This paper presents the Integration Study methodology, the resulting finished water goals, and the
treatment process design for the Twin Oaks Water Treatment Plant, which is part of the San Antonio Water System (SAWS) Carrizo
ASR Project. The Carrizo ASR Project is a conjunctive use water supply project that utilizes water from
the Carrizo Aquifer in South Bexar County, Texas. Phase 1 of the program consists of a new production well
field that is capable of producing 30 mgd. These initial wells will feed a new 30 mgd water treatment
plant (Twin Oaks) designed to remove high levels of dissolved iron, manganese, carbon dioxide, and
hydrogen sulfide. The treated groundwater will then be conveyed approximately 25 miles where it enters
the SAWS distribution system. Phase II of the project will increase the aquifer storage capacity of the
project to 60 mgd, and make provisions to utilize additional Carrizo Aquifer groundwater from Gonzales
County.
Since Edwards Aquifer groundwater only requires disinfection, the new Twin Oaks Water Treatment
Plant is the first potable water treatment facility to be constructed by SAWS. As described in this paper, the
design of the treatment process for this facility was influenced not only by the need to remove
contaminants from the south Bexar Carrizo groundwater, but by the recommendations of the Integration
Study, which proved that substantial treatment was also needed to reduce the possibility of water quality
impacts when the new water source is introduced into SAWS distribution system. Includes 2 references, tables, figures.