Indian Railways develops hybrid vacuum toilets

"A prototype has been made by modifying the standard flushing protocol of a vacuum toilet so as to create water seal and additional post flush cycles and this concept has been converted into a working prototype by Indian Railways as a first ever system of its kind to have been developed and built by any railway system in the world. This newly developed toilet has been fitted in one coach No. 153002/C FAC that is running in Dibrugarh Rajdhani for trail," read a government statement.

The prototype consists of a custom designed Vacuum toilet adapted from a commercially available vacuum toilet that is used in aircrafts which evacuates its discharge into a biodigester tank which is now successfully proven in the biotoilets of Indian Railways.

The biodigester tank is fitted underneath the coach and contains anaerobic bacteria that converts human fecal matter into water and small amount of gases before discharging the same on the ground/track.

"Typically, a conventional toilet or Biotoilet uses 10 – 15 liters of water per flush whereas the vacuum toilet consumes only appx. 500 ml of water for flushing. Water is a very precious natural resource therefore this innovation shall save water to the tune of at least 1/20th of the quantity that is used in the current design of biotoilets/conventional toilets. Further, in foreign countries where the train coaches that are fitted with Vacuum toilets, there is a “retention tank” underneath the coach that holds all the human waste that is flushed out by the toilet. These are very large tanks that need to be evacuated at the terminals stations," read a the statement.

"Since Indian Railways trains traverse the length and breadth of the country with journey times as long as 72 hours and generally over 50 passengers per coach, it is nearly impossible to hold the human waste in retention tanks on trains that travel such long distances. Also, the stationary facilities for evacuation of these holding tanks need to be maintained very carefully and meticulously or else their malfunction will render the entire train’s toilets unusable. The Municipal Corporations at cities where these ground-handling facilities are to be created have to be taken into confidence to allow one-shot rapid discharge of human waste of an entire train into their sewer systems, which may not be possible at all stations due to constraints in existing sewer system that are already in place,' it said.

By transferring the discharge of the vacuum toilets into biodigester, the need to create separate ground handling installation and creating additional sewer load on the Municipal Corporation will be done away with.