diffuCLEAR, the on-site air diffuser remediation service from Air Technology Ltd, has reduced energy use and Carbon Footprint at Severn Trent’s Lydney STW in Gloucestershire. Measurements of blower performance were made in 2010 and again pre- and post-treatment in 2013, so it was possible to gain a clear picture both of the effect of biofilm development on diffuser performance and the significant benefits of diffuCLEAR cleaning. Immediate savings were of the order of 15,500kWh, with process performance benefits too.
Lydney STW is a small, rural treatment works, serving a population equivalent of just over 20,000 with an average inlet flow of 6500m3/day. Three identical blowers pass air through 673 fine bubble ceramic diffusers used in ASP secondary treatment, two of which, before diffuCLEAR treatment, ran heavily loaded to maintain the DO setpoint. Air Technology checked the plant performance in 2010 and again in 2013 prior to diffuCLEAR treatment
Between 2010 and 2013, it was clear that plant efficiency had deteriorated as the biofilm and limescale had increased. Blower pressure had increased by around 20mbar in the normal operating range; indicating that extra pressure, and therefore extra energy, was required to force enough air through the diffusers to achieve target DO. Coarse bubbles seen in the ASP also suggested a less effective DO performance.
diffuCLEAR works by introducing an atomised mist of acid cleaning chemicals into the line that get to work reducing and removing the biofilm so air can pass efficiently through the diffuser heads. Although the effect increases over time, the immediate benefits were striking: within twelve hours of diffuCLEAR treatment, pressure with two blowers running flat out had dropped by 41mbar, and was now lower than it had been three years previously. This immediate benefit represents a reduction in energy cost of around 8-10%, equating to approximately 15,500kWh. Not only that, but the diffuser bubble pattern also returned to the optimal fine bubble aeration pattern. That may lead to further energy savings as DO targets are achieved at lower blower loads.
The effect of diffuCLEAR treatment is clear, providing significant direct and indirect energy savings. Further savings are made because diffuser arrays are remediated in-situ, with no need to remove or replace them. diffuCLEAR extends diffuser lifespan, and multiplies the time between major refurbishments.
As Stuart Allen, Assistant Energy Efficiency Manager of Severn Trent, put it, “The diffuCLEAR process was a great success. We were pleased with the results, and also very happy that there was no disruption to our work.”