wastewater in-plant training session 7 – solid stream

WASTEWATER IN-PLANT TRAININGSESSION 7 – SOLID STREAM

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Sponsor

Today’s Agenda

Welcome and Introductions

Opportunity Register Check-in

Solid Stream Opportunities

Dissolved Air Flotation

Compressed Air

Closing Remarks

Click To Edit Master Title StyleOPPORTUNITIES?

Report Outs

Opportunity Register

Energy Projects

Energy Project

VALUE MATRIX Step

Identify1

Opportunity#

Opportunity NameSavings

(1-10)

Cost/Effort(1-10)

Opportunity Description Location System* Date SubmittedCapital or

O&MSubmitted

By

1 Lower W3 Pressure 3 2

2

3

4

5

6

7

Jammin’ 4 Water

We Operate Multi-Billion, Multi-Million Dollar

Facilities With Someone Else’s Money

[insert Break slide]

Four Steps to Energy Self-sufficiency

Four steps to energy self-sufficiency1. Commitment to saving

energy throughout

organization

2. Energy generation

3. Process energy

conservation

4. Assess and refine

Can’t Generate Energy Without Using

the Gas Produced by Anaerobic Digestion

1. Commitment to saving

energy throughout

organization

2. Energy generation

3. Process energy

conservation

4. Assess and refine

To Increase Gas Production,

There are Essentially Three Options

CH4+CO2

Biosolids

CO2

1. Increase VS Load From Within the Plant

CH4+CO2

Biosolids

CO2

CH4+CO2

2. Optimize Digester Performance

3. Add External Carbon Source

CH4+CO2

Biosolids

CO2

FOG, food waste, other

Two Inputs: Maximize VS Load in Both

(the more primary sludge the better)

CH4+CO2

Biosolids

CO2

Primary sludge WAS

Maximizing Primary Sludge to Digester

CH4+CO2

Biosolids

CO2

Primary sludge

NO TSSset in primary clarifier effluents

A Very Simple KPI—Capture as Much as Possible

in Primary Clarifiers, Maybe CEPT

Maximizing VS in WAS

CH4+CO2

Biosolids

CO2

WAS

Three Considerations Setting SRTTARGET

1. Effluent ammonia requirement

2. Best sludge quality

3. Minimum SRTTARGET

that will satisfy 1 and 2

Minimum TSS (and VSS) Loss to Effluent

With Best Sludge Quality

CH4+CO2

Biosolids

CO2

↓ TSS

↑ WAS

Lower the SRT, Greater the MLVSS

Concentration

MLVSS = SRT×Q×Yg×(BODINF – sBODEFF)

VAB×(1 + b × SRT)

Optimize Secondary Treatment

(SRT control, minimum SRTTARGET, QRAS control)

0

10

20

30

40

50

60

70

80

90

100

Jan-05 May-05 Oct-05 Mar-06 Aug-06 Jan-07 Jun-07 Nov-07 Apr-08 Sep-08 Feb-09

Daily

SS

EC

Eff. T

SS

(m

g/L

)

Process

optimization

work started

If Not to the River,

Where Are These Solids Going?

0

10

20

30

40

50

60

70

80

90

100

Jan-05 May-05 Oct-05 Mar-06 Aug-06 Jan-07 Jun-07 Nov-07 Apr-08 Sep-08 Feb-09

Daily

SS

EC

Eff. T

SS

(m

g/L

)

Process

optimization

work started

1.5 tons of solids/day

not going to the South

Platte River

More VSS to Digesters, More Gas,

More Heat and Power

2,000

3,000

4,000

5,000

6,000

Jan-05 Jul-05 Feb-06 Aug-06 Mar-07 Sep-07 Apr-08 Nov-08 May-09

Avg.

Daily

Pow

er

Pro

duction

(kW

)

Least Cost Operation: Maximize VSPS,

Minimize VSWAS

CH4+CO2

Biosolids

CO2

Look Inside and Outside

(Upstream) to Optimize Digester Performance

Pumping: Thickening is ABSOLUTELY Critical

0

20

40

60

80

100

120

140

160

180

200

0 1 2 3 4 5 6 7

Slu

dg

e F

low

(1

,00

0 g

al/d

)

TS Concentration (%)

Removing 15,210 lb TS/d

Detention Time:

Thickening is ABSOLUTELY Critical

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6 7

Dig

es

ter

HR

T (

d)

TS Concentration (%)

0.9-Mgal digester receiving 15,210 lb TS/d

Heating Requirements:

Thickening is ABSOLUTELY Critical

0

10,000

20,000

30,000

40,000

50,000

0 1 2 3 4 5 6 7

Slu

dg

e H

ea

tin

g R

qm

t. (

1,0

00

BT

U/d

)

TS Concentration (%)

0.9-Mgal digester receiving 15,210 lb TS/d68 deg F incoming temp., 98 deg F operating temp.

Gravity Thickener

Gravity Belt Thickeners

Rotating Drum Thickener

Dissolved Air Floatation Thickener

DAFs Also Used in Lieu of Primary Clarifiers

in Liquid Treatment Train

CH4+CO2

Past Performance is Not Indicative

of Future Results

Simplification Explains A Lot

VS (Corganic) CH4

VA (primarily

CH3COOH)

CO2

2. Methane formers1. Acid formers

CO2

+ +

Biogas

Three Words Capture Process Control Approach

1. Stable

2. Consistent

3. Uniform

Objective of Process Control: Maintain Balance

VS (Corganic) CH4

VA (primarily

CH3COOH)

CO2

2. Methane formers1. Acid formers

CO2

+ +

Biogas

Objective of Process Control: Maintain Balance

Objective of Process Control: Maintain Balance

Objective of Process Control: Maintain Balance

2. M

eth

an

e fo

rmer

s

1. A

cid

fo

rmer

s

Objective of Process Control: Maintain Balance

1. Organic loading

2. Temperature

Really Only Two Things in Operators’ Control

Loading Pattern Hits Target for Daily Average,

But Neither Consistent nor Stable

VA Concentration Oscillates With Feeding

3,000

ALK

2,000

1,000

VA

0

Co

nc

en

tra

tio

n (

mg

/L)

Source: Schafer et al., WEFTEC 2014

0

-20 0 20 40 60 80

Gro

wth

Ra

te

Temperature °C

(°F)

(-4) (68)(32) (104) (140) (176)

Mesophilic ThermophilicPsychrophilic

Optimum mesophilicoperating range

Source: Schafer et al., WEFTEC 2014

Stable, Consistent, and Uniform

Temperature Essential

Stable, Consistent, and Uniform

Temperature Not Possible Without Good Mixing

0

-20 0 20 40 60 80

Gro

wth

Ra

te

Temperature °C

(°F)

(-4) (68)(32) (104) (140) (176)

Mesophilic ThermophilicPsychrophilic

Optimum mesophilicoperating range

If Co-Digesting Must Ensure

Mixture is as Uniform as Possible

CH4+CO2

Biosolids

CO2

FOG, food waste, other

Most Important Unit Process:

Performance Monitoring is Paramount

1. VA concentration

2. Volatile solids reduction

3. Gas production per VS destroyed

4. Gas composition

Heat Exchangers, Heat Loops & Spaghetti Bowls

Aerobic Digestion

Aerobic Digestion

Basically an aeration tank with a LONG retention time.

Aerobic digestion is often only “slightly” aerobic –blowers are run by “nose” on small facilities.

Very coarse bubble diffusers are used – like ¼” holes drilled along the bottom of the air pipe.

Can be a good place to retrofit blowers.

If your permit requires 38% reduction, is there a benefit to getting 45% or 50% reduction? What is the energy cost of that benefit? Other cost?

Nitrification unavoidable, denitrify (mixed not aerated) to lower aeration requirement

Depleted Carbon Reserves Leads to Cell

Death, Cell Contents Substrate to Survivors

Maintenance

O2

CO2, H2O

cell

Catabolism | Respiration

EnergyCarbon

reserves

Cell contents = BOD + nutrients

Dewatering Equipment Considerations

24 pt font on all first level

20 pt font on all second level. Shouldn’t go further than 2nd level.

Lots of Ways to Skin This Cat

Degremont Heliantis solar drier

Sludge Disposal

is #3 or #4 Expense for Many Plants

Power Costs – dewatering, pumping, washing, odor control

Recycle Costs – return streams

Disposal Costs – hauling and ultimate disposal

Polymer & Chemical Costs

Labor Costs

Maintenance Costs

Operational Considerations

If dewatering is a batch process at your plant

Does odor control run continuous?

Is building heating/cooling set to different temp at night than in day?

Can W3 water pressure be reduced because demand is reduced?

Would moving to longer run times eliminate a batch(and associated start-up/shut-down energy)?

Would shifting batching time of day reduce total plant electrical demand? Improve plant performance?

Diurnal Variation in Flow, NH3-N Concentration,

and NH3-N Load

0

1,200

2,400

3,600

0

12

24

36

0 6 12 18 24

NH

3IN

F(lb

/d)

NH

3IN

F(m

g5N

/L),

5Flo

w5(

MG

D)

Axis5Title

Inf5NH3EN5mg/L

Flow,5MGD

Inf5NH3EN5lb/d

Average5NH3EN5Load

Midnight MidnightNoon65AM 65PM

Influent NH3N, mg/L

Flow, MGD

Influent NH3N, lb/d

Average NH3N Load

6 AM 6 PM

First-shift Dewatering Operation

With No Return Equalization

0

1,200

2,400

3,600

0

12

24

36

0 6 12 18 24

NH

3IN

F(lb

/d)

NH

3IN

F(m

g5N

/L),

5Flo

w5(

MG

D)

Axis5Title

Inf5NH3EN5mg/L

Flow,5MGD

Inf5NH3EN5lb/d

Average5Load

Midnight MidnightNoon65AM 65PM

Influent NH3N, mg/L

Flow, MGD

Influent NH3N, lb/d

Average NH3N Load

6 AM 6 PM

Dewatering in Early Morning

Eliminates Bleed- Through

Operational Considerations

If you have a choice, what is the most efficient unit in the line-up?

Are you only scrubbing “odorous air” or are you scrubbing entire building volume?

Does cake handling equipment run continuous or only as needed?

Solids Stream Opportunity Hunt

Thickening

Digestion

Dewatering

30 min Divide participants into three teams, each to visit

one of the above areas and discuss ideas presented in

previous slides, in context of this site.

15 min Bring back three to five best ideas found, to share

with the group at the end of the hunt

Dissolved Air Flotation

65

Potential ways to save energy

Optimize the air-to-solids ratio in the dissolved air flotation (DAF) system by adjusting the supply air and/or by feeding the highest possible solids content.

Reduce air pressure

Reduce recirculation

Operate DAF thickener continuously and add polymers

• However, this can increase the O&M or labor costs.

Improved solids capture will benefit other downstream biosolids-treatment processes

• Thickening and/or dewatering

• Digester heating

Dissolved Air Flotation

66

DAF recirculation pump

15 hp pump operates at full speed

Install a VFD to allow flexibility to reduce recirculation

Equipment cost $2,500

90% speed = 20,000 kWh/year energy savings

DAF Example 1

67

DAF air compressor settings

Original

• 7.5 hp air compressor setting was 90 to 120 psi

Current

• 7.5 hp air compressor setting is 80 to 110 psi

DAF running normally with lower pressure setting

No cost

2,500 kWh/year energy savings

DAF Example 2

68

Reduce DAF recirculation pump and compressor runtime

With trickling filters running, plant wastes to DAF for six hours per day

Original

• DAF 25 hp recirculation pump and 40 hp air compressor run 24/7

Current

• DAF 25 hp recirculation pump and 40 hp air compressor run 9 hours per day

240,000 kWh/year energy savings

DAF Example 3

69

DAF Example 4 – Newer technology

70

Upgrade to dissolved air generation (DAG)

OriginalAir compressor, saturation tank, recycle pump

UpgradeDAG system

• Reduced energy consumption

Air Compressors……all Shapes & Sizes

Compressor Energy Sankey Diagram

Control Options & Performance

Compressed Air Dryers

Compressed Air Opportunities

Pressure Limiting UserIs one end-use driving up your pressure requirements?

What is the maximum pressure you actually require

Compressor ChecksDo you have more than one compressor?

Are they all operating, and do they have to be?

Compressor Pressure Setpoints

2 psi = 1%

Minimize pressure reductions

Filter & DryersDessicant or refrigerated?

Filters checked regularly

Acknowledgments

Thanks to the following partners for their support

in developing this curriculum