Drinking the Sea

Every day, the average person uses over 80 gallons of fresh water. Combine that with the fact that only 3% of the world's water is fresh water, and only a third of that 3% is readily accessible, and it starts to seem like we might not have enough water to go around. A nice visualization of that is below.

GIF Courtesy of Julian Glander

With the increasing concern brought by the California drought, the issue of conservation and production of fresh water is becoming more and more pertinent. California has begun to try to go proactive by building desalination plants (where they turn sea water into fresh water), but these plants can end up being huge sinks of energy.

Desalination Plants in California
Image Courtesy of the Bay Area News Group

Dr. Manish Kumar here at Penn State is currently working on a project that will hopefully lead to lower cost desalination, making it a more cost-effective solution for more locations. One of the biggest steps (and the most energy hungry steps) is reverse osmosis. You likely remember osmosis from high school biology: it's when water flows through a membrane from an area of low solute concentration to an area of high solute concentration (so like the left half of the image below). The system is trying to achieve 'equilibrium', where both sides have the same concentration of solute, in this case salt.

Image Courtesy of Axeon Water Technologies 

The really important stuff happens for us when we try to reverse the process (aptly named 'reverse osmosis). By forcing the water (through an application of pressure) the wrong way through the membrane, we can force the water to flow from high concentration to low concentration, yielding more fresh water than we came in with! And just like that, we turned salt water into fresh water.

Dr. Kumar's lab is attempting to find ways for this process to be more efficient. Specifically, there are two specific areas where his lab is trying to make strides. The first is how currently, salt particles will often 'plug up' the membranes, leading to lower throughput (and higher energy costs!). By disrupting salt gradients that often form next to these membranes using little things called 'micropumps' to keep the gradient at a minimum.

Colloidal 'Fouling' (left) and Disruption (right)
Image Courtesy of Manish Kumar

The other area also involves things getting in the way of the membrane and restricting throughput, but this time the concern is biological. Little bacterial colonies love to set up shop on these reverse osmosis filters, causing a substantial decrease in performance. His lab's solution to this isn't to put in toxic chemicals to kill the bacteria, but instead to give the bacteria a little of their own medicine, and introduce beneficial bacteria growth on the membranes, bacterial growth that will prevent the harmful bacteria from growing. What's even neater is the fact that they are able to regulate themselves and control the colony's thickness in order to prevent the bacteria from having a substantial impact on the performance of the membrane.

While it might not seem like the most enthralling subject matter, the concern with fresh water and what we can do to ensure that everyone has enough water every day is only becoming more and more important. I'll probably talk again about desalination and it's potential utilization in one of my later civic issue's blogs, although maybe with a little less science.

If you'd like to read more about Dr. Kumar and his research (he's doing a lot of really interesting things!) you can find his publications here.