In case of
chlorinated water there should not be C. aerogenes
at all and round the year it should fall to quality class 1.
Serious pollution is frequently heralded by intermediate
aerogenes cloacae types and their appearance should call
immediate investigation of source. Untreated deep well
supplies of those from other pure sources should fall
normally to class 1 and drop even to class 2 should call
fall immediate attention.
The earthy
taste in water is due to the presence of Actinomyces
and other moulds and their spores. If they are removed even
then the smell is present and some time it is due to the
mould growth on tape end. They are not detectable by
ordinary bacterial examination. For this purpose sample is
inoculated on to nutrient agar and Krainsky’s glucose
aspargin agar and incubated at 30 °C for 2 wks. Colonies
will appear as small circular, entire flat plaques very
adherent. Colonies may be colored and sporulation is shown
in white, gray and yellow powder on the colonies.
Sulphur
bactaria Beggiata and Thiothrax and iron
bacteria Leptothrix ochracea, Gallionella
ferruginea and Crenothrix poly spora should not
be present at all. Sulphur bacteria produces musty odor
while iron bacteria produces slimy reddish brown deposits.
Apart from
above given bacteria, the pathogens should not be present in
water.
IMPURITIES IN WATER
In addition
to minerals and metals which lower the quality of water and
render it unfit for drinking and other uses, there are some
bacteria as well which deteriorate the water quality.
Bacteria present in the water may be categorized as under:
A.
Natural water bacteria which
include Chromogenic and non-chromogenic bacteria,
fluorescent bacteria and cocci, etc. Some of these bacteria
are incapable of growth on ordinary laboratory media.
B.
Bacteria from soil which
include sporing and non-sporing organisms.
C.
Bacteria from sewage and animal
excrement which may include disease producing type i.e.
typhoid and paratyphoid bacteria, food poisoning and
dysentery types; putrefactive organisms, e.g. proteus type
and an-aerobic spore bearing bacilli; intestinal bacteria
such as the coli erogenous group, the fecal streptococci and
anaerobic spore bearing bacilli.
EVALUATION OF WATER QUALITY
Water
quality may be evaluated in following systematical
proceedings including physical, chemical, bacteriological or
biological analyses.
A.
Physical Test
i.
Temperature:
Temperature
measurement in most instances is very simple. An accurately
calibrated thermometer graduated into 0.1°C, with a range of
0-50 °C is adequate for this purpose. In case of large water
bodies, where reading at particular depth is required a
“broken capillary” thermometer is used. Thermometer is
reversed at the depth concerned, the capillary breaks and
reading then remains unchanged.
ii. Color:
Color is measured against various standards of which the
Hazen or Platinic chloride scale is prescribed in
American Public Health Association’s Standard Methods.
The basis for the scale being parts per million (ppm) of
platinum.
Water from
upland gathering grounds, which carry beds of peat values
150-200 Hazen. Extracts from vegetable debris and soil
results in lesser degree of color, sewage effluent
contribute to the coloration of streams and rivers. Unless
an underground source is suffering from a sensible degree of
pollution by surface water, yellow brown color is entirely
absent. For drinking, color showed is between 100-150 Hazen
or even less.
iii.
Turbidity:
Turbidity is estimated against standard suspensions of a
siliceous material such as foller’s earth, the silica scale
being based on standardization by photometric means. The
exact values are measured when metals are suspended but in
case of bacterial contamination, coloring is best technique.
The turbidity of those supplies conforming to the highest
standard of clarity never exceeds 1 or 2 ppm a turbidity of
5 is appreciable and 10 can be regarded as decidedly
objectionable.
iv.
Suspended Solids:
When
turbidity is above 100 ppm; a gravimetric estimation may be
necessary to indicate more clearly the quantity of matters
in suspension. Microscopic and microchemical analysis may be
applied as well.
v. Tastes
and Odors:
Taste and
odor have no numerical values because of variation from
person to person. It has got a “thresh-hold” beyond which it
is not useable. Water which is chlorinated produces
particular taste and odor due action with organic compound
because as such chlorine has no taste and odor.
Uncontaminated water from natural sources is not prone to
taste or odor apart from bitter, astringent flavor of
ferruginous supply and apart from some reduced or
deoxygenated waters drawn from beneath impervious strata or
from clay sand layers when an odor of sulphuretted hydrogen
may occur.
vi. pH
Value:
The pH of water is 7.0, which is neutral. It is
measured by pigmentation or pH meters. In natural water pH
ranges from 6.8 to 8.3.
vii.
Electrical Conductivity:
Electrical
conductivity is measured in terms of reciprocal megohms/cm3
at 20ºC. Electrical conductivity is a measure of salt
dissolved in water like that of pH.
B. Chemical
Tests
Organic
Tests
i.
Ammonical Nitrogen:
Ammonia in water is present in a free form
and as such it is not an impurity. But when it acts with Cl2
then it reduces the lateral strength to form bactericidal
effects in chloramination of water. In laboratories it is
measured by distillation of mildly alkalized water, the
ammonia in distillate being measured from the coloration
produced with Nessler’s reagent.
ii.
Nitrate and Nitrite:
Reduction of nitrate produces nitrite and
nitrate is a product of oxidation process of Nitrogen
compounds. At one hand it determines the amount of organic
matter in water and purity and bacteria present on the other
hand. In normal water they must be under 15 to 30 ppm. A
high nitrated water say 150 ppm, produces toxic effect for
babies fed on the dried milk which is reconstituted before
use. Nitrite is measured by the Griess Ilosvay method and
nitrate by Devarda’s alloy method by color matching.
iii.
Biochemical Oxygen Demand (BOD):
BOD of water is that depletion of oxygen in
solution brought about in the breaking down of organic
matter by aerobic bacteria. They give a better visualization
of organic matter in water. Standard BOD for good water is 1
ppm and for satisfactory 2 ppm beyond this limits it is not
useable for drinking.
Inorganic
Tests
i.
Alkalinity:
Bicarbonate salts of Ca, Mg and Na together
constitute alkalinity in water. The CaHCO3 form
the temporary hard water. In natural water it may range from
200 to 400 ppm, depending upon source. Alkalinity is
measured by simple acidimetric methods employing indicator
such as methyl orange and phenolphthalein. Calcium and
magnesium salts other than carbonates and bicarbonates such
as sulphate and nitrate form the hardness in water. Hard
water destroys the soap and this is used as a crude
technique to measure these salts.
ii.
Chloride; Sulphates;
Silica; Phosphate and Total Solids:
Rain water and oceanic water contains
chloride upto 5 ppm but streams, rivers and underground
water contains from 10 to 20 ppm. This is the standard for
drinking and 100 ppm indicates the pollution in water.
Chloride is measured by titration with standard silver
nitrate solution using potassium chromate as an indicator.
The quantities of sulphates are considered to be similar to
chloride in standard requirement and quantity in different
waters. Sulphates are determined by gravimetric estimations
following precipitation as barium-sulphate.
Amount of
silica present may vary from 10 to 30 ppm as SiO2.
Silica is determined by matching the color of the molybdate
complex or by gravimetric estimation. Phosphate in natural
waters occurs to the extent of parts per 10 million. For
useable quality it must be at 1 ppm level. Orthophosphate
can be measured by matching the blue complex, which is
produced from phosphomolybdate on addition of reducing agent
i.e. stannous chloride. Total solids are measured by drying
at 180 °C the water.
iii.
Na, K, Fe, Cu, Pb and F:
Sodium and potassium are no more danger to
the water quality. They are measured by gravimetric method.
Iron occurs
as Ferrous Carbonate. Its appreciable amount causes bitter
taste and help to grow the Iron bacteria in water. It must
be under 0.2 to 0.3 ppm in normal water. It is estimated by
simple calorimetric procedure with the thiocyanate. Copper
is also measured by this method by using rubanic acid.
Lead must be
less than 0.1 ppm in drinking water as it is heavily toxic
metal. It is estimated by new organic reagent procedure.
Flourine
upto 1.5 ppm is useful for dental caries. Fluorine is
estimated by matching the fading produced in a lake between
zirconium and alizarin.
C.Bacteriological Tests
The purpose
of the bacteriological tests is as fellow:
·
To determine the degree of excremental
pollution in new and old sources of supply.
·
To assess a treatment for use.
·
To ascertain the efficiency of purification
at various stages.
·
To locate the cause of immediate
contamination.
·
To ensure the final quality of distribution.
For the
bacterial count and assessment following test are conducted.
i. Coli-aerogenes
Test:
Among the
many methods used, plating is convenient and quicker one.
The presumptive culture is plated out on Maconkey agar or
eosins methylene blue agar and incubated at 37 °C in order
to obtain single, discrete and pure colonies. For further
differential test following five tests are conducted.
i). Acid
and gas Maconkey broth or brilliant green bile broth at
44°C.
ii). Test
for production of indole in a peptone water culture at 37°C.
iii). Methyl
red test carried out in glucose phosphate incubated at 30°C.
iv). Citrate
utilization test in Koser’s medium at 37°C.
v).
Production of acid and gas in lactose peptone water at 37°C.
ii.
Clostridium Welchii Test:
Among
different methods used, one easy to conduct and quick one
is, sulphite reduction test based on the fact that C.
Welchii produces a colony with a conspicuous black zone
of iron sulphide when grown on agar containing glucose,
sodium sulphite and iron. In order to destroy non-sporing
organisms the water should be heated to 80 °C for 10 minutes
before mixing with molten medium. The plate should be
incubated at 44 °C for 48 hrs. The C. Welchii appear
as large black area 3 to 5 mm or more in diameter with
irregular edges. This chemical reduction soon fades,
revealing an opaque colony in center.
iii.
Faecal Streptococcus Test:
For this
widely practiced test is Tellurite method. Strepto-cocci
will grow in fecal origin, a concentration of potassium
tellurite, which is inhibitory gram –ve and C. aerogenes
strains. A volume is incubated at 37 °C and positive tubes
indicate blackening of medium which is further confirmed by
microscopic examination, fermentation and heat resistance
tests.
iv.
Biological Test:
Biological
tests are conducted to evaluate the water quality for algae,
protozoa, protifera and polyzoa, etc. There are essentially
two methods by which plankton organisms can be counted under
the microscope. In one type of the method the organism are
counted direct in a drop of sample under standardized
conditions. The alternative is to separate the plankton from
a known volume of water and perform the count on this
concentrate. In this case, far fewer fields of view needs to
be examined than with a direct examination and by suitable
concentration it is possible to count the plankton even when
very few organisms are present.
TREATMENT OF WATER FOR QUALITY
To render
water consumable for human and livestock following
treatments are recommended.
A.
Water Softening
To make
water consummated its calcium, magnesium, bicarbonates,
sulphate and chlorides are essentially to be removed first.
For this purpose following two methods are widely used.
i).
Clark’s
Method:
On a large scale it is used to remove temporary hardness of
water for this purpose Ca(OH)2 is added.
ii).
Ion Exchange Method:
This method
is applied for softening permanent as well as temporary hard
water. For this purpose sodium zeolite is used. By passing
concentrated NaCl from Ca-Zeolite, Na2-Zeolite is
regained. The reaction, which occurs, is as follow:
Ca2+
+ Na2-Zeolite
Ca-Zeolite
+ 2Na+
Ca+2-Zeolite
+ 2NaCl Na2+-Zeolite + CaCl2
B.
Control of Biologics
Growth of
Plankton and Algae in river water is seasonal so it is
useless to have the storage. Plankton growth can be
controlled by using algicide which include cupper sulphate
and chlorine.
i.
Cupper Sulphate:
Depending upon the degree of Biologics development, CuSO4
can be sprayed under pressure varying from 0.1 to 5 ppm. It
is advisable to give first treatment of 0.5 ppm and repeated
after a day with 1.0 to 2.0 ppm, if no effect has been
produced.
ii.
Chlorine: Chlorine is applied prior to the addition
of water to the reservoir. It is used from 5 to 10 ppm.
C.
Bacterial Control
Reduction in
organic matter by oxidation and reduction in hardness occurs
as a result of algal action. To control the bacteria
following two procedures are applied.
i.
Chlorination:
Chlorination
is described earlier and chlorination stages include: Simple
chlorination; Ammaria chlorine treatment (Chloramination);
Super chlorination, Dechlorination and Break point
chlorination.
ii.
Ozonization:
It is done with O3, which is produced from
passage of high voltage current from air. The O3
is very unstable and react with oxidizing agent which
produces sterilization effect. If we compare chlorination
with ozonization then it is as:
Chlorination
is simple but ozonization requires a complex procedure and
apparatus. But it is over ruled when it gives the advantage
of odorless and tasteless water. The residium of chlorine in
water supplies give advantage of combating accidental
contamination which is not possible in case of ozone. There
is a maintenance expenses for ozone plant but not in case of
chlorine. Finally the cost is high in case ozone but
negligible in case of chlorine.
D.
Pollution Control
Every source
of pollution must be avoided to contaminate water. Few
scientists have mentioned the measures that includes are
such as (i) Avoid the water plant installations at public
places. (ii) Afforestation should be done to avoid the soil
source of contamination. For this purpose conifer trees
should be planted. (iii) Care should be paid to the proper
disposal of the sewerage water so that it can’t contaminate
water in pipe supply and at large scale as well.
EPILOGUE
The problem
is not the supply of water; earth has virtually the same
amount of water today as it did when dinosaurs roamed the
planet. The problem is simply people – or increasing numbers
and or flagrant abuse of one of or most precious, and
limited, resources. It is upto us that we need to use the
water resource judiciously, stop polluting this resource,
follow the hygienic standards to maintain its quality and
purity, follow measures to reduce the further degradation of
the environment leading to water pollution and above all to
conserve this vital resource for our coming generations.