When you receive a laboratory test report for chromium in water, it often lists separate measurements for hexavalent chromium (chromium-6) and total chromium. For North Kona, Hawaii County's public water system, data from the EPA's Unregulated Contaminant Monitoring Rule (UCMR3) shows all samples detecting chromium-6 above 0.03 micrograms per liter (µg/L), with values ranging up to 2.9 µg/L. Total chromium was similarly found, reaching up to 2.8 µg/L, well below the federal maximum contaminant level of 100 µg/L for total chromium. This information pertains to the municipal system serving nearly 30,000 residents and does not reflect individual home water quality.
How Oxidation State Changes Between the Well, the Distribution Main, and the Tap
Chromium in water exists primarily in two oxidation states: trivalent chromium (chromium-3) and hexavalent chromium (chromium-6). The form can shift due to chemical reactions as water moves from the groundwater source through the distribution system to your tap. Factors such as oxygen levels, pH, and the presence of other chemicals affect whether chromium-6 remains stable or converts to chromium-3, which has different properties. This means the chromium-6 concentration present in groundwater may not be the same as what reaches your faucet.
Trivalent Versus Hexavalent Chromium: Why a Total-Chromium Result Cannot Answer the Question
Total chromium measurements include all forms combined but do not specify the proportions of chromium-3 and chromium-6. Since chromium-6 and chromium-3 differ in their chemical behavior and potential health implications, knowing only the total chromium concentration does not provide a clear picture. For accurate assessment and targeted treatment, separate testing for hexavalent chromium is necessary.
How the Constituent Enters Groundwater or the Distribution System in This Region
In North Kona, the public water system sources its water from groundwater, where hexavalent chromium presence is influenced by natural geochemical conditions. The pattern of chromium-6 detection at moderate levels, as reported by EPA monitoring, reflects this geological context rather than industrial pollution. Chromium can also transform as it interacts with minerals and organic matter underground or within the distribution piping.
What Happens When This Problem Is Left Untreated for Years, Stated Without Exaggeration
Without treatment targeting chromium-6, it may persist in tap water at concentrations similar to those detected in the distribution system. Over time, this can affect water aesthetics such as taste and potentially cause minor staining of fixtures. Because the North Kona system has no health-based violations recorded, untreated chromium-6 at measured levels does not constitute a demonstrated safety concern. However, some households may prefer to reduce chromium-6 for additional peace of mind.
How Ion Exchange and Reverse Osmosis Differ in What They Do to Chromium(VI) Specifically
Two common technical approaches for addressing chromium-6 in residential water are ion exchange and reverse osmosis. Ion exchange uses resin beads that attract and hold chromium-6 ions, effectively lowering chromium-6 concentration over time before resin replacement or regeneration. Reverse osmosis pushes water through a semipermeable membrane, filtering out chromium-6 along with other dissolved solids. Ion exchange typically operates with lower water waste and may require less ongoing maintenance, while reverse osmosis can reduce a broader spectrum of contaminants, including chromium-6, while also impacting water hardness and mineral content.
For households in North Kona balancing these options, product solutions such as the Autotrol Chromium-6 Filter ship ready to configure and utilize ion exchange technology optimized for chromium-6. This equipment offers a documented approach tailored to the characteristics of local water, supporting effective chromium-6 treatment.
Closing
The data presented regarding chromium-6 in North Kona’s public water supply comes from EPA’s UCMR3 monitoring of groundwater sources serving nearly 30,000 people via more than 10,000 connections. No health-based violations have been recorded for chromium-6 in this system. For homeowners wishing to understand their own water quality, specific laboratory testing of household taps is essential. More details and official records are available through the EPA’s Safe Drinking Water Information System.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-01-12. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for North Kona (HI0000131), HI: 52 results across 2 listed contaminants, 52 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L
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