Polyquat colors water blue?

[bsimons]

Hi group

We have a 20 000 gallon water tank (with pump and sand filter) we use at or company for product testing. We don't use chlorine to control algae because it would increase corrosion of the stainless steel walls. Normally we use Hydrogen Peroxide, but that requires gallons and gallons to keep the levels up. Unfortunately we have been neglectful, and got ourselves a nice little algae colony.

On the advice of a local pool shop, we purchased a gallon of 60% polyquat, and dumped half of it into the tank. Two days later and the tank is far murkier than it was before! I can't tell if the colour is from an exploding algae colony, or the polyquat itself, but when I backwash the filter, the water stream has a definate blue hue, which matches the colour of the polyquat.

Has anyone else had this coloring problem using a "shock" dose of polyquat? Does it go away? What can I do to clear things up?

Brendan

[mwsmith2]

Generally, polyquat doesn't stop an algae bloom in progress, it's more of a preventative.

Furthermore, polyquat isn't blue. Are you sure that's what you got? Sounds to me like you got some sort of copper-based algaecide. This (and only this) is what needs to be on the label:

poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride]

Anything else is something you don't want.

Michael

[bsimons]

poly((oxyethylene dimethylimino) ethylene-(dimethyliminio) ethylene dichloride)

yep. And definately blue. What color is it supposed to be?

-Brendan

[bsimons]

In fact, this MSDS sheet agrees that polyquat (50%) should be a blue liquid. Now does it fade...?

[CarlD]

I've only used PolyQuat 60% and it's always brownish-black in color. Never blue. The ONLY effect I've ever noticed, even when I've dumped in 2 quarts, is FC dropping and needing to be boosted.

[bsimons]

I called our supplier and talked about the issue. She suggested that the colouring is not the Polyquat, but dead algae that is fine enough to pass through the filter.

I have turned off our pump, and will wait to see if it settles.

-Brendan