Geogenic versus Industrial Sources of Hexavalent Chromium
Chromium-6 in Arid, Alkaline Aquifers
Hexavalent chromium, also known as chromium(VI) or Cr(VI), can naturally occur in groundwater, particularly in arid and alkaline conditions common to parts of Fremont County, Wyoming. Such geogenic sources differ from industrial ones linked to metal plating or manufacturing.
Riverton's Surface Water Supply
The City of Riverton's water comes from surface sources, which typically carry lower risk of industrial chromium contamination than wells near industrial sites, but monitoring is essential.
Pathways for Chromium-6 into Water Systems in Fremont County
From Aquifers to the Distribution Network
Chromium-6 enters water systems through natural leaching from soils and rocks or from human activities. In Riverton, public water system monitoring has detected chromium-6 in treated water, indicating its movement through the source and treatment processes.
Role of Surface Water Sources
As Riverton uses surface water, chromium-6 presence reflects upstream environmental conditions and treatment efficacy rather than groundwater characteristics.
Interpreting Detections, Medians, and Ranges in Local Sampling
Understanding 'Detected' in EPA Records
Of 33 chromium-6 measurements in Riverton’s system data collected from 2013 to 2015, 4 showed concentrations above the reporting level of 0.03 micrograms per litre (ppb). 'Detected' means measurable, not that levels are hazardous or legally exceeded.
Median and Maximum Levels Measured
The median concentration of detected readings was 0.0509 ppb, with a highest measured value of 0.079 ppb. These figures fall well below the total chromium maximum contaminant level (MCL) of 100 ppb. No federal MCL specifically exists for chromium-6.
Seasonal and Multi-Year Variation Shown in Monitoring Data
Sampling Period and Frequency
The recorded data span from February 5, 2013, to August 5, 2013. This short time frame captures some seasonal variation in chromium-6 detected in treated water but not long-term trends.
How Concentrations Vary Over Time
Variations in chromium-6 detections may result from changes in source water quality, treatment performance, and environmental factors affecting chromium solubility and transport.
Differentiating Chromium-6 from Related Water Quality Issues
Distinction from Total Chromium Measurements
Total chromium measurements in this system showed no detections above 0.2 ppb reporting level, emphasizing the specific focus on chromium-6 as a subset of chromium species.
Chromium-6 Versus Other Metals
Chromium-6 behaves differently than metals like iron or manganese, with unique health and aesthetic considerations that require targeted management approaches.
Comparing Ion Exchange and Reverse Osmosis for Chromium(VI) Treatment
Ion Exchange
Ion exchange uses charged resin materials to capture and remove chromium(VI) ions from water. It is effective at targeting chromium-6 specifically but requires periodic resin regeneration.
Reverse Osmosis
Reverse osmosis forces water through a semi-permeable membrane, substantially reducing chromium-6 along with many other dissolved constituents. It also produces wastewater and requires pressure appliances.
Summary
Government sampling data for Riverton's water system in Fremont County indicate that chromium-6 appears at low, measurable levels in treated surface water, without exceeding regulatory limits. To know your household’s chromium-6 concentration, a private water test is necessary. The C-Series Chromium-6 Filter ships ready to configure and offers one documented approach to addressing chromium(VI) concerns after existing equipment fails.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2013-08-05. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for City of Riverton (WY5600047), WY: 66 results across 2 listed contaminants, 4 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L