Journal of Environmental Protection, 2014, 5, 42-53
Published Online January 2014 (
Low-Cost Sustainable Technologies for the Production of
Clean Drinking Water—A Review*
Sharmin Zaman1, Sabina Yeasmin2, Yasuhiro Inatsu3, Chiraporn Ananchaipattana4,
Mohammad Latiful Bari1#
1Food Analysis and Research Laboratory, Center for Advanced Research in Sciences, University of Dhaka, Dhaka, Banglad esh;
2Department of Genetic Engin eerin g and Biotechnology, University of Dhaka, Dhaka, Bangl adesh; 3Nat ional Food Research Institute,
National Agriculture and Food Research Organization, Tsukuba-shi, Jap an; 4Department of Biology, Faculty of Science and Te c h-
nology, Rajamangala University of Technology, Thanyaburi, Thailand.
Received November 12th, 2013; revised Dece mber 11th, 2013 ; accep ted January 5th, 201 4
Copyright © 2014 Sharmin Zaman et al. Th is is an o pen access arti cle dist ributed under the Creat ive Commons Attrib ution License,
which per mits unrestri cted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accor-
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property Sharmin Zaman et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian.
Water has always been an important and life-sustaining drink to humans and is essential to the survival of all
known organisms. Over large parts of the world, humans have inadequate access to drinking water and use wa-
ter contaminated with disease vectors, pathogens or unacceptable levels of toxins or suspended solids. Drinking
such water or using it in food prepa ration leads to widesprea d, acute and chronic i llnesses and i s a major cause
of dea th and misery in many countries. The UN estimates that over 2.0 billion people have li mited access to safe
wat er and nearly 800 millio n people lack eve n the most ba sic supply of cle an water. The main i ssue is the affo r-
dability of wat er purifying syste ms. Many people rely on boiling water or bottled water, which can be expensive.
Therefore, technologies that are cost effective, sustainable, ease of operation/maintenance and the treatment
processes wit h locally av ailable materials are required. In this article, some unique low -cost sustainable t echnol-
ogies available/or in-use, i.e. natural filtr atio n, riv erba nk filtra tio n, biosand filtration, membrane filtration, solar
water disinfection technique, biologically degradable materials such as moringa powder, scallop powder treat-
ment, and biosand pitcher treatments have been discussed.
Sustainable Technology; Clean Drinking Water; Low Cost; Bio-Sand Filtration; Natural Filtra t io n;
Solar Disinfec t ion
1. Introduction
Water has always been an important and life-sustaining
drink to humans and is essential to the survival of all
known organisms. Over large parts of the world, humans
have inadequate access to drinking water and use sources
contaminated with disease vectors, pathogens or unac-
ceptable levels of toxins or suspended solids. Drinking
such water or us ing it in food preparation leads to wide-
spread, acute and chronic illnesses and is a major cause
of de at h a nd mise r y i n man y count ri es. T he UN estimates
that o ver 2 billion people have limited access to safe wa-
ter. Of these, nearly 800 million people lack even the
most basic supply of clean water. There are few methods
commonly advocated for the disinfection of drinking
water at the household level. These include boiling of
water for about 10 minutes, or the use of certain chlorine
compounds available in the form of tablets (Halazone
tablets, or calcium hypochlorite tablets) or solutions (so-
dium hypochlorite solutions). These tablets have an ex-
piration date, and the instructions call for the addition of
1 to 2 tablets per liter o f water and waiting for 25 minutes
before use.
As each of these procedures has its own drawbacks,
These authors contributed equally to this work.
#Corresponding author.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
their application is extremely limited in the developing
regions of the world where water-borne diseases are pre-
valent, and the safety of drinking water supplies cannot
always be assured. Availability and costs are the only
part of the problem. In the case of boiling, for instance,
the need for about one kilogram of wood to boil one liter
of water is totally unjustifiable in fuel-short regions al-
ready suffering from aridity and desertification. Besides,
the disagreeable taste of boiled water often discourages
consumers. The addition of 1 to 2 drops of 5% sodium
hypochlorite solutio n per liter o f water re quires t he use o f
a dropper and liter measure, both being uncommon de-
vices in most homes. In view of these difficulties and
constraints, technologies that are cost effective and sus-
tainable must be developed. Sustainable operation of
these treatment processes with locally available materials
and ease of maintenance is required. In this revie w article,
we focused on the low-cost sustainab le techno logies availa-
ble or in-use for the production of clean drinking water.
2. Available Sources of Water
Water although covering 70% of the Earth's surface, most
water is saline. Freshwater comprises only three percent
of the total water available to humans. Of that, only 0.06
percent is easily accessiblemostly i n river s, lakes, wells ,
and natural springs. Even then, accessible water is not
necessarily safe drinking water. The freshwater sources
from which most of our drinking water is derived are
exposed to a variety of contaminants, many arising from
the unsafe production, utilization, and disposal of inor-
ganic and organi c compo unds.
Freshwater is available in almost all populated areas of
the earth, although it may be expensive and the supply
may not always be sustainable. Sources where water may
be obtained include:
1) Groundwater: The water emerging from some
deep ground water may have fallen as rain many thou-
sands of years ago. Soil and rock layers naturally filter
the ground water to a high degree of clarity and often it
does not require additional treatment other than adding
secondary disinfectants.
2) Upland lakes and reservoirs: Typically located in
the headwaters of river systems, upland reservoirs are
usually sited above any human habitation and may be
surrounded by a protective zone to restrict the opportuni-
ties for contamination. Bacteria and pathogen levels are
usually low, but some bacteria, protozoa or algae will be
present. Where uplands are forested or peaty, humic acids
can color the water. Many upland sources have low pH,
which require adjustme nt.
3) Rivers, canals and low land reservoirs: Low land
surface waters will have a significant bacterial load and
may also contain algae, suspended solids and a variety of
dissolved constituents .
4) Atmospheric water generation is a new technolo-
gy that can provide high quality drinking water by ex-
tracting water from the air by cooling the air and thus
condensing water vapor.
5) Rainwater harvesting or fog collection which col-
lects water from the atmosphere can be used especially in
areas with significant dry seasons and in areas which
experience fog even when there is little rain.
6) Desalination of seawater by distillation or reverse
7) Water supply network: Tap water, delivered by
domestic water systems in different countries nations,
refers to water supply network.
The most efficie nt way to tra nsport a nd deliver po table
water is through pipes. Plumbing can require significant
capital investment. Some systems suffer high operating
and maintenance costs. Because of these high initial in-
vestments, many developing nations cannot afford to
develop or sustain appropriate infrastructure, and as a
consequence people in these areas may spend hardship
for water. Over 40 countries in the world suffer from a
safe drinking water deficit, with an estimated 1.2 billion
people drinking unclean water on a daily basis and five
million people, mostly children, dying every year from
water-related diseases. The United Nations estimate s that,
by 2025, 2.7 billion people will not have access to safe
dri nking water. However, three major factors including 1)
untreated municipal and domestic sewage; 2) untreated
industrial effluents; and 3) agricultural run-off are attri-
buted to the freshwater crisis in developing countries.
3. The Challenge of Monitoring
Water Quality
Sustainable water quality management requires rigorous
and regular monitoring of water resources for all poten-
tial contami nants so that appropr iate actions can be taken
to prevent or remediate water pollution. B ut rigorous and
regula r water quali ty monito ri ng i s not a simple ta sk. T he
CWA (Clean Water Act, 1972) triggered engineering
changes in manufacturing processes and wastewater
treatment which led to significant progress toward clean-
er water in rivers and lakes of US. Today, hundreds of
new synthetic organic compounds, like pesticides and
volatile organics in solvents and gasoline, have been in-
tro duced int o the enviro nment o ver the las t four decades.
Moreover, improved laboratory techniques have led to
the discovery of a large number of microbial and viral
contaminants, pharmaceuticals, and endocrine disruptors
not detected or measured in the past. There is a growing
demand for monitoring pollutants at ultra-trace levels (i.e.,
below parts per million [ppm]) but requires adequate fi-
nancial and human resources.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
4. Technology Development Challenges
A grea t chal le nge i n vol vi n g te c hno lo g ic al d e vel opment is
the need to develop technology that is appropriate, rele-
vant, economic and sustainable to the stakeholders. On
the other hand, effective removal of emerging contami-
nants, synthetic chemicals, and pesticides, as well as
spills of chemicals into rivers is some of the challenges.
Technology implementation that provides safe and af-
fordable drinking water can markedly improve the human
condition for billions across the globe.
Drinking water treatment technologies have been used
and continuously developed over the ages. The earliest
known treatment method was the application of chemical
alum to contaminated water to remove suspended solids
by the Egyptians around 1500 BC (Lenntech 2009).
Heating, sand and gravel filtration was among the oldest
technology used as long ago as 2000 BC. Chemical ap-
plications of water treatment (like chlorine filtration)
were discovered in nineteenth century, and membrane
distillatio n was discovered in the twentieth cent ury.
In this review pap er, natural filtration, r iverbank filtra-
tion, sand filtration, membrane filtration, bio-sand filtra-
tions, combined physical and chemical treatments were
discussed. I n addition, membrane filtration s ystems, sola r
distillation and pasteurization system and other purifica-
tion systems in the developing regions were also dis-
4.1. Natural Filtration
Natural filtration has been employed since the beginning
of the written history. Quite simply, natural filtration
takes advantage of the soils that act as filters as the water
passe s thro ugh the m. In or der to under stand ho w wate r is
purified naturally, one must know the hydrological cycle
which is the cycling process of water molecules from the
ocean to the atmosphere, to the land and back to the
ocean, and the storage in various reservoirs. Simply, wa-
ter evaporated from the ocean eventually condenses as
water droplets in clouds. If the cloud grows large enough,
the droplets coalesce and fall as precipitation, mostly as
rain, sometimes as snow or ice. About 74% of all water
evaporated into the atmosphere falls as precipitation on
the ocean, mostly in the tropics, and about 26% falls on
the land. But the distribution of rainfall is very uneven.
Some of the water runs into streams, lakes, and rivers (as
shown in Figure 1), which return the water to the ocean
while some soaks into the ground (infiltrates) and be-
comes groundwater. The water then can percolate deeper
into the ground supplying water to subsurface reservoirs.
The rate of infiltration depends on: many factors such as
the type of soil. Sandy soils absorb water faster than clay
soils. Vegetatio n also can tend to delay runoff. While the
water content of the soil also plays an important role.
Figure 1 . Natural w at er sources.
Soils saturated with water absorb little more. T he rainfall
rate, whether a tremendous amount is a short period or a
prolonged period, have different absorption rate. Some
rainfall evaporates back into the air, or it is absorbed by
plants, which transpire the water into the air. This is
called evapotranspiration. Evapotranspiration describes
the transport of water into the atmosphere from surfaces
including soil, a nd from veget a tion (transpiration).
Purification o f water in liquid form ulti matel y depends
on natural filtration, chemical absorption and adsorption
by soil particles and organic matter, living organism up-
take of nutrients, and living organism decomposition
processes in soil and water environments. Human activi-
ties that compact soil, degrade soil structure in other
ways, contaminate storm water with pollutants, or alter
the composition of soil and water-based organisms,
eventually reduce or retard the natural water purification
process and cause accelerated movement of unfiltered
water through the system and into our water supplies.
Soils, especiall y in wetland and r iparian ar eas, alo ng with
vegetation and microorganisms play very important roles
in natural water purification. Microorganisms in soils,
wetlands and riparian areas either utilize or breakdown
numerous chemical and biological conta minants in water.
The most common form of natural filtration used cur-
rently is sand filtration in a natural setting. Also, simple
wells can be classified as using natural filtration, assum-
ing the soil isn’t contaminated and most of the water
dra wn from the well is a re sul t of rai nfall i n filtration. T he
best materials to be used for natural filtration are uncon-
solidated alluvial deposits due to high hydraulic conduc-
tivity. The greatest disadvantage of using unconsolidated
soil is that there is the possibility of the introduction of
anthropogenic contaminants from the land surface to
groundwater (typically alluvial aquifers are unconfined
aquifers). However, there are clear advantages: natural
filtration of appropriate travel time can induce a 3 - 5 log
reduction in microbes and protozoa [1]. A 1 lo g r ed uct io n
represents a 90% removal of the bacteria or protozoa.
Therefore, a 3 - 5 log reduction removes all unwanted
biological and viral components from water to an unde-
tectable—or at the very least, an acceptable—level.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
Ho weve r, due to the c hangin g red ox condi tions, t here ar e
often increased amounts of manganese and iron in natu-
rally filtered water, as well as the formation of some sul-
furous compounds that are malodorous. These negative
effects are eliminated when using rapid sand filtration,
but the advantages are also subdued, as will be seen in
the section below on sand filtration [2].
4.2. Riverbank Filtration
Riverbank filtration (RBF) is a water treatment technol-
ogy that consists of extracting water from rivers by
pumping wells located in the adjacent alluvial aquiferas
shown in Figure 2. During the underground passage, a
series of physical, chemical, and biological processes
take place between the surface water and groundwater,
and with sub surfac e, impro ving the quality of the surface
water, substituting or reducing conventional drinking
water treatment. In addition to the removal of pollutants
(particles, microorganisms, organic, and inorganic com-
pounds, etc.) there are two additional advantages of RBF.
The first is relative to the fact that the flow through the
aquifer acts as a barrier against concentration peaks that
may result from accidental spills of pollutants. The
second is the regulation on the temperature variations in
the river water: during winter, when air temperatures are
low, the filtered water is usually warmer than surface
water, and in summer it is cooler . The lowest variation in
temperature improves the quality and further processing
of the bank filtrate [2].
Riverbank Filtration: An Efficient and Economical
Drinking-Water Treatment Technology
Riverbank filtration technology has been a common prac-
tice in Europe for over 100 years, particularly in coun-
tries such as Switzerland where 80% of drinking water
comes from RBF wells, 50% in France, 48% in Finland,
40% in Hungary, 16% in Germany, and 7% in the Neth-
erlands [3]. In Germany, for example, 75% of the city of
Berlin depends on RBF, whereas in Düsseldorf RBF has
been used since 1870 as the main drinking water supply
[4]. In the United States, on the o the r ha nd , t his te chn i que
has been used for nearly half a century, especially in the
states of Ohio, Kentucky, Indiana, Illinois, among others
[5]. Other countries that have recently started imple-
menting RBF for drinking water supply are India [6],
China, and South Korea [7].
Riverbank filtration wells can be designed either verti-
cally (as the most common practice especially for the
extraction of low water quantities) or horizontally (for
higher extraction rates). Horizontal wells (sometimes
with a radial pattern), also known as collector wells, are
usually directed toward the river and extract water from
beneath the riverbed, whereas vertical wells extract water
along the riverbed [5]. Also, RBF wells can be distributed
paralle l to the river bank in galleries o r gro ups [8].
Organic pollutants such as pesticides, herbicides,
odorous compounds, oil sub-products, and pharmaceuti-
cals are of great concern for water quality. Riverbank
filtration has been extensively used for drinking water
pretreatment in places with such pollution problems [9,
10]. The removal and the behavior of organic compounds
during RBF depends on factors specific to pollutants such
as the hydrophobicity of the compound, the potential for
biochemical degradation, the amount of organic matter in
the aquifer, microbial activity, infiltration rate, biodegra-
dability, etc. [3]. Another aspect that apparently influ-
ences the removal of certain organic contaminants such
as antimicrobial residues is the redox condition of the
aquifer together with the travel time [11].
Although the RBF has proven to be efficient in re-
moving organic matter (total and dissolved organic car-
Figure 2 . Basic scheme of riverbank filtration and main attenuation processes (Adapted from Hiscock et al. [2]).
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
bon, TOC and DOC) as well as certain disinfection by-
products (DBPs) [5,12,13], if chlorination is used as the
disinfection method, there might be an increase in triha-
lomethane concentration. It could then be recommended
to use ACF before disinfection to reduce the amount of
TOC and thus the formation of trihalomethanes (THMs).
River bank-filtrate water usually requires additional
treatment before disinfection, such as activated carbon
filtration (ACF), ozonation→filtration→ACF, o r aeration→
filtration. This is especially common in rivers with high
concentration of ammonia, organic compounds, and mi-
The main limitation on the efficiency of RBF is the
cloggi ng of t he bed a nd the bank s of the r iver, wh ich de-
creases the hydraulic conductivity in the hyporheic zone.
This clogging can be caused by the infiltration of fine
sediments, gas entrapment, biofilm formation related to
microbiological activity, or the precipitation and co-pre-
cipitation of inorganic compounds, being the first of this
most influen tial factor in cloggin g fo r matio n. T he c urr ent
understanding of the processes and mechanisms behind
this technique are still very empirical. The use of this
technology in tropical countries is almost nonexistent
even though there is a great potential for exploring this
RBF in developing countries.
4.3. Slow Sand Filtration
4.3.1. Slow Sand Filters
Slow sand filters are used in water purification for treat-
ing raw water to produce a potable product. They are
typically 1 to 2 meters deep, can be rectangular or cylin-
drical in cross section and are used primarily to treat sur-
face water. The length and breadth of the tanks are de-
termined by the flow rate desired by the filters, which
typically have a loading rate of 0.1 to 0.2 meters per hour
(or cubic meters per square meter per hour). Slow sand
filters differs from all other filters used to treat drinking
water in that they use complex biological film on the
surface of the sand. The sand itself does not perform any
filtration func tion but simpl y acts as a substrate. T hey are
often the preferred technology in many developing/de-
veloped countries because of their low energy require-
ments and robust performance [14]. Typical configura-
tion of a housed slow sand filter system has been pre-
sented in Fig ur e 3.
Slow sand filters work through the formation of a gela-
tinous layer (or biofilm) called the hypogeal layer or
Schmutzdecke in the top few millimetres of the fine sand
layer. The Schmutzdecke is formed in the first 10 - 20
days of operation [15] and consists of bacteria, fungi,
protozoa, rotifera and a range of aquatic insect larvae.
The Schmutzdecke is the layer that provides the effective
purification in potable water treatment, the underlying
sand providing the support medium for this biological
treatment layer. The water produced from a well-ma-
naged slow sand filter can be of exceptionally good qual-
ity with 90% - 99% bacterial reduction [15]. U nlike o ther
filtration methods, slow sand filters use biological
processes to clean the water, and are non-pressurized
systems. Slow sand filters do not require chemicals or
electricity to operate. Slow sand filters require relatively
low turbidity levels to operate efficiently. In summer
conditions a nd in conditio ns when the ra w water is turbid ,
blinding of the filters occurs more quickly and pre-
treatment is recommended. Unlike other water filtration
technologies that produce water on demand, slow sand
filters produce water at a slow, constant flow rate and are
usually used in conjunction with a storage tank for peak
usage. This slow rate is necessary for healthy develop-
ment of the biological processes in the filter [16,17].
As they require little or no mechanical power, chemi-
cals or replaceable parts, and they require minimal oper-
Figure 3 . Typi ca l configuration of a hou sed slow s and f ilter s yst em.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
ator training and only periodic maintenance, they are of-
ten an appropriate technology for poor and isolated areas.
Slow sand filters, due to their simple design, slow sand
filter s have b een us ed in A fghani stan and other c ountries
to aid the poor. Slow sand filters are recognized by the
international Organizations and the United States Envi-
ronmental Protection Agency as being superior technol-
ogy for the treatment of surface water sources. Due to the
low filtration rate, slo w sand filters require e xtensive la nd
area for a large municipal system [16]. Many municipal
systems i n the U. S. initia lly u sed slo w sand filters, bu t as
cities have gro wn, they subsequently installed rapid sand
filters, due to increased demand for drinking water.
4.3.2. Rapid and Slow Sand Filtra t io n
Rapid sand filtration is mainly used in combination with
other water purification methods. The main distinction
from slow sand filtration is the fact that biological filtra-
tion is not part of the purification process in rapid filtra-
tion. Rapid filtration is used widely to remove impurities
and remnants of flocculants in most municipal water
treatment plant s. As a single p rocess, it is not as effective
as slow sand filtration in production of drinking water. In
general, slow sand filter s have filtration rates o f up to 0.4
m/hour, as opposed to rapid sand filters which can see
filtration rate s o f up to 21 m/hour.
A rapid filter passes quickly through the filter beds.
Often, it has been chemically pre-treated, (such as chlo-
rination or flocculatio n) so that little biolo gical activity is
present. Physical straining is the most important mechan-
ism present in rapid filters. Particles that are larger than
the pore size between the sand grains are trapped
smaller solids however can pass through the filter. Rapid
sand filtration removes particles over a substantial depth
within the sand bed. Rapid sand filters are usually
cleaned on a daily basis using backwashing, whenever
terminal head loss is reached. To clean the filter, the flow
of water is reversed through the filter bed at a high rate so
that all materials trapped between the sand will be
flushed-out. Rapid sand filters are suitable for large urban
centers where land scarcity is an issue, whereas slow
sand filters tend to be more s uitable for areas where land
is more available, since they need a much larger surface
area to treat the same amount of water. Slow sand filtra-
tion is simpler to operate than rapid filtration, as frequent
backwashing is not required and pumps are not always
4.4. Membrane Filtration
Membrane filtration technology (as shown i n Figure 4) is
simply the filtering of water through a sieve or semi-
permeable layer such that water molecules are allowed to
pass through, but bacteria, chemicals, and viruses are
prevented from passing. The most effective membrane
Figure 4. Membrane systems remove 0.05-micron particles
from w ater.
technology often require significantly more energy than
other membrane systems due to electrical or mechanical
systems required to maintain the pressure. The pore size
in the membrane can be significantly smaller, allowing
higher remova l rates o f contami nants. T he most co mmon
application of membrane technology is RO desalination
although the application of membrane technology has
been used for bacterial and protozoan removal as well.
Other membrane filtratio n including nano -filtration [NF],
ultra-filtration [UF], micro-filtration [MF]) and electro-
dialysis (ED) has also been used. All these membrane
filtration syste ms are pri marily used to purify sea water or
brackish water (water containing less salt that seawater,
but still more salty than WHO regulations). Reverse os-
mosis is used to take sali ne water and convert it into p ure
water. The technical measure of fresh water is to contain
less t ha n 1000 mg/l of salts or total dissolved solid s ( TDS )
and the World Health Organization has established a
baseline of 250 mg/l, which is also supported by the US
EPA [18]. Therefore, any water containing higher levels
of salts or TDS must undergo some sort of removal
The type of membrane media determines how much
pressure is needed to drive the water through and what
sizes of micro-organisms can be filtered out. For drinking
water, me mbrane fi lters can remove virtua lly all particles
larger than 0.2 umincluding giardia and cryptospori-
dium. Membrane filters are an effective form of tertiary
treatment when it is desired to reuse the water for indus-
try, for limited domestic purposes, or before discharging
the water into a river that i s used b y towns further do wn-
stream. They are widely used in industry, particularly for
beverage preparation (including bottled water). However
no filtration can remove substances that are actually dis-
solved in the water such as phosphorus, nitrates and
heavy metal ions. The overwhelming majority of tech-
nical papers and research articles produced on membrane
filtration focus solely on desalination. However, the use
of membrane filtration for pretreatment of RO plants is
becoming more common. The differentiation between
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
each is the pore size of the membranes (as they are con-
sidered porous, unlike RO membranes), with MF being
the largest po re-size and NF being the smallest. The abil-
ity of each filter to filter out contaminant is beneficial in
various environments, and the correct application of
membrane pore-size is largely dependent on the most
common contaminants in the feed water.
4.5. Solar Distillation
The basic concept of using solar energy to obtain drinka-
ble fresh water from salty, brackish or contaminated wa-
ter. Solar distillation is the use of solar energy to evapo-
rate water and collect its condensate within the same
closed s ystem. Unli ke other fo rms of water purificatio n it
can turn salt or brackish water into fresh drinking water
(i.e. desalination). T he structur e that houses the p roc ess is
known as a solar still and although the size, dimensions,
materials, and configuration are varied, all rely on the
simple procedure wherein an influent solution enters the
system and the more volatile solvents leave in the efflu-
ent leaving behind the salty solute [19]. The structure of
double pane solar s t ill has been shown in Fi g ur e 5.
Solar distillation of potable water from saline (salty)
water has been practiced for many years in tropical and
sub-tropical regions where fresh water is scarce. The rate
of evaporation can be accelerated by increasing the water
temperature and the area of water in contact with the air.
The pan is painted black or some other dark color to
maximize the amount of solar energy absorbed. It should
also be wide and shallow to increase the water area ex-
posed to air. The solar distilled water costs much less
than bottled water, therefore, this technology could be
useful in household application in many developing
Solar Pasteurization
Pasteurization is the process of disinfecting water by heat
or rad iation without bo iling. T ypical water p asteurization
achieves the same effect as boiling, but at a lower tem-
Figure 5 . Double-pane solar still.
perature (usually 65˚C - 75˚C), over a longer period of
time. Pasteurization is the use of moderate heat to kill
disease microbes. It is different from sterilization, in
which all microbes are killed. To pasteurize milk in a
continuous flow process, only 15 seconds at 71˚C is re-
quired. This modest heat treatment would also pasteurize
water. A solar pasteurization device is shown in Figure 6,
where water container put into the box and heated with
solar heat and pasteurizes water
The temperatures which will kill at least 90% of mi-
crobes within one minute are: 55˚C for worms, and cysts
of the protozoa Giardia, Cryptosporidium, and Entamoe-
ba; 60˚C for the bacteria Vibrio cholerae, Samonellatyphi,
Shigellaspp, and Enterotoxigenic Escherichia coli, and
for rotavirus, a major cause of infant diarrhea; 65˚C for
Hepatitis A virus. As the temperature increases above
55˚C for protozoa, or above 60˚C for bacteria and rotavi-
rus, the time required for 90% inactivation decreases sig-
nificantly. For example, 90%inactivation of these bacte-
ria at 65˚C requires only about 12 seconds, and 99.999%
kill would re sult from one minute at 65˚C.
From published data and our own experiments, we es-
tablished that heating contaminated water to 65˚C will
pasteurize the water and make it safe to drink [20]. As
batch heating of water will have the water temperatures
from 60˚C - 65˚C for several minutes, the cumulative
heat effect will reduce the level of live pathogens to zero;
similar to what is accomplished in milk pasteurization.
The water pasteurization indicator (WAPI) is a clear
polycarbonate tube, partially filled with a wax, and sealed
at both ends. The WAPI wax melts at 65˚C. The WAPI is
placed at the bottom of a container, which is heated by
sunshine. If the WAPI wax melts and falls to the bottom
of the tube, it verifies that pasteurization conditions have
been achieved [20].
Figure 6. A solar pasteurization devi ce in t he shape of a bo x
with a glass cover and a reflecting interior and folding lid.
The water container is put inside the box and heated with
solar heat. Source: CA WST [15].
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
4.6. Solar Disinfection of Water (SODIS)
SODIS is a simple and low cost technique used to disin-
fect contaminated drinking water. Transparent bottles
(preferably PET) are filled with contaminated water and
placed in direct sunlight for a minimum of 6 hours. Fol-
lowing exposure, the water is safe to drink as the viable
pathogen load can be significantly decreased. Simple
guidance for the use of SODIS i s given in Figure 7.
SODIS harnesses light and thermal energy to inactivate
pathogens via a synergistic mechanism [22]. Around 4%
- 6% of the solar spectrum reaching the surface of the
Ear th is in t he UV d omain, wi th ma xi mu m re po r te d value
of around50W/m2 [23]. UV radiation (200 - 400 nm) can
be classified as UVA (320 - 400 nm), UVB (280 - 320
nm), and UVC (200280 nm). UVC is absorbed by the
ozone layer along with a proportion of the UVB; there-
fore UVA represents the main fragment of solar ultravio-
let radiation reaching the earth’s surface.
Disinfection of water using solar energy has been car-
ried out since Egyptian times. The process was first stu-
died and r eported in scient ific literature b y London-based
scientists Downes and Blunt in the late 1870s [24] and
was effectively rediscovered as a low-cost water disin-
fection method by Acra et al. in the late 1970 [20,25].
Laboratory studies have demonstrated the effects of
key operational parameters such as light intensity and
wavelength, solar exposure time, availability of oxygen,
turbidity, and temperature [26,27]. The SODIS mechan-
ism is understood to involve a number of biocidal path-
ways based upon the absorption of UVA radiation and
thermal inactivation.
Direct UVA exposure can induce cellular membrane
damage and delay microbial growth [28]. The biocidal
action of UVA has also been attributed to the production
of reactive oxygen species (ROS) which are generated
from dissolved oxygen in water [29] and the photosensi-
tization of molecules in the cell, and/or any naturally oc-
curring dissolved organic matter that can absorb photons
of wavelengths between 320 - 400 nm, to induce photo-
Figure 7. SODIS process (adopted from Anthony Byrne et
al., [21].
chemical reactions [30]. The thermal effect has been at-
tributed to the high absorption of red and infrared pho-
tons by water. At temperatures below 40˚C, the thermal
effect is negligible with UVA inactivation mechanisms
dominating the inactivation process. Significant bacteri-
cidal actio n is evident at tempe ratures above 40 ˚C - 45˚C
with a synergistic SODIS process observed at tempera-
tures above 45˚C [22,26,30-32]. Studies to improve the
efficiency of the SODIS processes using low-cost, com-
monly available materials have been conducted [33-36];
however, the simple approach of exposing a 2 L PET
bottle to full sun for a minimum of 6 hours is the most
commonly promoted and practiced method. A graphical
description on the solar disinfection (SODIS) household
water treatment technique is given in Figure 8.
A number of low cost additives are capable of accele-
rating the SODIS in both sunny and cloudy weather,
which is indicated by recent laboratory and field experi-
ment. The additives are 100 to 1000 mM hydrogen pe-
roxide (both of the room and prominent temperature),
0.5% to 1% lemon juice, copper metal or aqueous copper
plus ascorbate ( with or without hydrogen peroxide) [37].
Improvement of SODIS with Locally Available
Materials: (A Study)
Dr. Rabbani and his research group [38] improved SO-
DIS technology with readily available materials like
bamboo tray, hay, polythene sheets, etc. as shown in
Figure 9, for ultra-poor people in rural or flood affected
coastal areas of Bangladesh. The idea is to collect and
absorb energy from sunshine and trap it in the device by
reducing heat losses as much as possible. In order to
make the tool very low cost, a horizontal water bed was
considered rather than an angle design. The relatively
clear water from river, canals or ponds was filtered
through several layers of ordinary clothes to get clean
water. Low cost additives (alum, moringa seed powder or
Figure 8. A graphical description on the solar disinfection
(SODIS) household wa ter tre a tment technique.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
locally available materials) could be added before clothes
filtration to improve the microbiolo gical status of water.
For the solar treatment, bamboo tray (75 c m d ia me t e r) ,
a flat rigid surface with raised ends, to hold water, as
shown in Figur e 9 was dyed black earlier and dried. A
polythene sheet was spread over the black bamboo tray
and water was poured to a depth not more than 2 cm [38],
which is equivalent to approximately 5.0 liters of water.
To stop evaporation another polythene sheet was spread
over the water so that it adheres to the water surface in all
places (Figure 9). Air bubbles (if any), interfere sunlight
entering to water should be removed to the ends by finger
pressure and movement.
Next, two thin air layers above the water was made by
spreading few strands of straw and two transparent po-
lyethylene sheet for heat i nsul atio n but a llo win g sun shi ne
to enter. Finally the polyethylene sheets were stretched
out using weights all around as s hown in Fig ur e 9.
In a c lea r su nn y d a y, it us ually ta ke s 1 .5 - 2.0 hours for
destroying all diarrheal microorganisms. After the treat-
ment, the top three polythene sheets should be removed
and the treated water can be collected in the polythene
sheet by holding the ends as shown in Figur e 9. This is
the ‘harvest’ of safe diarrheal microorganism free drink-
ing water and can be stored in clean containers for further
use. One family, may harvests 10 liters in a clear sunny
day (9 AM to 3 PM), which is enough for a family [39].
4.7. Combined Method of Disinfection: (A
New Study)
Simple technologies such as the app lication of plant co a-
gulant s such as Moringaoleifera to treat water have been
extensively reported. On the other hand, scallop powder
is a new biodegradable sanitizer, and reported to have
antibacterial and antifungal action. As this powder is
produced from natural sources thus doesn’t pose any ha-
zard to the environment, and biodegradable. In addition,
FS® and Ultra K1® is also commercial coagulants used
for treating turbid or cloudy water by pulling together
floating particles—including dirt, other solids, and some
pathogens. These compounds are cheap, readily available
and naturally biodegradable. [40] reported that Moringa-
seed powder alone has strong coagulant and antimicrobial
effect at low doses. On the other hand, 0.01% scallop
powder has strong antimicrobial activity under typical
environmental conditions. However, combination of
these two powders showed effective coagulating and an-
timicrobial capacity to reduce the turbidity and inactivate
the number of inherent microorganisms respectively;
including coliform and E. coli within 5 min. Similar ex-
perimental findings were observed when the mixture of
Moringaseed powder and sodium hypochlorite was used.
On the other hand, both the commercial ultra-K and FS
powder showed strong coagulant and antimicrobial effect
within 1 minute of application. When this treated water
passe d thr oug h nat ural b io -sand filtration (charco al, stone
and sand), the resulting water became potable. This small
scale work was done in the laboratory and there is a need
to scale-up this method to ascertain there reproducibility
of the results. The study report suggested that Moringa
seed powder and scallop powder are naturally available,
cost-effective, and nontoxic antimicrobial agents that
have potentials to convert pond water to drinkable water.
The treatment process was shown in Figure 10.
5. Regulatory Guidelines for Clean Drinking
Water (Updated)
Providing sufficient amounts of drinking water of a suit
Figure 9 . Sequence of setti ng up the s olar dis inf ectio n device
and the harvestof drinking water (Adapte d from Rab ba-
ni, [39].
Figure 10. Treatment process of water by moringa, NSP , Ultra K1, F S and followed by biosand fi ltrati on [40].
Mori ngaS eed
NSP Ultra K1FS Biosand Filtration
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
able quality is a basic requirement and ensuring the sus-
tainable, long-term supply of such drinking water is a
national and interna tional con cern. Water testing plays an
important part in ensuring the correct process of water
supplies, proven the safety of drinking water, exploring
disease outbreaks, and validating processes and preven-
tive actions. There are vital challenges in implementing
comprehensive and suitable water qualit y testing, mai nly
in low-resource settings. As a result, the ext ent and q ual-
ity of the information offered by water testing is often
insufficient to support effec tive decision-making.
The following microbial and physico-chemical para-
meters (Table 1) could offer useful info rmation on: 1) the
understanding the regulatory requirements; 2) the effects
of contamination o f drinking water; 3) water quality, a nd
changes in quality; 4) source of contamination, contribu-
tions and contact pathways; 5) the efficiency of inspec-
tion processes [41].
6. Conclusions
Despite the ambition of the Millennium Development
Goals (MDGs), water supply and san itation are still wor-
ryingly deficient in many co untries of this world. Due to
Table 1. Microbiological and other physical and biochemical parameter o f safe drinking water.
Microbi o lo gi ca l Pa ramet er Sanitary
survey Source water
characterization Treatment
efficien cy Treated
water Distribution system
(re growth) Outbreak
Total coli f or m NR NR SA S S S
Thermotolerant coliform SA SA NR SA S S
Esch erichia coli S S S S N/A S
Faecal streptococci (enterococci) SA SA N/A N/A N/A S
Total Bacteria (microscopic) N/A N/A SA SA S S
Viable Bacteria(microscopic) N/A N/A SA SA S S
Aerobic spore forming bac t er i a N/A N/A S S N/A S
Sulphite Reducing Clostridia NR NR N/A N/A N/A S
Clostridium perfringens SA SA SA N/A N/A S
Enteric Virus S S N/A N/A N/A S
Cryptos poridi um Oocysts & Giardia cy s ts S S NR N/A N/A S
Pathogens S S N/A S N/A S
Physico -chemical Parameter
Colour/Odor N/A SA N/A S N/A S
pH N/A N/A S N/A N/A S
Turbidity S S N/A N/A S
Solids (Total/Dissolved) S S N/A N/A N/A S
Conductivity S S N/A N/A N/A S
Particle size analysis N/A N/A N/A S N/A S
Dis infec tant residual N/A N/A N/A S N/A S
Organi c matter (TOC, BOD, COD) S S N/A N/A S S
Ammonia S S N/A N/A N/A S
Boron, Chloramines compounds S S N/A S S S
Nitrate/Nitrite S S N/A S N/A S
Sulphide as (H2S) N/A S N/A S SA S
Man ganese, copper, zinc, iron N/A N/A S S
Metal (lead , Arsenic , chromium) S S N/A S S S
Other anions and cations N/A N/A N/A S N/A N/A
Key, S: suitable, S A: suitable alt ernative, NR: not recommended, N/A: not applicable.
Low-Cost Sustainable Technologies for the Production of Clean Drinking WaterA Review
the rapid increase in population, increased urbanization
and industrial activities, and absence of a strong regula-
tory framework, water quality in these countries is im-
paired due to the high levels of contamination. Because
of the challenge of providing safe drinking water from
poor quality water sources, development of low-cost
technologies should be considered in these countries.
A major problem that people in developing countries
are facing is the abundance of organic micro-pollutants in
natural water resources. An e xample of the c onse quenc es
of this for public health is an increased number of birth
defects, spontaneous abortion, cancers, and disturbances
of central and peripheral nervous system. Hence, the re-
search on low-cost drinking water treatment tech nologies
should not only focus on removal of contaminants to re-
duce waterborne diseases, but also on the removal of mi-
cro-pollutants to prevent dangerous chronic diseases (in-
cluding cancer) in large scale drinking water treatment
Concerning the selection of a suitable method for mi-
crobial examination, it should be observed that no tech-
nique that is 100% sensitive, 100% specific exists. All
methods have advantages and disadvantages. Now the
challenge is to decide the method that performs the most
of the characteristics of the ideal method for the users’
practical background. Advantages should be optimally
exploited and disadvantages should be recognized. Dif-
ferent users may choose appropriate alternative tech-
niques based on two criteria: 1) corresponding tests to
resources and 2) corresponding tests to applications.
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