Since 2008, more than 4.5 billion gallons of water have been treated at Sanford Lab?s Waste Water Treatment Plant (WWTP). Over half comes from underground, while the rest comes from the Grizzly Gulch tailings. Once treated, the water is released into Gold Run Creek, which joins Whitewood Creek within a few hundred yards of the discharge pipe.
The water from the mine contains suspended solids?mostly iron, said WWTP Foreman Ken Noren. ?It looks like tomato soup.? To remove the iron, the water is pumped into a sludge removal tank.
A coagulant neutralizes the charge of the particles, and a flocculant, or clarifying agent, is added to the tank and mixed with the water for 15 minutes. The process causes the particles to form into clumps that can then be removed. ?Ideally, we want the chunks to be the size of a fingernail,? Noren said.
As the iron clumps together into ever-bigger chunks, it settles to the bottom of the tank. Within 20 minutes after the mixing has stopped, the iron is ready to be removed from the tank and the usable water continues through the treatment process.
Until recently, the process was done in the ?green tank? outside the influent building. ?We had problems with the ?floc line? freezing every year,? Noren said. And there were other issues. The bottom of the tank was flat, making it difficult to remove all of the iron. Additionally, the water in the green tank couldn?t be brought back into the plant to be processed, so it went to sanitary sewer to be processed and released by the city.
The green tank was removed and a new cone-shaped tank was placed inside the influent building. Noren said the new tank is easier to clean because of it?s shape, allows for better flocking results ?because there won?t be any temperature changes,? and will save money because less water will be going to sanitary sewer.