Overview of Energy Use both Electric and Gas

Energy Workshop

December 19, 2012

1

Introduction Wordelman

Overview of Energy Use

Electric Lowery

Natural Gas/Digester Gas Teague

Alternatives for Generation

and Savings Wordelman

Conclusion Wordelman

2

Understand current usage

Electrical

Natural gas/digester gas

Initial screening ideas

3

Electrical

Total purchased

Operating scenarios

Natural gas

Total purchased

Digester gas

Digester gas used flowmeter

Digester gas produced flowmeter

4

5

6

$0

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Mo

nth

ly E

lectr

ical

Co

st

$

kW

Ho

ur

Lima WWTP Monthly Electrical Purchase

kWhr per Month

Electrcial Cost

7

300000

350000

400000

450000

500000

550000

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650000

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800000

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kW

Ho

ur

Lima WWTP Electricity Purchased vs. Consumed Benefit of Microturbines

Purchased

Consumed

Capstone C65 microturbines consume approximately 22 cfm of biogas

Each turbine produces 60 kw electricity and 250,000 BTU/hr heat

At current energy prices this is worth about $43,000 annually

Use of the same amount of biogas for boiler heating only would be worth approximately $27,000 annually

Each unit can deliver ~ 8% of the plant’s electrical demand

8

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flo

w M

CU

F a

nd

Millio

n G

allo

ns T

reate

d

kW

Ho

ur

Lima WWTP Monthly Electrical Purchased

Monthly kWhr

Monthly Total Airflow MCUF

Million Gallons Treated

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Av

era

ge M

on

thly

Tem

pera

ture

F.

kW

Ho

ur

Lima WWTP Monthly Electrical Purchased

Monthly kWhr

Monthly Temperature

11

Screening 0.1% Grit Removal

0.2% Baxter Street 8.1%

Primary Tanks 1.5%

Aeration 35.5%

Sludge Pumps 8.4%

Final Clarifiers 0.5%

Nitrification 14.6%

Disinfection 0.2%

Digestion 9.5%

Dewatering 1.6%

Stabilization 0.1%

Admin Building 0.5%

Miscellaneous 19.3%

Breakdown of Energy Consumption %

12

Screening 587 Grit Removal

1,074 Baxter Street 45,388

Primary Tanks 8,212

Aeration 198,734

Sludge Pumps 46,805

Final Clarifiers 2,576

Nitrification 81,735

Disinfection 850

Digestion 52,866

Dewatering 8,765

Stabalization 572

Admin Building 2,928

Miscellaneous 108,121

Stabilization Energy Consumption (kWhr / Month)

13

Screening, $39 Grit Removal, $72

Baxter Street, $3,041

Primary Tanks, $550

Aeration, $13,315

Sludge Pumps, $3,136 Final Clarifiers, $173

Nitrification, $5,476

Disinfection, $57

Digestion, $3,542

Dewatering, $587

Stabalization, $38

Admin Building, $196

Miscellaneous, $7,244

Breakdown of Energy Consumption ($ / Month)

14

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 20 40 60 80 100 120

Typ

ical

En

erg

y C

on

su

mp

tio

n (

kW

h / M

illio

n G

allo

n)

Capacity (mgd)

Basic Activated Sludge

Advanced WastewaterTreatmentAdvance WastewaterTreatment With Nitrification

Chart Adapted from the Electric Power Research Institute Water & Sustainability (Volume 4): U.S.

Electricity Consumption for Water Supply

& Treatment - The Next Half Century (March 2002)

Lima Electrical Consumption

~1450 kwhr/MG

15

Lima ~19,000 kwhr/day

16

Typical Daily Electric

Consumption 10 mgd WWTP

per Process* kwhr/day Lima Consumption

Influent Pumping 1402 1513 (Baxter St.)

Screening 2 20

Aerated Grit 134 36 (Not Aerated)

Primary Settling 155 274

Diffused Air Aeration 5320 6624

Secondary Settling 155 86

Chlorination 27 28

Anaerobic Digestion 1400 1762

Belt Press Dewatering 384 292

* The Electric Power Research Institute Water & Sustainability (Volume 4)

Current electrical rate including all

charges is approximately $0.065/kWhr

17

AEO 2012

Reference Case EVA IHSGI Inforum

2010 6.7

2015 6.5 7.9 7.0 6.2

2025 6.7 8.0 7.4 6.2

2035 7.1 7.6 8.1 6.2

18

Average end user cost projection in 2010 cents per kWh from several sources.

Via the Annual Energy Outlook 2012 Report, U.S. Energy Information Administration (2012)

Minimum usage – minimum bill set on

60%

Power factor – less than 0.87

2011 – June 2012 average power factor =

85.8

19

Enernoc emergency load response

program – run generators

AEP energy efficiency/peak demand

reduction program – up to 50% rebate

20

Uses of Aeration

Mixing

Biological Oxygen Needs

21

Mixing Control Biological Control

Average Conditions

Five Aeration Tanks 8200 cfm 7872 cfm

Influent and Effluent Channels 2306 cfm 2306 cfm

Reaeration Tank 705 cfm 705 cfm

Total 11211 cfm 10883 cfm

Mixing Control Biological Control

Average Conditions

Four Aeration Tanks 6500 cfm 7872 cfm

Influent and Effluent Channels 2306 cfm 2306 cfm

Reaeration Tank 705 cfm 705 cfm

Total 9511 cfm 10883 cfm

22

Blowers – multistage centrifugal

Two 400 HP 4160 volt - 10,000 cfm

Two 350 HP 460 volt - 7,000 cfm

Diffusers

Aeration tanks EDI fine bubble diffusers

Channels and reaeration tank coarse bubble

Controls

Blower inlet throttling

DO monitoring

23

24

Types of diffusers

Tank depth

Surfactants

25

Electric

26

27

PST 5-7 Total CODPrimary Effluent Total COD

DATE

11/1011/3

CO

NC

. (m

g/L

)

400

300

200

100

PST 5-7 Total COD Mass ratePrimary Effluent COD Mass Loading

DATE

11/1011/3

MA

SS

RA

TE

(lb

/d

)

50,000

40,000

30,000

20,000

28

PST 5-7 Total CBODPrimary Effluent Carbonaceous BOD

DATE

11/1011/3

CO

NC

. (m

g/L

)

200

150

100

PST 5-7 Total CBODPrimary Effluent CBOD Mass Loading

DATE

11/1011/3

MA

SS

RA

TE

(lb

/d

)

20,000

10,000

29

PST 5-7 TSS

PST 5-7 VSS

Primary Effluent Solids

DATE

11/1011/3

CO

NC

. (m

gV

SS

/L) 200

150

100

50

0

PST 5-7 TSS

PST 5-7 VSS

Primary Effluent Solids Mass Loading

DATE

11/1011/3MA

SS

RA

TE

(lb

VS

S/d

)

30,000

20,000

10,000

0

30

PST 5-7 TKN

PST 5-7 Ammonia N

Primary Effluent Nitrogen

DATE

11/1011/3

CO

NC

. (m

gN

/L)

40

30

20

10

0

PST 5-7 TKN

PST 5-7 Ammonia N

Primary Effluent Nitrogen Mass Loading

DATE

11/1011/3MA

SS

RA

TE

(lb

N/d

)

4,000

3,000

2,000

1,000

0

31

PST 5-7 Total PPrimary Effluent Total Phosphorus

DATE

11/1011/3

CO

NC

. (m

gP

/L)

7

6

5

4

3

2

1

0

PST 5-7 Total PPrimary Effluent Total Phosphorus Mass Loading

DATE

11/1011/3

MA

SS

RA

TE

(lb

P/d

)

1,000

800

600

400

200

0

32

AT Pass 1

AT Pass 2

AT Pass 3

Total

Aeration Tank 1-5 Variable AirflowMaintain DO @ 2 mg/l

DATE

11/9/201211/7/201211/5/201211/3/201211/1/2012

AIR

SU

PP

LY

RA

TE

(ft

3/m

in (

20

C, 1

atm

))

15,000

14,000

13,000

12,000

11,000

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

33

AT Pass 1 DO

AT Pass 2 DO

AT Pass 3 DO

Aeration Tank Dissolved OxygenManually Adjusted Airf low

DATE

11/10/201211/8/201211/6/201211/4/201211/2/2012

DIS

SO

LV

ED

OX

YG

EN

(m

g/L

)

10

9

8

7

6

5

4

3

2

1

0

34

AT Pass 1 DO

AT Pass 1 Airflow

Aeration Tank Dissolved OxygenPotential Surfactant Effect

DATE

11/10/201211/8/201211/6/201211/4/201211/2/2012

Dis

so

lve

d O

xy

ge

n (

mg

/l)

10

9

8

7

6

5

4

3

2

1

0

Air

flo

w s

cfm

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

Current cost of aeration ~ $13,000/month

Denitrification

High efficiency blowers

Ultrafine bubble aeration

Decouple aeration and mixing (install

separate mixing systems)

Automated blower control

Combination of options above.

35

36

Total

26,027 MMBtu / year

$117,121 @

$4.50/MMBtu

Natural Gas

7,370 MMBtu / year

$33,165 / year

Digester Gas

16,457 MMBtu / year

$74,057 / year

Microturbine Heat Recovery

(Assume one running 24/7)

2,200 MMBtu /year

$9,900 / year

Microturbines

(Assume one running 24/7)

7,200 MMBtu / year

$32,400 / year used

Flare

2,246 MMBtu / year

$10,107 / year

Digester Heat

11,642 MMBtu / year

$52,389 / year

Building Heat

4,939 MMBtu /year

$26,670 / year

37

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Hea

t (M

MB

tu)

Natural Gas Purchased

$33,904 $24,560 $27,230

38

= $11.38/MMBtu assuming 3% inflation

39

40

41

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Heat

(D

em

an

ded

/Req

uir

ed

) (

MM

Btu

)

Gas Lower HeatingValue

Heat Required byDigesters

Note: Assumes 80% boiler efficiency.

42

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

110,000

120,000

130,000

140,000

150,000

160,000

170,000

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Gas P

rod

uc

ed

(F

t3 / d

ay)

Gas demand from one turbine

Gas demand from two turbines

43

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

0

10

20

30

40

50

60

70

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Dig

este

r G

as (

ft3 /d

ay)

% V

ola

tile

of

feed

slu

dg

e

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0

20000

40000

60000

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120000

140000

160000

180000

0

100

200

300

400

500

600

700

800

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Dig

este

r G

as

Vo

lati

le A

cid

s (

mg

/L)

45

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

0

500

1,000

1,500

2,000

2,500

1/1/2009 1/1/2010 1/1/2011 1/1/2012

Dig

este

r G

as

Alk

alin

ity

46

% D

ige

ste

r L

oa

d (

ba

se

d o

n lb

s v

s /

ft3

- d

ay

Septage and grease fed directly to the

digesters

Bring in supplemental feedstock

Digestion enhancement

47

Benefits Increased gas production

Reduce grease accumulation in primaries and other tanks

Reduce biological load to aeration Challenges

Requires plant modification to accept, store, and feed grease to digester

Digester upset, grease handling, and odor control are a concern

Requires cooperation of public Drawbacks

Greater public access to the plant is likely

More supervision may be required

48

Benefits Increased gas production

Reduced load to municipal landfills

Possibly some income from disposal fees (doubtful)

Community involvement in “green” project Challenges

Requires community or business support

Requires modifications to plant to bring in additional solids

Could require upgrades to handle and use additional gas if done on a large scale.

Possible digester upset without careful control Drawbacks

Increased solids management at plant

Increased complexity and labor at plant

Reduced gas production at landfill

49

Benefits

Increased gas production

Increased solids destruction

Achievement of class A biosolids possible with some systems

Challenges

Limited change for improvement in gas production if done alone

Drawbacks

Capital and operational cost must be weighed against benefit

50

By process

General

Baxter Street pumping

Preliminary & primary treatment

Secondary treatment

Effluent pumps

Solids processing & digestion

Electrical upgrades

Alternate energy

51

By type

Process modifications

Energy generation

Reduces energy consumption

Additional ideas

52

Today

Review alternatives

Brainstorming

Initial screening

Next

J&H develop alternatives

53

54

Rules: No bad ideas

No criticism of ideas

55

Brainstorming

City selection 5 dots

J&H selection

56

Channel Mixing

57

Aerated channels require mixing to keep solids suspended rather than a supply of dissolved oxygen.

Aeration tanks are deeper than channels. Currently all air is pressurized to the same pressure based on aeration tank depth, which wastes energy.

58

59

60

Baxter Street $36,728 Screening

$475

Grit Removal $869

Aeration Tank Air $113,598

Channel Air $47,219 / year

29% of total aeration Sludge Pumps

$37,875

Final Clarifiers $2,085

Nitrification $66,140

Disinfection $688

Digestion, 42,779

Dewatering $7,093

Stabilization $463

Admin Building $2,369

Miscellaneous $87,492

Cost of Channel Aeration ($ / year)

Separate blower and piping to operate channel aeration at lower pressure.

Mechanical channel mixing or “pulsed bubble mixing” Benefits

Reduced energy bills (estimated $20,000 / year at current energy prices)

Nitrogen removal possible

Simpler DO control and balancing (maybe?) Problems

Capital expense ($220,000 -$300,000)

Odor control

Depleted DO in first portion of aeration tanks

61

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