IV. Using water wisely A. Water pollution 1.Pollution= the introduction of harmful substances into the environment – Only 3% of the Earth’s water is drinkable – 75% of the drinkable water is trapped in polar ice caps 2.Point-source pollution= pollution that comes from a specific site – Can be controlled b/c you know where its coming from

3.Non-point source pollution= pollution that comes from many sources – More difficult to control because it doesn’t come from a single source – Hard to find the true source at times – Street gutters, fertilizers, draining from mines, salts from irrigation

B. Health of a water system 1.Dissolved oxygen: DO= oxygen dissolved in water – Water organisms need water to live – Below 4.0 mg/L in fresh water can stress & cause death to water organisms – Sewage, fertilizer & runoff can decrease DO – Cold water holds more DO than warm water – thermal pollution= when heated water is added to cool water & DO levels decrease

2.Nitrates= naturally occurring compounds of nitrogen & oxygen – Elevated nitrate levels can lower DO levels – Can come from fertilizer & animal waste runoff 3.Alkalinity= water’s ability to neutralize acid – pH below 6.0 is too acidic for most aquatic life

C. Cleaning polluted water= sewage treatment plants Primary treatment: – dirty water is passed through a large screen to catch solid objects – Then it is placed in a large tank where smaller particles or sludge can sink & be filter out 2.Secondary treatment= water is sent to an aeration tank to be mixed with oxygen and bacteria – Chlorine is added to the water to kill any residual bacteria & it is released into the river

3.Septic tank= large underground tank that cleans the wastewater from a household – Wastewater flows from the house in to the tank – Solids fall to the bottom and cleaner water from the top flows into into a group of buried pipes= drain field

C. Where the water goes 1.Less than 8% of water we use in our homes goes to drinking – Flushing toilet, doing laundry, bathing, water lawns/plants takes up the rest of the water 2.19% of water used in the world is used for industrial purposes – Cool & clean machines & products – 90% can be treated & released back into the environment 3.Water use in agriculture can drain natural aquifers – High plains (Ogallala aquifer) largest in North America is used heavily for irrigation 4.Conserving water at home by taking shorter showers, using low flush toilets, low pressure shower heads.