Removing zinc from contaminated groundwater

Sibelco has been operating in Lommel (BE) for over a century, mining high-quality silica sand for use in glassmaking and other applications.

The extraction and processing of silica uses significant quantities of water, but Lommel’s groundwater is severely contaminated by heavy metals that originated from a local zinc smelting site which operated until the mid 1970s. This means that sand production at Lommel uses water with elevated levels of zinc (approximately 3700 µg/L) which needs to be lowered to less than 600 µg/L before it can be safely discharged into the nearby Bocholt–Herentals Canal.

Problue V1

To treat water at Lommel, we conducted a series of pilot trials using BLUEGUARD®, a granular filter media composed of an olivine core with a surrounding shell of powdered olivine and a cementitious binder. BLUEGUARD® removes zinc and other heavy metals from water through adsorption and precipitation.

In the trials, water from the quarry was first pumped into a sand filter (1.5 m³) to remove larger particles. It then flowed to our Problue V1 up-flow system operating at normal pressure and filled with 1.2m³ of BLUEGUARD® on top of a layer of gravel. Filter capacity was 1.5 - 2m³/h with residence time ranges between 15 – 20 mins.

The graph shows zinc (Zn) levels up to 3700 µg/L (influent, blue line), thereby exceeding the discharge limit of 600µg/L (red line). The effluent (orange) line shows how BLUEGUARD® effectively removes Zn towards 0µg/L. After treating approximately 2,500m³ of water, Zn concentration starts to increase and reaches the discharge limit around 3,500m³. This results in an uptake capacity of over 6.5 mg/g for 3700 µg/L initial Zn concentration.

Other heavy metals present in trace concentrations in the feed water were effectively removed to extremely low concentrations without any anomalies.

The pilot trials demonstrated that BLUEGUARD
is a sustainable and cost-effective solution for the efficient removal of Zn and other heavy metals to bring water safely within discharge limits.

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