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RE: Pre Filter Application of Alum for Phosphorous Removal

TerryF — Wed, 07 May 2008 07:16:33 GMT

I agree with Wiff's comments.

However as you asked specifically about alum, typically a ratio of Al to P (to be removed) of about 3:1 is okay. Note that this is not Alum but aluminium. The actual alum dose rate will depend on the concentration of Al in the alum form you use.

Regards

TerryF

RE: Pre Filter Application of Alum for Phosphorous Removal

Wiff P — Tue, 06 May 2008 14:19:11 GMT

If the TSS is 10-15 mg/L and assuming typical suspended solids P content of 3%, your total P will be between .3 and .45 even if ortho (dissolved) P is zero. So if you're working to a total P of 0.3 mg/L may be a challenge. If you do BIO-P removal content of P in TSS will likely be even higher. Nonetheless, I assume you're using something like a cloth filter given the TSS you're shooting for and I've seen SBR's with cloth filters do this either with two point metal salt addition or blend of bio-P and trim with metal salt. You might do better with PAC (PolyAluminumChloride) for your trim dose, but some plants can achieve fairly low levels with ferric salts and poly combinations, ultimate choice depending on cost and on sludge disposal methods (in latter case some sludge options may not like to see higher levels of aluminum in sludge). Realize that the effectiveness of these coagulants is to drive soluble P quite low and at the same time help you achieve single digit TSS concentrations.

By the way some activated sludge plants are doing so well with their activated sludge fine tuning that they can get to 0.3 mg/l without a filter, at least in warmer weather. The more fine tuned the activated sludge plant and the more fine tuned the coagulant(s) dosage(s) the easier it is to get below 0.3 mg/L. Good operators routinely achieve miracles!

Pre Filter Application of Alum for Phosphorous Removal

01813603 — Tue, 06 May 2008 11:39:25 GMT

We desire to reduce TP from about 1 mg/l after secondary clarification and through the use of an enhanced biological TP removal system to .3 mg/l TP.

It is expected TSS post clarification will be about 10 mg/l to 15 mg/l.

We plan to use a filter and are considering the option of applying alum pre filter to reduce the TP from 1 mg/l to .3 mg/l.

Given the 15 mg/l TSS and the objective of .3 mg/l TP, can someone help in regards to (1) the amount of alum required to be added and (2) the resulting combined TSS load on the filter.

Thanks