Sewerage now handled with care


A state-of-the-art sewerage plant has recently been installed in Kaitangata.

The plant, produced in the United States, is a first for New Zealand, and is only employed at this site and a smaller location in Heriot.

“Before this, it was just an oxidation pond, where all the waste from Kaitangata would come and sit for 30 days, mixed by the wind, and then drained into the river,” Clutha District Council senior projects engineer Peter Ross, said.

“We’ve introduced barriers which force a zig-zag path, lengthening the treatment process to 60 days . . . The waste moves through the channel created by the barriers, and is captured in plastic cages called bioshells.”

The bioshells are made with an inner and outer cage which gives a greater surface area to catch suspended solids and other substances.

The whole build cost about $1.75million, and brings the Kaitangata operation into line with recently released government regulations regarding levels of bacteria and substances in the filtered waste.

There has also been the addition of a large processing plant beside the oxidation pond, where most of the refinement and filtration takes place.

Levels of different markers such as biological oxygen demand (BOD), ammoniacal nitrogen, and E. coli are monitored at the site

Mr Ross said the site consent limit for E. coli means “nine out of 10 consecutive readings need to be below 260 per 100ml . . . ours is less than six.”

It dwarfs its Heriot counterpart, with a 28 membrane module plant covering a 9500sq m pond. The Heriot site has five modules covering a 2500sq m pond.