WATERWISE Green Living

The re-use mantra

Treated waste-water can be pushed through a Vortex system to reduce odour  

Waste-water is emerging as a new challenge and opportunity in the cities of India. After large quantities of clean water is shipped into the city to meet the growing thirst of a large population and economy, 80% of it goes out as a stream rich in nutrients and organics.

Unmanaged, they lead to pollution of rivers, lakes, groundwater, soil and air with their noxious vapours. The collection, conveyance and treatment is a complex affair taxing the capabilities of even large institutions.

One remedy seems to be small decentralised systems which take treatment to levels as prescribed by the pollution control boards as well as enable reuse for such non-potable purpose as toilet flushing and for gardening. These systems use less energy, are compact and use biological methods to treat wastewater.

However, if the system is anaerobic, smell and odour in the end is an inevitable consequence which leads to complaints from users.

The Vortex system developed by the Auroville Centre for Scientific Research, near Puducherry, is a happy development on the odour reduction front. Working on the principle elucidated by the great naturalist and biomimicry experimenter Viktor Schauberger, Lars Kostedde of CSR has developed several experimental systems.

In a paper jointly written by Tency Baetens, Gilles Boulicot and Lars Kostedde a simple explanation is given on how the system works.

How it works

A Decentralised Wastewater Treatment System or DEWATS is the beginning of the process of cleaning and reusing wastewater. The DEWATS system consists of

- Pre-treatment in a settler tank where the sludge and scum are held and a small amount of digestion happens by bacteria. This can be preceded by an oil and grease trap if needed.

- Primary treatment in a baffled tank where the wastewater is made to go through anaerobic bacteria blankets which eat up material and clean the water

- Secondary treatment which can be done conjointly with the primary treatment or fixed to the end of the primary treatment. Here further anaerobic bacteria action on the wastewater is facilitated.

- Finally the VORTEX can be applied to this secondary treated wastewater.

The Vortex is a large transparent acrylic tube covered on the top with a small vent hole on the side for air. It has a funnel and a diaphragm at the bottom and a pump inlet through which the treated waste-water is pumped in. Due to the design of the system a beautiful vortex, like a whirlpool or a tornado or a waterspout, is created inside.

This natural formation enables the water to absorb oxygen heavily. The dissolved oxygen level in the water goes up reducing parameters like BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) which is what is demanded by legislation for the release of treated waste-water. BOD less than 20 mg/l is easily achieved and design efforts are on ensure that it is less than 10 mg/l also.

Efficient

The Vortex system uses minimal power, reduces BOD, is a great landscape feature and occupies very small space. It reduces and almost eliminates odours, kills pathogens and reduces nitrate levels too.

The water from the Vortex can be led into a designed pond with lilies, lotus and other plants. Fish can be introduced to reduce mosquitoes. The water can then be tapped from the pool for landscaping purpose and for toilet flushing. There is also the possibility that treated waste-water from conventional treatment plants can also be pushed through a Vortex system to reduce odours and to improve dissolved oxygen levels.

Persistence pays off

It is the persistence of Auroville CSR and its ability to experiment which has resulted in the development of such a system.

Institutions, apartments, layouts, small towns and even large cities with decentralised sewage treatment plants will find the Vortex useful.

Incorporating, treating and reusing waste-water for ecological and other purposes will clean up our rivers and lakes and provide water for reuse. This would be water wisdom.

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Printable version | Nov 25, 2020 3:06:14 PM | https://www.thehindu.com/features/homes-and-gardens/green-living/the-reuse-mantra/article6707964.ece

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