Imagine your toilet commode as a Sewage Treatment Plant (STP) which converts human waste into biogas that can be used as an energy source in your home and water that can be reused for gardening, with zero solid effluents let out.
In the city that has witnessed lakes turning into sewage pits, as numerous apartments even today let out untreated sewage into lakes in the absence of sewer network, the Defence Research Development Establishment’s (DRDE) bio-digester based eco-toilet could be an answer to the sewage woes.
The STP toilets, now being built into apartments, was an exclusive defence technology developed by Lohendra Singh, Director, DRDE, and his team in 1997 to solve high-altitude sanitation problems for defence personnel. “It is even today widely used on the Siachen Glacier, apart from the Leh-Kargil sector. The first time the technology was used for civilian purposes, Indian Railways partnered with DRDE in 2010 to make toilets across its entire fleet turn into bio-digester toilets, with a deadline of 2019,” said V. Vasudevan, a scientist on the bio-digester team in DRDE, Gwalior.
In 2014, DRDE for the first time implemented the technology at its residential colony Anusandhan Vihar, Bimarpur, New Delhi with 186 flats. Mr. Vasudevan, also a resident of the area, said that while they were using the biogas, the garden in the locality was completely maintained by reused water from the bio-digester.
Following this success, DRDE empanelled 55 private firms working in the eco-toilet sector as licensees for the technology, who are providing it for the residential and office sector across the country.
Bio-toilet
A bio-digester toilet was developed in 1997 by a Defence Research and Development Establishment (DRDE)-Gwalior team, led by its present director Lohendra Singh.
Technology was developed for high altitude, low temperature conditions for defence purposes. Widely used in Leh-Kargil sector and Siachen glacier.
In 2010, Indian Railways partnered with DRDE to turn all toilets in its fleet into bio-digester toilets, with a deadline of 2019 under the Swachch Bharat campaign.
The Lakshadweep island’s administration has placed orders for 12,000 bio-digester toilets to make all toilets on the islands eco-friendly.
The Ministry of Drinking Water and Public Sanitation signed an MoU with DRDE to promote this technology in rural areas under the Nirmal Bharat Abhiyan in 2012.
DRDE partnered with private industry in 2014 and made 55 private firms licensees for the use of the technology in residential and office sectors.
How does the technology work?
The toilets are connected to a bio-digester instead of a septic tank.
Each toilet commode can be connected to a bio-digester or a group of toilets in the building can be connected to one large bio-digester.
Faecal matter converted into bio-gas and water through anaerobic digestion.
Anaerobic digestion: is a process by which microbes break down biodegradable material in the absence of oxygen.
A bio-digester has two components:
Anaerobic microbial consortium: The microbial consortium is made of four clusters of bacteria belonging to hydrolytic, acidogenic, acetogenic and methenogenic groups with high efficiency of bio-degradation. Anaerobic bacteria will kill 99% of the pathogenic microbes associated with faecal matter.
Bio-digester needs to be charged with bacteria-enriched inoculum only during installation and after that the bacteria will self-multiply. Bacteria survives for a minimum period of 3 months when toilet is not in use. Bacteria will begin re-multiplying once toilets are back in use.
Specially designed fermentation tank: A metal/FRP made fermentation tank with provision for immobilising the bacteria in large numbers.
“The bio-digester-based toilets are best suited for areas with no proper sewer network. I have heard of Bengaluru’s lakes being polluted by sewage from apartments. Our toilet model may be best suited for the city’s requirements,” said V. Vasudevan, a scientist on the bio-digester team from DRDE, Gwalior.
“The frothing of lakes is due to letting sewage and phosphate salts into the lakes. The apartments around the lakes are to blame for the frothing. These toilets in apartments will do the most to rejuvenate the lakes,” said environmentalist A.N. Yellappa Reddy
Becoming popular
The DRDE’s bio-digester toilets are now fast becoming popular in an already crowded market for eco-toilets in the realty sector of the city.
Dr. Laxminarayana Burela, Chief Scientist, Shubhra Biotech Pvt. Limited, one of the licensees, said that they were working with an upcoming apartment project in the city to provide these toilets. The response had been positive in the Bengaluru and Chennai markets.
An upcoming residential project with 96 flats being developed by Arna Shelters on Bannerghatta Road is implementing the technology. Each commode in this project will act as an STP with zero sludge and only water for effluents.
“We have received many queries from builders in Bengaluru and a reputed firm is also in talks with us for a large order of these toilets to be provided in the city’s slums as part of the CSR initiative,” Dr. Burela said.
KSPCB not aware
S. Venkatesh Shekar, Senior Environmental Officer, Waste Management Cell of the Karnataka State Pollution Control Board, said while the concept sounded good, the KSPCB will have to verify the technology before throwing its weight behind it. “DRDO has not yet approached us. But, if we find the technology good, we can create awareness about it in the city,” he said.
It must be remembered that after the frothing and foaming of Bellandur and Varthur lakes, KSPCB had in June ordered apartments complexes with more than 50 dwelling units to install sewage treatment plants to ensure untreated sewage is not let into the lake.
Low-cost technology
The technology also costs a lot less than most of the other eco-friendly toilet technologies. A bio-digester for a single toilet costs around Rs. 30,000 in the market. However, this cost goes up if a bio-digester is put up for a cluster of toilets connected with a fermentation tank.
V. Vasudevan, a scientist on the bio-digester team of DRDE, said the cost will escalate based on the material used to build a common fermentation tank either with metal or concrete.
