Greeley Wastewater Treatment

As used water from homes and businesses enters the plant, large debris and sediment is removed from the waste stream by way of screening devices and settling tanks.

Primary Clarifiers allow heavy organic material, called primary sludge, to settle at the bottom of the large cylindrical tanks while the liquid stream flows over the top of the clarifier weirs. The sludge is transferred to the South side of the Cache la Poudre River, where it is treated separately, and the liquid flows by way of gravity to the secondary treatment process.

Treatment of wastewater is primarily a biological process. Bacteria and microbes (“bugs”) present in the waste stream are introduced to favorable environmental conditions that allow them to grow, reproduce, and remove pollutants that negatively impact water quality of the receiving stream. Some “bugs” are effective at removing phosphorus and particulate matter, storing it in their cells before being removed from the system during the solids treatment process. Others remove nitrogen by breaking down harmful ammonia and converting it to nitrogen gas, which makes up the majority of Earth’s atmosphere.

Secondary Clarifiers allow the bacteria and organic material to settle at the bottom of the tanks, leaving a clear “effluent” to overflow the top of the clarifier weirs. The solids are pumped from the bottom of these clarifiers back to the front of the secondary process so the “bugs” can continue to remove pollutants (return sludge) or they are pumped to the solids treatment side to be removed entirely (waste sludge).

The treated effluent flows to the UV disinfection building, where it passes across bulbs that emit ultraviolet light. This UV light effectively destroys the DNA of any remaining harmful bacteria, such as E. coli, preventing them from reproducing or causing harm to aquatic life.

Once the treatment process is complete, the treated effluent is discharged into the river meeting all treatment and pollutant removal requirements, or “discharge limits”. Concentrations of pollutants must always remain below these discharge limits. These limits are determined by the Colorado Department of Public Health & Environment (CDPHE) to ensure that the water quality of the Cache la Poudre River is in no way degraded due to the treatment plant’s discharge.

Primary sludge and Waste Sludge are transferred to large “digester” tanks that are maintained near 100-degree temperatures to help break down organic material and meet additional regulatory requirements. The bacteria involved in this biological process break down the wasted organic matter and generate a “biogas” that is beneficially reused to run boilers at the plant. These boilers help return hot water to nearby buildings in place of furnaces, and transfer heat to the digesters to help maintain their required temperature.
 

Once the digested sludge has been treated for a minimum of 15 days, it is pumped to a dewatering process where liquid is removed to help generate a soil-like “biosolid” that is hauled offsite. The Environmental Protection Agency and CDPHE provide regulations for how biosolids can be used. Currently, this treatment process produces a “Class B” biosolid, which can be land applied as a fertilizer for cover crops or livestock feed crops.

Greeley treats its wastewater with many advanced processes to meet all requirements and protect our environment. In addition, an adjacent solar array provides supplemental power to the plant. The array generates 10% of the plant’s annual energy requirements, at less than half the cost. This reduces operational electrical costs by nearly $40,000 annually.