New Water Treatment Plant to Play Crucial Part in Pit Dewatering Process

January 25, 2024

In preparation to dewater the proposed mine pit – pending an approved permit from the North Carolina Department of Environmental Quality (DEQ) – Albemarle has constructed a temporary water treatment plant (WTP) which will be used to clean and filter the pit’s accumulated rainwater before pumping it to South Creek Reservoir for gradual release into Kings Creek.

Treating the pit’s water requires a multi-step process to ensure the released water meet regulatory standards to preserve the integrity of Kings Creek and the river basin.

To begin treatment, water is conveyed by electrical pumps from the pit to the WTP where the water is mixed with an oxidant to remove sulfur. Filters are then used to collect any sediments and elemental sulfur from the oxidation process Hypochlorite is mixed in to remove ammonia and manganese. Lastly, the water is treated by ultrafiltration to ensure clarity and transferred to a finished water tank before being pumped to South Creek Reservoir which flows naturally into Kings Creek.

The treated water will be pumped to South Creek Reservoir at a gradual and controlled rate of 2,000-2,250 gallons per minute on average.

The solids collected after the initial filtration and ultrafiltration are non-hazardous, non-reactive materials such as elemental sulfur and dirt. These solids are collected in geobags allowing them to be consolidated and transported to a landfill services site for disposal.

“We are simply treating concentrated rainwater through the oxidation of sulfide, filtering, and increasing dissolved oxygen,” adds Joey Dean, Group Hydrologist at Albemarle. Dean compares the process to the filters we have in our refrigerators or under our sinks that filter out particulates from the water we use at home. The difference is the addition of non-harmful elements, to increase dissolved oxygen which is important for the protection of aquatic wildlife.

Water quality will be continuously monitored with in-process sensors for pH, clarity, dissolved oxygen, and temperature. There will also be weekly to quarterly sampling along various points in the creek. The dewatering process is anticipated to begin this spring, pending approval of the necessary permits, and is expected to last up to 18 months to complete.

The water treatment process was specifically designed for pit dewatering to mitigate odor during the process due to low dissolved oxygen at the depth in the pit lake. Project scientists are studying the interaction between the lowering water levels of the pit and how the pit water will mix with rainwater and the atmosphere. As the mixing of the new water dilutes the existing water, the new mixture serves to lessen the off-gas potential of the sulfur as the water level goes down. We will adjust the treatment strategy to address any odor issues through on-going monitoring of the water levels.

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