New Zealand council approve environmentally friendly sewage treatment

Central Hawke's Bay District Council in New Zealand has approved a new environmentally friendly sewage treatment option, using floating wetlands on existing oxidation ponds to treat waste in the region.

The new system uses floating wetlands on existing oxidation ponds to treat sewage. The plant roots grow down into the wastewater, taking up nutrients and treating the sewage through organisms that grow on the roots.

Once this procedure has taken place, the effluent is then dosed with chemicals and passed through a sand filter to remove phosphorus, before it is irradiated with ultra-violet light to kill pathogens. The final product is expected to be close to drinking water in standard, and is discharged into local rivers of Tukituki and Waipawa.

Central Hawke's Bay mayor Peter Butler said: "This has been the biggest decision this council has had to face in a number of years.

"In coming to this option ... we thought hard about what is right for the environment and affordable to the ratepayers of Central Hawke's Bay."

The construction cost for the sewerage treatment upgrade project to be budgeted in the council's Long Term Plan (LTP) was $6.2million (£3.1 million), and included other work required to bring parts of the existing sewerage treatment plants up to the latest standards.

Using floating wetlands was considered the best option above worm farm treatment, sequential batch reactors, a modified Bardenpho plant or anaerobic digestion. There was also an option of forest treatment, which would have required a new resource consent.

"The investigations and consultation carried out to reach this result have been extremely robust, and the end result, with considerable savings in cost to the ratepayers and the significantly improved quality of the treated effluent going into the rivers, was a great result for the efforts of councillors, staff, and the community as a whole," Mr Butler concluded.

Posted by Joseph Hutton