Safe, Clean and Drinkable Water Treatment Safe, Clean and Drinkable

Assignment You need to draw and label each step of the water treatment process Under each label explain what is happening in that step.

Water Treatment Since water is odorless, tasteless, and colorless we must test for specific contaminants such as bacteria, nitrates, arsenic and others. Natural supplies of potable water are very limited and do not exist in sufficient quantities to meet human needs. Humans have developed steps to treat the water so it can be used for a specific purpose such as drinking.

Water Collection Water is generally pumped from a lake or river to a treatment facility

Screening Most surface water intake facilities are equipped with some type of screening device to prevent large rocks, sticks, and other debris from entering the treatment system. Large bar racks with openings of 1 and 3 inches apart are commonly used for this purpose. They are designed specifically to prevent large materials that could damage the intake structure or downstream equipment from entering the treatment system.

Screening Bar racks are usually designed for manual cleaning. When the raw water source is a river and a bar rack is used, the rack is usually oriented to take advantage of the hydraulics of the river to keep the rack cleaned. Although trash racks have little effect on turbidity, they do serve an important function in keeping large solids out of the treatment system

Coagulation The addition of alum, lime and other chemicals are added to the water causing particulates to clump together

Flocculation The water is then shaken to form larger clumps which are known as flocs.

Sedimentation The water stands for approximately 24 hours, in which time the clumps settle to the bottom.

Filtration The water passes through filters, some made of layers of sand, gravel, and charcoal that help remove even smaller particles.

Disinfection A small amount of chlorine is added or some other disinfection method is used to kill any bacteria or micro-organisims that may be in the water. At this stage the water is aerated

Storage Water is placed in a closed tank or reservoir in order for disinfection to take place. The water then flows through pipes to homes and businesses in the community.

Clean Water Substance removed during the treatment process include: Suspended Solids Bacteria Algae Viruses Fungi Minerals Chemical Pollutants

Virtual Water Treatment http://www.epa.gov/ogwdw/watertreatmentplant/flash/index.html

Saltwater to Freshwater How much water on Earth is Saltwater Can we make it into freshwater Is it cost effective

Assignment You need to create a flow chart explaining each step in the desalination process On the bottom explain why people do not use this process more

Desalination Any of several processes that remove some amount of salt and other minerals from saline water. Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential byproduct of desalination is salt. Desalination is used on many seagoing ships and submarines.

Desalination One of the most expensive sources of fresh water. The water sells—depending on site conditions—for between $1,000 and $2,500 per acre-foot (the amount used by two five-person U.S. households per year) Largest plant in nation in San Diego, Ca