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Algae Growth in WWTP Clarifiers

Algae Growth in WWTP Clarifiers

(OP)
What are your opinions on algae control in secondary clarifiers? Some of the alternatives I know/have heard of are:

1. Install a cover over the entire clarifier
2. Install sun shades for the effluent troughs only
3. Install an automatic brush/cleaning system
4. Increase manual cleaning frequency

RE: Algae Growth in WWTP Clarifiers

If circular clarifiers I use round road sweeper brushes sized to fit the channel. The bridge pulls them round. If you cut them in half to they can be sized to fit over the tops of the weirs and clean those too. Cheap and simple.

RE: Algae Growth in WWTP Clarifiers

At some wastewater treatment plants, the operators place chlorine tablets in the weirs to control algae. It seems to work.

Placing covers over the weirs amd effluent troughs will eliminate the algae. The automated brushes will not stop the algae, but will scrape the algae off.

RE: Algae Growth in WWTP Clarifiers

Super chlorinate routinely and add covers works in the Australian warm water high sunshine environment.

“The beautiful thing about learning is that no one can take it away from you.”
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http://waterhammer.hopout.com.au/

RE: Algae Growth in WWTP Clarifiers

(OP)
I had an operator claim that covers require a lot of maintenance and therefore don't really result in a net benefit over periodic manual cleanings.

What maintenance could there be for a cover?

RE: Algae Growth in WWTP Clarifiers

Period manual cleanings are quite a bit of work and there are some safety issues associated with the cleaning.

With the covers, you lose the ability to see the weirs. If the covers are made of stainless steel, there should be little maintenace.

There are no simple answers. Some times it ends up being individual preference. Perhaps the operator has experience with poorly made covers.

RE: Algae Growth in WWTP Clarifiers

Our secondary clarifiers are circular and come equipped with brushes in the channels. The operators occasionally hose off the clarifiers with reclaimed plant water from the chlorine contact channels. There doesn't seem to be any algae growth in the secondary clarifiers. However, our aeration basins get the occasional algae blooms which are broken apart with reclaimed water.

RE: Algae Growth in WWTP Clarifiers

I have seen a chlorine piping ring setup which chlorinates the water as it spills over the weirs into the effluent trough. I would think that the things to look out for is to ensure the chlorine system stops if the flow to the clarifier is interrupted. You do not want to kill the bugs. The other thing is that you want to use chlorine gas as opposed to sodium hypochorite. With sodium hypochoritle the diffuser holes will plug up very quickly.

RE: Algae Growth in WWTP Clarifiers

I have seen a chlorine SUBMERGED piping ring setup which chlorinates the water as it spills over the weirs into the effluent trough. I would think that the things to look out for is to ensure the chlorine system stops if the flow to the clarifier is interrupted. You do not want to kill the bugs. The other thing is that you want to use chlorine gas as opposed to sodium hypochorite. With sodium hypochoritle the diffuser holes will plug up very quickly.

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