive sediments in water transfer systems

Consolidation of cohesive sediments has an effective role in the critical stresses of erosion of sediments deposited in reservoirs and water channels. Knowing the behavior of fine-grained sediments can have a significant effect on the operation and maintenance of water structures. Therefore, in this study, the effect of urban wastewater, which is used as a renewable resource in drought conditions, is considered on the deposition and consolidation of cohesive sediments in transmission systems. For this purpose, the stages of consolidation of sediments were performed for four time intervals of 1, 3, 14 and 28 days using deposition columns and for three concentrations of 0, 30 and 60% wastewater and
for three initial concentrations of sediments of 200, 300 and 400 g/l. The results showed that the initial concentration increases with the sediment deposition depth (H/H0) and the initial concentration of sediments up to 300 g / l affects the consolidation process. Thus there is no significant difference between the initial concentrations of 300 to 400 g / l. It was also found that the consolidation stages in pure water and the fluid containing 60% of the wastewater are very close together, but fluid containing 30% of the wastewater shows a different behavior. By analyzing the percentage of exchangeable sodium (ESP) for different percentages of wastewater and at the end of 28 days consolidation, it was
found that the change in H/H0 for different percentages of the wastewater is the same with changes in ESP. The cause of the dispersal phenomenon in a fluid containing 30% of the wastewater can be explained by fluid chemistry and substitution of calcium instead of sodium ion in clay particles.