Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | SEPTEMBER 2016 | 17 Project focus Wastewater treatment Severn Trent saves energy with aeration switch Project focus S evern Trent is set to reap significant energy savings aer successfully trialling an innovative alternative to traditional blowers and compressors in its wastewater operations. The midlands utility spotted the potential in Lontra's innovative Blade Compressor as an alternative to the blowers and compressors which are used to pump air into wastewater to feed the micro-organisms that clean it. As such, it undertook an extensive site trial and performed exhaustive tests that have proven ● Blade Compressor technology used in successful full-scale trial ● 20% energy saving shown compared to traditional blowers ● Estimated saving of £1.8M per year predicted with roll-out It requires regular, large scale investment to maintain the quality standards demanded by regulators, politicians and customers. The activated sludge process relies on the injection of air into wastewater to encourage the large scale growth of natural bacteria that break down impurities it contains. The traditional compressors, or "blowers", used to inject air into wastewater use vast quantities of electricity, costing Severn Trent alone over £9M a year. This is more than half the entire cost of wastewater treatment in the region. Across the UK staggering 1% of the entire country's total electricity usage goes to wastewater treatment and aeration. Given the cost of electricity consumption – and the associated CO2 emissions – for a long period, Severn Trent Water had been investigating alternative solutions with lower energy costs, improved operational efficiency and reduced environmental impact. Their answer eventually came in the form of the Lontra Blade Compressor. A modern innovation to maximise efficiencies The Blade Compressor is a step change in air compressor and blower technology, best imagined as a piston and cylinder, but with the cylinder wrapped around. With a traditional piston and cylinder machine, as the piston drops down in the cylinder, it draws in air above it and, as it goes up again, it compresses air in front of it. As the Blade Compressor's piston, or "blade" rotates, it draws in air behind it in the same way as the piston dropping down in the cylinder. As it gets back to the starting point, it has drawn in a complete volume or air behind it. Yet unlike the traditional piston and cylinder that has to stop and change direction, the blade passes through a disc and the volume of air that was trapped behind the blade is now in front. This means that it has an almost continuous cycle of drawing in air behind and compressing air in front. A new geometry that is quieter, smoother and most importantly, far more efficient. In the case of Severn Trent Water, the first step was to work out just how important the Lontra technology could be to its business and so the company worked for over a year with Lontra on a study evaluating its the effectiveness of the equipment as a game changing solution for the global water and wastewater industry, delivering a step change reduction in electricity usage, maintenance costs and CO2 emissions. Severn Trent's wastewater treatment works operate around the clock, handling more than 2.5 billion litres of wastewater every day. Operating and maintaining the vast network of sewers and treatment works is a huge and resource intensive engineering challenge. The Blade Compressor is an alternative to traditional aerators Jenny Rhode STRaTEgiC BuSinESS DEvEloPMEnT DiRECToR lonTRa