inclined plate settler 1

[pdprao]

we need to install Inclined plate settler IPS, for make-up water pretreament for cooling tower with IPS claifier. The capacity is about 125cum\hr with output tubidity level less than 10 NTU with input level of 100 NTU.
I am intrested to know , how to finalise the detention time for IPS. Wheher detention time criteria is relevant in case of IPS?. Some maufacturers claim it is not relevant in case of IPS or tube settlers .

 

[sbush]

I haven't used plate settlers, but I have used 60-degree angle tube settlers for many years. Since the mechanism that accelerates the settling rate is the same for both technologies, then it might be safe to assume that what is true for one is true for the other, but you should check this out further.

With tube settling, the hydraulic loading rate is controlled by the type of solids encountered by the application. For instance, in a routine water treatment applciation: 2 to 3 gpm / sq. ft. of plan area is typical for a 24 inch tube axis length, while a 3 to 4 gpm / sq. ft. range is typical for a 36 inch tube axis length. By comparison, an application involving metal hydroxides would range from 1.0 to 1.4 for 24" and 1.5 to 2.1 for 36".

For any mechanically-induced settler system to work successfully, it must receive water that contains fully formed floc with very little "micro" or pinpoint floc. In order to achieve these conditions, a properly design flocculation chamber is necessary and this design is highly dependent upon detention time and proper mixing.

S. Bush

http://www.water-eg.com

 

[bimr]

Why are you worried about detention time? I don't think the detention time is relevant. Detention time is not something that is commonly specified.

I recall from memory, that plate settlers normally have about a 10-20 minute detention time. You will probably find that the flow hydraulics inside of the plate settler is probably more important than detention time.

I agree with Sbush that flocculation is more important then detention time. The stream must be flocculated before entering the plate settler.

I might add that sidestream treatment of the cooling tower is probably more cost effective than treating the makeup.

 

[Murphy625]

Ok.. Maybe I am off the mark here or missing something but here goes.

Retention time for what? No matter the manufacturer of the clarifier, the amount of volume you will be able to send threw it will depend on what it is your trying settle out.

If your asking about how long the flokulant needs to bake, it doesnt need but a few seconds but it does need to be mixed in a seperate tank. (usually just above the clarifier with a gravity overflow feed into the top and a wide body, low RPM mixer paddle that doesnt shear the flock apart).
Its also a good idea to put a small drain hole in the bottom of the mix tank so it drains itself when not in use. This will help to stop any bacteria from growing there if the water your treating is warm.

Hope this helps.

Murph