Title page for ETD etd-121698-120457


Type of Document Master's Thesis
Author Nair, Arthur William
URN etd-121698-120457
Title Investigation of the Effects of Sequential Anaerobic, Anoxic and Aerobic Zones on Dissolved Oxygen Transfer Parameters in a biological Nutrient Removal Pilot Plant
Degree Master of Science
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Randall, Clifford W. Committee Chair
Little, John C. Committee Member
Love, Nancy G. Committee Member
Keywords
  • Alpha
  • biological nutrient removal
  • dissolved oxygen transport
  • KLa
Date of Defense 1998-12-01
Availability restricted
Abstract
ii

INVESTIGATION OF THE EFFECTS OF SEQUENTIAL

ANAEROBIC, ANOXIC AND AEROBIC ZONES ON THE

DISSOLVED OXYGEN TRANSFER PARAMETERS IN A

BIOLOGICAL NUTRIENT REMOVAL PILOT PLANT

by

Arthur William Nair

C. W. Randall, Chairman

Environmental Engineering

(ABSTRACT)

Bench and pilot scale determinations of the volumetric oxygen transfer coefficient, KLa,

were performed on an improved A2/O biological nutrient removal (BNR) pilot plant.

Effluent from a full scale primary clarifier, used as pilot plant influent, was found to have

an alpha (ratio of process to clean water KLa) of 0.71 as determined in a 21 liter bench

scale reactor and an alpha of 0.332 as determined in a 0.45 m 3 aeration basin of the 2.4 m 3

pilot plant. Alpha of a 1:1 mixture of primary clarifier effluent with pilot plant return

activated sludge was determined to be 0.94 at bench scale and 0.71 at pilot scale. An

assay of alphas through the initial non aerated treatment zones of the pilot plant using the

bench scale reactor indicated that alphas peaked in the effluent of the first anaerobic zone

(alpha equal to 1.01) and were lower in the second anaerobic zone and first anoxic zone.

An assay of alphas in the three pilot plant series sideline aeration basins indicated that

alpha was maximum in the first aeration basin (alpha equal to 0.905) and were lower in the

second and third aeration basins (0.716 and 0.661 respectively). A consistent increase in

average surface tension was noted from the first to second to third aeration basins,

however the differences were not statistically significant. A comparison of pilot plant

alphas determined in the first aeration basin following anaerobic nominal hydraulic

retention times of 0.0, 0.21, 0.43, and 0.64 hours yielded alpha values of 0.71, 0.94,

0.64, and 0.74 respectively. Like the assay using the bench scale reactor, the alpha values

at pilot scale peaked following treatment in only one anaerobic zone (nominal HRT of

0.21 hours). The study concludes that short exposures in an initial anaerobic reactor as

required for biological phosphorus removal may benefit oxygen transfer efficiency through

increased alphas, however the benefits of long periods of anaerobic reaction time (over 0.43

hours) are uncertain.

Keywords: Volumetric oxygen mass transfer coefficient, KLa, alpha, BNR, anaerobic

reactor

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