CFPUA is looking into complaints of sulfur smell reported over the weekend by some customers in the Monterey Heights water system, which provides groundwater in an area south of Monkey Junction.
The odor is believed to have been caused by the introduction of sulfur dioxide, a gas commonly used in food processing and preservation, into one well in the system. The concentrations that resulted in the drinking water were below those found or allowed by regulators in many foods.
The sulfur dioxide was in a gas cylinder supplied to CFPUA as part of an order for chlorine. CFPUA is looking into why the incorrect chemical was supplied and how a similar incident may be prevented in the future.
The tank distributed sulfur dioxide to the water system for about 10 hours sporadically Saturday and Sunday. CFPUA began looking into issues related to the well after a sensor alerted staff that no chlorine was being added to it. Chlorine is added to disinfect and reduce odors that occur naturally in water pumped from Monterey Heights system wells.
About a half-dozen customers served by the Monterey Heights system called CFPUA on Sunday evening to report a sulfur smell in their drinking water.
CFPUA crews have been flushing the water system and monitoring levels of chlorine at a number of points. The presence of chlorine residuals in the water indicates the absence of sulfur dioxide.
Sulfur dioxide is a gas, so information about potential health effects are chiefly focused on inhalation. Sulfur dioxide is found in foods such as wine and some dried fruits. The Food and Drug Administration considers 10 parts per million or less of sulfur dioxide to be an “insignificant amount” in food. Federal regulators allow a total concentration of sulfur dioxide in wine as high as 350 parts per million.
Sulfur dioxide also is used in some drinking water treatment to control chlorine residuals.
Based on estimates of the amount of sulfur dioxide added and the volume of water distributed from the well, along with the dilution that would have occurred as that water mixed with that from other wells, the concentrations of sulfur dioxide in drinking water was calculated to be less than 5 parts per million, a concentration significantly less than those levels cited in food regulation.
CFPUA is consulting with the N.C. Department of Environmental Quality and New Hanover County Public Health as part of its review of the incident.