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High Rate Renewable Energy

Production with the Static

Granular Bed Reactor (SGBR)

Tim Ellis, Ph.D., P.E., Associate Professor

Dept. of Civil, Constr. & Environ. Eng.

Iowa State University

Ames, IA 50011

tge@iastate.edu, 515-294-8922

Introduction

Short overview of anaerobic digestion

Definition of high rate systems

Developments at Iowa State

University

Case studies

Anaerobic Treatment

Historically, anaerobic organisms

Slow growers

unstable (failed systems led to “stuck

digesters”)

Anaerobic treatment is a net energy

producer

Potential to produce equiv. 50,000 bpd

Save 20,000 bpd in aeration costs

Anaerobic yield is ~20% of aerobic

yield

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Anaerobic Digestion in Developing Countries

Community Biogas Plant, China

Biogas Cookstove

Renewable Energy at

Treatment Plants

Low vs. High Rate Waste

Treatment

Modern wastewater treatment plants

have been using high rate (low F:M)

systems for over 100 years for aerobic

treatment

For anaerobic treatment which produces

energy, we’ve been using low rate (high

F:M) systems

◦ Few alternatives to conventional AD

◦ Conventional AD requires long

detention times, heating, mixing

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High Rate Anaerobic Systems

Separate solids retention time (SRT) from hydraulic retention time (HRT). ◦ SRT = mass of solids in system (g) / daily rate of solids

wasted (g/day)

◦ HRT = Volume of Reactor / Flow rate

Can achieve much high organic loads due to retention of biomass.

Higher organic loads makes more economical design due to smaller reactor.

High Rate (low F:M)

Digestion

In 1980’s Lettinga - UASB reactor

Upflow process washed out flocs

Led to anaerobic granule development

Detention times of 1 day or less.

Requires a low solids wastewater

Requires recirculation pumping, and gas solids liquid separator

Typically requires heating to 35ºC to operate satisfactorily

influent

recirculation

pump

baffles

granular

sludge

gas

bubbles

three

phase

separator

biogas

flocculent

sludge

distribution

baffle

effluent

weir

effluent

UASB

granule gas bubble

floc particle

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Anaerobic granules

Current Research and

Development at Iowa State

University

New high rate system

Maximize biomass density (low F:M)

Minimize effluent solids

Meet NPDES permit requirements for

surface water discharge in some

instances

Maximize potential to generate

renewable energy in the form of

biogas

SGBR Defined

High-rate, downflow

anaerobic reactor

Biomass=Anaerobic

granules (seeded from

existing reactors

containing granules)

Submerged Biomass

Gas filled headspace

Gravel underdrain

influent

gravel

underdrain

granule

bed

water level

effluent

biogas

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SGBR vs UASB

0 4 8 12 16 20Organic Loading Rate, g/(L•d)

50

60

70

80

90

100

CO

D R

em

ov

al, %

UASB (Jeison & Chamy)

EGSB (Jeison & Chamy)

UASB (Yan & Tay)

UASB (Fang and Chui)

UASB (Zoutberg & Eker)

UASB (Ramasamy et. al.)

UASB (Jhung & Choi)

AFF (Jhung & Choi)

UASB (This study)

SGBR (This study)

SGBR

UASB

Organic Loading Rate, kg/m3 d

CO

D R

em

ova

l E

ffic

ien

cy,

%

0 2 4 6 8 10 12OLR, kg COD m-3 d-1

20

30

40

50

60

70

80

90

100

CO

D R

em

ova

l, %

This Study

EGSB (Núñez & Martínez)

25 C ASBR (Massé & Masse)

UASB (Ruiz et al.)

AF (Ruiz et al.)

Comparison with other systems

(slaughterhouse wastewater)

SGBR achieved

greater COD

removal than

other systems

Short Start-up Time

(Pork Slaughterhouse in Iowa)

0

20

40

60

80

100

0 5 10 15 20 25 30

Time (Days)

Rem

oval

eff

iency

(%

) .

TSS COD

REACTOR STARTUP

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0

1000

2000

3000

4000

5000

6000

7000T

SS

co

nce

ntr

atio

n (

mg

/L)

.

0

20

40

60

80

100

Rem

ov

al e

ffie

ncy

(%

) .

InfluentEffluentRemoval

0

3000

6000

9000

12000

15000

0 50 100 150 200 250

Time (Days)

CO

D c

on

cen

trat

ion

(m

g/L

) .

0

20

40

60

80

100

Rem

ov

al e

ffie

ncy

(%

) .

InfluentEffluentRemoval

SG

BR

Results –

Pork

Sla

ughte

rhouse

SGBR Results – Landfill leachate

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18 20

OLR, kg/m3.d

CO

D R

em.,

%

This Study

Berrueta et al.

Lin et al.

SGBR

Tulare, CA

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Existing Lagoon 7-d detention time, poor performance periodically

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Tulare, CA Operating Results

Backwashing Efficiency

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Summary

Simple, effective and economical method to

treat a wide variety of municipal, industrial, and

agricultural waste streams and produce a

renewable source of energy

Recirculation pumping, mixing, baffling, heating

not required with SGBR

Stability of system ensured by its ability to retain

active biomass (measured SRTs from 8 to 20

years!)

Hydraulic detention times typically 12 – 24

hours

Questions?