Investigation of Filtration Mechanisms Involved in the Removal of Engineering Nanomaterial From Drinking Water
- Author(s): CHEN, CHEN
- Advisor(s): Walker, Sharon L
- et al.
The overarching goal of this study was to systematically investigate how engineered particles behave in engineered filters under a range of relevant solution chemistry conditions. Specifically, the approach was to conduct a combination of fundamental and applied experiments, looking at engineered particles transport in idealized conditions, followed by those simulating actual scenarios in the filtration stage of drinking water treatment. It was confirmed that the leading factors in engineered particles destabilization which leads to their removal include the type and concentrations of salts in solution, and the process operating conditions (ionic strength and coagulant residual). Ultimately, through the systematic variation of these parameters in the proposed micromodel experiments described below, the conditions for optimal engineered particles destabilization and removal was determined.
This dissertation work has allowed for the following observations. In the 2D micromodel, the removal efficiency of latex nanoparticles and food grade TiO2 in filtration is sensitive to the particle aggregate size, surface charge, and surface composition. The model was built to show single collector removal efficiency as a function of particle size and ionic strength, as well as predict the behavior or deposition location on collector of any nanoparticles entering the filtration system in order to improve the field of environmental nanotechnology. Furthermore, the predictions generated from the present work parallel those of the constricted 3D model, for instance, the collector size and average velocity. Ultimately, this research could be applied in place of 3D columns when designing filters for water and wastewater treatment.
Finally, the role of coagulant residual, TiO2 structure, and solution chemistry on the removal efficiency were studied as well in simulated water (AGW and ASW). Results from this study indicate that for all TiO2 suspensions, the greater coagulant residual concentrations increased the removal efficiency up until 0.5 mg/L alum, above that threshold the effect of coagulant residual were negligible. This collection of studies provides critical insights into the importance of understanding particles size and coagulant residual concentrations more impactful and in realistic environments. These studies demonstrate the need to update more tests such that they more
accurately reflect real exposure scenarios simulating environmental conditions.