Mobile Treatment Unit for septage emptying and safe disposal in Dindigul, India

Aaron Forbis-Stokes1,2

Arumugam Kalimuthu3, L. Peter3, Marc Deshusses1

1Duke University, Dept. of Civil & Environmental Engineering, Durham, NC, USA2Triangle Environmental, Durham, NC, USA

3WASH Institute, Kodaikanal, India

Background

2

Urban septage treatment solutions are needed at

decentralized level

38% of urban households in India62% of households in cities <1 million

Background

3

Treat and discharge septage onsite.Save time, fuel, and money.

Mobile Treatment Unit – Technology overview

4

MTU uses off-the-shelf separation technologies to produce a clean

effluent quickly and cost-effectively

Septic Tank

Centrifuge

Holding Tank(58 µm mesh)

Dual-Media(Pebbles & Sand)

GAC(#4x8 mesh)

MF (x2)(10 & 5 µm)

UF(0.02 µm)

Discharge

Solids collection(Compost/Disposal

Partial UF return

Methods

• Phase I – 1 unit• No backwash

• Operational: Pressure, flow & power every 15 minutes

• Treatment: First pass & final pass sample each location

• Phase II – 4 units (3 new)• Reverse flow backwash every 30

minutes

• Operational: Pressure, flow & power every 15 minutes

• Treatment: Final pass septage & UF effluent

5

Target flow: 3,000 L/hrPressures: membrane life and fouling

Effluent quality: Meet Indian discharge standards

Operational performance – Phase I

0

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Flo

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)

Time (h)

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Initial flow-rates decreased and did not fully recover.

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Volume treated (L)TM

P (

bar

)

Time (h)

MF UF

Operational performance – Phase I

7

Rapid increase of Transmembrane Pressure for MF

Treatment performance – Phase I

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Total Coliform (CFU / 100 mL)

10

100

1,000

10,000

100,000

1,000,000

Effluent meets Indian discharge limits

1

COD (mg / L)

Phase I Conclusions

9

Phase I Challenge Phase II Improvement

Maintain high target flow rates Routine backwashing during run

Rapid MF fouling Increase MF surface area

Occasional high solids tanks Additional low-cost pre-screening

Standard India CPCB WASHi Effluent

pH 6.5-9.0 7.7 ✔

COD (mg/L) [old, not in new] 100 66 ✔

BOD (mg/L) 30 24 ✔

TSS (mg/L) 100 103 ✘

Total Coliform (CFU/100 mL) 1,000 83 ✔

0

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Flo

w r

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)Time (h)

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Operational performance – Phase II

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MTU-1

MTU-3MTU-4

MTU-2Flow rates maintained,

TMP decreased

Treatment performance – Phase II

11

Expenses

$9.317

$3.617

$132

$2.620

$0

$5.000

$10.000

$15.000

$20.000

$25.000

$30.000

$35.000

Traditional septic MTU

CapEx

Hardware

Monitoring

Filtration

Vehicle

12

$0

$2

$4

$6

$8

$10

$12

$14

$16

$18

MTU

OpEx($ / 3,000 L Septic tank)

Cleaning

Power

Diesel

Filtration

Vehicle

$46 typical fee for 3,000 L septic tank

Case Study: MTU in Kerala

13

• 4 MTUs sent to Kerala in response to severe flooding, August 2018

• First 9 days:• 330,000 L septage treated• 34,965 beneficiaries

• Aug. 25th – Dec. 14th 2018: • 156 septic tanks emptied• 918,222 L treated• ~200,000 beneficiaries• Effluent samples met all discharge

standards

Next steps

Patent:Filed and awaiting finalization

Commercialization In discussion with partners

Interested customers: relief agencies, small-scale entrepreneurs

Automation:Improve operation efficiency, decrease operator requirements

14

Thank you!

15

Arumugam Kalimuthu Marc Deshusses Aaron Forbis-Stokes

akalimuthu@washinstitute.org marc.deshusses@duke.edu aaron@triangle-environmental.com

Program Director Professor Sanitation Technology Consultant

WASH Institute Duke University Triangle Environmental

www.washinstitute.org www.sanitation.pratt.duke.edu www.triangle-environmental.com

Additional slides

16

0 20.000 40.000 60.000

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Volume treated (L)

TMP

(b

ar)

Time (h)

MF UF

0 10.000 20.000 30.000

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Volume treated (L)

TMP

(b

ar)

Time (h)

MF UF

Operational performance – Phase II

17

MTU-2 MTU-4

MF no longer foulingLow TMP,

likely undersized pump