Water New Zealand Web Forum

CluthaDC · Joined: 04 Apr 2007 Posts: 24 Location: Balclutha, NZ

Help!!
A ghastly green algal slime has established in an open clarifier tank at one of our Water Treatment Plants, and is clogging the launders which consequently are needing frequent cleaning. I'm told it typically thrives in warmer nutrient-rich water. The raw water source is a natural stream which is doubtless enriched by farm run-off. Has anyone had experience with this stuff? We thought of pre-chlorinating to kill it off, but any suggestions are most welcome! cheers.
_________________
Hank Stocker
Water Services Manager
Clutha District Council

Wicca · Joined: 09 Aug 2008 Posts: 6

Greetings Hank,

We had a problem similar to that up here in Otorohanga. Mad

We covered the clarifier with a shade screen and have reduced the growth by over 50%. Could just be coincidence or could be part solution.
So far we are happy with the results though

Cheers
Jon

Rob · Posted: Thu Nov 19, 2009 8:19 am Post subject:

They use the shade cloths quite a bit in Aussy for that situation.

It's a bit risky prechlorinating ahead of clarifiers in case you generate disinfection byproducts. You could also end up with taste issues from the break down of the algal cells.

Kevin McKay · Joined: 23 Apr 2007 Posts: 4

If you are considering dosing with chlorine ...it would be better to dose with chlorine dioxide. Chlorine Dioxide is more effective against slime, as it is able to penetrate the surface layers. Also unlikely to get chlorinated organics/chloramines as disinfection by products.

CluthaDC · Joined: 04 Apr 2007 Posts: 24 Location: Balclutha, NZ

Thanks guys,
We have been offered the opportunity to trial a proprietry ultrasonic device (cost about $5k), which may solve the problem. I'll keep you posted. cheers.
_________________
Hank Stocker
Water Services Manager
Clutha District Council