Palmerston North City Council required a review and improvements to the performance of their Anaerobic Digestion Systems at the Palmerston North Wastewater Treatment Plant (WWTP).
Calibre Consulting’s anecdotal evidence suggested long-term under-performance had been occurring. Our team undertook hydraulic residence time testing on the digesters to reveal that nearly 50% of the reactor volume was poorly mixed and had been for many years despite a number of previous reviews.
Calibre Consulting acted as process designers, as well as mechanical and electrical commissioning engineers. First our team undertook hydraulic residence tests and from these recommended a short-term, transitional mixing system, followed by a longer term solution. The short-term solution improved performance sufficiently, allowing a single digester to accept the entire plant’s waste sludge. This allowed the second reactor to be removed and upgraded.
The modifications made to the system increased the system capacity more than 300%. On Calibre Consulting’s recommendation the council developed the facility into a co-digestion facility for combined source segregated trade sludges and waste, as well as biosolids. As a result the gas production has increased three-fold, resulting in an upgrade payback period of less than three years.
• Enabled new revenue streams
• 300% digester capacity increase
• Green electricity export to grid