CONTROLLED CARBON SOURCE ADDITION TO AN ALTERNATING NITRIFICATION DENITRIFICATION WASTE-WATER TREATMENT PROCESS INCLUDING BIOLOGICAL P-REMOVAL

The paper investigates the effect of adding an external carbon source on the rate of denitrification in an alternating activated sludge proc ess including biological P removal. Two carbon sources were examined, acetate and hydrolysate derived from biologically hydrolyzed sludge. P reliminary batch experiments performed in 5 liter bottles indicated th at the denitrification rate can be instantaneously increased through t he addition of either carbon source. The amount by which the rate was increased depended on the amount of carbon added. In the main experime nts performed in a pilot scale alternating process, the addition of ei ther carbon source to the anoxic zone also resulted in an instantaneou s and fairly reproducible increase in the denitrification rate. Some r elease of phosphate associated with the carbon source addition was obs erved. With respect to nitrogen removal, these results indicate that e xternal carbon source addition may serve as a suitable control variabl e to improve process performance.