Water Filtration and Disinfection 2009

8/8/2019 Water Filtration and Disinfection 2009

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2009

21

Water Filtration

andDisinfection

This training was prepared by the U.S. Department of Agriculture (USDA) team of Sylvana Li (Branch Chief, Rural Development and Natural Resources - USDA Foreign AgriculturalService, email: [email protected]), Matt Murphy, and David Gallagher (both Development Resources Specialists - USDA Foreign Agricultural Service, emails:[email protected], [email protected]), George Hernandez (Forester - USDA Forest Service, email: [email protected]), and Jon Fripp (Civil Engineer -USDA Natural Resources Conservation Service, email: [email protected]). The USACE provided funding support for the USDA team.


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Why do we filter water?

For drinking

For irrigation


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Types ofPollutants

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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Municipal Treatmentmost includes these steps

Settlement / sedimentation

Filtration

Disinfection

(chemicaltreatment)

Water SupplyModified from Robert A. Perdue Water Treatment Plant

Water Source


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Municipal Treatment

Can Provide Large Quantities of Safe WaterOften Big Operations

ExpensiveTraining Required to Operate


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Treatment Plants Can Be Small

Photos from Jerry Bernard

This one treats waterfrom a small pondfor a residence

This system treats and packages water for a school


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Low Cost Treatments

Boiling

Chemical

UV/Solar

Distillation

Filtration Biological Filtration

Water treated with any of thesemay need additional treatment!


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Boiling

Boil water for 10 minutesBoiling will kill mostpathogens

Does not remove saltDoes not removesedimentsDoes not remove mostchemicalsDoes not help with muchimprovement of taste or

smell


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Chemical

Can be added directly tothe waterIt will kill most pathogensLeaves a smellDoes not remove saltsDoes not removesediments

Does not remove mostchemicals

Chlorine BleachChlorine Powder

Chlorine TabletsChlorine LiquidGranular Calcium HypochloriteIodine

These chemicals canbe dangerous!

Can use bleach


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ChemicalCan use bleach

for 1%: use 10 drops/literfor 2-6%: use 2 drops/liter

for 7-10% use 1 drop/literDouble the dose if the water iscloudy

one cap of Clorox for every 2gallons (7.5 liter) of water.


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Do not use too muchUse Regular Clorox BleachDo not use bleach with fabricsoftener or other additives


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Mix the treated water. Allowthe treated water to settle for

30 minutes.

Smell the water. The treatedwater should have a slight bleach

odor. If it does not have an odor,repeat the treatment.Taste a little of the treated water.If it has a strong taste of chlorine,

spit the water out. Allow thecontainer of treated water to situncovered for another 30 minutesor pour the water back and forthbetween two clean containers.


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Chemical

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

Question:

Using a 5.8% chlorineHow many drops to purify water ina two liter bottle?

Answer:2 liters x 2 drops per liter = 4drops

Remember to mix it and allow it tosettle

Do not use too much


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UV/Solar

Paint bottle blackLeave in sun for 6 hoursExposes water toultraviolet rays from sun

Raises temperatureKills some pathogensDoes not remove saltDoes not remove

sedimentsDoes not removechemicalsDoes not help with muchimprovement of taste orsmell

B ili d t hi h l


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Distillation

Heat

Boils water

Water intovapor Cool water turnswater vapor into

liquid

Kills most pathogensRemoves salt

Removes sedimentsRemoves many chemicalsCan help with improvementof taste or smell

Boiling produces water vapor which leavesbehind pollutantsWater vapor is allowed to cool and turn

back into water


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Di till ti


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Can use distillwater on a stove

Distillation

Stove Top Distillation1. Put the dirty water in the pot2. Place a collection cup in the

pot

3. Clean the lid and turn itupside down

4. Boil the water5. The water condenses on the

lid of the pot and falls intothe collection cup.

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Food coloring wasplaced in the water to

represent pollutantsNotice the water in thecollection cup is clear

Stove Top Distillation

Distillation

Slow and takes energy

Distillation


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Can use the sun to distill water

Distillation

Solar Distillation

SolAqua Model 550 Rainmaker

Photo from Jeff Wheaton

Distillation


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Solar Distillation

1. The sun heats the water2. The water evaporates3. The water condenses on the glass4. The water runs down to the

collection tray

Only pure water rises to the top

Distillation


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Must have a sunny day

Very slowCan take a few hours

to get a small amount

Solar Distillation

Solar Distillation Distillation


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In the summer, about8 square feet of glass

will produce 1 gallonper dayAbout half in thewinter.May need severalunits

Filtration


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Filtration

Cloth Filter1. Tie a cloth around

the lid of a jar orbucket

2. Pour the dirty waterthrough the cloth

3. The cloth will catchthe larger dirt pieces

Filtration


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Cloth Filter A good way to removelarge sediments

Does not remove small

sediments May be good enough for

some sprinkler or dripirrigation

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

Filtration


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Filtration

Fast Sand Filter1. Clean bucket or barrel2. Fill with 20-40 cm of sand and

gravel in layers

3. The smaller material is on topand the larger material is atthe bottom

4. As water flows through the

sand, the sediments catchbetween the sand particles.

.

.

.

...

.

.

.

... ..

.

.

.

.

..

..

.

. .

.....

.. .

... ... ....

Filtration


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Simple Good for preparing water for

drip or sprinkler irrigation Often used as a pretreatment

Fast Sand FilterA good way to remove sediments

Does not kill pathogensDoes not remove saltDoes not remove chemicals

Does not help much with improving taste or smell

Filtration

We will now go through thesteps to build a fast sand filter

Filtration


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Filtration

First separate sand

and gravel with sieve

Construction of a

fast sand filter

Filtration


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Then wash the sandand gravel in clean

water

FiltrationConstruction of a

fast sand filter

Filtration


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fast sand filter

Select a clean bucket or barrelDrill a hole on the side at thebottom

Put a pipe or hose through thehole this is the outlet pipeThis pipe or hose must havemany small holes in it

Filtration


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fast sand filter

Seal the end of the outlet pipe or hose toforce the water through the small holesSeal around the hole in the bucket

Filtration


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t at oConstruction of a

fast sand filter

You can wrap the

outlet pipe or hosewith fabric

Filtration


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Construction of a

fast sand filter

Place a fewcentimeters of smallrocks on the bottom,

covering the pipeThen place a layer ofsmall pebbles on therocks

Filtration


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Construction of a

fast sand filter

Place a few inches ofcoarse sand on thesmall pebbles

Then place a 20-30cm of finer sand ontop of that

Filtration


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Construction of a

fast sand filter

Place a layer of the small rocks on

topInstall the inlet pipeThis pipe should also have holes.Cap the end of this pipe

Filtration


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Construction of a

fast sand filter

Pour the water throughinlet pipeIt will go through the filter

And out the outlet pipe

Filtration


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Construction of a

fast sand filter

Most of the sediments are collectedin the top layersYou will need to periodically scrapeaway this layer and clean the sand

Do not drink it!

Filtration Water flows rapidly through the fastd fil 2 5 h


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Construction of a

fast sand filter

sand filter 2 to 5 meters per hour

Answer:15cm x 15 cm x 3.14 = 729

square cm729 square cm X 2 m/hr = 145.8liters in one hour

Question:If we have a fast sand filter

that has a 30 cm diameteropening.How many liters of water canbe filtered in 1 hour?


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Slow Sand Filter

Filtration


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Simple Slow mainly for drinking water

Some additional treatment may benecessary

Used all over the world (Nicaragua,Honduras, Mozambique. Nepal,

Cambodia, Kenya, Haiti, etc)

Slow Sand FilterRemoves sediments

Will kill many pathogensDoes not remove saltWill remove some chemicalsWill help some with improving taste

or smell

We will now go through the steps to build a slow sand filter

Photo from CMS

/Connor

Filtration


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A slow sand filter is built verysimilar to a fast sand filter.The big difference is that theoutlet pipe goes out of the top

Construction of a

slow sand filter

Filtration


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Construction of a

slow sand filter

This keeps the good microbes

wet.They must not dry outBe sure that the outlet pipe is5 to 10 cm above the sand

It is also a good idea to usefiner sand in the upper layersDo not use dust it may clog it

Filtration


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Construction of a

slow sand filter

The dirty water must be graduallyput through the filters so to notdisturb the good microbes.In this example, it is done with

many small holes put in the lid.A small trickle of water brings airto the microbes

Filtration


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Construction of a

slow sand filter

The good microbes are alreadypresent in dirty waterIn 2 to 3 weeks, they will colonise

the upper few centimetres of thesand and begin to eat thepathogensNew water must be added daily.

This feeds the good microbes,brings them air, and makes surethey do not dry.

Filtration


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Construction of a

slow sand filter Dirty water in

Clean water out

Do not put chlorine inthe water that goesinto the filter it may

kill the good microbesBut adding a littlechlorine to the outflowwater may be a good

idea


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FiltrationC t ti f


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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 goodmicrobes by removing the largerpieces of dirt

FiltrationC t ti f


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Construction of a

slow sand filter

Can use differentmaterials to make aslow sand filter

Clay potsare good


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ConstructionSteps


It takes some time to filter water.Water slowly flows through the slow


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Photo from CAWST

Construction of a

slow sand filter

y gsand filter - 10 to 20 cm per hour.

Answer:15cm x 15 cm x 3.14 = 729

square cm729 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 diameteropening.How many liters of water canbe filtered in 1 hour?

1 gal = 3.78 liter1 in = 2.54 cm

SummaryLow Cost Treatments


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Low Cost Treatments

Water treated with any of thesemay need additional treatment!

Pollutant

Method Pathogens Chemical SaltSediments

/ dirt

Odour and

Taste

Boiling

Chlorine

UV/Solar

Distillation / still

Solar Still

Stovetop Distillation

Cloth Filter

Fast Sand FilterSlow Sand Filter

Method is effective at removing many of these pollutants

Method provides some removal of pollutant

Method is not effective at removing pollutant

Test TimeWhat Pollutants might be here?If we wanted to use this water for


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If we wanted to use this water fordrip irrigation, what filtrationwould be useful?

Answer: for sediment/ dirtywater use a cloth filter or afast sand filter

Test TimeWhat Pollutants might be here?If we wanted to use this water


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Answer: for sediment/ dirtywater use a cloth filter or afast sand filter

for drip irrigation, what filtrationwould be useful?

Test TimeWhat Pollutants might be here?If we wanted to use this water


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Answer: for sediment/ dirty water and forpathogens, use

A fast sand filter then a slow sand filterFast sand then chlorineFast sand then boiling.Fast sand then distillation.all may need additional treatment

for drinking, what filtration wouldbe useful?

Test TimeWhat Pollutants might be here?Could we use this water for


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drinking?

Answer: This water is probably contaminated

with pathogens, chemical and other pollutants.It can probably not be safely treated with thetechniques we discussed.

Test the water!Indicator tests

Rapid quick results


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p qSimpleDetailed tests

More preciseRequired more expertise and

time

Do not recontaminate filtered ordisinfected water


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disinfected water

Make sure you use clean containers thathave not been used to store chemicals

Store water carefully Use tops on containers

Monitor distribution

Clean Water has a lot of good uses


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The End

Water Filtration and Disinfection 2009

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