CVEN 5534

Metro Denitrification exercise.

Objectives

1. Configure Modified Ludzack Ettinger (MLE) process in the Metro activated

sludge process by implementing an anoxic zone in the current aeration basin

volume and recirculating nitrified mixed liquor from the end of the aerated

zone back to the anoxic zone.

2. Test the

effect of the size of the anoxic zone at Metro on

effluent nitrate. Changing the volume of the

anoxic CSTR(s) affects anox. (SRTanox) (see notes). Select a value for

this between 0.5 and 1.5 d. and use the value for aer that you computed from

Tuesday’s class, and note that Vanox/Vaer = anox/aer. Test the effect of

increasing/decreasing the anoxic zone (CSTR) volume. Remember that the

effect of a long SRT is to make more COD from decay available for

denitrification, which has the advantages of not consuming oxygen as it does

in the aerated process and also consuming more of a contaminant, nitrate.

3. Test the sensitivity of denitrification at Metro to carbon limitation by

changing the influent COD – experiment with the readily degradable and

slowly degradable fractions.

4. Test the sensitivity of denitrification to nitrate limitation by varying the

mixed liquor recirculation rate (MLR). Currently at Metro MLR is

approximately equal to the influent flow rate.

5. Which of the three operational parameters provides the lowest effluent

nitrate? What are the associated costs? Are there undesirable effects such as

increasing oxygen consumption in the aerated zone? Higher ammonia in the

effluent? Or other?

QW

Q + QRAS

Q+QRAS+MLR

MLR

QRAS

Q + QRAS

Anoxic Tank Aerobic Tank

SNO,aer