Environmental Loading Patterns of Emerging Contaminants in Reclaimed Waste Water.

The reuse of treated wastewater for groundwater recharge is an effective way to provide advanced treatment and water storage in the desert southwest. Contaminants such as human drugs, found in treated effluent, have been identified as a potential problem for use of this water. The town of Gilbert, Arizona maintains a 28.3 ha facility designed to recharge 15,150 m³ day^-1 through recharge basins constructed on native soil previously used for agricultural production. Average infiltration rates at the facility are 0.1 m day^-1 resulting in a total annual application of more than 5.5 X 10⁶ m³ or the equivalent of 20 m of water infiltrated to groundwater. The water used for infiltration is from a tertiary treatment facility that treats municipal wastewater from a residential community with a population of approximately 200,000. Incoming water was collected and analyzed for a suite of pharmaceuticals. Composite samples were collected for a week at five different times throughout the year. Pharmaceuticals were concentrated from the water samples using solid phase extraction and analysis was carried out using LC-MS-MS. Temporal patterns of pharmaceutical loading rates are reported using daily, weekly and seasonal time scales for the recharge facility.