Context
The Brihan Mumbai Municipal Corporation (BMC) has tied up with Indian Institute of Technology (IIT-B) for in-situ treatment of sewage in nullahs in the city.
What is N-Treat technology?
- N-Treat is a seven-stage process for waste treatment that uses screens, gates, silt traps, curtains of coconut fibres for filtration, and disinfection using sodium hypochlorite.
- According to the detailed project report for N-Treat, it is a natural and environment friendly way for sewage treatment.
- It’s set up takes place within the nullah channels that is through the in-situ or on-site method of treatment, and does not require additional space.
Stages involve in the Process
- Screening
- The first stage involves screening to prevent the entry of floating objects such as plastic cups, paper dishes, polythene bags, sanitary napkins, or wood.
- IIT-B has proposed to install three coarse screens, the first with 60 mm spacing for removal of large floating matter, the second with 40 mm spacing, and the third with 20 mm spacing.
- Slit trap
- The second stage has proposed construction of a silt trap, which creates an inclination and ‘parking spot’ on the bed of the nullah for sedimentation.
- Bio zones
- The next three stages are installation of ‘bio zones’ in the form of coconut fibre curtains that will act as filters and promote growth of biofilm to help in decomposition of organic matter.
- A floating wetland with aquatic vegetation planted on floating mats has been proposed.
- Florafts
- Aside from a floating bed on the surface, IIT-B has proposed suspending floating rafts vertically, called florafts.
- Their hanging roots would provide a large surface area for passive filtration as well as development of microbial consortium.
- In the floating wetlands, plants acquire nutrition directly from the water column for their growth and development, thus reducing the organic as well as inorganic pollutants.
- The final stage for sewage treatment will include disinfection using sodium hypochlorite, to kill the bacteria in the water.
