Economic Water Purification in Developing Countries, JWALKUP

1 Economic Water Purification in Developing Countries

Jed Walkup

Abstract

Lack of safe drinking water poses of the largest health problems in developing countries

today. Often times, contamination is caused by poisoning due to toxic materials like arsenic, or

by pathogens and bacteria like E.Coli and other fecal coli forms. Chemistry not only offers an

understanding of these problems at the chemical level, but it also reveals fundamental

solutions. Technology for these parts of the world needs to be simple and cheap due to the

economics of the countries in need. This paper reviews technology that exists which fulfills

these criteria. The SONO filter is a good answer to arsenic issues and has shown to be efficient

in Bangladesh, India. The total cost of the filter is about $40 for five years.8 The filter uses only

local materials, offering the availability factor. Biosand filters are often the response to

pathogen contamination and had good results when tested in Haiti. These filters cost about

$25 a piece and can easily be mass produced.10 They also can use local and available resources.

Finally solar disinfection of water is reviewed from two differing sources. The first revealed the

best results in West Bengal, India. This study also was the most simple of the two. The other

looked at solar disinfection of rainwater in South Korea. This study contrasted the use of

absorbing versus reflecting sunlight. The results were not as promising in the first study, but

due to sunlight intensity in that location, these results shouldn’t be expected to remain the

same across the globe. All of these technologies have something to offer the world and further

steps can be taken to optimize them for use in the developing world.


Introduction

Safe drinking water is a basic need of life and is currently lacking in many developing

countries around the globe. In 2006, according to WHO/UNICF, there were approximately 884

million people reliant on unsafe drinking water and the World Health Organization (WHO)

estimates over 5 million deaths a year due to this issue.1Technology exists to purify drinking

water. However, this technology is often not available to the places which need it the most due

to cost. Two out of three people living in developing countries live on less than 2$ a day and

the other one out of three live on less than 1$ a day.2 Through knowledge in chemistry, I

believe the issues and causes of unsafe water can be better understood and therefore solved.

The goal of this paper is to explore the chemistry of the simple, natural and cheap methods

which exist to bring clean water to those regions which have the greatest needs.

As seen in figure 1,3 some of the greatest needs for drinking water purification occur on

the continent of Africa and in India. Much of this paper will explore needs and technology

based on these regions. Some Latin American countries, though not to the degree of African

countries, still experience critical problems with drinking water safety. Much of the cheaper

technology developed has been done in places like Nicaragua and Haiti, but the technology

often targets the same issues addressed in other parts of the world.

The structure of this paper starts by introducing the most common water contaminants.

Next, particular technologies addressing a focused general problem are discussed. The

technology is broken down into its set-up, the chemistry behind it and the experimental results.

A conclusion is made about the usefulness of the technology based on the criteria set in the


introduction paragraph. Further needed research is then discussed on the development, before

transitioning to a new technology or contaminant.

Leading Causes of Unsafe Water

In order to integrate the use of cheap water purification technology, we will focus on

the main causes of unsafe water which contribute to a significant percentage of the regions in

need. The first issue to be reviewed is that of arsenic (As) in drinking water. Most of the

world’s water “naturally” has an arsenic concentration of about 2.5 ppb.4 However; the World

Health Organization’s (WHO) guideline limit for arsenic in water is about 10 ppb.1 Arsenic

poisoning (arsenicosis) is caused by a long term exposure to inorganic arsenic (III) and (V). The

main issue with arsenicosis is that inorganic arsenic is a known carcinogen. It is also thought to

cause or aggravate issues with diabetes, cardiovascular diseases and disruption of hormone

levels.4 As shown in Figure 2,5 the low-income countries experiencing large problems with

arsenic are Argentina, Mexico, Bangladesh, Mongolia and Taiwan. Though the poisoning of

water is an issue, it does not rank first in the world’s water issues.

The largest contributor to unsafe drinking water is the presence of microbes due to

human and animal excretion contaminating the water.6 According to WHO, 2.2 million of the

deaths which occurred in 2004 were due to diarrheal diseases which are linked to microbes in

water.7 Total coli form and Fecal coli forms, like Escherichia coli (E. Coli), are the most often

tested of said microbes.


Arsenic

Arsenic in surface water usually exists as the As(V) species in H3AsO4. However, natural

reducing conditions are present in underground water, so it is important to consider As(III) in

well water. As(III) can be oxidized to As(V). As(III) is present in water as arsenite (AsO33-) which

can be oxidized to As(V) arsenate (AsO43-) via (Eq. 1).4,8

As(III) + O2- +H2O As(IV) + H2O2, then As(IV) + O2

- As(V) (1)

In solution, As(V) is an oxyanion as arsenate ion, AsO43-, or one of its protonated forms:

HAsO4-2

, H2AsO4- or H3AsO4 The arsenate ion can then be easily precipitated as an insoluble

salt.8

SONO Arsenic Filter

In Bangladesh, arsenicosis is a major issue and much work is being done on the arsenic

problem. Hussam and Munir have proposed a simple yet effective filter (figure 3),8 called

SONO, which have been installed in literally thousands of homes since its patent in 2002. The

filter consists of two plastic buckets stacked on top of each other. The top bucket typically has

a 45 L volume and the bottom has a 23 L volume.8

The top bucket contains 3 layers for filtration. The top layer is about 10 kg of a coarse

river sand (CRS) taken from local rivers and washed before placement. The CRS is an inactive

layer and serves as “a course particulate filter, disperser, flow stabilizer and to provide

mechanical stability”.8 Groundwater enters and all iron(II) present is naturally oxidized in this

layer by oxygen, and then precipitated as solid Iron Hydroxide:


Fe2+(aq) + O2(g) + H2O(l) Fe(OH)3(s). (2)

Also in this layer, As(III) is converted to As(V) via (Equ. 1). This top layer needs replaced (or

rewashed) every year to ensure adequate water flow. The next layer is 5-10 kg of a composite

iron matrix (CIM). This is the active layer where complexation of arsenic and other toxic metals

can take place. The iron cation, present in the CIM, bonds with arsenate ion to produce the

solid salt ferric arsenate:

Fe3+ + AsO43- FeAsO4(s). (3)

This solid salt binds tightly to the composite iron matrix and is inactive to put arsenic into the

water. The bottom and final layer in the first bucket is a mixture of CRS and brick chips (BC)

supplied from local brick manufacturers. These are thoroughly washed and bleached before

use. This layer serves as a “protection barrier for the free-flow junction outlet”.8

The bottom bucket’s top layer is another 10 kg of wet CRS. The next layer down is wood

charcoal (WC) taken from firewood used for cooking. Although this layer is inactive to arsenic, it

adsorbs organic matter.8 This activated carbon has a surface area of about 1400m2/g which is

internal and structured with many pores. These pores allow many contaminant molecules to

become trapped within the carbon. 9 The final level in the bottom bucket is fine river sand (FRS)

mixed with BC. The FRS serves by catching any residual particulates and again the BC are used

to stabilize the layers above and flow rate. The two buckets are connected by a water line and

a tap. Finally, leaving the bottom bucket are two taps used to collect the purified water.8


To test the effectiveness of the SONO filters, six were selected from six different wells to

filter real groundwater contaminated with arsenic at input levels between 32μg/L and 2423

μg/L. All six filters yielded water with less than 10 μg/L of Arsenic. These six filters had all been

in use for different time periods (2.3-4.5 years) at the time of the reports and all have remained

effective throughout their time in use. The lifetime of the filters is not experimentally known,

but was theoretically calculated to be 14 years using the freundlich isotherm for the CIM

(equation 4).8

log(X/M)= logK + (1/n)logCf (4)

Here X stands for adsorbtion of As in μg/L, M is mass of CIM in g, Cf is μg/L of free arsenic, K is

the adsorption capacity and n is the adsorption intensity. In their calculation K=129.2 and n = -

1.9. The calculation is based on 300 μg/L of As input at 80L/day to a filter containing 10,000 g

of CIM. Assuming these factors, it would take 14 years for the filter to achieve the maximum

contaminant limit allowed in Bangladesh (50 μg/L). In Bangladesh, the filter flow rates were

fixed to 20-30L/hr to ensure long time use. The filter with a 4.5 year life has yielded about

125,000L of purified water!8

The SONO filter requires no regular maintenance apart from yearly cleaning the top

layer of sand in the first bucket. The makers also claim the system does not foster pathogenic

bacteria on its own. However, they still recommend pouring 5L of hot water in the input

monthly to account for unsanitary handling of water or possibilities of present pathogens.

There have not been any recorded health issues resulting from consuming SONO filtered

drinking water. At the time of writing this paper, the SONO filter cost a family about $40 for 5


years! This very affordable filter was projected to have benefited about half a million people

when the paper was written.8 The same principles of this filter could be easily used in other

parts of the world where arsenicosis due to drinking water is an issue.

Areas of this filter that could use further research are that of the arsenic waste and that

of pathogen removal. It is important to test how to use or dispose of the complexed arsenic

waste to avoid further contamination of water. Also, the efficiency of the filter in removing

pathogens has only been speculated and not tested. If this filter truly prevents or even

removes pathogens, then it could improve its selling point and efficiency.

Biosand Filter

One of the leading pathogenic filters is the biosand filter developed by Dr David Manz in

1990.10 The biosand and SONO filters are very similar in both design (figure 4)10 and technique.

The container for this device is made from a concrete mold which can be re-used, allowing for a

cost of about $25 US dollars per filter! Inside the mold, a pvc pipe runs from the bottom up the

inside of the mold and out to an exit spigot. The bottom layer is gravel, followed by a layer of

course sand. These help to control flow rate and keep above layers from clogging the pvc tube.

Above the course sand is a large layer of fine sand where most of the filtration takes place. The

spaces between sand particles allow for mechanical trapping of contaminants to take place. A

diffusion plate is placed a few inches above the sand to create room for oxygen flow. This

oxygen permits aerobic respiration to take place in the upper 5-10 cm of sand where organic

nutrients lay. This (what?) creates a biologically active layer of microorganisms which feed on


bacteria and parasites present in the input water. 10 This use of aerobic treatment is popular in

waste water management in developed countries as well.9

This simple filter was used and tested in Haiti in the mid 2000s through 107 selected

households. The main water problem in Haiti was E.Coli bacteria contamination. E.Coli count

was measured in colony forming units per 100 ml (cfu/100ml). 25% of the sampled households

relied on a water source containing 0-10 cfu/100ml (considered reasonable range), 46% on

counts of 11-100 cfu/100ml E.Coli and 18% were above 100 cfu/100ml E.Coli. The efficiency

was measured by equation (5)10. All samples with a 0 cfu/100ml E.Coli count (10 filters) were

dropped for this calculation.10

[(Ecoli count Entered) – (Ecoli count Out)]/(Ecoli Count in) * 100%. (5)

It was found that the average removal efficiency was 98.5%. WHO’s standard for E.coli is 0

cfu/100ml and although 20% of the cases were above this, 97% of the filters yielded an out put

measurement in the reasonable range (0-10 cfu/100ml).10

Little regular maintenance is necessary for this filter, as only periodic stirring of the top

5-10cm of sand is required to re-suspend the trapped particles so they can be scooped out.10

The ease of the filter combined with its price and its E. coli removal efficiency makes this

product a good choice in developing countries. Further research needs done on the filter’s

ability to remove other bacteria and pathogens. Also, it makes sense that this filter could be

combined with an arsenic filter. This might look like simply increasing the amount of FRS and

adding a diffusion plate to the SONO filter.


Solar Disinfection Methods

When dealing with pathogenic contamination of water, it is often suggested to boil

water, but even this pushes the economic limits in some developing countries due to lack of

fuel for heat. Therefore, it is necessary to turn to a more natural source which can render

bacteria inactive; the sun. Solar radiation emitted by natural UV rays can kill pathogens with

sufficient intensity and exposure. The theory behind this uses the idea of first order kinetics

and Mukherjee et al propose the following equation (5).11

N/No = e-KIT (5)

In this equation No is the initial density of bacteria present, N is this density after time T

(exposure time to sunlight) has passed. I is the intensity of solar radiation and K is the

inactivation rate constant.11

Testing in West Bengal, India

Mukherjee et al have proposed that storing water in transparent glass (or plastic)

bottles in the sunlight for a few hours can be enough to kill harmful pathogens under the right

conditions.(citation) This was demonstrated in an experiment which took place in West Bengal,

India. Water samples were taken from a local pond known to have multiple coli forms

(including fecal coli form). Three experiments were then set up. Some bottles were made half

black by use of colored tape to test the theory that black absorbs thermal infrared rays

quickly.11 In the first experiment, glass bottles with 300ml capacities were used, half were fully

transparent and the other half were half black. Total coli form and fecal coli form count were


measured every 2 hours for a total of 4 hours. The second experiment involved an equal

number of 300ml glass and Polyethylene terephthalate (PET) bottles; all of which were half

black. These were left in the sun for 6 total hours with measurements for total and fecal coli

form occurring every 2 hours. The final experiment involved a large 2.5L glass bottle made half

black. This was left in the sun for 6 hours with measurements every 2 hours. To obtain

maximum sunlight, the experimenters put the bottles in the sun between the hours of 9am and

3pm. The results of this experiment were promising. After two hours in the sun, the first

experiment revealed a 20% removal of total coli form and 41% removal of fecal coli form for

transparent glass bottles. This compares to an 89% removal of total coli form and 83% removal

of fecal coli form for half black glass bottles. After just 4 hours in sunlight, all the bottles had

over 90% of all measured bacteria removed. For experiment 2, 95% of total coli form and

99.9% of fecal coli form had been removed from all of the bottles in 6 hours! The half black

bottles only made a significant difference in the first 2 hours, where an increase in rate of

deterioration was observed. Also glass bottles allowed for a quicker deterioration rate in the

first 2 hours. After 4 hours the results differ only slightly between color and type. After 6 hours

the differences in container type and color are negligible. 11

The 2.5 L container revealed that 50% of total removal occurred from 10:30-11:30 am

and 40% removal between 2:30 pm and 4:30 pm. Only 10% removal occurred between

11:30am and 2:30pm. The experimenters explained that “sunrays are tangent to the earth’s

surface in the morning and evening and approximately perpendicular at noon.” This means

that tilting the bottle at an angle parallel to the latitude of the location allows for maximum UV

radiation throughout the day. 11


This study concludes that the use of sunlight is a useful means to naturally remove

pathogens from water. With materials that tend to be available (clear bottles) and some

education on using sunlight to its best potential (time of day and tilt angle), this technique

could prove to be very useful in the developing world.

Testing in Seoul, Korea

In 2009 Muhammad Tahir Amin and Mooyoung Han published a separate article

observing the effectiveness and limits of Solar Disinfection (SODIS). The article also discusses

the use of harvesting rainwater followed by SODIS. 12 This experiment’s theory can be

compared to developing countries although it took place at Seoul International University in

Seoul, Korea. These experimenters used the university’s roof water harvesting system (RWH),

as shown in figure 5, 12 to collect and test rainwater. Similarly to the experiment done in West

Bengal, India they used Polyethylene terephthalate (PET) bottles to contain the water samples.

Also, some bottles were colored with black paint for UV absorption while others were fixed

with reflective material (aluminum foil) for UV reflection. “Sunlight radiations were monitored

on-site with a SP-110 Pyranometer (Apogee instruments Inc., Logan, USA) connected to a

datalogger (DT80 Series 2) recording 1 minute averages in Watt/m2 (W/m2)”.12 The samples

were left in the sunlight from 9am to 3pm every day for a year while monitoring took place.

They found that reflective bottles were most efficient for sunlight intensities less than

700W/m2 because the weaker sunlight does not have a strong enough thermal effect, therefore

disinfection occurs more from radiation. However, at sunlight intensities above 700 W/m2 the

thermal effect is better relied on for disinfection. Therefore the bottles with black paint are


more preferable in this condition. Although, bacterial inactivation clearly took place, there was

no total disinfection (100% deactivation) of the bacteria at any season in any bottle. Their

findings for the effects of total coliform and fecal coliform count, however, were in good

agreement with the West Bengal, India study.12

Though SODIS is not 100% effective, it could still be a good option for developing

countries that have nothing better. More research needs done to find a way to increase the

effectiveness of SODIS, in view of it being the most economical way to remove pathogens from

water. It should also be noted that sunlight intensity is stronger in areas like Africa and India, as

compared to Korea (see figure 6) 13. Therefore these experimental results do not translate

world wide.

Summary

It seems plenty of technology is available for developing countries who suffer due to unclean

water. There is apparent progress in making water pure using cheap and simple methods to

allow developing countries to be self supporting once they have the equipment and training

needed. The SONO filters are a great fit for areas suffering from arsenicosis due to drinking

water. Areas experiencing illness due to pathogens and bacteria in water should turn to

biosand filters. Both these technologies are simple and relatively affordable, especially if

government grants are involved as was the case in Haiti. 10 Although sufficient work has been

done, it seems more research could aim at incorporating filters which attack multiple problems

like arsenic and pathogens. Also, more time, money and energy should be spent looking at

SODIS, especially in countries which receive intense sunlight as shown in figure 613. SODIS, if


found effective, could be of the most economic means to remove pathogens and bacteria from

water due to its availability and price. Wherever the sun shines, water could be cleaned. Since

the sun is not owned by any man, the only cost would originate from the water containers and

nothing else. In the end, an understanding of chemistry can bring clean water and therefore

life to those who need it around the world.


Figures

Figure 1: Percent of population with access to safe drinking water. 3


Figure 2: World map of arsenic contamination in water5


Figure 3: Schematic Diagram of SONO filter8


Figure 4: Schematic of Biosand Filter10


Figure 5: Rain Water Harvesting (RWH) System used at Seoul Nation University in Seoul South

Korea. 12


Figure 6: measured average intensity of sunlight on the earth’s surface.13


References

1. World Health Organization (WHO). Water Sanitation and Health.

http://www.who.int/water_sanitation_health/diseases/arsenicosis/en/ (accessed November

8th, 2011).

2. Water.Org. http://water.org/ (accessed November 8th, 2011).

3. JMP. http://www.wssinfo.org/data-estimates/maps/ (accessed November 9th, 2011).

4. Baird, Colin.; Cann, Michael. Environmental Chemistry, 4th ed.; W.H. Freeman and Company:

New York, 2008; Chapter 15.

5. Kinniburgh, D.G.; Smedley. Arsenic Contamination of Groundwater in Bangladesh. BGS

Technical Report WC/00/19. [Online] 2001, 2, 3-16,

http://www.bgs.ac.uk/arsenic/bphase2/reports.htm 3(accessed November 9th, 2011).

6. World Health Organization (WHO). Microbial Aspects, Guidelines for Drinking-water Quality.

2011, 4, 117.

7. World Health Organization (WHO). Mortality Trends, The global burden of disease:2004 update.

2004, 66.

8. Hussam, Abul.; Munir, Abul K. M. A Simple and Effective Arsenic Filter Based on Composite Iron

Matrix: Development and Deployment Studies for Groundwater of Bangladesh. Journal of

Environmental Science and Health Part A. 2007, 42, 1869-1878.

9. Baird, Colin.; Cann, Michael. Environmental Chemistry, 4th ed.; W.H. Freeman and Company:

New York, 2008; Chapter 14.

10. Duke WF, Nordin RN, Baker D, Mazumder A. The use and performance of BioSand filters in the

Artibonite Valley of Haiti: a field study of 107 households. Rural and Remote Health. [Online]

2006, 6: 570. http://www.rrh.org.au/articles/subviewnew.asp?ArticleID=570 (accessed

December 6th, 2011).

11. Mukherjee, P.; Maity, P.B.; Jana, J.; Chatterjee, D. Use of Solar Radiation for Upgradation of

Microbiological Load of Contaminated Surface Water with the Help of Improved Container

Designing, Journal of the IPHE. 2006. 3. 46-50.

12. Amin, Muhammad Tahir; Han, Mooyung. Rood-harvested rainwater for potable purposes:

application of solar disinfection(SODIS) and limitations, Water and Science Technology,2009.

60.2. 419-431.

Comment [HOF1]: The title should come before the authors.

http://www.who.int/water_sanitation_health/diseases/arsenicosis/en/

http://water.org/

http://www.wssinfo.org/data-estimates/maps/

http://www.bgs.ac.uk/arsenic/bphase2/reports.htm

http://www.rrh.org.au/articles/subviewnew.asp?ArticleID=570


13. NASA. 2008. NASA Surface meteorology and Solar Energy (SSE) Release 6.0 Data Set, Clear Sky

Insolation Incident On A Horizontal Surface. http://eosweb.larc.nasa.gov/sse/ (Accessed 12/4

2011)

Documents

Economic Water Purification in Developing Countries, JWALKUP