Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | OCTOBER 2015 | 27 M ethane is an inevitable by-product of the sewage treatment process, and as an effectively 'free' fuel source, many site operators will already be reclaiming it to produce heat and power. Add in the fact that regulations on greenhouse gas emissions are getting increasingly stringent – methane is roughly 25 times more damaging than carbon dioxide in this respect – and there's no questioning the appeal of this green energy source. The concept of combined heat and power in the water industry is not new and many operators will already be aware that operating a CHP system isn't quite as straightforward as simply siphoning off methane and burning it. Biogas reclaimed from sewage can contain contaminants that clog up or eat away at equipment, reducing its lifespan and driving up operating costs. Avoiding this requires careful selection of filtration and processing solutions, and knowing what's right for your plant is vital. What are the advantages of installing a biogas CHP system? The biggest draw is that the fuel you're burning is effectively free; installing a CHP system allows a company to turn its methane from a waste by-product into a reliable revenue stream. Though the exact details will vary from site to site, the payback period for investing in a CHP system can be as little as 12-18 months. As they take advantage of the heat that would be wasted at a conventional plant, CHP installations also tend to be much more efficient than mainline power stations. Conventional electricity generation is typically only 40 per cent fuel- efficient, while CHP systems can see this figure rise to over 75 per cent. What do I need to know before I start investigating CHP at my site? Before you start shopping around for a new CHP system or consider upgrading your existing plant, it's important to know your electrical load profile – specifically the base load profile rather than the mean or peak. When it comes to heat you need to know your demand in both kW and Celsius, as the ideal CHP configuration can vary widely according to both the amount and the temperature of heat required. Finally you need to work out how much you currently pay for heat and electricity. This will allow you to RICHaRd Russett GEnERal ManaGER EnGinEERinG, FinninG UK & iREland Cooking on gas Combined heat and power (CHP) systems are a great of way of generating energy from the methane produced in sewage treatment, but there are a number of considerations when specifying and installing the right system In the know Getting to grips with… biogas CHP systems

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