Queenstown Lakes District Council capital works manager Ken
Gousmett inspects a spray nozzle that will irrigate a crop
of lucerne with treated effluent from the Lake Hawea
sewerage plant. Photo by Mark Price.
When Lake Hawea people flush their toilets tomorrow they
will, for the first time, be helping to feed sheep and cattle
in the Upper Clutha basin.
Instead of the town's treated liquid effluent being left to
seep into the ground, and then the Hawea River, it will be
sprayed over a 2.3ha lucerne paddock.
And when the lucerne grows, it will be harvested and sold to
Using nitrogen-rich human waste as a fertiliser for animal
fodder crops is far from new, but it has never been in
fashion in Otago where effluent has traditionally gone into
waterways and landfills.
The Queenstown Lakes District Council's $450,000 ''add-on''
to its Lake Hawea sewage-treatment system is the first in the
province to change that.
Capital works manager Ken Gousmett said the new Lake Hawea
system was a trial but, if it panned out, a similar system
could be used for Wanaka's effluent.
He said other Otago local authorities would be watching with
The existing Hawea sewerage system is centred on a ''pretty
conventional'' oxidation pond built in 1988.
The wind, and some machinery, aerate the effluent in the
pond, allowing ''the bugs'' to break it down.
The sludge sinks to the bottom while the water, or treated
effluent, runs out of the pond into trenches and then soaks
into the ground.
The new system simply takes this treated effluent and pumps
it into a spray-irrigation system with risers and nozzles,
laid out across a piece of council-owned ground soon to be
sown in lucerne.
Mr Gousmett says the treated effluent should help produce
three, four or even more crops per year.
''It has a lot of good things in it, as well as bad things
Safeguards are in place to ensure the spray does not drift on
to the neighbouring farm. Spray nozzles are large to avoid
creating a fine mist, and a weather station will shut down
the system when winds reach 30kmh. It will also operate only
The system will also be shut down for two days before the
lucerne is mown and baled, and those doing the work will need
to be dressed appropriately and work in certain ways.
The lucerne will be cut, baled and carted away, and stock
will not graze the crop directly.
Fonterra does not allow crops grown with the assistance of
''human wastewater'' to be fed to lactating cows.
The dairy giant did not respond to an Otago Daily Times
question about why it had such a rule.
Mr Gousmett said the irrigated crop would be fenced off from
''It's treated effluent but it still has lots of bugs in it -
pathogens - and it's not suitable for human contact."
Mr Gousmett said one of the main drivers for the new system
was the Otago Regional Council's gradual strengthening of
consent conditions to improve water quality in waterways.
The disposal of effluent, and particularly sludge, has been a
major issue in the Lakes district for several years, and the
Lake Hawea trial is partly about boosting public confidence
in using it in agriculture.
Mr Gousmett hoped it would demonstrate how treated household
effluent could be used by farmers safely, beneficially and
without upsetting their neighbours.
''We need to prove it. We need to show it. It will take a
couple of years to do that. It's not going to happen in one
The Taupo District Council leads the way in New Zealand,
spraying treated effluent on pastures on a large scale.
The Taupo system produces 9000 bales of haylage and provides
the council there with $400,000 of income annually.
Mr Gousmett said how much farmers would pay for the Lake
Hawea lucerne had yet to be seen. An agricultural consultant
was handling that part of the process.
However, he said, the lucerne production was secondary to the
main aim of disposing of effluent in a way less likely to
harm the environment.