This training was prepared by the U.S. Department of Agriculture (USDA) team of Otto Gonzalez-USDA Foreign Agricultural Service (Team Leader), Jon Fripp (Civil Engineer) and Chris Hoag (Wetland Plant Ecologist)-USDA Natural Resources Conservation Service (Civil Engineers). Fripp and Hoag were the primary authors of this material. The U.S. AID provided funding support for the USDA team. Water Filtration

Why do we filter water? For drinking For irrigation

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

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

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

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

Pollutants get into our water in a variety of ways

It is a problem all over the world.

Municipal Treatment most includes these steps Settlement / sedimentation Filtration Disinfection (chemical treatment) Water Supply Modified from Robert A. Perdue Water Treatment Plant Water Source

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

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

Low Cost Treatments Boiling Chemical UV/Solar Distillation Filtration Biological Filtration Water treated with any of these may need additional treatment!

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

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!

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

Chemical for 1%: use 10 drops/liter for 2-6%: use 2 drops/liter for 7-10% use 1 drop/liter 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

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

Distillation Heat Boils water Water into vapor Cool water turns water vapor into liquid Kills most pathogens Removes salt Removes sediments Removes many chemicals Can help with improvement of taste or smell Boiling produces water vapor which leaves behind pollutants Water vapor is allowed to cool and turn back into water

Distillation Stills These can be bought They can be made Durastill model 4696A Takes a lot of energy Takes skill to operate These machines can be dangerous!

Can use distill water on a stove Distillation Stove Top Distillation 1.Put the dirty water in the pot 2.Place a collection cup in the pot 3.Clean the lid and turn it upside down 4.Boil the water 5.The water condenses on the lid of the pot and falls into the collection cup.

Food coloring was placed in the water to represent pollutants Notice the water in the collection cup is clear Stove Top Distillation Distillation Slow and takes energy

Can use the sun to distill water Distillation Solar Distillation SolAqua Model 550 Rainmaker Photo from Jeff Wheaton

Solar Distillation 1.The sun heats the water 2.The water evaporates 3.The water condenses on the glass 4.The water runs down to the collection tray Only pure water rises to the top Distillation

Must have a sunny day Very slow Can take a few hours to get a small amount Solar Distillation 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 Distillation El Paso Solar Energy Association

Filtration Cloth Filter 1.Tie a cloth around the lid of a jar or bucket 2.Pour the dirty water through the cloth 3.The cloth will catch the larger dirt pieces

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 Filtration

Fast Sand Filter 1.Clean bucket or barrel 2.Fill with cm of sand and gravel in layers 3.The smaller material is on top and the larger material is at the bottom 4.As water flows through the sand, the sediments catch between the sand particles

Simple Good for preparing water for drip or sprinkler irrigation Often used as a pretreatment 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 Filtration We will now go through the steps to build a fast sand filter

Filtration First – separate sand and gravel with sieve Construction of a fast sand filter

Then wash the sand and gravel in clean water Filtration Construction of a fast sand filter

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

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

Filtration Construction of a fast sand filter You can wrap the outlet pipe or hose with fabric

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

Filtration Construction of a fast sand filter Place a few inches of coarse sand on the small pebbles Then place a cm of finer sand on top of that

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

Filtration Construction of a fast sand filter Pour the water through inlet pipe It will go through the filter And out the outlet pipe

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!

Filtration Construction of a fast sand filter Water flows rapidly through the fast sand filter – 2 to 5 meters per hour Answer: 15cm x 15 cm x 3.14 = 729 square cm 729 square cm X 2 m/hr = liters in one hour 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?

Filtration Slow Sand Filter Also called a biologic sand filter 1.Clean bucket or barrel 2.Fill with cm of sand and gravel 3.A pool of water is maintained in the bucket over the sand. 4.A biologic layer of good microbes forms on the top of the sand 5.As water flows through the sand, the good microbes eat the bad microbes. 6.Also, sediments catch between the sand particles and in the layer of good microbes ,.,…,.,.,,….,…….

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

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 Filtration Construction of a slow sand filter

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

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

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.

Filtration Construction of a slow sand filter Dirty water in Clean water out 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

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

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

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

Photo from CAWST Filtration Construction of a slow sand filter It takes some time to filter water. Water slowly flows through the slow sand filter - 10 to 20 cm per 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 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?

Summary Low Cost Treatments Water treated with any of these may need additional treatment!

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

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 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 Test Time What Pollutants might be here? If we wanted to use this water for drinking, what filtration would be useful?

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.

Clean Water has a lot of good uses The End