Water and Wastewater.com Help Forums

YaBB Newbies

Offline

I love Water and
Wastewater.com

Posts: 13

Company or Organization: Village of Liberty WWTF

Phosphorus removal
May 02^nd, 2012, 7:18am

Hi everyone, I have a question about phosphorus removal. I have run some inside tests of our phosphorus removal throughout our plant. I am using a Hach pocket colorimeter that reads orthophosphate and I am multiplying it by the factor .326 (as per the book) to get our results. Here are my results:
Inf 3.52 P
oxidation ditch 1.12 P
clarifier .883 P
Eff .903 P

My question is why is the phosphorus level higher in the effluent location than it is in the clarifier supernant? None of the samples are filtered. We currently use polyaluminum chloride to chemically remove phosphorus and we add that in the weir of the oxidation ditch so it has time to mix in the flume to the final clarifiers.
Thanks, Rebecca

Back to top

IP Logged

Eric Raj

God Member

Offline

As long as it flows,
I'll treat it!

Posts: 518

Gender: male

Company or Organization: City of Bedford

Re: Phosphorus removal
Reply #1 - May 2^nd, 2012, 8:18am

Rebecca.

Those two results are rather close to being the same. But it could simply be from some of the organisms in the clarifier effluent decomposing and releasing phosphorus into the water.

This could also possibly come from organically bound phosphorus that has become unbound.

It might also simply be the natural variance between sample volumes taken by you.

~Eric

Back to top

IP Logged

BendelBoy

Senior Member

Offline

Free the STOAT

Posts: 317

Gender: male

Company or Organization: wrc plc

Re: Phosphorus removal
Reply #2 - May 2^nd, 2012, 9:57am

Are these average values or spot samples? If you are quoting a spot sample, then you need to account for whatever hydraulic delay might be working with the diurnal profile.

You also need to look at the meter accuracy as to whether the difference is significant; as already pointed out, ther are natural variances in samples, and at low concentrations small background effects can matter, such as what might be picked up or broken down in the effluent channel.

Back to top

IP Logged

Anabaena YaBB Newbies Offline I love Water and Wastewater.com Posts: 26 Gender: Company or Organization: public works	Re: Phosphorus removal Reply #3 - May 2^nd, 2012, 9:11pm Rebecca, I have tracked this similar issue at our facility. If these are grab samples taken at these spots near the same time it is more than likely hydraulic delay as mentioned above. I'm assuming you use flow proportion on the chemical feed. It is normal for us to see this. I hope this helps. David
Back to top	IP Logged

Liberty WWTF YaBB Newbies Offline I love Water and Wastewater.com Posts: 13 Company or Organization: Village of Liberty WWTF	Re: Phosphorus removal Reply #4 - May 3^rd, 2012, 7:01am Thanks everyone for the information. I had a feeling it was due to variances in the grab sample or due to hydraulic loading since the results were so close. I just wanted to verify if my assumptions were correct!
Back to top	IP Logged

Peakman

Ex Member

Re: Phosphorus removal
Reply #5 - May 9^th, 2012, 4:19pm

Just have a quick check on the dates on the cuvettes and make sure you use the best range for your expected values. Also do a couple of tests for each sample point. I've recently gone through a couple of dozen boxes of these things. The 348's will read down to about 0.3 but are not exact values, as lab results will confirm. The 349's would be a better range but when you consider the results in real terms these are tiny amounts of difference.

Back to top

IP Logged