A HOMEOWNERS GUIDE TO APPROACHING THE MAXIMUM CONTAMINANT LEVEL GOAL (MCLG) FOR ARSENIC OF 0 PPB – A CASE STUDY

The US-EPA has recently decreased the maximum contaminant level (MCL) for arsenic in public drinking water from 50 to 10 parts per billion (ppb). The new 10 ppb limit falls within the “high” risk category of one in 150 people contracting cancer from long-term consumption of such water. In order to be at a “low” risk (a level of less than 1 in 10,000 risk factor for cancer), the recommended arsenic level is at or below 0.5 ppb. This level coincides more closely with the EPA's non-enforceable, health-based Maximum Contaminant Level Goal (MCLG) of 0 ppb.

This project investigates the long-term As occurrence in a private well in Orange County, North Carolina (the Piedmont) and the performance of different As treatment technologies to lower the arsenic level. The investigated private well has As levels of 4-8 ppb, however attempts were made to reduce the As to the MCLG of 0 ppb for the house. The study is based on As measurements by a high-resolution Inductively Coupled Plasma Mass-Spectrometry (ICP-MS) at Duke University with a detection limit of 0.005 ppb. This lower detection level enables us to monitor even small As variations in groundwater and the effectiveness of different treatment technologies for As remediation. In-home water filtration options included treatment with a whole house water softener, installation of a reverse osmosis system attached to the kitchen sink, small ferric iron filters installed along the inflow to the kitchen sink faucet, and a whole-house iron oxide filter. Multiple measurements made over a period of >1 y indicate that the granular ferric oxide media reliably reduces initial arsenic levels down to a zero arsenic level. The small point-of-use granular ferric oxide filters are easy to install and offer a cost-effective alternative to bottled water.