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Joined: 12/4/2009
Posts: 1
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I am looking for some ideas and/or feedback on chemical phosphorus removal in a small RBC system.
The plant has three primary settling tanks prior to the RBC. The RBC effluent goes to a clarifier, the RAS is pumped to the 2nd of the 3 primary tanks. Clarifier effluent passes thru a roto-strainer prior to the clearwell and is then pumped up the hill for sub-surface disposal. Solids are trucked off-site periodically thru the year. The plant design peak flow is 300 m3/d and our summer peak flows are ~120 m3/d. This is a seasonal resort area and our winter flows average ~15 m3/d. The Total P levels spike in the summer to 7-9 mg/L and far exceed our permit of < 1 mg/L.
Currently alum is dosed into the effluent side of the RBC. Not quite sure of the dosing rate right now, I will add when I calculate it.
I am considering trying ferric chloride, liquid alum, ferric sulphate, and PAC. I need a robust system as the plant is not monitored daily. Also, I have newer and inexperienced operators to monitor the system.
Finally, the BOD and TSS on the final effluent is < 10 / <10. I have sent in a sample recently for dissolved P as well as Total P. I know the solids handling is terrible in this sytem and am sorting that out as well. Any suggestions regarding the chemical P removal are appreciated.
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Joined: 10/7/2009
Posts: 10
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You might check out sodium aluminate, however, it does require being kept relatively warm at all times during storage otherwise it will crystallize. But it does precipitate out phosphorus. I have seen it do this in primary basins along with the primary sludge.
~Eric
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I have heard that lanthanum compounds can be used very effectively for P removal.
David Wichern, aka "Dedalus"
Dedalus Environmental
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You may want to look at primary clarifier eff. P conc. as well as the inf. P Establishing sol P vs. TP is good idea too. it might help in calculating dose more accurately. But...<1 P limit means you've got to shoot for 0.5 mg/l P at sec clar eff. and calculating dose at that low a level can't be done accurately. trial and error, jar tests on Pri Eff highly recommended.
Depending on conditions in Pri clar 1,2,3 you will get P release under anaerobic conditions. More frequent solids removal may help lower P conc and you might want to do that before chemical addition to maximize process first then find out what chem needs are. Good Luck!
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Joined: 4/22/2010
Posts: 2
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Hi
We have air extended plant, suddenly begin to appear a floating sludge at aeration and settlement tanks. The appearance of this sludge look like a clod of earth with a gelatinous consistency, and appear in a regular hour.
The oxygen in aeration tanks is ok.
Any clue about what could cause this.
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Just wanted to update everyone. The alum dosage has been between 30 -50 mg/L and ~ 90% of the Total P is dissolved. I have managed to reduce the Total P to ~ 2 mg/L using the alum with low flows throughout the system (< 40 m3/day). I am switching to a PAC in the next month to reduce my dosing rate in anticipation of higher average daily flows. The next step it seems is a decent solids removal program, although my options are limited to removal by vac truck.
All suggestions are appreciated. So often a new set of eyes (or another brain) sees things out of place we have become conditioned to.
Thanks,
TMc.
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It seems to me that you have old sludge;just increase your wasting.
Just be mindful of how much you waste; espciall if you are trying
to nitrify.
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