Ammonia and Phosphorous removal in municipal wastewater treatment plant with extended aeration.

Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater and
septage, which treats about 12000 m3 d-1 of municipal wastewater and 8000 m3 d-1 of septage, and analyzed
for solids, COD, ammonia, nitrate, orthophosphate, polyphosphate and total phosphorus. Ammonia is
almost completely eliminated within the plant. Orthophosphates show a removal of about 28%, while total
phosphorus is removed by about 15%. The mean value of the ratio (phosphorus eliminated)/(COD eliminated)
in mg g-1 is 8. Assuming suspended-growth nitrification and denitrification kinetics as proposed in
literature, the percentage of nitrifiers in the activated sludge population is estimated at 1.1%. Assuming
that phosphorus removal in the aeration tank is proportional to cell formation, which in turn is proportional
to substrate elimination, the phosphorus content of the activated sludge is estimated at 0.031 gP (gVSS)-1.