TREATING CONTAMINATED WATER: PREDICTING REACTIVITIES OF AQUEOUS ORGANIC CONTAMINANTS WITH HYDRATED ELECTRONS, AND DEVELOPMENT OF A BIOGARDEN TO MANAGE GREYWATER DISCHARGE IN MONTEVERDE, COSTA RICA

Advanced reduction processes (ARPs) that generate highly reactive solvated electrons (e-aq) are a promising method for the destruction of conventional and emerging aqueous organic contaminants. While there is a large database of contaminant reactivity with e-aq in the literature, there is little information on the detailed elementary mechanisms for reduction of multifunctional group compounds and the impact of those functional groups on reactivity. As it is difficult to determine specific mechanisms through experiments and time consuming to measure reactivity, the development of computational approaches to elucidate mechanisms and predict reactivity is becoming increasingly important. In chapter 2, I use density functional theory to calculate the aqueous-phase one electron reduction potential (E∘red,aq) of 251 diverse conventional organic compounds. I then use E∘red,aq to investigate the occurrence of three possible reduction mechanisms (association, concerted cleavage, stepwise cleavage) at all reactive sites and develop linear free energy relationships (LFERs) between E∘red,aq and the experimentally measured rate constant. Using the LFERs, I predict the reactivity of the Environmental Protection Agency per- and polyfluoroalkyl substance (PFAS) priority subset (EPA-75). In chapter 3, I develop group contribution methods (GCMes) for each reduction mechanism for 262 aliphatic and aromatic organic contaminants. The GCMes effectively predict compound reactivity through chemical structure fragmentation. The LFER and GCMe tools can be used to screen thousands of organic contaminants for degradability by homogeneous and heterogeneous ARPs, along with prioritizing them for further study. Although Costa Rica has established water discharge laws, a lack of enforcement and resources has resulted in greater than 95% of all greywater discharged to the environment untreated, leading to eutrophication and an increased risk to public health. The Monteverde Zone, located at the top of the Guacimal watershed, is a key player in this issue, as greywater discharged in this zone flows downstream, impacting a large number of communities. While centralized water treatment is currently not feasible in this developing country, biogardens are an affordable, decentralized, nature-based solution to Costa Rica’s greywater problem that utilize filtration techniques, plant uptake, and microbial degradation to effectively treat greywater. In chapter 4, I design and construct a horizontal sub-surface flow biogarden system for the Centro Educacion Creativa K-12 school, located in the Monteverde Zone, that effectively treats the campus’ greywater to compliance levels. In addition to engineering a natural and effective treatment system, I use the biogarden as a local pilot project to educate the Monteverde community on the greywater issue and biogarden development