The Christchurch Wastewater Treatment Plant (CWTP) has traditionally used gas and diesel fuelled engines to generate heat and power from biogas produced in sludge digesters. Until 2013 three engines provided this function – two 400kW Allen dual-fuel engines and one 1,550kW Waukesha gas engine. The two 400 kW Allen engines were at the end of their economic life.
The goals of the replacement project were to achieve integration between the powerhouse and the process, thereby relieving operational constraints, and to improve the site's disaster resilience with respect to power generation. Underlying both of these goals was the desire to reduce the operator workload required to effectively manage the plant by simplifying operation.
Successful completion of this project has resulted in improved automation, relieving the operator of the need to actively manage the engine power output, better utilisation of site resources, and a power generation system that can accommodate loss of mains power or fuel gas and maintain CWTP operations in emergencies.