Energy-efficient sewage treatment with Atlas Copco screw blower technology

Northumbrian Water, a provider of water and sewerage services in the north-east of England, has chosen Atlas Copco screw blower technology to help reduce energy consumption and minimise service costs at its sewage treatment works in Newton Aycliffe, County Durham.

The company needs a constant, reliable supply of air in the region of 480 mbar for aerobic treatment of wastewater at its Newton Aycliffe site. The process uses bacteria to break up waste particles and requires large amounts of air to be blown into the aeration tanks to maintain the desired level of dissolved oxygen within the wastewater containment system - a biological process that typically uses up to 70% of the energy consumed on site.

There is a changing perspective within the water industry that the widely used lobe blower design principle no longer meets the needs of today’s low-carbon economy and that operators can benefit substantially from energy savings through the replacement of conventional lobe equipment with innovative screw technology. Thus, Northumbrian Water decided to replace one lobe blower with the Atlas Copco ZS screw blower technology.

On completion of the installation, Northumbrian Water carried out a comparison performance test between the existing lobe blowers and Atlas Copco’s ZS technology. It revealed that the existing lobe blower used approximately 19% more power for the same output. Based on these test results and continuous reliability issues with the lobe blowers, it was decided to replace a second lobe blower with an Atlas Copco ZS90-VSD, low-pressure, oil-free rotary screw blower.

The blower unit comprises a complete package based on a simple internal principle: precision timing gears maintain minute clearances between two intermeshing dry screw elements that never touch. No lubrication is required in the compression space and specially designed seals prevent any rotor bearing oil from entering the compression chamber. Intake air is compressed between the rotors and their housing and oil-free, pulsation-free air at pressures of approx 480 mbar is delivered at an output rate of more than 4000 m³/h dependent on process demand.

Northumbrian Water has now placed a third order with Atlas Copco to replace the remaining two lobe units installed at the Newton Aycliffe wastewater treatment plant with a further two ZS 90 screw blowers.

Alan Harle, the Northumbrian Water engineer who conducted the comparison tests, commented: “From an operational perspective, Atlas Copco’s ZS blowers have performed well, especially when compared with the incumbent blowers, and we are very pleased with the 20% improvement we have already seen. I would say that the proof is in the pudding.”