THE IMPACTS OF RECYCLED WATER IRRIGATION IN SAN ANTONIO, TX

San Antonio has implemented the use of recycled water as a supply for municipal irrigation systems, power plant cooling, and to augment flow of the San Antonio River. Supplementing municipal water supplies with recycled water is becoming more common in urban areas, but is limited in scope due to public concerns, and is not typically used for direct aquifer recharge or agricultural irrigation. Proponents of recycled water use argue that these limitations are based on public perception alone, and that scientific findings show little risk of biological or chemical contamination. However, recycled water generally has relatively high concentrations of salts and nitrate, which may impact the ability of soil to retain nutrients and sustain some microbial populations.

The effect recycled water irrigation has on soil microbial community composition and leachate chemistry was examined in this work. Triplicate samples of St. Augustine sod were watered with either recycled water, tap water, or deionized water. Qualitative and quantitative analysis of leachate included leachate volume, turbidity, pH, cation analysis, as well as spectroscopically-determined anion and contaminant concentrations. Culture-independent techniques were used for microbial community analysis. Leachate chemistry results indicate higher phosphate and sulfate concentrations when recycled water is used, but does not represent greater leaching than tap water. DGGE results, which will show differences in microbial community composition, are still pending, but differences in DNA extraction efficiency suggests that microbial abundance and/or diversity vary between treatments. Our data supports the use of recycle water in aquifer recharge zones as water quality will not undergo significant chemical changes. Further testing will help to determine if the use of recycled water in agricultural irrigation impacts productivity.