Colorado Water Treatment Plant Aims to Reintroduce Fish to Creek

 

The Colorado Department of Public Health and Environment and the Environmental Protection Agency opened the North Clear Creek Water Treatment Plant in July of 2017. The new facility is located at the south end of the city of Black Hawk, a popular gambling destination about 30 miles west of Denver.

In 1859, gold was discovered near Black Hawk, Central City and Idaho Springs making it Colorado’s leading mining center. Mining continued in Clear Creek and Gilpin counties until about 1950. Meanwhile, acidic drainage from abandoned mines carries metals such as iron, manganese, zinc, copper and cadmium. Throughout the years, these toxic materials have destroyed the North Clear Creek, killing the aquatic life within.

“This is the beginning of the ecosystem for this area of Colorado,” said Paul Winkle of Colorado Parks and Wildlife. The creek feeds into Clear Creek, which is a major drinking supply for more than 350,000 residents. It’s also used for kayaking, rafting, fishing, wildlife watching and gold panning.

The plant treats contaminated water from the Gregory Incline, the National Tunnel and Gregory Gulch, at flows ranging from 150 to 600 gallons per minute, removing around 350 pounds of contaminants per day.

In addition to cleaning up the stream, the main objective of the North Clear Creek facility is to establish a brown trout fishery. Without the Colorado Department of Transportation (CDOT), this objective wouldn’t have been possible.

Located next to Highway 119, site was created as part of a CDOT road curve-straightening project which aimed to address multiple fatalities occurring in the area. CDOT also created a mile of streambed for the brown trout which contained mix of deep and shallow water, fast and slow water, and sun and shade. The construction began on the $19 million plant in December 2015.

Water Treatment Process & Tuthill Blowers 

Tuthill Blower Packages are utilized in the water aeration process in the plant. The added air oxidizes the dissolved metals and the pH is raised to about 9.5. This forces the metals to drop out of solution.

The high-density sludge process sends metal hydroxides into a conditioning tank where they are coated with lime and sent back through the system up to 30 additional treatment cycles. This process will remove metals from the water, creating a dense filter cake material sent to landfills.

Chemicals are categorized as acids or bases. Acids dissolve heavy metals while bases cause dissolved metals to solidify. Scientists use the pH scale to measure the acidity or alkalinity of solutions .

Pure water has a neutral pH of 7. Acidic solutions have a lower pH value, while alkaline (basic) solutions have a higher pH value. Solutions on both ends of the pH scale are caustic and can damage living tissue.

Treatment plants manipulate pH to remove dissolved metals from water. First, a base is added to contaminated water, raising pH and reducing acidity. As the pH value rises, dissolved metals change to a solid state. Since the metals are denser than water, they fall to the bottom of the tank, where they can be removed. Clean water flows into a trough near the top of the tank. Because this process makes the water more basic, acid is added until the pH level of the treated water falls and is safe for fish and people when it is discharged back into the creek.