Building a Better World Award Edendale Wastewater Treatment Plant by maclaren1


									Building a Better World Award

Edendale Wastewater Treatment Plant

Vermiculture Takes Hold in Southland

New Zealand’s first worm-based sewage treatment system is now successfully operating in
Southland. It could have nationwide application.

Southland District Council originally asked MWH to help it develop a conventional aerated lagoon
wastewater treatment plant for Edendale and Wyndham. These small, rural communities have
around 1,500 residents and had previously been on a septic tank system. Following extensive
research, MWH, SDC and Biofiltro New Zealand Ltd developed an alternative worm-based option
using technology that is common in Chile but has not been used before in the English-speaking

Project Manager Murray Sorrell says the process was not straightforward and required eighteen
months of research and consultation, a study tour to Chile, convincing the sceptics, and the
development of new process review procedures. However, now the plant is successfully operating
he says it could be the catalyst for many similar plants.

“The solution provides an efficient and economical treatment system for medium to small
communities. It also has good environmental outcomes and is finding acceptance within Maori
cultural practices. Having successfully implemented this system in Southland, I think there are a
number of communities throughout New Zealand who will find it is a better solution than the pond
system. It also provides significant advantages in solids management and allows for the solids to be

The prototype for the biofiltro system was originally developed at the University of Chile in Santiago
twenty years ago. At Edendale, the sewage is piped into the site and sent through a self-cleaning
filter system which collects solids. The wastewater is then sprayed on a packed bed of sawdust,
rocks and bacteria. Worms within the sawdust bed provide aeration and consume the bacteria and
organics in the wastewater to create humus. This humus will be removed annually, is easily handled
and potentially useful – it Chile it is often sold to farmers.
The system had been designed to take up to 528,000 litres of sewage a day with two additional
underground holding tanks capability of containing 100,000 litres each. Murray says because the
treatment process is natural and sustainable it requires low operator and power requirements. The
footprint of the site is also far smaller than a traditional facility.

The Edendale / Wyndham Wastewater Treatment Plant cost $1.5million to develop, an estimated
saving of $1million from the originally proposed scheme.

For more information on this project or the technology involved please contact Murray Sorrell,
Senior Engineer based in MWH Christchurch, Ph 03 343 8735 or Email

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