4 Purifying Water through the Hydrologic Cycle 1. The sun provides energy for water to evaporate this resembles the process of distillationEvaporation leaves behind minerals, heavy metals, and other dissolved substances.
5 Purifying Water through the Hydrologic Cycle Water vapor condenses and falls as precipitation raindrops and snowflakes are nature’s purest form of water containing only dissolved atmospheric gasesHowever, human activities release a number of gases into the air making today’s rain less pure than it used to be
6 Purifying Water through the Hydrologic Cycle 2. Bacterial ActionWhen raindrops strike the soil, they collect impuritiesBut, as the water seeps through the ground the bacteria in the soil feed on those impurities and repurify the water
7 Purifying Water through the Hydrologic Cycle 3. FiltrationAs water seeps further into the ground, it passes through gravel, sand, and rockThis allows bacteria and suspended matter to be filtered out
8 Municipal Water Purification Major Steps1. Screening2. Prechlorination3. Flocculation4. Settling5. Sand Filtration6. Post chlorination7. Optional Further TreatmentRead article on pages and define these termsEnded here with period 8
9 Chlorination of WaterRead article on page 90 and outline the 3 methods of chlorination.What is a potential problem with water chlorination?
10 Chlorination and THM’s Ways to eliminate THM health risk1. Pass water through activated charcoal filter.Can get rid of THM’s but expensive to install and operate.2. Use ozone or UV light instead of chlorinationWon’t protect the water from contaminants once it has left treatment plant
11 Hard WaterHard Water is water containing an excess of dissolved calcium (Ca2+) ions, magnesium (Mg2+) ions, or iron (III) (Fe3+) ionsAs water flows through limestone, chalk, and other rocks, these ions seep into the water
12 US Groundwater Hardness Is Your Water Hard or Soft?
13 How do we soften water??? Water Softening Lab 3 ways 1. Sand Filtration2. Treatment With Calgon3. Treatment with an Ion-Exchange Resin