INVESTIGATING BIOLOGICAL METHODS FOR IMPROVING REVERSE OSMOSIS BASED DESALINATION OF BRACKISH GROUNDWATER IN BEXAR COUNTY, TEXAS
Determination of the brackish water source most suitable for this study was performed by evaluating the aqueous chemistry of 45 brackish groundwater wells in Bexar County, TX, along with six samples from three locations across Texas. Geochemical data was obtained from the USGS national brackish groundwater database (McMahon et al., 2016) and saturation index (SI) of minerals were calculated using PHREEQC. TDS range between 1 - 5 g/L and is composed of mainly: Na+ (270±185 mg/L), K+ (15±9 mg/L), Ca2+(274±183 mg/L), Mg2+(82±76 mg/L), total Fe (0.2± 0.3 mg/L), HCO3- (261±73 mg/L), Cl-(597 ± 738 mg/L), SO42-(1,037 ± 765 mg/L), and SiO2 (16±7 mg/L). The sample site chosen provides three stages of brackish groundwater for experimentation. This will be useful when determining viability of SRB in high TDS water. This location also had one of the highest concentrations of sulfate (446-2618 mg/L). Preliminary experiments show the sulfate reducing bacteria are most productive when provided with an external carbon source (sodium acetate) at the same molar concentration as the sulfate present in the brackish water. Both acetate and sulfate decreased over time with SRB present. Future experimentation involves expanding from low TDS samples used in the preliminary experiments to the two higher brackish samples for comparison in efficiency and survival requirements of SRB.