Water Filtration

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Water Filtration
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• Why do we filter water?
• For drinking
• For irrigation

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Types of Pollutants

• Pathogens

Where do they come from? Why do we care?
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Types of Pollutants

• Chemical

Where do they come from? Why do we care?
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Types of Pollutants

• Salt

Where does it come from? Why do we care?
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Types of Pollutants

• Dirt
• Odor
• Taste

Where does it come from? Why do we care?
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• Pollutants get into our water in a variety of ways

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• It is a problem all over the world.

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Municipal Treatmentmost includes these steps
Water Source
Water Supply
Modified from Robert A. Perdue Water Treatment
Plant
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Municipal Treatment

• Can Provide Large Quantities of Safe Water
• Often Big Operations
• Expensive
• Training Required to Operate

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Treatment Plants Can Be Small
This one treats water from a small pond
Photos from Jerry Bernard
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Low Cost Treatments

• Boiling
• Chemical
• UV/Solar
• Distillation
• Filtration
• Biological Filtration

Water treated with any of these may need
additional treatment!
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Boiling

• Boil water for 10 minutes
• Boiling will kill most pathogens
• Does not remove salt
• Does not remove sediments
• Does not remove most chemicals
• Does not help with much improvement of taste or
  smell

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Chemical

• Can be added directly to the water
• It will kill most pathogens
• Leaves a smell
• Does not remove salts
• Does not remove sediments
• Does not remove most chemicals

• Chlorine Bleach
• Chlorine Powder
• Chlorine Tablets
• Chlorine Liquid
• Granular Calcium Hypochlorite
• Iodine

These chemicals can be dangerous!
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Chemical

• Can use bleach
• for 1 use 10 drops/liter
• for 2-6 use 2 drops/liter
• for 7-10 use 1 drop/liter
• Double the dose if the water is cloudy
• Mix it well
• Allow to settle for 30 minutes
• Smell the water, it should have a slight bleach
  odor.
• If not repeat

• Do not use too much
• Use Regular Clorox Bleach
• Do not use bleach with fabric softener or other
  additives

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Chemical
Question Using a 5.8 chlorine How many drops to
purify water in a two liter bottle?
Answer 2 liters x 2 drops per liter 4
drops Remember to mix it and allow it to settle
Do not use too much

• for 1 use 10 drops/liter
• for 2-6 use 2 drops/liter
• for 7-10 use 1 drop/liter

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UV/Solar

• Paint ½ bottle black
• Leave in sun for 6 hours
• Exposes water to ultraviolet rays from sun
• Raises temperature
• Kills some pathogens
• Does not remove salt
• Does not remove sediments
• Does not remove chemicals
• Does not help with much improvement of taste or
  smell

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Distillation

• Boiling produces water vapor which leaves behind
  pollutants
• Water vapor is allowed to cool and turn back into
  water

Water into vapor
Cool water turns water vapor into liquid
Boils water

• Kills most pathogens
• Removes salt
• Removes sediments
• Removes many chemicals
• Can help with improvement of taste or smell

Heat
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Distillation

• Stills
• These can be bought
• They can be made

• Takes a lot of energy
• Takes skill to operate

Durastill model 4696A
These machines can be dangerous!
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Distillation
Can use distill water on a stove

• Stove Top Distillation
• Put the dirty water in the pot
• Place a collection cup in the pot
• Clean the lid and turn it upside down
• Boil the water
• The water condenses on the lid of the pot and
  falls into the collection cup.

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Distillation
Stove Top Distillation

• Food coloring was placed in the water to
  represent pollutants
• Notice the water in the collection cup is clear

Slow and takes energy
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Distillation
Solar Distillation
Can use the sun to distill water
Photo from Jeff Wheaton
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Distillation

• Solar Distillation
• The sun heats the water
• The water evaporates
• The water condenses on the glass
• The water runs down to the collection tray

Only pure water rises to the top
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Distillation
Solar Distillation
Must have a sunny day

• Very slow
• Can take a few hours to get a small amount

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Distillation

• Solar Distillation
• In the summer, about 8 square feet of glass will
  produce 1 gallon per day
• About half in the winter.
• May need several units

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Filtration

• Cloth Filter
• Tie a cloth around the lid of a jar or bucket
• Pour the dirty water through the cloth
• The cloth will catch the larger dirt pieces

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Filtration

• Cloth Filter
• A good way to remove large sediments
• Does not remove small sediments
• May be good enough for some sprinkler or drip
  irrigation
• Does not kill pathogens
• Does not remove salt
• Does not remove chemicals
• Does not help much with improving taste or smell

It is often a good first step
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Filtration

• Fast Sand Filter
• Clean bucket or barrel
• Fill with 20-40 cm of sand and gravel in layers
• The smaller material is on top and the larger
  material is at the bottom
• As water flows through the sand, the sediments
  catch between the sand particles.

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Filtration

• Fast Sand Filter
• A good way to remove sediments
• Does not kill pathogens
• Does not remove salt
• Does not remove chemicals
• Does not help much with improving taste or smell

• Simple
• Good for preparing water for drip or sprinkler
  irrigation
• Often used as a pretreatment

We will now go through the steps to build a fast
sand filter
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Filtration
Construction of a fast sand filter
First separate sand and gravel with sieve
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Filtration
Construction of a fast sand filter
Then wash the sand and gravel in clean water
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Filtration
Construction of a fast sand filter

• Select a clean bucket or barrel
• Drill a hole on the side at the bottom
• Put a pipe or hose through the hole this is the
  outlet pipe
• This pipe or hose must have many small holes in it

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Filtration
Construction of a fast sand filter

• Seal the end of the outlet pipe or hose to force
  the water through the small holes
• Seal around the hole in the bucket

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Filtration
Construction of a fast sand filter

• You can wrap the outlet pipe or hose with fabric

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Filtration
Construction of a fast sand filter

• Place a few centimeters of small rocks on the
  bottom, covering the pipe
• Then place a layer of small pebbles on the rocks

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Filtration
Construction of a fast sand filter

• Place a few inches of coarse sand on the small
  pebbles
• Then place a 20-30 cm of finer sand on top of that

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Filtration
Construction of a fast sand filter

• Place a layer of the small rocks on top
• Install the inlet pipe
• This pipe should also have holes.
• Cap the end of this pipe

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Filtration
Construction of a fast sand filter

• Pour the water through inlet pipe
• It will go through the filter
• And out the outlet pipe

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Filtration
Construction of a fast sand filter

• Most of the sediments are collected in the top
  layers
• You will need to periodically scrape away this
  layer and clean the sand

Do not drink it!
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Filtration
Water flows rapidly through the fast sand filter
2 to 5 meters per hour
Construction of a fast sand filter
Question If we have a fast sand filter that has
a 30 cm diameter opening. How many liters of
water can be filtered in 1 hour?
Answer 15cm x 15 cm x 3.14 729 square cm 729
square cm X 2 m/hr 145.8 liters in one hour
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Filtration

• Slow Sand Filter
• Also called a biologic sand filter
• Clean bucket or barrel
• Fill with 20-40 cm of sand and gravel
• A pool of water is maintained in the bucket over
  the sand.
• A biologic layer of good microbes forms on the
  top of the sand
• As water flows through the sand, the good
  microbes eat the bad microbes.
• Also, sediments catch between the sand particles
  and in the layer of good microbes.

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Filtration

• Slow Sand Filter
• Removes sediments
• Will kill many pathogens
• Does not remove salt
• Will remove some chemicals
• Will help some with improving taste or smell

• Simple
• Slow mainly for drinking water
• Some additional treatment may be necessary
• Used all over the world (Nicaragua, Honduras,
  Mozambique. Nepal, Cambodia, Kenya, Haiti, etc)

Photo from CMS /Connor
We will now go through the steps to build a slow
sand filter
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Filtration
Construction of a slow sand filter

• A slow sand filter is built very similar to a
  fast sand filter.
• The big difference is that the outlet pipe goes
  out of the top

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Filtration
Construction of a slow sand filter

• This keeps the good microbes wet.
• They must not dry out
• Be sure that the outlet pipe is 5 to 10 cm above
  the sand
• It is also a good idea to use finer sand in the
  upper layers
• Do not use dust it may clog it

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Filtration
Construction of a slow sand filter

• The dirty water must be gradually put through the
  filters so to not disturb the good microbes.
• In this example, it is done with many small holes
  put in the lid.
• A small trickle of water brings air to the
  microbes

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Filtration
Construction of a slow sand filter

• The good microbes are already present in dirty
  water
• In 2 to 3 weeks, they will colonise the upper few
  centimetres of the sand and begin to eat the
  pathogens
• New water must be added daily.
• This feeds the good microbes, brings them air,
  and makes sure they do not dry.

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Filtration
Construction of a slow sand filter
Dirty water in

• Do not put chlorine in the water that goes into
  the filter it may kill the good microbes
• But adding a little chlorine to the outflow water
  may be a good idea

Clean water out
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Filtration
Construction of a slow sand filter

• Eventually, the water flow will slow down
• The upper layer of sand will be clogged with dirt
  and too many good microbes
• Scoop out the top layer and replace the sand
• Run water through the slow sand filter for 2 to 3
  weeks to reintroduce the good microbes

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Filtration
Construction of a slow sand filter

• Can be combined with a fast sand filter to make
  two stage treatment.
• This will extend the life of the good microbes by
  removing the larger pieces of dirt

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Filtration
Construction of a slow sand filter
Can use different materials to make a slow sand
filter
Clay pots are good
Photo from CAWST
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Filtration

• It takes some time to filter water.
• Water slowly flows through the slow sand filter -
  10 to 20 cm per hour.

Construction of a slow sand filter
Question If we have a slow sand filter that has
a 30 cm diameter opening. How many liters of
water can be filtered in 1 hour?
Answer 15cm x 15 cm x 3.14 729 square cm 729
square cm X 10 cm/hr 7.29 liters in one hour
Photo from CAWST
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SummaryLow Cost Treatments
Water treated with any of these may need
additional treatment!
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• Test Time
• What Pollutants might be here?
• If we wanted to use this water for drip
  irrigation, what filtration would be useful?

Answer for sediment/ dirty water use a cloth
filter or a fast sand filter
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• Test Time
• What Pollutants might be here?
• If we wanted to use this water for drip
  irrigation, what filtration would be useful?

Answer for sediment/ dirty water use a cloth
filter or a fast sand filter
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• Test Time
• What Pollutants might be here?
• If we wanted to use this water for drinking, what
  filtration would be useful?

• Answer for sediment/ dirty water and for
  pathogens, use
• A fast sand filter then a slow sand filter
• Fast sand then chlorine
• Fast sand then boiling.
• Fast sand then distillation
• .all may need additional treatment

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• Test Time
• What Pollutants might be here?
• Could we use this water for drinking?

Answer This water is probably contaminated with
pathogens, chemical and other pollutants. It can
probably not be safely treated with the
techniques we discussed.
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Clean Water has a lot of good uses
The End