From Inception to Implementation: How Pragmatic Design Improves Water Sustainability

S. Pearson (Beca) & B. Everitt (Tauranga City Council)

Sustainable measures have been installed at Tauranga City Council’s (TCC) new Waiāri Water Treatment Plant (WTP) to reduce energy consumption through plant design and optimization, and to consider sustainable and operator centric buildings. The recently constructed Waiāri WTP provides 30 ML/d capacity with a future design capacity of 60 ML/d using coagulation, clarification, membrane filtration and disinfection (sodium hypochlorite). The WTP is also a zero liquid discharge facility with all liquids either recycled and sludge physically removed from site, a process rarely used in New Zealand. The plant will serve growth in Tauranga over the next 30+ years.

TCC utilised one of the Energy Efficiency Conservation Authority’s (EECA’s) grant co-funded programmes ‘industrial design advice’, to develop energy conservation measures to reduce both carbon and power consumption in the final WTP design and construction. The identified energy savings from this assessment were equivalent to approximately 500,000 to 600,000 kWh and 80 to 90 tonnes of CO2 per year with an estimated payback period of 14 years.

This paper discusses the overall energy approach and final gains achieved from the energy review on the operational Waiāri WTP, how these were included in the design, and the importance of being adaptive and collaborative to maximise energy efficiency outcomes.

This includes designs to reduce intake pumping costs, solar energy, processes to maximise treatment component life and reduce chemical use, alternative heating processes, rainwater capture and water re-use.

This paper then outlines the key metrics being developed and reported on through the WTP control system for energy consumption, and how these will be used to monitor performance and efficiency. These metrics are not commonly used and could be more universally adopted across other operational facilities. 

Sustainable materials and construction items were also considered in the early design stages and built into the Waiāri WTP, including permeable pavements and surfacing, and green star building elements. This paper discusses the considerations into these elements, challenges with procurement and design, what was implemented, and lessons learnt to consider for future projects.