UCLA

This thesis addresses two major groundwater pollution problems: high fluoride concentrations in groundwater from matrix acidization, and release of tertiary butyl alcohol (TBA) from Leaking Underground Storage Tanks (LUSTs) into the groundwater. High fluoride concentrations are detrimental. Aluminum (Al3+) and iron (III) (Fe3+) ions in the subsurface can prevent the fluoride removal. This paper shows that calcium carbonate can precipitate 200 milligrams per liter (mg/L) of fluoride and 200 mg/L of aluminum or iron (III) in batch mode. Fluoride removals of up to 95% were achieved when dissolved calcium carbonate was used at a [Ca2+]/[F-] molar ratio of 2:1. Aluminum or iron (III) ions did not hinder, and in some instances, improved the fluoride removal. PHREEQC geochemical model was consistent with the findings.

Since the 1980’s, LUSTs have released millions of gallons of petroleum products containing TBA into the groundwater. TBA was banned in early 2000. The United States Environmental Protection Agency (EPA) considers TBA to be potentially carcinogenic to humans based on its proven carcinogenicity to animals. The State of California has a non-enforceable notification level (NL) of 12 micrograms per liter (�g/L) but has not established a maximum contaminant level (MCL) in drinking water for TBA. Toxicity, sources, and environmental transformation related to TBA are discussed; developing an MCL, addition of TBA as a contaminant of concern in the California Water Resources Control Board’s “Low Threat Closure Policy”, and developing more stringent protocols for TBA treatment are recommended.

As high as 88% of LUST sites in Southern California were closed with TBA higher than its NL between 2016 and 2019 fiscal years (FY). 25% of the time, TBA concentrations remained higher than 2,300 �g/L during 2016-2017 FY, higher than 7,600 �g/L during 2017-2018 FY, and higher than 4,434.3 �g/L during 2018-2019 FY. The maximum TBA plume lengths increased as much as 70% from 2016 to 2019. Aerobic bioremediation, currently the most effective method of treating TBA, was employed at only one site. Reducing TBA to safe levels requires specific and a targeted treatment approach.