Wastewater Treatment Plant Process
How Louisville treats its wastewater
The Louisville Wastewater Treatment Plant (WWTP) cleans sewage from homes and businesses before releasing the water back into Coal Creek. The plant is located on the east side of Louisville, about a quarter mile from where it discharges into the creek. The current plant was built in 2017 and can treat up to 2.53 million gallons of wastewater per day.
Step 1: Screening & grit removal
When sewage arrives at the plant, the first job is to remove solids. Fine screens pull out rags, sticks, and other debris. Then a spinning grit removal system catches sand and small particles the screens missed. After that, the flow is measured and pumped into the treatment basins.
Step 2: Biological treatment
The heart of the plant is a process that uses tiny living organisms (microorganisms) to clean the water. The wastewater flows through five zones in large concrete basins, each with a specific job:
- Sludge Zone. Microorganisms from later in the process are sent back to the beginning. The longer they stay in the system, the better they get at breaking down waste.
- Anaerobic Zone. Special organisms called PAOs absorb phosphorus here. They can hold up to 8% of their body weight in phosphorus — much more than any other known organism.
- Anoxic Zone. Bacteria convert harmful nitrates into harmless nitrogen gas, which floats up and out into the air.
- Swing Zone. This zone is flexible. In winter it gets extra air; in summer it doesn't. This lets operators adjust the process based on what the microorganisms need at different times of year.
- Aerobic Zone. Air is pumped in here so bacteria can convert ammonia into nitrates. Those nitrates are then sent back to the anoxic zone to be turned into nitrogen gas. Smart sensors adjust how much air is pumped in, which saves electricity.
Step 3: Settling and secondary clarifiers
After the biological treatment basins, the water flows into large settling tanks called clarifiers. The solids sink to the bottom, and clean water rises to the top and flows out. The settled solids are either sent back to the beginning of the treatment process or moved on for further processing.
Step 4: Disinfection
The clean water passes through an ultraviolet (UV) light system. The UV light doesn't kill harmful bacteria — instead, it damages their DNA so they can no longer reproduce. This removes threats like E. coli, giardia, and cryptosporidium. After UV treatment, the water is released into Coal Creek. In dry months, the plant's discharge makes up the majority of the water flowing in Coal Creek.
Reuse Water
Some of the treated water doesn't go to Coal Creek. Instead, it gets filtered further and stored in a 3-million-gallon tank. This "reuse water" is pumped to the Louisville Sports Complex, Miner's Field, Coal Creek Golf Course, and Community Park for irrigation. Reuse water also contains nutrients that are good for soil and plant growth.
Solids & Biosolids
Leftover solids go through a thickening process to remove extra water, then sit in digesters for about 20 days. During that time, the microorganisms break down further. The remaining material — called biosolids — is hauled to farms in Weld County, where its high nutrient content is used as a natural fertilizer.
Monitoring
Certified operators run tests on the water every day to make sure the plant meets strict state and federal clean water standards. An alarm system monitors the plant 24 hours a day for equipment problems or anything outside normal operating range.