Zinc and Stormwater FAQs
Zinc is a bluish-white, shiny metal that is typically extracted from ore deep within the earth’s crust.[vi] Zinc is the 24th most abundant element in the earth’s crust. In soil, the average zinc concentration is 64 ppm.[vii] Dissolved zinc (Zn2+) and particulate zinc (Zn), are forms commonly found in stormwater. Zinc in these forms can make its way into waterways and human freshwater drinking sources through stormwater runoff.
Common sources of particulate and dissolved zinc in stormwater runoff are from industrial activities such as metal galvanizing and zinc roofing material. Approximately one-third of metallic zinc is used in galvanizing, a process used to coat steel products for weather resistance.[x] Zinc oxide is also another common compound used as a protectant. Zinc oxide is found in rubber, tires, photocopy paper, paints, enamels, pharmaceuticals, and cosmetics. Zinc is also commonly used as an electrolyte for batteries.
Raw zinc (image courtesy of Wikipedia)
Zinc can make its way into drinking water sources and aquatic habitats through stormwater runoff in high enough concentrations to have negative effects on humans and wildlife. Although zinc is an important dietary element for humans, zinc should be removed from stormwater because ingesting large amounts of zinc can cause stomach cramps, anemia and can decrease good cholesterol.[i]
Concentrations of 5 mg/L and up can impart an unpleasant taste to water.[ii] In marine waters, aquatic species suffer acute effects from zinc at 90 μg/L. Adverse effects of dissolved zinc, including altered behavior, blood and serum chemistry, impaired reproduction, and reduced growth, occur to salmon at very low levels (5.6 μg/L in freshwater).[iii] In mammals, ingesting large amounts of zinc can cause infertility and underweight offspring.[iv]
Zinc can be present in stormwater in both particulate and dissolved states. Enhanced, passive media filtration can be used to remove particulate zinc. If further reduction is necessary to remove dissolved zinc, advanced polishing technologies can be added. Both types of BMPs combined in a treatment train will remove total zinc from stormwater prior to discharge to help facilities meet benchmarks or NALs. Learn more about the Aquip passive media filter and the Purus metals polisher combined for an advanced level of zinc removal from stormwater.
Zinc in rooftop runoff is typically found in a dissolved state. Dissolved zinc can be removed from rooftop stormwater runoff by running it through an advanced, polishing media filter connected to a downspout. Our downspout units provide this advanced level of rooftop stormwater runoff treatment. Find out more about our Zinc-B-Gone downspout filtration units.