Low cost Production and distribution of desalinated sea water

My favourite challenge and experimentation

-Sai Sandeep Yelchuri

CHALLENGE: How can freshwater (desalinated water) be produced from the sea and distributed to every household at a minimal cost like electricity?

DESCRIPTION: With the continuous depletion of groundwater resources, unpredictable rainfall, and drying up of rivers, it is very important to find a sustainable alternative for finding freshwater. Having an enormous coastal line of 7516.6 Kms, India has a wonderful opportunity in the form of seas and an ocean. But, purification or desalination of this seawater is very costly. Considering the requirement(across various states) and their financial conditions, it is difficult to go ahead with the available technology. Even after processing the seawater, distributing it to every household across the country would be a herculean task. So, the idea is to look for a solution that can desalinate seawater and distribute it at a very low cost. For a metaphorical reference, we can look at how electricity is produced and distributed at a reasonable cost to every household and industrial facility.

SCOPE OF EXPERIMENT: As mentioned earlier, we identified two sub-problems within this challenge,

1. High cost of production

2. Difficulty in distributing across the country

Due to the paucity of time, I’ve picked up only the first problem for this experimentation exercise.

BRIGHT SPOT: For low-cost production, the main criteria to be considered are ‘Low cost of setup and maintenance’ and ‘Feasibility in implementation’.

Bright Spot 1^[1]: Initially, I looked around if someone is doing something similar, at a very low cost. I came across an experiment performed by an Indian American high school boy, Chaitanya Karamchedu, who discovered a way to filter out salt from seawater at a meager cost using an absorbent polymer. Though it is an extraordinary idea that reduces the cost to a great extent, there is no mention of how to scale it, as the polymer used is costly and difficult to manufacture.

Bright Spot 2^[2]: After extensive research over the internet, going through various research papers and news articles, I came across an article published in the ‘Journal for Water Science & Technology,’ by a few young scientists in Egypt. These researchers used a process called ‘Pervaporation,’ which is a two-step process of filtering and vaporizing. The filtering is done using a polymeric membrane, while the vaporizing, and consequently condensation produces freshwater.

Although pervaporation as such is not new, it was associated with quite an expensive and complicated membrane production. This is probably the reason why it has not been put into full use. But this team of scientists developed a new type of membrane, which is salt-attracting and is embedded with Cellulose acetate, aka fibre from wood pulp. This idea of using the Wood pulp as a membrane appeared to a Bright spot for me, as it is very cheap and easy to make, and also highly efficient. Though not implemented yet in a larger setup, the second solution seems to be very promising.

For more information on the bright spots, refer the Additional Notes section and References.

SOLUTION (Chosen for experimenting): The solution chosen for experimenting is based on the second bright spot mentioned above. We use the Pervaporation method using ‘Wood Pulp’ as a membrane for filtering out salt from water. Though the cost of the membrane is lowered, the energy required for the process is still costly and is a limited resource. So, as an alternative to the traditional energy sources, we plan to use the solar panels for the energy requirements.

STORYBOARDS:

Before

After

LOOKS-ALIKE PROTOTYPE:

1-DAY EXPERIMENT:

What hypothesis will it test: The current solution is aimed at creating a new process that will desalinate seawater at a low cost. There are two parts in/ the solution that should be validated:

• Whether the current process works in producing freshwater from seawater.

• Whether the process we designed results in lower cost desalination(per Cu. Metre) compared to the existing industrial processes.

What will we do:

To conduct this experiment, we can follow the process(shown above) given in the research paper published^[2].  

This is a laboratory experiment and we just need to procure the required apparatus and chemical (Cellulose acetate). As per the description given in the research paper, this experiment can be certainly completed in one day.

Important difference:

In an actual industrial setup, the source for the electric heater in step 4 and Leibig condenser in step 7 and 8 is the solar panels installed on the plant.

Cost of experiment:

It is best to approach a University/research laboratory for conducting this experiment. It will reduce the costs to only the cost of Chemical required (cellulose acetate) and rentals.

If we want to conduct the experiment on our own, as per online sources the following are the costs for the material required:

Material	Price(in Rs)
Cellulose acetate	158
Leibig condensor	91
Cooling centrifuge (You can use other cooling methods like a small cooling chamber that can reduce costs to near 1000)	1000
Air blower	449
Thermometer	107
Total	1804

*Please refer to the appendix to find the references for each price^[3]

As it is an experiment, we are considering the costs of energy required is negligible

Measuring the success: Currently, the success can be measured on the two-hypothesis mentioned above:

1.     Is the process, producing freshwater from salty seawater? You can use Salinity sensors^[4] available in the market to detect the change. If the salinity is low, we can confirm that the process is working and can consider the first part as a success.

2.     Is the process producing 1 Cubic meter of freshwater at a low cost compared to the traditional desalination processes used in industries? If the cost of production(per cubic meter) is less than $1, the industry-standard neglecting energy costs, we can consider the second part as a success.

ADDITIONAL NOTES:

Bright Spot 1: The polymer used filters out the 90% of the water molecules that are not bonded to the salt, as opposed to the existing methods that tried to break the bonds between Water and salt molecules (that constituted 10%).

Bright Spot 2: The new membrane used is not only very cheap to make, but it is also highly efficient. According to the researchers, it can handle highly concentrated seawater, and remove contaminants. What is more, it is not only useful in terms of freshwater production, it can also be used for capturing environmental pollutants and salt crystals.

REFERENCES

1. Bright Spot1:
https://www.indianeagle.com/travelbeats/portland-indian-chaitanya-karamchedu-makes-saltwater-drinkable

2. Research Paper:
https://pdfs.semanticscholar.org/3bde/7ff2a17fb442ce24a2efba8a315c881c98b2.pdf

3. Costs of materials for experiment:

1. https://www.sterlitech.com/cellulose-acetate-membrane-filters.html
2. https://www.indiamart.com/proddetail/leibig-condenser-200-mm-15836435988.html 
3. https://www.amazon.in/dp/B01GFTEV5Y/ref=cm_sw_em_r_mt_dp_U_2XjnDbBEA7MRX
4. https://www.moglix.com/aeronox-500w-air-blower-an20/mp/msn2qreqc5takp?gclid=EAIaIQobChMIgNW73sDG4wIVziMrCh0EyAI3EAQYASABEgJPM_D_BwE
5. http://tiny.cc/lk709y

4. Salinity Sensor:
https://www.pce-instruments.com/english/measuring-instruments/test-meters/salt-meter-pce-instruments-salt-meter-pce-pwt-10-det_5852847.htm?_list=kat&_listpos=1