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Microalgae from natural saline habitats in the southwestern United States were isolated and screened for rapid growth potential and ability to store intracellular neutral lipid, a precursor for renewable liquid fuel sources. After preliminary screening of isolated strains, Nitzschia communis (Rabenhorst) was selected for optimization of growth rate and lipid yield. Nitzschia communis was subjected to two media types (SERI I, II) with different major ion compositions designed to mimic natural saline groundwater aquifers in the arid Southwest. Growth rates were determined through 4 days of logarithmic growth, followed by 2 days of physiological stress (nitrogen deprivation) and subsequent measurement of neutral lipid accumulation. Poststress intracellular neutral lipid increases were documented by utilizing the fluorochrome Nile Red with fluorometric analysis and epifluorescent microscopy. Growth rate was slightly higher in SERI Type I medium, whereas lipid yield was higher in SERI Type II medium. Rapid growth and appreciable lipid yields were observed over a broad range of temperatures (20°–30° C) and specific conductances (10–70 mS·cm−1). The highest lipid yields were observed at elevated conductances (between 40 mS·cm−1 and 70 mS·cm−1). Substitution of individual salt concentrations from SERI Type II into SERI Type I medium indicated that increased lipid yield in Type I medium was associated with a reduction in MgCl2 concentration.

Frequent episodes of algal-related tastes and odors (T & O) in drinking waters in metropolitan Phoenix, Arizona prompted initiation of a three-year project in July 1999 to investigate the occurrence of T & O metabolites and to develop a comprehensive management strategy to reduce the problems in drinking water supplies in arid environments. Two metabolites, 2-methylisoborneol (MIB) and geosmin, have been identified as compounds responsible for the earthy-musty tastes and odors in water supplies. Both were detected in the water supply system, including source rivers, reservoirs, canal delivery system and water treatment plants. Higher concentrations of MIB and geosmin occurred in distribution canals than in the upstream reservoirs indicating that significant production of the T & O compounds occurs within the canal system. A baseline-monitoring program has been established for the complex water supply system, with special emphasis on the canal system. Efforts are underway to investigate possible correlations between physical/chemical parameters, algal composition and biomass, with the occurrence of MIB and geosmin. In addition, several physical and chemical treatments are planned for the canal system to reduce algal growth and related MIB and geosmin concentrations.