What Is Return Activated Sludge (RAS)?
After wastewater passes through the aeration basin, the mixture of treated water and microorganisms flows into a secondary clarifier. Here, heavier biological solids settle to the bottom. A portion of this settled biomass — the Return Activated Sludge — is pumped back into the aeration tank.
This return process maintains a stable population of microorganisms, allowing the system to break down incoming organic material effectively. Without consistent RAS pumping, the biological process could collapse, leading to poor treatment performance.
Cornell Application:
- Cornell pumps are ideal for moving RAS from secondary clarifiers to aeration basins.
- Our pumps provide the low-shear handling necessary to avoid damaging delicate biological floc.
- Cornell’s N-Series solids-handling pumps are commonly selected, offering robust performance and long wear life in abrasive, solids-rich sludge environments.
What Is Waste Activated Sludge (WAS)?
To keep the treatment process balanced, plants must remove excess biomass. This portion, known as Waste Activated Sludge, is pumped out of the clarifier and sent to thickening, digestion, or dewatering processes.
WAS pumping controls the mean cell residence time (MCRT) in the aeration basin, ensuring that the microbial community remains in balance. Proper WAS management is critical for stable operations and compliance with discharge permits.
Cornell Application:
- Cornell pumps are used to transfer WAS to downstream sludge handling processes.
- Our Delta impeller designs provide higher efficiency while reducing plugging — a frequent challenge in sludge pumping.
- For abrasive sludge, Cornell’s high-chrome iron construction extends pump life and lowers total cost of ownership.
Why Cornell Pumps Excel in RAS/WAS Service
- Durability: Cornell pumps are engineered with heavy-duty bearings, oversized shafts, and wear-resistant materials.
- Efficiency: High hydraulic efficiency reduces power consumption over long operating hours.
- Versatility: With a wide range of impellers and materials of construction, Cornell pumps can be tailored to specific plant conditions.
- Low Maintenance: Features like the Cycloseal® sealing system extend seal life by keeping grit and fibers out of the seal chamber.
Supporting Wastewater Professionals Worldwide
From small municipal plants to large metropolitan treatment facilities, Cornell pumps help operators reliably manage RAS and WAS flows. By combining rugged construction with efficiency and ease of service, Cornell delivers pumps that wastewater professionals can trust for decades of operation.
