In 1986 the District constructed the original 0.5 million gallons per day (MGD) lagoon facility on 25 acres at our current location (6501 WCR 26). The District initiated an engineering study in 1999 to begin developing a long-range plan for wastewater treatment. At that time it was decided that expanding the lagoons to a capacity of 1.5 MGD would consume most of the original 25-acre plant site and make the future transition to a mechanical system very difficult and expensive. The decision was made to transition immediately to a mechanical plant.

The current 3.0 MGD facility was constructed on a 40 acre site and placed into operation in March 2002. In an average day the facility receives 2.8 MGD of raw wastewater, which is treated to meet limitations established by the U.S. Environmental Protection Agency and Colorado Department of Public Health and Environment before being discharged to Oxbow Lake and on to the St. Vrain River.

The plant uses an extended aeration activated sludge process to treat the wastewater. Activated sludge is a biological treatment process that uses naturally occurring organisms to decompose the wastes. No chemicals are used to treat the wastewater that is released to the St. Vrain.

When raw wastewater enters the plant it passes through a preliminary treatment process in the Headworks Building. Two mechanical bar screens collects larger solids in the flow stream, such a paper towels, feminine hygiene products and anything else that can be flushed or put down a drain. These items are mechanically dewatered before being conveyed to a dumpster for disposal. Following the bar screens the flow passes through a two vortex grit separators which removes heavy solids such as egg shells, sand and rice. The separators are concrete cylinders with a horizontal paddle turning slowly inside, creating enough current to keep the suspended particles from settling out while allowing the heavier solids to settle out and collect in the bottom of the collector. These solids are then pumped to the biosolids pond for treatment.

From the Headworks Building the screened and de-gritted wastewater is pumped to one of two aeration basins. The basins each hold 2.3 million gallons of water and are where the secondary treatment occurs. Large blowers are used to add air to the water as it passes through the basins, hence the term “aeration basin”. Oxygen is added to promote the growth of microorganisms that break down the organic material in the water and improve the settling characteristics of the remaining solids. The organisms include bacteria, fungi and protozoa. From the aeration basins the “mixed liquor” flows by gravity to final clarifiers, where the settleable solids (RAS) and floatable material (scum) are separated from the water. From the clarifiers the RAS is pumped back to the aeration basins where the microorganisms are reintroduced to the food in the influent flow. Plant staff monitors the quantity of microorganisms in the process, and excessive organisms (waste activated sludge, or WAS) are pumped (“wasted”) to the biosolids pond. The floatable solids are skimmed off the top of the water surface and pumped to the biosolids pond.

The clear effluent flows over the weirs in the clarifiers and on to the Operations Building, where it is disinfected with ultraviolet light. Two new banks of Trojan UV light tubes are in the effluent channel where the effluent passes through the lights (see picture below) and any remaining organisms are genetically altered so that they cannot reproduce and die off in a few hours, before reaching the St. Vrain River.

The plant staff consists of:

Plant Manager: Doug Wertin
Plant Operator: Penny DeMille
Plant Operator: Chuck Bray
Plant Operator: John Ford