UC Riverside

The overall aim of this PhD research was to identify mechanisms involved in the removal of nanomaterials in conventional water treatment. This project was developed based upon the need for assessing current water treatment infrastructure, and its capacity of effectiveness in removing nanomaterials. The bulk of this dissertation investigated "primary treatment" steps of coagulation, flocculation, and sedimentation, simulated by full-scale and micro-scale jar tests. The remainder of the dissertation has been the development of a 2D micromodel flow cell to simulate the filtration stage. The model nanoparticles used in this research were primarily Degussa P25 titanium dioxide (TiO2), with select experiments using meso-2,3-dimercaptosuccinic acid coated TiO2, and fluorescently-labeled polystyrene latex microspheres.

Overall, >one-log removal was seen for the model groundwater for all coagulants at a constant dose of 50 mg/L, and across the range of particle concentrations tested (10, 25, 50, and 100 mg/L). In surface water, >90% removal was observed with FeSO4 and Al2(SO4)3, but <60% when using FeCl3. Additionally, removal was most effective at higher nanoparticle concentrations (50 and 100 mg/L) in AGW when compared to ASW. In the presence of more complex scenarios, results showed that removal was most efficient in the presence of divalent cations (Ca2+), and in the absence of NOM and nanoparticle coating, achieving >1 log removal. However, with the presence of nanoparticle coating and NOM, removal decreased to a maximum of ~80%.

Finally, a 2D micromodel flow cell was designed and fabricated to demonstrate a new tool for the investigation of nanoparticle filtration. Specifically, the micromodel allows for direct visualization of pore-scale physico-chemical processes by using an array of 2D silica cylinders through which a model nanoparticle (i.e. fluorescent nanoparticles) can be transported. Through the development of this 2D system, future studies can compare filtration phenomena to a 3D macro-scale column experiment. Thus far, this study accomplished the following 1) fabrication of micromodels and construction of the experimental set-up, 2) development of a robust cleaning protocol for micromodel re-use, 3) demonstration of technique and confirmation that filtration trends (i.e. attachment efficiency) between our micromodel and published data from column experiments can be compared.