You know the idea that making a lot of money is reward for solving the big problems of the world? This is only partly true. Some of the richest men on earth never solved any problems. Despite that, it’s always better and it always offers more personal satisfaction and fulfillment in life if you make your fortune while going down in history as someone who changed the world for the better.
So talking about problems, here’s one waiting to be solved which will reward the brain that finds a good answer to it: affordable desalination of sea water.
There are not enough freshwater sources inland that could be purified for everybody’s domestic use, so taking the water out of sea water is an option that several countries make use of. Even then, a good number of people in the world still do not have access to clean water.
The problem with desalinating sea water is that it is a capital-intensive process.
If you follow the news very well, a sea water desalination plant built at Teshie in Accra cost the Ghana Water Company millions in losses and generated a lot of controversy until the company decided to shut it down. Ghana Water Company was losing about 6 million Cedis every month. Also, not long after the plant began operations, some residents in Teshie were complaining about the saltiness of their water supply.
Typically, the cost of clean desalinated sea water is twice the cost of purified freshwater sources. As the process is itself expensive, so also is the necessary infrastructure. Construction of a small seawater desalination plant with an output capacity of just 2 million gallons of water per day, can cost more than $30 million. A regular water treatment plant of the same capacity can cost less than half of that.
Though efforts have been made around the world to find more affordable methods, some things you cannot take away, like the corrosiveness of sea water. It always means the machines have to be made of tough, non-reactive metals.
The processes most commonly used in desalination are thermal distillation and reverse osmosis. In the first, water is boiled into vapour and then condensed back into water by cooling, separating it from the salt. In reverse osmosis, water is forced at high pressure through a semi-permeable membrane that the salt cannot pass through.
Reverse osmosis is the more favoured method since it requires less energy. Even then, it can still use up to five times or even ten times the electricity that a regular water treatment plant would use. And it could also pose some environmental hazard. Half of the sea water drawn in becomes purified. The other half becomes a concentrated salt solution that needs to be disposed off safely.
Several answers to the high cost of sea water desalination have been in the works over the years. Some of them are promising and mostly try to tackle the problem through materials engineering: more efficient, more affordable semi-permeable membranes. On the whole however, it looks like whoever finds a radically different way to purify sea water at a low cost would have taken a big step to striking nice profits, not to mention the achievement that such a discovery would represent and the fact that many more people could have access clean to clean water because of that.
Got any ideas?