26 February 2013

Bugs save ratepayers millions

They saved the world from Martian invaders in H.G. Well’s 1898 classic ‘War of the Worlds’ and they are at it again – this time saving the ratepayers of South Taranaki millions of dollars!

A report on the trial using bacteria to remove sludge from the Hawera Wastewater treatment pond, presented at last night’s (25 February) South Taranaki District Council (STDC) meeting, has shown excellent results with an estimated 22% of the sludge removed over the last 9 months.

Report author, STDC operations and projects manger, Viv Eyberg says the results are extremely positive and believes the innovative solution to sludge removal will be able to be used across all Council wastewater ponds.

“I understand this unique trial is a New Zealand first in municipal wastewater systems and will save the Council and our ratepayers $3.7 million over the next four years.”

“Calculating the amount of sludge reduced is not an exact science, however we have conservatively calculated a 22% reduction which is about 18,700 cubic metres,” he says.

Mr Eyberg says the process while unique is all natural.

“The process basically involves putting bacteria which produce enzymes (called exoenzymes) into the wastewater pond. These exoenzymes help break the organic waste in the pond down into a soluble form which can then be more easily consumed by the bacteria. The process of converting the larger particles of sludge into a soluble food is very slow and can be affected by temperature. However once the organic waste has been broken down it’s then rapidly consumed and is largely converted into carbon dioxide (CO2) and water, along with new bacterial cells. The bacteria which produce the exoenzymes are naturally occurring and have not been modified in any way,” he says.

“There is 85,000 cubic metres of sludge in the Hawera Wastewater pond which, using the traditional method, would involve mechanically dredging and separating the sludge. This is a relatively expensive process which also requires a site to bury the sludge,” says Mr Eyberg.

To date the biological trial has cost $164,000 with the final cost of total removal estimated to be $646,000. This represents a saving of $3.7 million from the $4.38 million that had been budgeted for sludge removal in the Council’s Long Term Plan.

However, as well as the financial benefits the report also highlights the environmental benefits of biological sludge removal which are considerable when compared to simply sending the sludge to landfill.

Based on the trial’s results the Council endorsed the future use of biological removal of sludge in other wastewater treatment ponds within the district, starting with Waverley in spring/summer 2013/14.

STDC Chief Executive, Craig Stevenson says his Council is delighted with the results so far. “Nationally beneficial reuse or responsible disposal of bio-solids is a big issue and it’s great to see STDC is at the forefront of an innovative solution that is environmentally responsible and saves our ratepayers a great deal of money. This solution has the potential to save the local government sector tens of millions of dollars and I understand there is already a lot of interest from other Council’s around the country.”

ENDS

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