August 14 2013

Wet weather spills eliminated

The largest single point source of pathogens entering the Whangarei harbour during storms has been eliminated now that a new treatment process at the Kioreroa Road plant is operational.

The treatment process, that includes 512 ultraviolet (UV) lamps, was switched on for the first time during the storm on 2 August and treated 23,600 cubic metres of rain diluted wastewater.

Up until now this water would have gone directly into the harbour.

The process killed a staggering 99.998% of the bacteria that passed through it, turning the potentially hazardous wastewater into something that was better than the quality required for swimming.

Whangarei District Council Waste and Drainage Manager Andrew Carvell said that the process works by irradiating bacteria, viruses and other pathogens with high intensity light that damages their ability to grow or replicate via a process not too dissimilar to that which causes sunburn.

“In the recent storm we estimate 726 trillion (725,985,000,000000) E.coli bacteria were killed that in the past would have gone into the harbour during a major rain storm,” he said.

“The great thing about the new system is that we now have more treatment capacity than can actually be pumped to the plant, meaning everything will now be treated.

“This $3million project concludes Stage 1 of the Councils wastewater improvement programme that aimed at dealing with the big sources of wastewater spills during storms.

“Other projects completed in the past five years to reduce wet weather spills include the Okara pump station upgrade and the Hatea storage tank and treatment facility.

The new UV system was built under two main contracts; a civil construction contract with United Civil Construction Ltd ($1.3M) and an equipment supply contract with Filtec NZ Ltd ($1.2M).

“It doesn’t stop there though,” Mr Carvell said.

“This financial year the Kamo Road sewer will be upgraded and we are going to renovate the wetlands along Kioreroa Rd.

“More work will be done to improve the treatment process at Kioreroa Rd and focus on problem areas in the city which suffer localised effects during wet weather,” he said.

ends

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