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Working wonders with waste water
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The potential of SBT is amazing, apart from providing clean water for recycling, it can generate employment and its suspended solids can be used as culture grade fertiliser.
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Sujata K. Lakshmanan
The need to conserve the available water resources cannot be more emphasised anywhere than in a thirsty city like Visakhapatnam. Such a process requires even recycling of the waste water by chemically treating it, so that it can be utilised for certain activities, thereby reducing the pressure on the fresh water sources for such purposes.
``If properly treated, the waste water can be made safe enough for irrigation and gardening, groundwater recharge and dicharging into water bodies at least and made even potable at best,'' says Sujata K. Lakshmanan, who has moved to Vizag from Mumbai where she was witness to a unique waste water management technology in operation.
Called soil bio-technology (SBT), it has been developed by the Department of Chemical Engineering of the Indian Institute of Technology (Powai) under the tutelage of H.S. Shankar, and can be gainfully applied for processing organic solid wastes and liquid wastes.
The distinctive feature of SBT is that it engages bacteria, earthworms and mineral additives to process the waste water, with the treatment plant looking like a garden. The treated water can be freely let into water bodies.
In what way SBT is different from the conventional effluent treatment technology (activated sludge process)?
Says Sujata: "The conventional effluent treatnment tehcnology cannot provide water that is suitable for aquatic life. Fish that are released into such treated water do not survive even for a few days. The conventional system does not remove the odour and nitrates and inadequately handles the removal of ammonia, though it fulfils the regulations of the Central Pollution Control Board (CPCB). In fact, these deficiencies are not even mentioned since the removal of nitrates and ammonia are not mandatory under the CPCB regulations.''
SBT not only removes the colour of the waste water but also its odour completely, she notes.
What are SBT's capabilities?
SBT has a wide range of applications in waste water treatment in the following ways:
---It can decentralise sewage treatment by a large-scale effluent treatment plant (ETP) by organising the same at small community levels.
---It can restore dying river systems affected by pollution.
---It is ideal for industrial organic waste water processing.
---It can retrofit failed ETPs based on conventional systems. ---It can renovate the water in swimming pools.
The SBT plant's design can be modified into a 'biotower' of sorts, in case there is a space problem in setting up such a plant.
An amazing aspect of SBT, which has a great potential for employment generation, is that apart from providing clean water for recycling, it yields a culture grade fertiliser by way of suspended solids. Another great advantage is that the SBT process does not generate waste.
How economical will SBT be as compared to conventional effluent treatment?
``For setting a 500-cubic-metre-per-day plant on a 2,000 square metre area, the cost of designing, construction and commissioning of an SBT plant will be around Rs.36 lakhs, as against Rs.1 to 2 crores for a conventional ETP. The recurring cost of an SBT plant is only Rs.2.50 per cum. per day, excluding electricity, manpower and additive, whereas it would work out to Rs.3.40 per cum. per day in an ETP. Besides, an SBT system can be of any size, unlike in ETPs which are usually of a large scale,'' explains Sujata.
Two SBT plants, operated by IIT-Mumbai, are currently functioning effectively in a private golf course and in the Naval Dockyard, according to her.
For technical details, one can contact the Dean (Research and Development) of IIT, Powai, Mumbai-400076 [ Tel: 022-25767030/25767031. e-mail: dearrnd@cc.iitb.ac.in ].
R. SAMPATH
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