Desalination and Purification of Water using a Solar Powered Hydrogel Multistage

Abstract

The United Nations has a goal to supply clean water and sanitation for all. This goal sprouts from the fact that one in three people do not have access to clean drinking water. Clean water is an essential resource for our survival, yet we waste and pollute it. 2.5% of the Earth’s water is fresh yet only 0.5% is drinkable. As well as this, our already meager water resources are being threatened by climate change as weather patterns change and sea levels rise. An example of this is San Diego’s water supply which comes directly from the Colorado River but, due to a change in weather patterns, the Colorado river level is falling forcing San Diego to look elsewhere for clean water (2). Another example is Melbourne’s, and many other Australian cities’, water supply that took a heavy hit during the Millennium Drought. To fix problems like this desalination plants are being built. However, the processing of water in these plants is expensive ranging from 1,000 to 2,000 US dollars per acre-foot (of water), 10’s to 100’s of millions per year in maintenance (3) and billions to build the plants in the first place. The construction of these plants also require infrastructure that developing countries, countries that need clean water the most, simply do not have. The current and mainly used methods of desalination are reverse osmosis and thermal evaporation (2). Thermal desalination isn’t commercially viable due to its intensive energy requirement so reverse osmosis plants have become the favored design. However, these plants have many consequences such as toxic waste pollution and killing of local wildlife (2). This industry is crucial to humanity’s survival, yet it has so much room for improvement. Despite humanity’s access to a large supply of salt water and polluted fresh water, we are without an efficient and versatile means of making it safe to drink. This study aims to change that. This study aims to design, build and test an easy to use, highly efficient, solar powered and portable water purification method that can be used across the globe. This design will produce water via highly efficient evaporation which will cleanse it of contaminants, including microplastics. In this study a water vaporization enthalpy decreasing chitosan and PVA hydrogel was synthesized and freeze dried repeatedly at -80C to stimulate the expansion of pores within the hydrogel. Additionally, a multistage of these hydrogels was designed and is undergoing construction and testing in tandem with a solar tracking nested paraboloidal solar concentrator. It is hypothesized that this design will have a purification rate of 10L per hour. The testing of the purification rate will depend on the quality of the prototype and the prototype’s heat capacity. This design will also undergo field trials that will test its ease of use and its resistance to damage. The results of this study will determine the feasibility of this design in the real world and whether it can realistically be of benefit to those without clean water.