Download Water Treatment 2

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/watertreatment
plant/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 fiveperson U.S. households per year)
• Largest plant in nation in San Diego, Ca