If You're Considering Flow Rate Alone When Choosing a Carbon Filter
A common misunderstanding is to select a granular activated carbon filter based only on how much water it can handle per minute. However, when treating volatile organic compounds (VOCs) like those monitored in Wailuku's water system, the time water spends in contact with the filter is more critical than flow rate alone.
VOCs are solvent compounds such as 1,1-dichloroethane, chloromethane, and MTBE, which can be present in water supplies. Removing them effectively requires enough contact time with activated carbon media to adsorb these compounds. Selecting equipment based on flow rate without regard to contact time can reduce effectiveness, as short contact times may not allow the filter to capture VOCs adequately.
The C-Series VOCs & Industrial Chemicals Filter ships ready to configure with design features emphasizing contact time, ensuring better treatment performance where VOC presence or concern exists.
If You Interpret 'Not Detected' as Meaning the Compound Isn't There
Laboratories report VOCs as 'not detected' when their instruments do not measure concentrations above specific method detection limits, such as 0.03 micrograms per litre (µg/L) for 1,1-dichloroethane or 5.0 µg/L for MTBE. These figures represent the smallest concentration reliably measurable, not the absence of the compound.
For example, EPA data on Wailuku's public water system from 2013-2015 showed no detected levels above these reporting limits for several VOCs. This means any presence would be below those limits, not necessarily zero. Understanding this helps in deciding whether to pursue further testing of your household water and selecting appropriate treatment technology that can address low levels if needed.
If You Know That Seasonal Water-Table Changes Affect VOC Plume Position
VOCs originate from sources that can form plumes underground. Seasonal shifts in water tables can cause these solvent plumes to move relative to a well's intake location. In surface-supplied systems like Wailuku’s, this dynamic means VOC concentrations can fluctuate over time and place.
Households considering water treatment should keep in mind that a single VOC test provides a snapshot that may not represent future conditions. Because the public water system covers over 20,000 connections for about 74,500 people, wide area sampling reflects overall source conditions but cannot define individual household tap water VOC levels.
If You Are Reading Terms Like 'Detected', 'Median', and 'Range' in Public Sampling Records
The reported data for VOCs come from EPA's Unregulated Contaminant Monitoring Rule (UCMR3) and include terms like 'detected', 'median', and 'range' as statistical summaries:
- Detected means the compound was measured above the laboratory’s reporting level.
- Median is the middle value when all detected results are ordered from lowest to highest, providing a central tendency.
- Range spans from the lowest to the highest detected value in the dataset.
For Wailuku's system, the record shows no detections above reporting limits for VOCs monitored, implying all measurements were below these thresholds during 2013 to 2015 sampling.
If You Want a Practical Example of Interpreting Median and Range Data
Imagine a homeowner examining the EPA water system record. For MTBE, the system had 22 samples with zero detections above 5.0 micrograms per litre (parts per billion). The median and range for detected values do not appear because there were no detections above that level.
This does not guarantee the homeowner's tap water has zero MTBE; it only confirms that large concentrations were not measured in the system's samples over that period. Home testing is needed to establish specific household water quality, especially if there is concern about solvents or VOCs.
Closing Thoughts
The EPA’s public water system record for Wailuku, Maui County, reflects broad monitoring of volatile organic compounds in the surface water source serving more than 74,000 people. No health-based violations related to VOCs have been reported for the system, indicating regulatory compliance and general source water quality.
Households weighing technical approaches for VOC treatment might consider the C-Series VOCs & Industrial Chemicals Filter, designed for effective VOC removal through attention to contact time and suitability for residential use. For precise water quality at your tap, specific testing is recommended to guide treatment decisions.
For more detailed system data, the EPA’s SDWIS public water system record for Wailuku is available at the EPA website.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-02-20. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Wailuku (HI0000212), HI: 280 results across 7 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level