Reverse Osmosis (RO) Treatment for Secondary Contaminants in Brackish Groundwater at a Public Water System (PWS)
The drought in Texas has diminished the availability of water in some of the sources in the state. As a result, public water systems (PWSs) are evaluating water sources that have not previously been considered, such as brackish groundwater. The brackish water sources often need treatment to be used as drinking water, and desalination is the most typical treatment utilized by water systems. When facing a water shortage, the time required to place a new water source into service can be critical. As a response, the TCEQ has developed a streamlined brackish-groundwater-desalination-project review process while still ensuring that the required quality and quantity of drinking water are provided. The TCEQ will therefore allow the use of computer modeling in lieu of on-site pilot studies for reverse osmosis (RO) filtration treatment for secondary contaminants from a groundwater source.
Read the engineer’s directions for requesting an exception for reverse osmosis. The staff guidance document describes the information the PWS’s professional engineer will need to submit in order for the TCEQ to review the modeling data.
How is this different than before?
Previously, for the TCEQ to approve alternative treatments, such as RO, a licensed professional engineer was required to provide pilot test data, or data collected at similar full-scale operations, to demonstrate that the proposed treatment will produce water that meets the requirement of Title 30 TAC Chapter 290, Subchapter F: Drinking Water Standards Governing Water Quality and Reporting Requirement for Public Water Systems. With the release of the new staff guidance document, the public water system, through their licensed professional engineer, can receive approval from the TCEQ based on a streamlined approach:
- The staff guidance allows the use of computer modeling in lieu of on-site pilot studies for RO filtration treatment for secondary contaminants from a groundwater source. The computer model results will provide the capacity and water quality information necessary for TCEQ to approve an exception. Computer modeling data will provide the design basis for approving the exception to use RO treatment for brackish groundwater. The TCEQ will still allow the submittal of pilot data to support the exception request if the engineer determines that pilot testing better addresses the needs of the water system.
- To further assist drought stricken communities, the TCEQ will offer concurrent reviews of plans, specifications and exception requests. The Professional Engineer should submit both the exception request (with the computer modeling data) and the plans and specifications at the same time for review using the plan review submittal form.
Which projects can use computer models instead of on-site pilot studies?
Groundwater sources with elevated secondary contaminants (such as total dissolved solids) would be eligible to use computer models instead of on-site pilot studies. This would exclude sources deemed groundwater under the influence of surface water because the computer models do not model for biological contaminants. The computer models also do not include, or currently do not accurately model, primary contaminants (such as arsenic).
How did the TCEQ decide to allow computer models instead of on-site pilot studies?
The TCEQ worked with a group of stakeholders to identify potential alternatives to pilot studies for brackish groundwater RO membrane filtration treatment and provide solutions for the development of additional water supply options for the state. Based on input from stakeholders on the reliability of computer modeling for brackish groundwater RO treatment plant design, TCEQ has determined that these computer models can effectively demonstrate membrane performance for a specific RO configuration. See the agendas and minutes for the stakeholder meetings.
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