Using Biomass as a Heat Source for Sludge Drying at the paraparaumu Wastewater Treatment Plant
Annual Conference
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The Paraparaumu Wastewater Treatment Plant uses a thermal sludge drying process to produce a Grade ‘A’ stabilised biosolids. This treatment plant previously used a diesel boiler which provided heat via a high pressure hot water circuit to a rotary drum dryer. In 2008, the diesel boiler was identified as a) being a significant contributor to the overall carbon emissions for the Kapiti Coast District Council and b) as having a high operating cost, particularly with rising diesel prices. Cardno BTO investigated alternatives by conducting a holistic biosolids options study, utilising multi-criteria analysis, that determined the best solution was the installation of a biomass (wood fuel) boiler to replace the existing diesel boiler.
A 500kW high efficiency reciprocating grate boiler supplied from Austria was installed in 2010, along with an associated fuel store and feed system. The boiler is capable of operating with wood chip, wood pellets, hogged fuel and other biomass. The new system has been an operational success, reducing sludge drying fuel costs by 50%, and reducing the Council’s overall carbon emissions by 22% compared to 2007 levels.