Understanding Bexar County's Water Source and Supply
The residents of Bexar County receive their drinking water primarily from the San Antonio Water System (SAWS), a community water system that serves over 2.6 million people with surface water sources. This water undergoes treatment and testing before reaching the taps of more than 880,000 connections across the area.
The Purpose and Limits of the UCMR3 Survey for Chromium-6
The third Unregulated Contaminant Monitoring Rule (UCMR3), conducted by the EPA between 2013 and 2015, included testing for chromium-6 (also known as hexavalent chromium or chromium(VI)) in community water systems such as SAWS. The goal was to understand nationwide occurrence and concentrations of this contaminant in public water supplies. For SAWS, 145 results were reported; chromium-6 was detected above the reporting level (0.03 micrograms per litre or parts per billion) in 136 samples. The highest reported measurement for chromium-6 was 1.8 ppb, with a median detection of 0.096 ppb.
It is important to note that these results are system-wide and represent the water before it reaches any particular household. These detections are measurements only, not violations or indications of unsafe water. For precise knowledge of your home's water quality, conducting a specific test at your tap is necessary.
Sources of Hexavalent Chromium: Geogenic vs Industrial
Chromium-6 can occur naturally (geogenic) in certain groundwater conditions that are arid and alkaline, which can be relevant in parts of Texas. Alternatively, it may come from industrial activities, such as metal plating, but in the case of Bexar County's main water supply, testing focuses on surface water sources managed by public utilities. Understanding the origin helps inform treatment choices.
Gathering Essential Information Before Treatment Decisions
Before considering treatment options for chromium(VI), it is recommended that homeowners:
- Obtain their own water test results, specifically measuring chromium-6 concentrations at the tap.
- Know the water source type (well or public supply) for their household.
- Understand any other water quality factors that might influence treatment needs.
Having this information ready will support selecting an appropriate water treatment approach tailored to chromium-6 levels and overall water demand.
Potential Effects of Untreated Chromium-6 in Water Over Time
Chromium-6 is a specific oxidation state of chromium that differs from total chromium measurements. While no health-based EPA violations have been recorded for SAWS, prolonged exposure to chromium-6 in drinking water at elevated levels is a subject of ongoing scientific evaluation. Untreated chromium-6 presence can affect water aesthetics and may contribute to health risks depending on concentration and exposure duration.
Comparing Ion Exchange and Reverse Osmosis for Chromium(VI) Management
When considering treatment technologies for chromium-6, ion exchange and reverse osmosis (RO) are two commonly used methods with different operational principles:
- Ion Exchange: This process can selectively remove chromium(VI) ions by exchanging them with other ions on resin beads. Ion exchange systems can be designed to handle specific contaminants efficiently depending on water chemistry.
- Reverse Osmosis: RO uses a semipermeable membrane to physically separate chromium(VI) and other dissolved solids from water. This method typically removes a broad range of contaminants but requires consideration of water pressure and waste water.
Choosing between these methods depends on factors such as chromium-6 concentration, water demand, and other water quality parameters.
Why Total Chromium Results Are Not Enough to Assess Chromium-6 Presence
Testing often measures total chromium (both trivalent chromium, Cr(III), and hexavalent chromium, Cr(VI)) combined. However, the toxicity and treatment response vary significantly between these two forms. Total chromium results do not specify chromium-6 levels. Therefore, a test that specifically targets hexavalent chromium is essential for a clear understanding and appropriate treatment plan.
For context, SAWS reported a highest total chromium measurement of 6.3 micrograms per litre with a median of 0.26 micrograms per litre, both well below the federal maximum contaminant level for total chromium of 100 micrograms per litre.
Effective Treatment Aligned with Your Chromium-6 Demand
For households in Bexar County choosing how to address chromium-6 in their water supply, the C-Series Chromium-6 Filter offers a documented technology designed to meet specific chromium(VI) demand figures measured at the point of use. This system ships ready to configure for your home's water treatment needs, providing a targeted approach to managing chromium-6 concentrations consistent with your water testing results.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-12-04. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for San Antonio Water System (TX0150018), TX: 290 results across 2 listed contaminants, 229 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L