Low-Cost Water Purification Systems for Rural Thailand

8/9/2019 Low-Cost Water Purification Systems for Rural Thailand

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Low-Cost Water Purification Systems for Rural Thailand

Rafael Bravo Jingwen Du

[email protected] [email protected]

Neil Gallagher

Vidhi Kacharia

[email protected] [email protected]

Abstract

Many communities in developing countries lack clean water. In these countries contaminatedwater has a significant impact on numerous lives. Fortunately, efficient and cheap waterpurification systems can make easy access to clean water a reality. We have designed a waterpurification system for a rural village in Thailand. Before the design process, we reviewed

documents from Engineers Without Borders and the World Health Organization for ideas andproper procedures. The village requires an effective and economical process to purify a localunderground source of water. Our design targeted three specific common underground watercontaminants: sulfur, Giardia lamblia, and turbidity. In designing the system, we consideredmaintainability, cost-effectiveness, and accessibility of resources. Our design consists of a clothfilter to reduce turbidity, an original cascade step-drop aeration system to eliminate the sulfurcontent, and a slow sand filter to filter the Giardia lamblia and other possible particles ormicrobial contaminants. We constructed a prototype using readily available and easily accessedmaterials such as wood, PVC, plastic, sand, and gravel. Testing our prototype using local riverwater, we found that the system effectively eliminated turbidity and reduced toxicity.

Introduction

Purified water is essential to living ahealthy life as such, everyone should haveaccess to it. As part of our attempt to makeclean water easily accessible to third worldcountries, we worked in collaboration withthe Rutgers Chapter of the EngineersWithout Borders (EWB) in designing awater purification system and constructing aprototype for rural Thailand. The ultimate

goal of our project is to have our waterpurification system put into use in a villagein Thailand.

One of the major constraints of ourproject is the inability to collaborate with thecommunity that will be using the system.Communication and teamwork is essential

to the success of any water system. Theengineers must educate and convince thecommunity of the benefits and advantages ofthe purification system. If the communitydoes not approve of the system, potentialmisuse and degeneration of the system mayoccur. Because of the physical andtechnological difference between us andrural Thailand, we had to design our systemwith a small amount of specific informationabout the village we were designing thesystem for.

The village that we are designing forconsists of approximately six hundredpeople and is situated in the middle of theforest. The nearest city is Nong Bua whichis roughly 3 hours away from the village bycar. As a result, it is essential to use


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materials that are easily accessible to thecommunity. The local water source is anunderground spring located 5 meters belowthe surface. Unfortunately, the water isvisibly and chemically contaminated. The

villagers seek to use this groundwater fordrinking, washing clothes, and cooking.The goal of our water purification system isto eliminate the common contaminants ofsulfur, Giardia, and turbidity in thecontaminated ground water. The majordesign decisions of our project are:

Cascade Step Drop: The cascadestep-drop effectively aerates thewater, releasing the hydrogen sulfideinto the environment out of the watersupply.

Cloth filter A cloth filter is used toreduce the turbidity.

Slow sand filter The slow sandfilter filters the Giardia lamblia aswell as many other commoncontaminates.

Constructing a prototype using basiceveryday materials to ensure easyaccessibility and maintenance for theusers.

Background

Targeted Contaminants

Giardia: One of the contaminants our grouphad to deal with was Giardia. Giardia iscommonly found in the feces of infectedhumans or animals, which can seep throughthe ground and infect ground water. Uponconsuming the contaminated food or water,

the consumer runs the risk of contractinggiardiasis. Once the person or animal hasbeen infected, the Giardia lives in theintestines and is passed on in the feces of theindividual. Symptoms of infection include:diarrhea, stomach cramps, upset stomach,and nausea. These symptoms usually takeone to two weeks to become noticeable, and

some individuals can go years withoutshowing any symptoms. This makesoutbreaks of giardasis difficult to quicklydetect and stop. (See Figure 1)

Figure 1: Giardia Lamblia is a relatively largeparasite commonly found in groundwater

because of fecal contamination.

There are ways to eliminate Giardia.It is highly immune to chlorinationtherefore, chlorination is not considered aneffective measure against it. Giardia is arelatively large microscopic parasite,making it easier to filter. Filters of pore size1 micron or smaller are effective.

Sulfur: A gaseous contaminant, sulfurcontaminates ground water in the form ofhydrogen sulfide. If consumed, hydrogensulfide most affects the nervous system.Sulfur reacts with the iron in cells and stopsthem from respiring. The body containsenzymes that render hydrogen sulfideharmless, but it can be overwhelmed if toomuch hydrogen sulfide is consumed. If notdetected, hydrogen sulfide can cause avariety of problems including fatigue, poormemory, and fluid in the lungs. (See Figure2)

Hydrogen sulfide occurs naturally inunderground rock, and can be a problem inground water, but not flowing surface water.This is because hydrogen sulfide dissipateswhen it comes into contact with air. For this


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reason, aeration is usually all that isnecessary to remove this contaminant.Chlorination is also effective, as even asmall amount of chlorine can react withhydrogen sulfide to produce a yellow,

tasteless and odorless precipitate.

Figure 2: Solid Sulfur Crystals. Sulfur is usually

founded in underground water in the form of

hydrogen sulfide. Hydrogen sulfide can be

easily eliminated with simple aeration

processes.

Turbidity: turbidity refers to a cloudinesscaused by suspended particles in a quantity

of water. (See Figure 3)Turbidity is anaesthetic problem as well as a health issue.Higher levels of turbidity often result in agreater risk of intestinal problems anddiseases. Though usually unintentional as inthe above example of using chlorination tocreate harmless sulfur precipitate, turbidityshould be minimized. The villagers wantwater that is aesthetically appealing.

Turbidity is often a problem in

ground water because loose soil will readilymix with the water supply. Turbidity isrelatively easy to prevent as suspendedparticles can be filtered using a method assimple as a cloth filter. This is due to thelarger size of the contaminating particlescompared to the size of microscopic

organisms. Turbidity is an uncomplicatedproblem compared to these contaminants.

Figure 3: Turbidity Demonstration. Turbidity

refers to the cloudiness caused by suspendedparticles in a quantity of water.

Water Purification Methods

Slow Sand Filter: A slow sand filter is arather simple, yet effective method forfiltering biological contaminants as well assuspended particles. Slow sand filters purifywater by having it flow at a low velocitythrough several layers. The first such layer isknown as the Schmutzdecke. This thin layer

is created by allowing microbes to growover a thick filter bed of fine sand. The sandis suspended over the bottom of the tank bya layer of gravel that prevents the fine sandfrom escaping the bed with the water beingpurified. The goal is to make the systemrequire no energy input. Therefore, theentire system runs due to gravity.

The Schmutzdecke is automaticallycreated in the sand simply by letting the

sand sit in the flowing water. TheSchmutzdecke works by trapping thecontaminated bacteria in the flowing water,and thus purifying it. This mutualrelationship between the Schmutzdecke andthe people who benefit from its purificationcan be so powerful that almost allpotentially dangerous bacteria can be


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extracted from a water supply. The layer isusually very thin, concentrated in less than 5cm of space. If the layer grows thicker than5 cm, it can clog the system. For this reason,the top layer of sand and Schmutzdecke

must be periodically scraped off as it grows.The filter bed serves the purposes of

giving the Schmutzdecke a support to growon as well as participates in the filtrationprocess itself.

The sand used should be as fine aspossible, as this layer helps to filter thewater. This bed constitutes the majority ofthe filter which is 0.8 meters. The finallayer which includes large rocks, small

rocks, and gravel amounts to about one foot.(See Figure 4)

Figure 4: Slow Sand Filter. Water flows into the

slow sand filter. The schmutzdecke transforms

organisms into harmless organic compounds.

The minuscular grain size of the sand traps and

filters various particles and organisms such as

Giardia. The increasing grain size gravel at the

bottom prevents the sand from seeping down.

The Slow Sand Filter is a cheapsolution that is easy to create and maintain,which alone makes it a strong candidate forimplementation. This is due to its lack ofcomplex materials and low maintenance thatsimply involves scraping the top layer aboutonce a month.

Slow Sand Filtration is also veryeffective. It is can filter almost allcontaminants out of a water supply ifproperly designed. Our model does notinclude a Schmutzdecke, due to our lack of a

constant supply of contaminated waterneeded to keep the layer alive, but thishandicap does not hamper the filterseffectiveness against Giardia, which is arelatively large microorganism.

Cascade Air Drop: this system is a modifiedversion of the step aerator. These systemswork by having the water flow downminiature waterfalls and exposing the waterto the air. The water moves diagonallyacross the system in a zigzag with a 5 inch

drop when the water changes direction. Thissystem works effectively by not onlyaerating the water when it is dropping, butalso exposing it to air while it flows fromside to side. (See Figure 5)

Aeration can be used to facilitatechemical reactions involving air to create aharmless precipitate out of a toxic chemical.It is also used to allow harmful gasestrapped in the water to escape into the air by

bringing them close enough to the air inorder for them to break away from thewater.

Figure 5: Cascade Aerator Diagram. This form

of aeration system uses miniature waterfalls to

increase the oxygen level of the water and

remove chemicals.


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Cloth Filtration: cloth filtration is the simpleprocess of using cloth to block the flow ofsuspended particles in a water supply. Theporous nature of the cloth acts as amembrane to let the water flow through

while trapping the larger contaminants of thesystem, such as dirt and sand, andeffectively removing them from the watersupply.

Cloth filters are very simplyimplemented, as common material such ascotton cloth can be used and the cloth has tobe simply stretched in the pathway of thewater so that it is forced to flow through.

Design

In order to replicate the conditions ofrural Thailand, we limited the materials andcomplexity of our water purification system.We wanted to use materials that can bereadily purchased by the community in ruralThailand. For this reason, we would able toconstruct the system easily andinexpensively in Thailand. The communityshould not have to make a big investment inimplementing and maintaining the system.

The main components of our system arewood, PVC piping, cloth, sand, and gravel,all of which we assumed inhabitants of thearea in question would have easy access to.The community has some access to a nearbycity in which materials can be purchased andused.

Furthermore, many of theconstruction materials can be easily replacedby local resources. The constructionmaterials of the final design do not have to

be the exact materials used in the prototype.With the exception of the sand and gravel,the other materials can be easily replaced bysimilar materials. For example, wood canbe substituted with bamboo or any strongconstruction materials. The PVC pipe canbe replaced by other piping materials. Thebuckets and tanks that we used in our

prototype do not limit the material choice inthe construction of the system in Thailand.Any storage material that is adequately largecan be used and will not alter the integrity ofthe purification system. Its role is merely

for storage purposes.In addition, educating the

community members to use and repair thesystem became a major concern in ourdesign process. We could not use a complexfiltration system because it would bedifficult for the community members tooperate and understand. Therefore, ourdesign was a water purification system thatoperates entirely due to the force of gravity.

The design is made up of threeseparate purification systems, each of whichremoves a specific group of contaminantswhich we have determined to be ofsignificance in the given situation. Our taskwas to eliminate sulfur, Giardia lamblia,and a moderate level of turbidity, therefore,each system treats one of these impurities.The water we dealt with consisted of a sulfurconcentration of less than 2 mg/l. The sulfuris in the gas form of hydrogen sulfide.

Although the community members will beusing groundwater, for the purpose of oursimulation, we will be starting ourpurification process from a storage tank, notdirectly from the ground.

The Design

We began our design with a waterstorage tank containing the contaminatedwater. There is a hole on the side of thestorage tank for the water to flow out. A

cloth filter is attached over the hole to screenout the turbidity (See Figure 6). Next, thewater flows out of a screened hole through apressure valve that regulates the flow rate.The flow rate keeps the water flowing at aconstant velocity. It then flows into acascade step-drop system to aerate thewater, allowing the sulfur to dissipate into


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of the holes on the bottom of the slow sandfilter into a clean water storage tank.

The Prototype

In our prototype, we used a five

gallon galvanized tank as a storage tank.The tank has a inch hole drilled on its sidewhich allows the water to flow out of thestorage tank. The hole is covered with acloth filter because turbidity must beremoved before the water enters the cascadestep-drop system. We drilled a in. hole onthe side of the tank. A 3/4 inch galvanizedfloor flange (See Figure 8) was attachedwith screws over the hole. To secure thescrews, a special type of glue was applied.

We used caulk to furthermore seal theadapter cover to prevent any leaks. We thenattached a 3/4 in. male threaded brass hosebibb (see Figure 9) as our pressure valve tocontrol the flow rate. An adapter was todirect the water to flow directly from thestorage tank into the cascade step-dropsystem.

Figure 8. in. galvanized floor flange is

used to secure the pressure valve to thestorage tank

Figure 9. In our prototype, we used a 3/4 in.male threaded brass hose bibb as a pressurevalve.

We used four 2x4s wooden planks toconstruct the main frame for the cascadestep-drop. The step-drop main frame isapproximately 4 feet tall and 2 feet wide.There are 5 inch spaces between each plank.These four planks stood atop a 2 feet widewooden base. We constructed the actualstep-drop by attaching PVC piping that wascut in half horizontally to the main frame.We cut semicircles out of plastic sheets. Atthe end of each step, we used caulk to sealthe plastic semicircles to prevent the waterfrom overflowing out of the system. Theprototype has a total of 7 step-drops.

At the end of the cascade step-drop,the water falls into a bucket. In a real-lifesituation, the water would go into anotherrubber tube and fall into the slow sand filter.If we were to build the entire waterpurification structure in one piece usinggravity to direct the flows, the structure

would stand at approximately nine feet inheight. Due to the space limitations, wedivided our prototype into two parts. In ourprototype, we manually poured the waterfrom the bucket into the slow sand filter.

The slow sand filter is constructedout of two plastic trash cans. We sawed the


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bottom out of one of trash can. Afterturning the bottomless trash can upsidedown, we put it on top of the other trash can.Then we glued and taped the two together toform a three feet tall tank. Any storage

material that is adequately high and strongenough to support the water and sand shouldbe able to substitute this design.

We placed a 0.8 m thick layer of fineplay sand as our first top level. The finesand is followed by a layer of all purposegravel. The bottom level consists of largeand small rocks. The layers consist of rocksof increasing grain sizes to prevent thesmaller sand and/or rocks from seepingthrough. At the end, we placed a piece of

cloth to furthermore contain the rocks andprevent the sand from seeping down withthe water. At the bottom of the slow sandfilter, we drilled numerous little holes whichwould allow the purified water to flow outof the slow sand filter into a clean waterstorage tank.

The slow sand filter is supported bya wooden structure that holds it over an openstorage tank. For our prototype, we

substituted the clean water storage tank witha five gallon galvanized tank. The cleanwater tank would ultimately be connected toa distribution system for the community.

Our design requires no input energyto operate. Each process and eachconnection between the various filters runsentirely because of gravity. Moreover, thematerials that we used to build our prototypeare relatively common and cheap. The cost

and energy factors played major roles in ourdesign and construction. As part of theEWB goals, we tried to use the localresources available to the community so thatthey may easily be repaired and maintained.

It took us approximately three daysto build the prototype. Because theprototype is meant to produce purified water

for merely twelve people, the real systemmust be much larger. The storage tank, slowsand filter, and collection buckets have to beaugmented to supply water to about sixhundred people. Our group has never been

to Thailand and therefore, we did not knowthe precise characteristics of the country.We based our design on facts we gainedfrom research and engaging in conversationwith EWB members that have worked indeveloping countries and/or have detailedknowledge on such missions. We had toassume that the community in Thailand hadaccess to the materials we used. However,we managed to keep our materials simpleand substitutable.

It cost less than $200 to build ourprototype. Knowing the villagers inThailand earn about $4 an hour, we tried tominimize our cost. We believe thatimplementing this design in Thailand willnot cost more than $5000, which is half thecost EWB members are spending on eachproject.

It takes about two hours for ourdesign to run six liters. Therefore, the

system would have to run 24 hours a day inorder for a sufficient amount of water to bepurified. This is achievable because thesystem which would be implemented wouldnot need solar energy or human energy tofunction.

Results

Our team was able to carry out twotests: a simple functionality test and apurification test. We obtained 6 liters of

water from the Raritan River, and allowed itto run through the system. The whole testtook about two hours to complete. Thepurified water was significantly clearerwhen compared to control samples that werestored from the same river water (See Figure10). As our second test, we looked atsamples of the river water and the purified


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water under a simple microscope. Therewere microbial organisms and sediments inthe river water. We did not find anyparticles or organisms in the purified water.There were only water bubbles. This

showed that our purification system waseffective in eliminating microbial activitiesand reducing turbidity.

Figure 10. Comparison of the river water and thepurified water. The clearer bottle on the left isthe result of our purification system. Thecloudier water on the right is the original riverwater.

Related Work

Throughout our project, we workedin collaboration with members fromEngineers Without Borders (EWB).Engineering Without Borders (EWB) is anorganization that seeks to use engineeringand technical skills for humanitarianprojects. It is dedicated to designing andimplementing engineering projects indeveloping communities around the world.Besides local civil engineering projects, the

organization expands internationally in anattempt to provide basic necessities such aspurified water to all parts of the world,especially in developing countries. Itsfundamental goal is to apply concreteengineering knowledge to real worldsituations.

The EWB works to improveagriculture, construction, education, andhealth. More relevant to our project, theEWB worked on five projects in Thailanddealing with water. They included a water

purification system, a water delivery system,and a portable water supply. The EWB isfaced with the challenging task of designingfunctioning mechanisms while taking intoconsideration the peoples point of view andhow much they are willing to maintain thesystems and fund them.

The EWB designed, over the courseof two years, a prototype system to purifywater that we used as a basis to build ourmodel. According to the prototype, the

contaminated water leads to a pressurecontrol tank to verify that the right amountof water flows through the rubber piping.EWBs design uses the process ofdistillation to disinfect the contaminatedwater. Distillation is the act of purifying aliquid through heat exposure. The steamcondenses into a pure liquid and thepollutants remain in a concentratedremainder. This was done by having thecontaminated water flow through rubber

tubing placed under a dome made ofaluminum foil that would direct naturalsunlight towards the tubing. As a result, thewater would be free from any microbial andchemical contaminants. To prove to theinhabitants of the community that the wateris purified, there is a temperature controlgauge that shows that the water has met itstemperature requirement. From the rubberpipe, the purified water leads into a storagetank where is can be utilized for

consumption. Though this design is suitablefor areas that exhibit sunlight throughout theyear, it would not be adequate for Thailand.The climate in Thailand fluctuates betweenvery dry months and monsoon season.

Our design is more practical thanEWBs because it can function throughout


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the year and does not depend on externalfactors such as the weather. It does notrequire expensive equipment such as atemperature gauge which is easily brokenand not easy to replace. The equipment we

used for our design can readily be found inThailand whereas equipment such as thepressure control gauge in EWBs prototypecannot. All aspects of our design can besubstituted with local materials, making itmore convenient than EWBs design. Wehave built an actual prototype and tested itby running river water through it and resultshave come out positive.

A second system we researched andconsidered greatly was the Filtron. The

Filtron is a very convenient waterpurification system. It is a ceramic filterthat is saturated with colloidal silver. Thefilters can be press-molded, formed by hand,or turned on a potters wheel before beingfired in a brick kiln. Made from a blend ofclay and sawdust, the filters block the largerwater-borne particles while the colloidalsilver inactivates bacteria small enough toget through the filters minute holes. Thedevice has been proven 98% to 100%

effective in eliminating bacteria andbacterial indicators. However, educationand proper maintenance are vital to replicatethese results in everyday household use.This design is convenient for households butcannot be aggravated to accommodate acommunity consisting of about six hundredpeople. Also, the colloidal silver can beexpensive and difficult to find in developingcountries such as Thailand.

Future Work

The prototype we constructed,though successful in filtering contaminatedwater,is currently very labor intensive. Itrequires the user to manually lift the waterfrom one part of the system to the next aswell as lift the contaminated water from the

ground to begin the purification process.This is inconvenient because a communitymember would have to maintain the watersystem 24 hours a day in order for it to run.There are several solutions to this. To

retrieve the water from the ground, a pumpcould be set up. This could be poweredelectrically. However, because of costconcerns, a power wheel could be installed.This could be powered by a bicycle or amerry-go round that children could play on.

At irregular hours an alternatesource of energy could be used such as awater wheel or wind power. To transfer thewater from the cascade step-drop aerationsystem to the slow sand filter, the design

could be replicated on a hillside so thatgravity could sustain the process andpumping would not be required. If there areno such hillsides by the ground water, apumping system would have to be used tobring the water from the cascade system tothe top of the slow sand filter. The cascadestep drop could be placed on top of the slowsand filter so the water would lead directlyfrom one filter to the next. Additionally,due to the difficulty and impracticality of

producing the Schmutzdecke (biologicallayer) in the slow sand filter, we negated thisfrom our prototype. The Schmutzdecketakes about 7 days to fully develop andtherefore we could not use it in our design.It would be added in the actual constructionand implementation of the design.

The prototype is not to scale soassuming it runs 24 hours a day and thecontaminated water storage tank is

constantly refilled, the prototype couldsupport twelve people. The actual designsslow sand filter, aeration system, and storagetank would be aggrandized to provide waterto about 600 people.

The original EWB model, discussedin related work, took two years to design


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and it was still deemed unsuitable. Ourmodel was designed and constructed overthe course of three weeks. For this reason, itshould not be viewed at as a designanywhere near a finished plan. A more

complex system and a completeunderstanding of the village where thesystem would be built are required to createthe ideal purifier.

Conclusion

The purification system constructed,though effective in its limited scope, is farfrom a completed design. The reader mayrecall that the model EWB produced over ayear of planning was found poorly suited to

the climate in rural Thailand. Our model hadto be created over a far more restricted timeframe, with about a week and a half forplanning and about three days for building.

A system that could actually assistthe community has to be planned, approved,built and maintained by that community.Our group was given only the most generalinformation about the town, and it isimpossible for anyone to build a system that

would suit this community with basicsalone. When the EWB actually goes toconstruct this system, it will be cateredexactly to the people it is planned to support.

The prototype also does not solve theproblem of extracting the ground water. Wewere tasked specifically with focusing onthe purification aspect the system and notthe powering of it.

That said there is still a chance that

our system, in some form, will one day seeimplementation. It has been designed totarget the specific contaminants that arecurrently a problem in the community. Itwas built with minimum cost and minimumuse of complex technology. This makes ourpurification systems components practicalto be replicated in rural Thailand.

Acknowledgements

We would like to thank thefollowing people for all their support,encouragement, and help throughout ourresearch project experience:

New Jersey Governors School ofEngineering and Technology for giving usthis great opportunity

Blase Ur, NJGSET Program Coordinatorfor editing our paper, taking us to buymaterials, and keeping us organizedthroughout the experience

Wanda Duran for editing our paper,providing us with materials, motivating, andguiding us

Engineers Without Borders for itsassistance, information, and prototype toguide us with our project.

Reema Shah and Christine Mau for sharingtheir detailed knowledge of the subject,sacrificing their time to help us, and guidingus through the project.

Nancy Twu for getting us access to amicroscope to test our water.

References

"Slow Sand Filtration for Water Treatment."Oasis Design. June 1991. Colorado State U.17 July 2008.

"Giardiasis Fact Sheet." Centers for Disease

Control and Prevention. 17 Sept. 2004. 14July 2008.

"ToxFAQs: Hydrogen Sulfide." Agency forToxic Substances and Disease Registry.Department of Health and Human Services.


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17 July 2008.

"Slow Sand Filtration." Tech Brief. 2007.National Drinking Water Clearing House. 17

July 2008.

Shop Home Depot. 17 July 2008. The HomeDepot. 17 July 2008.

"How Aeration Removes or ModifiesConstituents." OP-Aeration. 8 July 2008.

"Giardia Fact Sheet." Washington StateDepartment of Health. 2008. 9 July 2008.

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Low-Cost Water Purification Systems for Rural Thailand