Desalination Plant For Salt Farmers in Kutch

By : Aashaka, Amanat and Shashank

May 2018

Introduction

The team was allotted the topic of toxic gas detection inside brine wells in Kutch.  After a field visit and a team split, they decided to do more than just detecting the gas. They started working on a way to make in and out movements of brine wells quick, easy and safe. Upon discussion with salt farmers in second field visit, the farmers drew their attention to graver issues they face in the region, like, limited availability of water for daily use, lack of primary health care services and transportation in the region. The salt farmers stay for 8 months in the Rann of Kutch. They then move to their villages which can be more than 40 km far. They carry 1000 - 1500 litres of water when they are moving to Kutch from their villages. The tankers that supply water, cannot supply water for the first two months due to the swampy conditions. The salt farmers ideally use about a 100 litres of water everyday. 75 for washing and bathing and 25 for drinking. They compromise on bathing and washing for the first 2 - 3 months. The tanker services are unreliable even after the initial months.

 

Motivated to solve the water crisis, providing an efficient and cost effective supplementary source of freshwater to the salt farmers in the Rann of Kutch, was taken up as the final project.

 

Field Visit Insights - Visit 1

The first farm had 4, 20 ft deep, functioning brine wells which were connected to 3 motors working on solar panels in day and diesel pump at night. The wells being situated in a region with a higher water table had comparatively lower depth. They also saw well digging tools and salt pans. The team went deeper into Rann next day, coming across wells ranging from 50 to 60 ft. The team observed different support structures inside the wells. The first well that the team saw had concentric concrete rings for support. The second well, on the other hand, had bamboo sticks for support as well as for up and down movement in the well. Most of the wells, however, did not have any mechanism to support its structure. Later in the evening, team visited Naya Kharagao, a village established in the British times for salt farmers. There the team interviewed people of the Agariya community asking them about salt farming, brine wells, challenges they face and improvements they look forward to."Gas toh Mr India jaisa hai, dikhai nahi deta", 40 years old, Ramesh Bhai said on the tragic problem of toxic gas leakage in wells. " Peewana pani ni dikkat che" said Vallabh Bhai bringing into light how fresh water tanker only reaches in the months of December - January, creating drinking water problem from October to January. The team thanked the villagers for their warmth and support, and left for their accommodation with richer insights.

 

Brainstorming (Quick, Easy, Safe Well Access)

A brainstorming session was used to ideate into the possibilities of different ways people can go “up”. This was in line with the need of the people to get out of the well. Sketching was used as tool to ideate. The wildest of ideas ranging from canons to drones, big wheel to skates and even as far as an underground rail were considered. Over time as we built upon our previous wild ideas we started reaching ideas with more deeper thought put into them and ideas that with time and thought were becoming more and more structured. The brainstorming session also helped explore into what surplus features might the user expect or require in the product. Then small but at the same time important insights were taken from all these wild ideas to create a learning experience for the team. Using all these insights we now move on to the conceptualisation phase where these learnings and ideas will be looked into thoroughly and compiled in various permutations and combinations to help create a product that has the positives and avoids the negatives.

Mind Map

Field Visit Insights - Visit 2

Upon discussion with salt farmers in second field visit, the farmers drew their attention to graver issues they face in the region, like, limited availability of water for daily use, lack of primary health care services and transportation in the region. After hours of dialogue with the farmers, and among themselves, the team decided to work on ‘Desalination of water’. When farmers move into Rann in the beginning of season they carry with themselves approximately 1500 litres of water, which they have to sustain for next 2 months as water tankers can’t access Rann in the season because of swampy conditions. Erratic water supply during rest of their stay in the region creates problems too. Having seen many small desalination setups themselves, they realized there was no use of working on the problem from scratch. They started working on how to increase efficiency of already existing models.

 

Brainstorming (Brine Water Desalination)

The insights and questions the team came to from the brainstorming session were following:

1. RO-based desalination v/s classical evaporation condensation based

a. We chose classical way because of abundance of sunlight and wind, and existing solar panels

2. Have two separate tanks - one for evaporation and other for condensation v/s Have a single evaporative unit with condensation at top of the unit. The first allows easy control over the evaporation and condensation tank parameters. The second is more common as it is difficult to guide water vapour through valves and outlets without it condensing. We decided to go for the former one.

The next questions we asked were -

1. How to make the evaporation rate faster?

a. Increase the surface area of the heated water

i. Have capillaries with increase water

ii. Have porous stones which soak water

b. Increase more heat

i. Insert metal rods inside

    1. Connect the rods to the solar panel to have continuous heat source

ii. Use reflecting material outside the evaporation tank to trap more sunlight

iii. Colour the tank black

2. How to make the condensation faster

a. Make the condensation tank cooler. Put it in sand/mud/earth.

b. Put water vapour adsorbing material inside the condensation tank

3. How to collect condensed water?

4. How to maintain the tanks?

a. Use plastic based food grade tanks which don’t get corroded

b. Have a sweeping mechanism for salt gathered at the bottom of tank. We are routing the water left over after a day to the nearest salt pan with the help of a pipe. Either let the salt go with the water flow, or allow a detachable collection pit for the salt at a lower level where the salt can be pushed into by a swiper.

 

Pre-prototype experimentation

We tested whether there was a difference in the evaporation rate for the different ways in which we had put up water - metal rods, reflecting surface, cotton capillary, black cover, saline water.

We couldn't find much difference in the amount of water evaporated and timing, it was an experiment which required more diligence and care in smallest of measurement. We then moved to create a representational prototype and see if it worked. The water didn't collect in the tank as expected. Here we found the problem of collecting water to be noteworthy. So the condensation tank idea was dropped and instead, we went to collecting water from the top of evaporation tank.

Literature Survey

We went through papers like https://www.sciencedirect.com/science/article/pii/S1877705812045316 on methods for desalination using renewable energy, especially sun and wind.

The multistage flash distillation process in which a low pressure is also used to vaporize water in a flash was a good option to consider, however a costly one because of the creating low pressure. Hence we decided to go against it. We did get one insight of performing evaporation in stages for better efficiency.

 

Prototype

One of the prototypes we made had an inclined roof made of acrylic sheets, to collect water. It was heated by heating rods connected to solar power. Our prototype allows the water which hasn’t evaporated to be directed to the salt pans. This water is more concentrated than the water input.

We didn't have too much time for a user test, so the future plan is to test this prototype out, using saline water. We would also like to incorporate more ways to increase the efficiency of the plant.

For Questions /  Contact us at summerschool@sristi.org

Society for Research and Initiatives for Sustainable Technologies and Institutions (SRISTI)

Address: AES Boys Hostel Campus, Near Gujarat University Library & SBI Bank, Navrangpura, Ahmedabad-380 009, Gujarat, India.

Phone: 079-27913293, 27912792,

Email: info@sristi.org