The Water Cycle

What are some things that you think are in your water?

List of various organisms/chemicals in water before treatment… Nitrates Phosphates Sulfates Soil Bacteria (Fecal Coliform) Lead Magnesium Calcium Iron Dissolved Oxygen Calcium Carbonate Chlorine Arsenic Pesticides Sand, Clay Hydrogen sulfide gas Manganese More…

How does this all get into the water? Water goes through a cycle like the carbon seen in the previous section You are probably more familiar with the water cycle than the carbon cycle, so this should be review. The water cycle is called the hydrologic cycle and describes the movement of water through the hydrosphere

Water has to be cleaned.. When we drink water, it is normally processed and the type of water depends on the process used – City water goes through a water treatment plant – Pond water goes through reverse osmosis system – Well water normally goes through filtration system similar to reverse osmosis Let’s look at each process a bit closer..

Water Treatment Process Five primary steps for treatment of water: 1.Disinfection chlorine is added 2.Coagulation and flocculation Alum (compound) is added to cause tiny particles to clump together and sink 3.Sedimentation Heavier material in water settles and metals removed

Water Treatment Process 4. Filtration – Process removes sediment and other materials suspended in the water 5. Corrosion control – pH is adjusted with compound to reduce corrosion in plumbing systems Often UV radiation occurs next to remove any remaining bacteria/viruses that could be in water Then water is distributed to customers.

Reverse Osmosis System Water passes through a membrane to remove minerals found in water such as radium, sulfate, calcium, magnesium, potassium, etc. Used with mechanical filters and activated carbon filters to 1. Mechanical filter removes large particles 2. Reverse Osmosis system removes minerals 3. Activated carbon filter removes organic compounds (pesticides, etc.)

Other Water Treatment Systems Water softeners (ion exchange) – Treats hard water while removing bad odors, colors, tastes – Water passes through resin beads coated with positively charged sodium ions. These ions exchange places with calcium, magnesium, and other “hard” ions in the water. – Some columns contain negatively charged chloride or hydroxide ions to remove nitrates and fluoride from water.

The goal of all of these systems? To filter out the things found in the water that we can not drink safely. What if we don’t have the ability to pay for an expensive system or have city water? Then what? What do third world countries do to filter water and make it safe to drink?

Great Cheap Filters Some countries use a sand based filter to get out as many impurities that they can. Let’s see how great a filter utilizing sand really is. Activated carbon can also be used, and is often used for removing impurities in fish tank systems here, but can be helpful where other resources are not available

Let’s Create an Experiment.. Design an experiment looking at various materials and how well they filter water. You will be given “dirty” water. The goal is to see which material will filter the “dirty” water the best. All of the materials you can use are on the back tables for you to use in creating your lab.

Please include the following in your lab write up 1.Goal of lab (what are we trying to test?) 2.Materials list (what do you need?) 3.Setup (how are you going to set up lab?) 4.Hypothesis (which material do you think will filter the best and why?) 5.Data Tables (scale of “clean”? Actual numbers?) 6.Conclusion (what happened in the lab? Were your predictions right? Why or why not?)