Renewable energy drive turns water company to stone
31 Aug 2007
The utility company installed RWA45 stonewool insulation from Rockwool to maintain an optimum temperature in the sludge digester tanks; boosting the plant’s methane production and powering a pioneering gas generation plant, used for electricity generation.
Wessex Water’s project supervisor John Ford explains: “A constant 40°C must be maintained as the digested sludge moves successively through six tanks, before discharging to the mesophilic digester. The correct temperature is essential for efficient digestion and gas production.”
The sludge digester is part of the three-year Bristol Advanced Sludge Scheme, which aims to reduce the volume of sludge disposed to as part of the EU Urban Waste Water Treatment Directive and increase the volume of off-gas for power generation.
The new tanks will help produce an estimated £50,000 worth (70,000m3) of additional methane per week from the treatment plant for electricity generation.
The methane feeds the five 1.1MW gas engine dual fuel generators, which provide electricity to the WWTW and heat the digesters, currently the plant produces methane equivalent to £800,000 worth of green energy per annum.
The glass-lined steel tanks are insulated with 75mm of Rockwool RWA45 stonewool insulation slabs, which are curved to fit. The installation is protected by profiled steel sheeting, cut to shape and sealed.
Kirk Liquid Management Solution (KLMS) installed the six 13-metre high by 8-metre diameter digester tanks complete with insulation and cladding.
“The cylindrical tanks have a relatively complex geometry, which is more difficult to insulate effectively, said KLMS sales director Andrew Peace. “The flexible RWA45 panels were used on the tank walls so as to take up the curvature yet ensure secure jointing.”