Pre-Chlorination prior to slow sand filtration 1

[ch81pc]

Hi

I will be responsible for commissioning a pre-chlorination system for the control of zebra mussels in the near future. I would be interested to hear from anyone with regards suitable dose rates (as a Cl2 residual)needed to kill the mussels, together with any tips or suggestions for operating such a plant up-stream of slow sand filtration.

Many Thanks

Paul

 

[JonGatPCNA]

There is quite a bit of info on line on Zebra Mussels that should help you prepare. The circumstances of your system and potential for zebra mussels will determine the appropriate dosages and it's difficult to evaluate that without understanding more about your project.

A very good resource is the "Practial Manual for Zebra Mussel Monitoring and Control". Chapter 5 is quite extensive on Chlorination. (You can find the book on Amazon for $129new). It will give you the tools and knowledge to prepare. Good luck on startup!

Jon Gribble, PE
Paterson Candy North America
A Division of Black & Veatch
Water Treatment Design-Build Process Contractors

 

[ch81pc]

Thanks Jon,

I have ordered a copy of the manual! I am interested to know of any experience you might have with such systems prior to slow sand filteration? My concern is of a chlorine residual making it onto the beds and wipping out the good bugs in the filter skin.

Thanks again

Paul

 

[JonGatPCNA]

Paul -

I have some experience starting up similar systems; however, you've confused me with the comment about "good" bugs on the skin of a slow sand filter. A chlorine residual you will likely not leave any bugs whatsoever unless they have a strong resiliency against oxidation. The mussels being a multicelled organism can withstand quite a bit, whereas smaller or single cell organisms simply don't have the body mass to resist a chlorine residual.

Perhaps you could explain the process you will be starting up and it's purpose to better understand what you are asking.

Jon Gribble, PE
Paterson Candy North America
A Division of Black & Veatch
Water Treatment Design-Build Process Contractors

 

[ch81pc]

Thanks Jon,

The system will be used to dose sodium hypochlorite at around the 2ppm level to raw water (prior to pre-ozonation and rapid filtration) in order to kill the adult mussels during their "non-breeding" period. Once the adult mussels have been removed the dose of hypo will be reduced to around the 0.5 ppm level to prevent re-infestation during the warmer months. I am interested to know of any control methods I can implement or any experiences in operating such a system that will help to prevent any residual chlorine from reaching the slow sand filters and killing the schmutzdecke.

Thanks again

Paul