New algae in Seddon stream survives without sunlight

Seddon's water supply is sourced from Black Birch Stream in the Awatere Valley, and algae in the stream is a new ...
SCOTT HAMMOND/FAIRFAX NZ

Seddon's water supply is sourced from Black Birch Stream in the Awatere Valley, and algae in the stream is a new addition to the waterway. (File photo)

The algae clouding Seddon's water has never before been found in the stream where the town sources its drinking supply.

Small, brown bits of algae have plagued the town's water for the past month, and Marlborough District Council scientists say the algae strain is a new discovery in the Black Birch Stream.

The outbreak is the first of its kind to affect the town's water, and has been clogging up pipes and blocking water filters.

Council operations and maintenance engineer Stephen Rooney said further samples were taken from the water source on Monday.

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Algae typically bloomed in warm conditions and died as temperatures dropped, but this was not happening in Seddon, Rooney said.

Alkaline levels in Black Birch Stream have risen post-quake. (File photo)
FILE

Alkaline levels in Black Birch Stream have risen post-quake. (File photo)

"Algae uses photosynthesis to flourish and grow. When the spores get into the pipe and without sunlight we would expect that they would die off, but that hasn't been our experience," he said.

"This is all new to us, we are theorising how to get rid of this."

Seddon's water was sourced from the bed of the Black Birch Stream.

The supply did not provide clean filtration for households, and a boil water notice was in place for the township.

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The chemical composition of the stream had changed since the November earthquake, with a rise in alkalinity noted by council scientists.

"That change may be encouraging or making the water more favourable for this type of algae," Rooney said.

It remained to be seen how the algae strain was introduced to the stream, Rooney said.

The council maintained there were no health concerns with the algae.

The algae was an inconvenience to people and the council was working to remove the organism from the water supply, Rooney said.

Machinery to deepen the stream's intake pipe would be at the site within the next fortnight. It was hoped this would prevent the algae from entering the water, Rooney said.

Council had secured land above the Seddon War Memorial for a new water treatment plant budgeted at $4.4 million that would provide clean drinking water to 200 homes in the township.

A completion date of February next year was likely, Rooney said.

The plant would provide compliance with the national drinking water standards and enable the township's boil water notice to be reviewed and lifted.

 - The Marlborough Express

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