university of california, irvine... · title: rosso (2018) doe aeration webinar v3.pptx author:...

Copyright © 2018 Diego Rosso

FUNDAMENTALS OF AERATION: DIFFUSERS SCIENCE AND TECHNOLOGY

Diego Rosso University of California, Irvine


Dewatering

Aeration

Digestion

Other

Chemicals Pumping

(MOP32, 2009)

WASTEWATER AND ENERGY

49%

Aeration cost = 45-75% of plant energy (w/o influent/effluent pumping)

Rosso and Stenstrom (2005) Wat. Res. 39: 3773-3780


The Iceberg Paradigm

www.sedonakarma.com

AERATION SYSTEM CapEX

AERATION SYSTEM OpEX


Fine-pore diffuser variety


Membrane strips and panels


Chicken feeder (coarse-bubble)


Air spargers (coarse-bubble)


FINE- vs. COARSE-BUBBLE

•  Very high SOTE (%) •  Low α•  Overall higher αSOTE (%) •  Prone to fouling

© 2001 Michael K. Stenstrom

•  Low SOTE (%) •  High α•  Overall lower αSOTE (%) •  No fouling issues


α: THE MOTHER OF ALL FUDGE FACTORS

Cost efficiency O2 requirements

ê ê ê ê AFR = f (1/α, 1/SOTE, AOR)

↑ ↑ ↑ ↑ $$$ ww, aerator ww

SOTE = Standardized Oxygen Transfer Efficiency

(O2 transferred / O2 fed)

α =(k

La)

process water

(kLa)

clean water


Alpha and SOTE

FINE-BUBBLES COARSE-BUBBLES

alpha


THE MYSTERIOUS ALPHA FACTOR

•  Alpha is variable with time and along the process, not a constant

•  Fine-pore diffusers: 0.2 – 0.6

•  Fine-bubbles from jets: 0.5 – 0.7

•  Coarse bubbles: 0.5 – 0.7

•  Different alpha with different loads

•  When bubbles coalesce in sludge, alpha drops for all diffusers

•  Alpha is site-specific and should not be guessed


AERATION EFFICIENCY TESTING

CPU

OTR = (kLa·V) [Csat-(DOexc+DOneeded)] = kgO2/d = $$$/d

Off-gas


O2,IN - O2,OUT

αSOTE (%) = ________________

O2,IN

OFF-GAS TESTING SETUP

HOOD

Guy with a Ph.D.

OFF-GAS ANALYZER


Automated off-gas monitoring

OXYGEN TRANSFER EFFICIENCY(%)

OFF-GAS TEMP. (oC)

OFF-GAS FLOW (m3/(m2h))

TIME (h)


!

POWER DENSITY (W/m3)

ENERGY INTENSITY (Wh/m3)


Site-specific evaluation of diffusers

SUMP PUMP

AERATION TANK

FEED

DISCHARGE

OFF-GAS ANALYZER

INSTRUMENTATION PANEL


The Plight of Fouling

CLEANED FOULED


Blower challenges


Blower limits

Discharge pressure is often limiting!


Examples of Cleaning Benefits

0-1 3-7 8-11 12-170

5

10

15

20

25

30

35

<DW

P>(inchH

2O)

T imein operation (months )

C ontro l

R F 1

R F 2


Summary

•  Oxygen transfer efficiency and the alpha factor are dynamic!

•  Fine-pore diffusers have the highest efficiency but also the highest pressure drop

•  Fouling is an inevitable plight of fine-pore diffusers: clean them or don’t buy them

•  Coarse bubbles have high alpha and low SOTE, fine-bubbles vice versa

•  α is dynamic and is a function of the bubble, not of the make/model of the aeration system

•  In-situ measurements most accurately quantify the necessary design values

•  Third-party verification is paramount


DIEGO ROSSO

[email protected]

wex.uci.edu

university of california, irvine... · title: rosso (2018) doe aeration webinar v3.pptx author:...

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