5 replies to this topic

Problem that occured in wastewater treatment plant (electronic plant):

-sometimes floc is underdeveloped in the flocculation tank.

I am a trainee in a factory. I was given a task to improve the wastewater qualilty. So, my question is: is it necessary to control the pH for raw water in sump tank in order to improve the floc formation in flocculation tank. Any solution to improve the waste treatment system?

Our current system contain the following packages:

-sump tank
-coagulation package
-flocculation package
-incline clarifier
-sludge thickener
-pH adjustmeny tank
-sampling tank

Can somebody enlighten me on this matter? I am also very glad to hear yours experience in wastewater treatement if u all wanna share with me.

Thank you very much :-)

[P.K.Rao]

Julia,

Floculation does require control on pH. A pH of 8.5 to 9.5 is ideal. Floc quality depends upon several factors such as concentration of floculant dosed, pH, speed of mixing and the chemical nature of the effluent. You can make a few experiments with laboratory floculator and strike at the most suitable conditions. Aluminium sulfate and lime are the two chemicals used for floculation. Ferrous sulfate, lime, fuller's earth
and chlorine are also used sometimes but they are a somewhat more difficult to control.

P.K.Rao

P.K.Rao,

Can you please clarified me on the following matter?


Current system:

-sump tank.(no pH control here)
-coagulation tank(have pH control to range of pH7-9 by using acid or caustic)
-flocculation tank(no pH control)

Is it i need to do the adjustment of pH in flocculation tank to 8.5-9.5?
OR
just adjusting the pH in coagulation tank to 8.5-9.5 because the water in flocculation tank is come from coagulation tank.

Is it pH for coagulation process same as pH for flocculation process?

[P.K.Rao]

Julia,

Generally pH is maintained in the floculation tank where floculant is dosed there. Perhaps you are calling the settling tank as coagulation tank where no pH control would be neded. However your system needs careful study.

P.K.Rao

P.K.Rao,


Thank you for your reply.

[THCooke]

There are different coagulants that work better at different pHs. If you can get a slight floc to form, which sounds to be the case, you are achieving the charge destabilization around te colloids, which is the primary job of the coagulant. What might be most effective is to add a polymer to bring the destabilized colloids together. As previously mentioned, jar testing will go a long way to determining this.