Mechanical engineering students create self-filtering water barrels

Throughout our day, most of us probably aren’t worried about where we’re going to go when we get thirsty: the myriad of water fountains and soda fountains make beverages an easily accessible commodity. Not all parts of the world are fortunate enough, however, to have such access to clean, filtered water. In fact, most third-world countries struggle to develop a sustainable supply of clean water.

A group of senior mechanical engineering students at Carnegie Mellon University attempted to solve that problem by developing a filtration mechanism that filters water as it is transported. The filtration consists of a big barrel that contains a smaller barrel inside of it, with a handle attached for pushing motility. The concept behind the design is that as the barrel is rolled along the ground, the motion caused by pushing the big barrel filters the dirt away from water and stores the purified, clean water in the mechanism’s smaller barrel.

“We had already seen some ideas out there that filtered water, and others that rolled the water using barrels, but we wanted to create something that filtered while you rolled,” said Deepak Ravi, one of the senior mechanical engineering students on the project, in a University press release.

The beauty of this water filtration system is that it filters water as it is transported, and it is industrially very simple in design. The filtration system contains only a few simple parts that amount to no more than $200 in cost, and requires no power input other than the physical pushing of the barrel by users during transportation of water.

The system uses a Sawyer water filter and relies on a process called reverse osmosis. The basic design behind a reverse-osmosis water filter is that the filter is made of a porous substance that allows water to flow through it. Because water is in the liquid phase, it is able to deform and flow through the filter without any issues; any solid particles, however, cannot fit through the pores in the filter, and instead become trapped in the matter of the filter.

The efficiency of a reverse-osmosis filtration device is dependent on its pore size: the smaller the pores are in the filter, the more solid particles it can trap. The Sawyer filter in the water barrel mechanism filters water as the barrel is pushed, conflating the issue of filtration and transportation into one solution.

Other types of water filtration mechanisms do exist, such as ion exchange or activated carbon. In these filtration devices, water is passed through a chemical that adsorbs the dirt and other particulates that contaminate the water. While these types of filters are popular, they can get pricey due to the cost of the chemicals required for filtration.

The advantage of using the Sawyer filter is that is does not need to be replaced, making it a one-time purchase that does not need to be refurbished over time, unlike the activated carbon or ion-exchange filtration mechanisms. Additionally, the group used a recycled industrial barrel as opposed to purchasing a new one to cut down on the cost of the device. The barrels are usually thrown away after they are used, so this senior project finds an exceptional application for what would otherwise be considered garbage.

Although this prototype was designed as part of a graduation requirement, the group of seniors is hopeful that their design is able to grow into something bigger than just a class project.

The group calculated that if mass produced, the cost of the barrel filtration mechanism could be reduced from $200 to just $40. The seniors are hopeful that they can find a company willing to mass produce their filtration system, allowing their design to reach thousands of impoverished people in developing countries. “If someone wants to manufacture our system and get it down to that $40, none of us would be upset,” said Anna Mirabella, another one of the seniors on the project, in a University press release. “It would be awesome to have had a small part of something big.”