Phosphorus Removal

[lamojai]

Has anyone have familiarity with biologic phosphorus removal in a anaerobic fermentation tank associated with a WWTP? What equations have you used to calculate amount removed. Assume ~1 hour residence time in tank. I am looking at Equation 15-67 in Manual of Practice # 8 WEF WWT Design.

Thanks!

 

[bimr]

Anaerobic "fermentation" tanks are not normally used for biological phosphorous removal.

10 to 30 percent of the influent phosphorus is removed during the typical secondary aerobic biological treatment.

If you have anoxic conditions, you may have phosphorus released from cells under anoxic conditions.

 

[lamojai]

I'm attempting to get P and N removal at an old WWTP and want to reuse the existing basins in rebuilding this plant. Things in pathetic shape. This is a new proposed AeroMOD plant. The old plant's were not well thought out, but the new design seems well thought out.

This proposed tank is right behind grit removal w/ residence time of ~ 1 hour. My understanding is that Phosphorus will be released in solution. A selector tank is next and the influent is mixed with the clarifier return and then on to the aeration tank. The P will be taken up from solution for biomass synthesis for biochemical
synthesis in the aeration tank. Some of the mixed liquor, and solids that have accumulated on the floor of the basin beneath the aeration grid, are removed to a digester. So some of the P is removed from the process. The next portion of the treatment train is an anoxic basin where air is pulsed on and off on a two hour basis. Denitrification will occur at this point in the process. From there the mixed liquor goes to a clarifier where the solids will be returned to a selector tank and mixed with influent prior to entering the aeration basins or removed to a digester.

 

[bimr]

It is doubtful that you would get any phosphorus stripping in the anoxic basin as the retention time is so small.

Also, limited design data is available for what you are trying to accomplish. Don't know of any equations that you can use to predict the performance. The expected results will depend greatly on the design and performance of the final clarifier as well as the BOD/P ratio.

Overall, it is reasonable to expect that the performance of your system to be similiar to what can be obtained with the SBR process. As shown in this paper, when BOD to P ratios are favorable, the anoxic/anaerobic first stages (combined with appropriate organic loading rates and HRTs can result in significant TP removal down to 1 to 2 mg/l. Note that phosphorus removal requires management by skilled staff.

http://www.epa.gov/ORD/NRMRL/pubs/625r00008/tfs8.pdf

Since you mentioned AeroMOD plant, why don't you get an opinion from them.