WEF Discussion Forums
Operation and Maintenance
Chlorine survival in activated sludge
I know that any chlorine added ahead of an activated sludge system (like for cleaning of weirs) has no chances to survive activated sludge and will not register in the effluent as CPO (unless it is added there for disinfection). However, does anybody have any direct data, experience or reference related to that?
We have chlorinated our activated sludge system at up to 5.0 mg/L for a couple weeks for filiment organism control and there was no chlorine residual in our effluent from the activated sludge sustem.
I assume that the dose was 5 mg/L per influent flow, correct?
No, we chlorinated the RAS at 5.0 mg/L so the total influent into the activated sludge system would have been 1.5 mg/L based on relative flows. I should have been more thorough in my posting.
Cleaning of secondary settlement tank weirs with calcium hypochlorite is a regular practice in our WWTP , as a result we have never found any residual in the downstream.
For filiment control i hit my RAS at 200 Lbs/day and have no residual in the effluent.
Hey there this may be a bit off topic but we have been spraying and dosing our activated sludge tanks at the RAS and have had no problems with cl2 levels in the effluent climbing. I was just told to keep a close eye on the bugs to make sure we were not killing off the good bugs as well as the filamantrous. That being said the reason we have been spraying our tanks is we have this tan colored foam that will not go away. We have tried vaccuming it, spraying them with water, and dosing with cl2 at the RAS. This foam does not seem to be effecting our lab results,settle or effluent it is more of a personnal vendetta to get rid of it now !! lol. If anyone has encountered this problem or has any insight on it, I would love to hear from ya.
Also we believe the foam was created by old sludge to begin with and we have also cranked the wasting up and added fresh molasses ahile ago.