McAllen Public Utility Reuse And Water Supply Planning

Plummer performed a potable water reclaimed water feasibility study for McAllen Public Utility (MPU) under the United States Bureau of Reclamation Title XVI Water Reclamation and Reuse Program. The objective of the study was to evaluate alternative water supply options for MPU with a focus on potential direct potable reuse, indirect potable reuse, and brackish groundwater reclamation opportunities. At the time of the report, MPU obtained drinking water almost exclusively from the Rio Grande. Additionally, demands were projected to exceed supplies between 2030 and 2035. MPU’s main goal for the project was to evaluate water supply strategies that would mitigate the projected supply shortage while also diversifying its water supply portfolio to reduce dependence on the Rio Grande. 

Plummer evaluated a number of reclaimed water strategies to mitigate the projected future supply deficit and compared these strategies against other traditional water supply options available to MPU. Nine reclaimed water strategies were initially selected for consideration, but a screening workshop with City staff reduced the list to one direct potable reuse option, two brackish groundwater reclamation options, and one hybrid option. The four reclaimed water options were then evaluated in detail by assembling preliminary treatment trains based on effluent water quality from MPU’s wastewater treatment plant and available groundwater quality data. For the options that incorporated reverse osmosis treatment, Plummer also evaluated disposal methods for the residual concentrate stream. 

Plummer prepared opinions of probable construction cost and annual operating and maintenance costs for each of the reclaimed water strategies. Ultimately, Plummer recommended that the City pursue brackish groundwater blending initially and brackish groundwater desalination later in a second phase.