WATER TREATMENT IN DEVELOPING COUNTRIES
Water contamination has been a serious public health concern all over the
world even in developed countries. According to the World Health
Organization (WHO), improvements in drinking water, sanitation,
hygiene, and water resource management may reduce the global disease
burden by 10% .
One of the Millennium Developed Goals is to decentralize drinking water
, making it available globally, therefore reducing the risk of health
complications and morbidity all across the globe. In developing
countries, the most common form of contamination comes from water
that has been stored in poor conditions , urging the need for better water
treatment technologies.
It is imperative to treat water for bacteria and other chemical/microbial
components that may compromise public health safety. Advanced and
affordable water treatment technologies are continue to be developed to
provide assistance to those who cannot afford clean water. Prevention
strategies such as treating water, educating guidelines for the safe storage
of drinking water, and practicing improved sanitation techniques, can
significantly reduce the risk of deadly waterborne diseases.
METHODS:
SODIS(Solar Disinfectation):SODIS is a simple and inexpensive
method that has been proven to be effective in removing pathogens and
bacteria in contaminated water. A study in Cameroon presented two-cross
sectional surveys and intervention regarding SODIS. Prior to the
intervention, diarrhea was found amongst 34.3% of children. After the
intervention, the risk of diarrhea was reduced by 42.5% . Another study
in Pakistan consisted of 24 experiments that used 1.5-liter Polyethylene
terephthalate (PET) bottles filled with water from water sources in
Karachi, Pakistan . In these experiments, it was shown that SODIS
reduced 100% of pathogens when used correctly.
Membrane filtration:A major advantage of membrane filtration is
that it is versatile. This water treatment can be produced and adapted to
filter out almost any substance ranging from pathogens, bacteria, arsenic,
and other harmful chemical pollutants . It also requires no chemicals,
little maintenance, and has a long lifespan . However, this is not always
suitable for use in developing countries due to costs. Most of the
available membranes in markets are relatively expensive in comparison
with other treatment options such as solar disinfection. However, many
researchers/scientists are working on creating the membranes for a
cheaper price. The other disadvantage of the membrane filtration systems
is that they can waste a lot of the water as brine which can be difficult to
get rid of .
Biosand filtration:Biosand is one of the simplest filtration systems to use
since it requires little knowledge to prepare/install/use. The only
requirements are to change the top layer of sand periodically and know
how to pour the water over the sand. The products needed for biosand
filtration can be made locally, at a low cost and they have a long life span
.The biosand filtration filters out not only pathogens such as bacteria and
protozoa, but can also filter out inorganic materials that can make water
turbid . About 81–100% of bacteria and protozoa are filtered out on
average . The major drawback to biosand filtration, is that it requires
constant maintenance since the sand must be replaced often. If the sand
on the top of the filter is not replaced, not only will the filtration be
ineffective, the water that is being filtered can become even more
contaminated .
Chlorination:Chlorination is presently a commonly used, effective
method for removing bacteria and viruses from drinking water. Numerous
studies have shown the complete removal of bacteria in drinking water. In
seven randomized, controlled trials, chlorination has resulted in
reductions of diarrheal disease incidence among users ranging from 22–
84%.It is very cheap method.A major drawback to this method is the risk
of potential long-term health issues, such as colorectal cancers , as well as
the lower disinfection effectiveness in turbid waters and the lower
protection against protozoa.
Arsenic treatment:In many part of the developing countries, arsenic
contamination is becoming a serious and emerging critical concern. One
of the technologies that is designed to remove arsenic from drinking
water, oxidation filtration, removes arsenic from iron and manganese
containing groundwater . This process requires less investment and has a
low operating cost which is why this technology is widely accepted by
developing countries . However, other technique such as precipitation/co-
precipitation, which are used to treat both drinking water and wastewater,
has a higher cost but is very effective at treating arsenic and other
pollutants . There are other low cost technologies such as ion exchange,
filtration, and adsorption, as well as bioremediation which require
training and education for proper maintenance and operations .
TESTS TO CHECK WATER QUALITY
Before the water is supplied to general masses it is checked that after
treatment it is within the standards as prescribed by The Bureau Of Indian
Standards(BIS) as prescribed under Indian Standard 10500:2012, which is
the specification for drinking water so far. Thus several tests are
conduccted on the treated water.Testing procedures and parameters may
be grouped into physical, chemical, bacteriological and microscopic
categories.
1) Physical tests:indicate properties detectable by the senses.Colour,
turbidity, total solids, dissolved solids, suspended solids, odour and taste
are recorded.
Colour in water may be caused by the presence of minerals such as iron
and manganese or by substances of vegetable origin such as algae and
weeds. Colour tests indicate the efficacy of the water treatment system.
Turbidity in water is because of suspended solids and colloidal matter. It
may be due to eroded soil caused by dredging or due to the growth of
micro-organisms. High turbidity makes filtration expensive. If sewage
solids are present, pathogens may be encased in the particles and escape
the action of chlorine during disinfection.Acceptable limit is 1.
Odour and taste are associated with the presence of living microscopic
organisms; or decaying organic matter including weeds, algae; or
industrial wastes containing ammonia, phenols, halogens,
hydrocarbons.While chlorination dilutes odour and taste caused by some
contaminants, it generates a foul odour itself when added to waters
polluted with detergents, algae and some other wastes.
2) Chemical tests:determine the amounts of mineral and organic
substances that affect water quality.
pH, hardness, presence of a selected group of chemical parameters,
biocides, highly toxic chemicals, and B.O.D are estimated.
PH is a measure of hydrogen ion concentration. It is an indicator of
relative acidity or alkalinity of water. Values of 9.5 and above indicate
high alkalinity while values of 3 and below indicate acidity. Low pH
values help in effective chlorination but cause problems with corrosion.
Values below 4 generally do not support living organisms in the marine
environment. Drinking water should have a pH between 6.5 and 8.5.
Harbour basin water can vary between 6 and 9.
B.O.D. It denotes the amount of oxygen needed by micro-organisms for
stabilization of decomposable organic matter under aerobic conditions.
High B.O.D. means that there is less of oxygen to support life and
indicates organic pollution.
3) Bacteriological tests:show the presence of bacteria, characteristic
of faecal pollution.
MANAGEMENT OF WASTE GENERATED FROM WATER
TREATMENT
Sewage sludge or waste sludge is a residual product from the
treatment of urban and industrial wastewater. Sludge, originating
from the waste water treatment process, is residue either moist or
mixed with a liquid component, generated during the primary, the
secondary and the tertiary treatment.
Routes for sludge disposal:
1)Landfilling:Organic matter decomposes in a landfill and is not
available for plant growth. In same time more organic matter in
landfill means more landfill gas produced. Landfill gas if not
captured and used, contribute considerably to the climate changes
effect. Leachate can contains several compounds such as ions, heavy
metals, organic compounds and micro-organisms .
2)Incineration:Different types of incineration may be considered as
sludge disposal routes: Mono-incineration, Incineration with other
wastes, Co-incineration when sludge is used as a fuel in plants whose
purpose is the generation of energy or production of material
products such as coal power plants or cement plants, Alternative
process: wet oxidation, pyrolisis, gasification, pyrolisis-gasification,
pyrolisis-combustion. It is an expensive disposal option for sludge
Problem of residues, which are about 30% of the input mass. They
may be regarded as hazardous waste – a cause of the contamination
by heavy metals When sludge is incinerated the organic matter is
decomposed mainly to carbon dioxide.
3)Using of sludge in agliculture(Landspreading): The agricultural sector
needs supply of nutrients and organic matter (humus) to compensate for losses through
harvest, grazing.Sewage sludge serves both purposes, primarily as a supplier of micro-
nutrients and organic matter but also as a supplier of nutrients such as nitrogen, potassium
and phosphorous. Sewage sludge contains compounds of agricultural value but it can also
contain pollutants. Compounds of agricultural value include organic matter, nitrogen,
phosphorus and potassium, and to a lesser extent, calcium, sulphur and magnesium.
TYPES OF WATER TREATMENT PLANTS
Contaminated wastewater can cause a major problem and incite panic
amongst residents in the area. That is why the presence of industrial
wastewater treatment plants that are effective and thorough is
essential. There are four ways in which a water treatment plant can
operate: Effluent Treatment, Sewage Treatment, Common and
Combined Effluent Treatments, and Activated Sludge Treatment.
1)Effluent Treatment Plant:Used by some leading companies in the
pharmaceutical and chemical industries, effluent treatment methods
are effective in the removal of non-toxic and toxic chemicals to
purify water. ETPs also aid in the protection of the environment and
is the home of wastewater management and industrial effluents.This
treatment method removes both toxic and non-toxic materials, dirt,
debris, pollution, grit and polymers from the drugs. As ETPs are
essential in the removal of any and all pollution, this treatment
system is also installed to reduce the overall chance of pollution.
2)Sewage Treatment Plant:The process of removing contaminants
from household sewage water is referred to as domestic wastewater
treatment. To do this, the process utilizes physical, chemical, and
biological methods to remove both physical and biological
contaminants from the water. This aids in producing a waste stream
that can be reused in the environment. Doing a pre-treatment process
will help in removing additional materials found in the raw
wastewater. The process of straining the sewage water to remove
objects from the system itself results in clean water that’s safe to
consume and use in both homes and businesses.
3)Common and Combined Effluent Treatment Plants:Some
smaller-scale industries are unable to accommodate treatment
systems, which is where both common and combined effluent
treatment plants come in. A CETP is usually placed in the areas that
house small-scale industrial units. The main goal of a CETP is to
lower the cost of the treatments for smaller industries that are
individually owned. Both common and combined effluent treatment
plants help in regard to wastewater management without having the
need to spend a large amount of money.
4)Activated Sludge Plant:This plant type incorporates a similar method
to that of a sewage treatment plant. An activated sludge treatment plant
needs to be maintained on a regular basis in order to prolong its lifespan.
Doing so will not only extend the plant’s life but it will also ensure that
the water within is being treated properly and safely. Examples of the
methods used in ASP include conder ASP, biopure, diamond vortex,
bison, crystal eco and biodigester.
