Natural Decentralized Wastewater Treatment Systems

Auroville Centre for Scientific Research

Decentralised waste water treatment principles and devices

Treatment for organic wastewater from domestic and industrial sources

Treatment of wastewater flows from 1-1000 m3/d

Achievement of discharge standards

Tolerance to inflow fluctuation

Minimal dependence on external energy, minimal maintenance

Using gravity instead of pumps, avoiding valves

Aiming towards reliable and long-lasting devices

Priority given to anaerobic technology in warm climatesand aerobic technology in cold climates

Reuse of wastewater and its contents

Pre-treatment deviceSettler

SettlerPre-treatment 1st treatment

Baffled tank reactor

Anaerobic filter

Planted gravel filter

Polishing pond

Natural treatment of waste water occurs by channeling the effluent through several devices:

Pre-treatment is done in a Settlera device which separates the liquid from the solid, retention time is only 2 hours.Pollution reduction is around 30%

First treatment takes place in a Baffled Tank

A device with several identical chambersthrough which the effluent moves from top to bottom.Retention time is 24 hours.Pollution reduction is around 80%

Second treatment takes place in a anaerobic filter

A device filled with a filter material (cinder)through which the effluent moves from top to bottom.Retention time is around 8 hours.Total pollution reduction is around 90%At this stage CPCB standards are metbut the effluent still has an odour

Third treatment takes place in a planted gravel filterA structure filled with gravel material and planted with water resistant plants, who provide oxygen to the passing effluent.Retention time is 1½ day.Pollution reduction is around 90%

Post treatment takes place in polishing pondsFitted with aquatic plants and fishes.It is through this device that the water transforms from a lifeless state into living water again.Ponds with aquatic plants are an efficient wayto combine wastewater treatment,

landscaping, aesthetics and water reuse, the pond can also act as a storage device.

Overview of the different devices

Underground anaerobic process Above ground level aerobic process

CPCB standards are met at this point, except for the smell control

RawSewage

OutletSettler

OutletBaffledReactor

OutletGravelFilter

OutletPond

BOD5

COD

1086

880

7060 56

571

457

2520 18

0

200

400

600

800

1000

1200

mg/l

GOKALDAS: BOD and COD reduction in different modules

Treatment efficiency

Auroville Dewats systems1995-2009

Surya Nivas, 2003 – 12 users

Solar Kitchen, 1998 – 40 m³

Samasiti 25 PE

‘Outside’ Dewats systems2000 - 2009

Aravind Eye Hospital, Pondicherry, 2003 – 500 m³

GIDC Dewats projectBhuj city

Bhuj Greenbelt Project

Surya Nepal Pvt Ltd(subsidiary of ITC)

Surya NivasNepal

Post Tsunami Dewats projects2006 - 2009

Kadambadi settlementNagipattinam

Perangipettai – Bharati Nagar – Irula settlement

Waste water treatments in temperate and cold zones are based on aerobic systems which incorporate processeswhich are designed to work on high oxygen solubility in water.

O2 solubility can reach 11 to 12 mg of O2 / litre of water.

In warmer climates the oxygen solubility can be as low as 2 to 3 mg O2 / litre of water above 35 degrees C°.

For this reason cold climate solutions are not easily applicablefor a tropical environment,

anaerobic solutions are better alternatives.

Vortex

ATS – Algal Turf ScrubbersAlgal are grow in shallow basins for

Cleaning water pollution, including heavy metalsIn the process Biomass is grown and harvested for Energy

- gas methane/ethanol/butanol- Bio-diesel – bio-aviation fuel

Note: solar energy absorption by algal is 45 to 50%,increase in biomass doubles/24 hrs, during the process algal absorbs CO2 and gives off oxygen

ATS needs Start up capital investmentSpace requirements

Integrating ATS –Algal Turf Scrubbers

the use of algaefor cleaning toxic

waste water

Auromode

“And justify the light on Nature’s face.”

Anaerobic filterplatform for cinder

Distribution boxes

Top covers