When brainstorming possible uses for the reverse osmosis (RO) brine, one of the first ideas we came up with was to use the brine in place of water in a public restroom facility. This solution could easily use brine to flush human waste and it would provide a hygienic method of storing the waste- improving public health in the community. In order to make this solution economically viable, it would be a good idea to incorporate a “pay-per-use” system at this facility. Local residents would be familiar with this system because it is a similar one used at Sarvajal franchisee locations and it would create an economic opportunity for another local resident.
Being a more socially minded person, I started my research with the current practices and cultural norms of the region and how these norms would affect the ultimate physical structure of the facility. Currently, in most rural areas of India there is no central water or waste infrastructure and open defecation around the villages (often in nearby fields) is common. This poses obvious risks to public health, especially considering India’s rapidly growing population. It became apparent that any public restroom facility would need to be accompanied with an educational program on how to use the facility and why it is needed, because residents may never have seen any such facility.
A critical consideration is the social stigma associated with removing and handling human waste. It is a job only performed by the lowest castes of Indian society. Our group recognized this as a potential barrier to implementation, but since we did not know which of the 100+ Sarvajal locations we would be working at, we did not yet know the exact social dynamics of the villages. No resolution for dealing with this stigma was determined, but it was left open for further consideration and development once more site-specific information was obtained.
Another important societal norm I discovered was the need for women to preserve their modesty in all situations. Since the only place available to relieve oneself was outside, this often meant that women had to wake up before sun rise or wait until sunset to relieve themselves, in order to avoid being seen in a revealing position. In order to accommodate modesty concerns, a public restroom facility would need to have two rooms (one for each gender), doors, and a roof.
The need for privacy, and therefore an enclosed space, made the next task of how to eliminate foul smelling odors crucial. I did not want to incorporate a ventilation system because I wanted to keep the cost down in hopes of making this solution scalable to multiple franchisee locations. After researching a variety of public restroom facility designs, I choose a system with a holding tank below ground. In a holding tank containing brine, the waste would be below the surface of the brine, foul odors would be greatly reduced; increasing the likelihood that such a facility would actually be used.
This research into structural design also lead me to a system known as “pour-flush” system. After a person uses the facility they would turn on a faucet to fill a bucket with water (or in our facility with brine) and then pour it into the hole to flush the waste down into the holding tank. This method seemed the most practical because it would ensure that brine was always present in the holding tank. It was also very simple to construct and use; it would not require a lot of technical maintenance.
My next step was to review the water quality to make sure that any contact with the brine during the pour-flush process would be safe. Around this time, our group held a solutions symposium with some engineering students to get technical feedback on our solution designs. One student mentioned that my design seemed to be on the right track, but that I needed to check to see if our brine contained sulfates. When sulfates come into contact with organic material (such as human waste) it reacts to form hydrogen sulfide. Concentrations as low as 0.00047 ppm create the typical “rotten egg” odor, 50-100 ppm can cause damage to the eyes and if the concentration reaches 320-530 ppm pulmonary edema becomes likely and death can occur (USEPA). After the symposium I checked the water quality data sent to our group by Sarvajal- almost every franchisee location has sulfate in their ground water; which would ultimately be concentrated in the brine after the reverse osmosis process.
Upon learning this information, it was determined that further research and development on this solution should be suspended. While I still believe that a public restroom facility would have a profound impact in the village(s), given the potential chemical reactions this solution is not feasible to pilot test with current technology and budget restraints.
USEPA. (1980). Health and Environmental Effects Profile for Hydrogen Sulfide p.118-8. ECAO-CIN-026A