Worm Composting For Sewerage Plant

Worm composting will be used to improve environmental performance and minimise costs at the Council’s new wastewater treatment plant in Kaeo.

The new plant, which should be operational in July, will use wriggler worms to boost the effectiveness of traditional sewage treatment processes.

Infrastructure and asset general manager David Penny says the treatment process will still rely on screens, settling ponds, biological filtration and wetland cells to polish treated effluent.

However, composting worms will be added to the filter screening process to aerate the filter medium, promote good bacteria activity, improve the level of treatment and lower energy costs.

Mr Penny says the composting technology has been designed in-house and draws on an international concept.

Because there is an element of risk, the plant has been designed so that ultra-violet light treatment can be added to the polishing process at a later date if necessary.

"At this stage, we are relatively confident that will not be necessary and we will comfortably be able to meet the water quality standards in the new resource consent."

The Council will consider using worms at other wastewater treatment plants if worm composting at the Kaeo plant proves successful.

Mr Penny says the quest for innovation had largely been led by rising costs of meeting ever-increasing water quality standards.

Another difficulty has been the variation in the required standards from scheme to scheme.

The Council is having ongoing discussions with the Northland Regional Council about the question of uniformity and the need to take a whole-of-catchment approach to lifting water quality standards.