The site of a former zinc smelter in the eastern United States, whose soil and groundwater were contaminated after decades of zinc production, posed a significant treatment challenge: the water in the newly created retention ponds had a dissolved zinc level of about 10 ppm, well above discharge limits of <0.47 ppm.
In order to begin redevelopment, the owner proposed a system to be put into place that could make the water safe for discharge and operate persistently as the ponds refill with rainwater and leach zinc. The construction schedule required that the solution be in place immediately. Evoqua Water Technologies was contacted in March 2013 to develop a complicated solution. In addition to a tight deadline, requirements included a solution that was compact, low in capital cost, and as self-sustaining as possible, requiring minimum operator involvement or on-site processing.
Evoqua’s recommendation was a configuration of the Vantage® PTI series multimedia filter and WWIX tanks equipped with Evoqua’s SCU™ specialty media. SCU media was designed to remove trace levels of metals such as mercury, lead, cadmium, nickel, zinc, copper, and chromium from complex wastewater to levels not possible with standard ion exchange resins. This
class of adsorbents can routinely achieve levels below 1 ppb for most metals.
With proven results that the recommended WWIX configuration could meet zinc limit, volume and timing requirements, the customer approved an installation. This consisted of Evoqua’s Vantage Pre-Treatment Industrial (PTI) multimedia filter for 50-100 micron particulate removal, bag filters for 10-micron particulate removal, as well an array of ten Evoqua IX-48 48-inch diameter vessels equipped with SCU specialty media to remove the zinc to safe discharge levels.
Evoqua enabled the developer to meet remediation requirements for zinc contaminated groundwater so they could move ahead with development for the site.
The system was installed in July 2015, meeting the customer’s deadline for remediation. A pumping system draws 350-500 gallons per minute from the retention ponds for treatment, maintaining safe water levels in the ponds as they continue to refill from rain and spring water. Compared to large on-site treatment alternatives, the Evoqua met the customer’s need for low cost and low profile solution. With remediation needs met by the Evoqua solution, the developer is now free to take the project to the next stage.