"It's the best environmental outcome, spread out over enough time to make it affordable."
Mr Crimp said pressure from Government to stop discharges into waterways prompted the council to investigate options.
Wastewater includes water from washing machines, sinks, showers, baths, sewage from toilets and trade wastes.
The community doesn't accept this disposal method any more, said Mark Allingham, SWDC group manager infrastructure services.
"We know expectations are changing, and we are making a decision now for our grandchildren to make sure they have a healthy environment in which to live, work, and play, but won't be lumbered with excessive debt to pay for it."
Mr Allingham said they spent four years researching treatment techniques to find the most environmentally effective and affordable options.
It is proposing land-based treatment by irrigation for Greytown and Martinborough and a membrane plant for Featherston, to eventually stop water pollutants, such as phosphorous and nitrogen, from entering local rivers, streams and lakes.
Currently, wastewater enters a main oxidation pond, is treated through UV filtration to kill bugs and then discharged into local waterways.
Under the proposal, instead of going into the waterways, it will be sprayed onto land already owned by council near Papawai Marae and at Pain Farm, near Martinborough's current plant.
By 2015, the council expects a quarter of Martinborough's wastewater - about 21 Olympic-sized swimming pools - won't go into the Ruamahanga River every year.
Twenty years after that, they expect to have 100 per cent land-based treatment.
The land-based option is not proposed for Featherston, which does not have enough land available for the volume of wastewater flowing through its pipes.
"Our investigations indicate up to 74 per cent of the wastewater reaching the treatment plant is groundwater or stormwater, most likely from a mix of leaking pipes and illegal connections," said Mr Allingham.
Mr Crimp said because phosphorus and nitrogen are nutrients on land but not in water, they can actually help the council to grow crops that could be sold to minimise the rates bill.
Mr Allingham said work on the three treatment plants will be done simultaneously.
"We want to do this once and do it right, and I am really comfortable that we will achieve that.
"We have some of our own local challenges, but the technology we are proposing is operating successfully in similar communities all over New Zealand, so we see very little risk."
Resource consents are being submitted to Greater Wellington Regional Council
Mr Allingham encouraged anyone interested to make a submission or ask the council any questions.
