Desalination

1. Desalination

2. What is desalination? • Def: the extraction of freshwater from brackish or salt water • The more salt the water contains, the more energy it takes to desalt it • Removing the salt from seawater costs about five times as much as removing salt from brackish water • Two types: • Distillation • Reverse osmosis (most widely used)

3. Distillation • A process in which salt water is heated to a point of evaporation. The vapor then trickles into a separate container holding just freshwater • Different types: • solar

4. Survivorman Les Stroud: Episode Kalahari Desert uses distillation too! Greeks were one of the first to use distillation (4th century BCE)

5. Reverse Osmosis • Def: A process of desalination that uses osmotic pressure to force salt water across a membrane, leaving the salts behind.

6. Ackk! Expensive! • The pricey cost of a desalination plants limits its use in poorer nations • Desalination costs include: • Machinery and the complex infrastructure of the plants • Salary of skilled technicians • Transportation of water to and from the plant • Energy it takes to actually desalinize the water

7. Environmental Impact • Energy used to fuel desalination process releases greenhouse gases • Demand for freshwater is rising due to population increase • Leftover salt is dumped back into the ocean • Raises water temperature and increases salinity

8. All is not lost… • Alternative energy • Solar and wind (Perth, Australia) • With the leftover salt, some plants: • Dilute it and gradually release it into the ocean • Use it for industrial purposes • Give it to fish farms, where there’s less salt • Give it to farms that cultivate salt-tolerant plants, like seagrass

9. What needs to be done… • People in general just need to become more water-wise, then we wouldn’t need desal. plants as much. • Develop more efficient technology for desalination • More use of renewable energy sources • Population management?