Water quality: Water in pure form is not found in nature. It is a best solvent and attract

a lot of impurities. Rain water is assumed to be pure, even water vapor condensing in

the air Contains solids, dissolved gases and salts. As it touch surface, percolating into

the soil or runoff occurs, some contaminants may be removed while new one will be

added. The materials found in water are living organisms, solids, dissolved organic

and inorganic. Some of these are harmless and desired for health while others are

harmful. Drinking water or potable water is water of sufficiently high quality that it can

be used without risk of immediate or for long term safe for drinking , pleasant in taste

and suitable for domestic use. Such water may be unsuitable for some industrial use.

Contaminated or Polluted water is one which contains suspended or dissolved

materials which makes it unsuitable for its intended use. Two types of criteria is used

for for drinking water quality. One is the World health Organization Guidelines and

another is the Standards adopted a number of countries.

World Health Organization Guidelines: These are the guidelines related to human

health and is advisable for developing as well as for developed counties for adaptation.

There is no compulsion for a country either to adopt it or not. It help member countries

of WHO to adopt it and provide safe water to community.

Standards : A number of countries developed their own criteria for drinking water.

This criteria is termed as standards. In these standards some are adoptable by the

agency providing water and other are advisable.

Drinking water standards are of two categories. Primary standards and Secondary

standards

Primary Standards: The standards which are enforceable by Govt. Agency for protection

of human health are known as primary standards. These standards specify the Maximum

Contaminants Levels (MCLs) based on health related criteria for drinking water . In setting

the MCLs the authorized agency is to balance the public health benefits of the standards

against the technology available and economically feasible. The water supply authorities

who violate these standards are to face punishment. e.g. Arsenic 0.05 mg/L; Mercury

0.002 mg/L; Beryllium 0.001 mg/L

• Secondary Standards. These standards are unenforceable guidelines based on aesthetic

like color, taste and odor for drinking water. It is up to the water supply agency either to

adopt it or not. Such sets of unenforceable levels are known as Maximum Contaminant

Level Goals (MCLGs). These goals are set at levels that present no known health

effects, including a margin of safety , regardless of technological feasibility or cost. Like;

Arsenic 0 mg/L; Mercury 0.002 mg/L; Beryllium 0. mg/L

Drinking Water Standards of US EPAPrimary Standards MCL (maximum contaminant level)

Contaminant Limit• Total coliforms (av. Number/ 100 mL) 1

• Total coliforms (max number/ 100 mL) 5• Turbidity (ntu) 1-5

• Inorganic chemicals (mg/L)• Arsenic 0.05• Cadmium 1.0• Chromium 0.01• Fluoride 0.07-

2.4• Lead 0.05• Mercury 0.002• Nitrate (as N) 10.00 • Selenium 0.01• Silver 0.05• Radionuclides (pCi/L)• Gross alpha 15• Ra-226 + Ra-228 5• Gross beta 50 • H-3

20,000• Sr-90 8• Organic Chemicals (µg/L)• Endrin 0.2• Lindane 40• Methoxychlor 100• Toxaphene 5

Contaminant Limit• 2,4_D 100• 2,4,5-TP 10• Trihalonethanes 100 • Benzene 0.05• Carbon trtrachloride 0.05• 1,2 Dichloroethane 0.05• Trichloroethylene 0.05• Para-dichlorobenzene 0.75• 1,1 Dichloroethylene 0.07• 1,1,1 Trichloroethane 2.0• Vinyl chloride 0.02

• Secondary Standards RCL (recommended contaminant level)

• Contaminant Limit• Chloride 250 mg/L• Color 15 units• Copper 1 mg/L• Iron 0.3 mg/L• Manganese 0.05 mg/L• Odor 3 TON• pH 6.5-8.5• Sulfate 250 mg/L• Total Dissolved Solids 500 mg/L• Zinc 5 mg/L

• Monitoring: water supply schemes are required to provide safe drinking water to community.

There are standards and guidelines established by various countries/organizations that

guarantee provision of safe water free of contaminants that have negative health effect when

using such water. To minimize negative impact of impurity in drinking water regular sampling and

analyzing of water quality is essential. The purpose of water quality monitoring is to check the

physical, chemical and biological characteristics either they are suitable for intended purposes

like drinking, swimming, irrigation ,industrial purposes or not. To regular analyze samples of

water from different sources like surface or ground water and compared it with available

standards are known water quality monitoring. Monitoring is essential for continuous record for

department. If there is any contaminant or a group of contaminants present in drinking water

then mitigation measures are required to eradicate or minimize these contaminants. A regular

monitoring is required to check that water supply system meets public health standards or not.

Monitoring requirements vary for the following reasons.

• (i) Regulations of a country drinking water agencies specify samples locations and acceptable analytical

methods. (ii) Identify whether the quality of water is fulfilled the requirements used for intended purpose or

not. (iii) The frequency of monitoring for a contaminant may vary based on the type of water source. (iv)

Surface water system need monitoring more frequently than ground water because of the occurrence of

contaminants are more variable over time.(v) characterize waters and identify changes or trends in water

quality over time (vi) identify specific existing or emerging water quality problems. The source of water if

do not detect or detect at low levels can monitor less frequently.

Physical, Chemical and Biological Quality/Characteristics of water/ wastewaterSuspended: 1.0 – 100 μ; colloidal 100-3μ -1 μ : Dissolved 10-3 μ – 10-5 μ

Physical characteristics: Physical characteristics are those characteristics that respond to the

senses of sight, touch , smell or taste. Suspended solids, turbidity, color, taste and odor and

temperature are physical characteristics.

Suspended Solids: Solids suspended in water consists of inorganic or organic particles or of

immiscible liquids. Inorganic solids like clay, silt and other soil constituents are common in surface

water. Organic materials like plant fibers and biological solids (bacteria, algal cells etc) are common

constituents of surface water. These materials are often natural contaminants resulting from the

erosive action of water flowing over surfaces. Other suspended materials may result from human use

of water. Domestic wastewater usually contains large quantities of suspended solids. Industrial use of

water may result variety of suspended impurities of organic and inorganic nature. Immiscible liquids

like grease, oil are often found in wastewater.

Impacts: Suspended materials are objectionable in water. It is aesthically displeasing and provides

adsorption sites for chemical and biological impurities. Some of the Suspended organics may be

degraded biologically, resulting in objectionable byproduct. Biologically active suspended solids may

include pathogenic microorganisms.

Use: suspended solids parameter is used to measure the quality of wastewater influents, to monitor

several treatment processes, and to measure the quality of the effluents. EPA standards are 30 mg/l .

Turbidity

Turbidity is a measure of the extent to which light is either absorbed or scattered by suspended

particles in water. As the adsorption and scattering processes are influenced by size and surface

characteristics of the suspended materials, turbidity is not a direct quantitative measurement of

suspended solids. Turbidity in surface water result from the erosion of colloidal material like clay,

silt, rock fragments, vegetable fibers, soap, detergents, household and industrial activities and

microorganisms.

Impacts: The colloidal particles and biological organisms associated with turbidity provides sites

for adsorption of chemicals that may be harmful or cause undesirable taste and odors.

Disinfection of turbid water is difficult because of the adsorptive characteristics of some colloids

as well as provide shield to organisms from the disinfectants.

In natural water bodies, turbidity interfere with light penetration. Also the turbid particles

accumulation in porous streams result in sediment deposit that adversely affect the flora (plant)

and fauna (animal) present in the streams.

Unit: Nephelometry turbidity units (NTU) or Formazin turbidity unit (FTU) are used. According to

EPA drinking water MCL is 1.0 FTU.

Color

Pure water is colorless, but water in nature is often colored by foreign substances. Water whose

color

is due to suspended matter is known as apparent color, while due to dissolved particles is true color.

Sources: Water picks up tannins and humic acid from organic matter like plant leaves, weed or wood

Caused yellowish-brown hues. Iron oxides cause reddish water and manganese oxides cause brown

or blackish water. Industrial waste from textile and dyeing operations pulp and paper production, food

processing, chemical production and mining, refining and slaughter house operations may add

substantial colors to water in receiving steams.

Impacts: Colored water is not aesthetically acceptable to the general public. Consumers tend to

choose clean, non colored water of poor quality over treated \potable water supplies with an

objectionable color. Highly colored water is unsuitable for laundering, dyeing, paper making,,

beverage

and dairy production. Thus color of water affects the organic compound causing true color exert

chlorine demand and thereby seriously reduce the effectiveness of chlorine as disinfectant. Some

compounds of naturally occurring organic acids and chlorine formed Trihalomethanes (THMs)

carcinogenic in nature.

Taste and odor and TemperatureA number of substances with which water comes into contact in nature or during human use may

impart taste and odor. These includes minerals, metals and salts from the soil, end products from

biological reactions, and constituents of wastewater. Inorganic materials produce taste Without

odor. Alkaline materials imparts a bitter taste to water, while metallic salts give a salty taste.

Organic material, produce both taste and odor. Biological decomposition of organics may also

result in taste and odor producing liquids and gases in water.

Impacts: Taste and odor are displeasing for various reasons, as water is to be tasteless and

odorless. Consumer prefer to use tasteless, odorless water that might pose more health threat.

Temperature: It is one of the most important parameter in natural surface water system. Water

temperature plays an important role in biological species present and their rate of activity.

Temperature has an effect on most chemical reactions that occur in natural water system. It also

have a pronounced effect on the solubility of gases.

Sources: The temperature of natural water bodies response to many factors, the ambient

temperature being the most effective one. Generally, shallow water bodies are more affected by

ambient temperatures than the deeper bodies. The use of water industries for dissipation of waste

heat and discharge of the heated water to receiving water bodies increase the temperature.

Impacts: At lower temperature the biological activity like utilization of food supplies, growth

reproduction etc. is slower. If temperature is increased biological activity also increase. The

viscosity of water increase with decreasing temperature. Max. density of water occurs at 40C.

Chemical characteristics of waterChemical parameters are related to the solvent capabilities of water. Total Dissolved Solids (TDS)

alkalinity, pH, hardness, Organic and inorganic dissolved impurities are the chemical characteristics.

TDS: The materials left in water after filtration for the suspended solids are dissolved

solids. This materials are left as a solid residue upon evaporation of the water. TDS is expressed in

mg/ l. The organic fraction can be measured by heating the TDS at 550± 50 C0. The organic residues

will be evaporated while inorganic residues will be converted into ashes. TDS = Organic + inorganic

thus organic residues = TDS - inorganic

Sources: Dissolved solids result from solvent action of water on solids., liquid and gases. Dissolved

solids may be either organic like decay products of vegetation, from chemicals and from organic

gases. The inorganic dissolved in water are minerals, metals and gases which come in contact with

these substances in atmosphere on surface and within the soil. Materials from decay products of

vegetation, chemicals and gases are organic sources.

Impacts:- Dissolved minerals, gases and organic constituents may be producing displeasing color,

taste and odor. Some chemicals may be toxic and carcinogenic.

Alkalinity: Alkalinity is the quantity of ions that will react to neutralize hydrogen ions. Thus it is a

measure of the ability of water to neutralize acids.

Sources: The major constituents of alkalinity are hydroxyl (OH -), Carbonate (CO3 ) and bicarbonate

(HCO3 ). These compounds result from the dissolution mineral substances in the soil and

atmosphere.

Inorganic and organic contaminants

Inorganic contaminants: The sources of trace metals associated with the natural processes of

chemical

Weathering, soil leaching and with human activities like mining and manufacturing processes.

These materials are generally toxic. Arsenic a by product of copper and lead smelting, also a

component

of some agricultural insecticides, present widely distributed in water at low concentration. Arsenic is a

well known poison, carcinogenic in nature and can be fatal in high doses . Cadmium a metal toxic

released to atmosphere from industries of battery producers and electroplaters. Cadmium is taken up at

all levels of food chain from microorganisms to humans. Human consumption of leafy vegetables, fish,

and drinking water is the usual method by which cadmium enter our bodies. Its effect on human bodies

are in form of lungs, kidney problems and joint pains. It is possibly a carcinogenic. Fluoride is the

naturally occurring form of fluorine, found in soil and rocks. Low concentration of fluoride caused dental

caries in children ‘s teeth. The optimum dose makes teeth more resistant to decay, at high concentration

cause fluorosis (discoloration) and loss of teeth. Lead and mercury are associated with chronic effects

on nervous system. Nitrate can interfere with oxygen transfer in the blood of Infants and caused

Methemoglobinemia or blue baby disease. Selenium a trace metal naturally occurring in soils derived

from sedimentary rocks. Surface water and ground water having variable concentration of selenium. It

can produce gastrointestinal and dental problems, while silver is toxic in high dose.

Short duration problem is acute, longer is chronic and change of tissues are carcinogenic

Alkalinity

In addition to their mineral origin, these substances can originate from CO 2 present in atmosphere and

microbial decomposition of organic materials. The reaction are

CO2 + H2O ↔ H2 CO3 (i) H2 CO3 ↔ H+ +HCO3 (ii) (bicarbonate) HCO3 ↔ H+ +CO3 (iii) (carbonate)

CO3 + H2O ↔ HCO3 + OH- (iv) (hydroxyl or hydroxide)

The relative quantities of each are a function oh pH. Hydroxyl ion concentration are significant

at pH≥ 10, the carbonate concentration below 8.3 are not significant. The bicarbonate concentration

are usually in the range of pH values of 4.5 to 8.3.pH : pH is a measure of the free hydrogen ion (H+) concentration in water. Water and other chemicals in solution will ionized to a greater or lesser degree. The ionization reaction of water may be written

as HOH ↔ H+ + OH- .The concentration of H and OH can be written as [H][OH] = Kw = 10-14 at 20 C0

Taking log of both sides Log [H] + Log [OH] = -14 let ( – log )= p then pH + pOH = 14. pH= -log[H+]. In neutral condition [H] = [OH] ; hence pH = pOH = 7. Thus pH is the negative logarithm of hydrogen ion concentration. Increasing acidity leads to higher values of [H]; thus to lower values of pH. Low pH is associated with acidity, high pH with causticity (alkalinity). Acceptable value for drinking water is 6.5 to8.5

pH( Hydrogen ion concentration)1----------------------------7------------------------14 Acidic Basic

• Signifance:- chemical coagulation disinfection water softening corrosion control

Hardness

The concentration of multivalent metallic cations (Ca2 +, Mn2+, Sr2 +, Al3 + ) in solution is hardness. The

common anions are bicarbonate (HCO3, carbonate (CO3 ), Chloride (Cl - ), sulfate (SO4) and NO3)

Hardness caused to prevents leathering (foam) still water becomes soft. Ground water usually have

more hardness as compared to surface water. It is not necessary to remove hardness of water for

drinking purposes, but for industrial utilization hardness removal is essential, because the hard water

are likely to cause Scaling trouble in boilers and in hot water pipes. The other impacts are the

precipitates formed by hard water adhere to the surfaces of tub, sink, dishwasher and other

containers. Types of Hardness: Two types of hardness are Temporary and Permanent Hardness.

Temporary Hardness:- If HCO3, and CO3 of Ca and Mg are present in water, such hardness is

Carbonate or temporary hardness. It can be removed by boiling of water.

Permanent Hardness:-The presence of sulphate, chloride and nitrates of calcium and magnesium is

Permanent or non-carbonate hardness. It cannot be removed by boiling of water. Some chemicals

like

lime soda or activated carbon or ion exchange process can be used to remove permanent hardness.

Generally surface water softer than G.W.

Soft water = 0-75 mg/L as calcium carbonate; Moderately Hard = 75 -100 mg/L as CaCO 3.

Hard water 100 - 300 mg/L asCaCO3 and very hard water >300 mg/l as CaCO3.

The maximum recommended standard for drinking water is 500 mg / l

Natural Process of Hardness

. In natural process as rain water enters the

top soil, the respiration of

microorganisms increases the CO2

content of the water. The CO2 reacts

with water to form carbonic acid

(H2CO3).The lime stone (CaCO3 and

Mg CO3) reacts with carbonic acid

forming calcium carbonate [Ca(HCO3)2]

and magnesium bicarbonate

[Mg(HCO3)2]. The Calcium and

Magnesium carbonate are insoluble in

water , while bicarbonate are soluble in

water causing hardness in water.

Similarly the Gypsum (CaSO4 ) and Mg

SO4 may also cause hardness of water

present in subsoil layers.

Top soil Bacterial Action CO2

Sub soil CO2 + H2O H2CO3

Lime stone CaCO3(s)+ H2CO3 Ca (HCO3)2

MgCO3 (s) + H2CO3 Mg (HCO3)2

Rain

Inorganic contaminants

Inorganic contaminants: The sources of trace metals associated with the natural processes of

chemical

Weathering, soil leaching and with human activities like mining and manufacturing processes.

These materials are generally toxic. Arsenic a by product of copper and lead smelting, also a

component

of some agricultural insecticides, present widely distributed in water at low concentration. Arsenic is a

well known poison, carcinogenic in nature and can be fatal in high doses . Cadmium a metal toxic

released to atmosphere from industries of battery producers and electroplaters. Cadmium is taken up at

all levels of food chain from microorganisms to humans. Human consumption of leafy vegetables, fish,

and drinking water is the usual method by which cadmium enter our bodies. Its effect on human bodies

are in form of lungs, kidney problems and joint pains. It is possibly a carcinogenic. Fluoride is the

naturally occurring form of fluorine, found in soil and rocks. Low concentration of fluoride caused dental

caries in children ‘s teeth. The optimum dose makes teeth more resistant to decay, at high concentration

cause fluorosis (discoloration) and loss of teeth. Lead and mercury are associated with chronic effects

on nervous system. Nitrate can interfere with oxygen transfer in the blood of Infants and caused

Methemoglobinemia or blue baby disease. Selenium a trace metal naturally occurring in soils derived

from sedimentary rocks. Surface water and ground water having variable concentration of selenium. It

can produce gastrointestinal and dental problems, while silver is toxic in high dose.

Short duration problem is acute, longer is chronic and change of tissues are carcinogenic

Organic Contaminants

• Organic impurity in water may be either natural or synthetic. Natural contaminants are usually

caused color, taste and odor, while synthetic are considered as a potential threat to living

organisms including human itself. The organic materials present in water may be changed by

treatment processes, and become dangerous or unpleasant. The three groups of organic

contaminants are;

• Chlorinated Hydrocarbons (Synthetic Organic Chemicals (SOCs)). SOCs are compounds used

in the manufacture of a wide variety of agricultural and industrial products. They include

pesticides and herbicides. These organic materials are persistent both in nature and within

human body. The common example of these SOCs are endrin, lindane, methoxychlor and

toxaphene as insecticides, while 2, 4-D, and 2, 4, 5-TP are herbicides. Lab. test shown its

carcinogenic effect.

• Volatile Organic Chemicals (VOCs): These are synthetic chemicals that readily vaporize at room

temperature. These include degreasing agents, paints thinners, glues, dye, benzene, carbon

tetrachloride, and vinyl chloride etc. These chemicals are widely distributed in water. These

chemicals are expected to be carcinogenic in nature.

• Trihalomethanes (THMs): These are the byproduct of water chlorination process or enter in water

from industrial processes. When natural organic substances from decay vegetation, like humic

acid and fulvic acid are treated with chlorine, bromine or iodine THMs are resulted. They include

chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromodichloromethane(CHBr2Cl), and

Bromoform CHBr3). THMs are carcinogenic in nature and their presence in drinking water is

undesirable.

Biological Bacteriological water Quality

Aquatic organisms range in size from smallest single-cell microorganism to largest fish. All these biological

community are the water quality parameters upto certain extent, A water body having large number of aquatic

species indicate good quality, while less number show low quality. Some organisms can be used as an indicator of

the presence of pollutants like; Pathogens: A Pathogen is an agent that cause infection in a living host. These

organisms are not native to aquatic system and usually require an animal host for growth and reproduction. It can

be transported by water system and reach to human/animal causing disease. It capable of infecting or transmitting

disease to human known as water borne disease. Following are the water borne Pathogen.

Bacteria: Bacteria is a single cell microorganism, found in water, wastewater, soil, air and milk. Bacteria are

reproduce by binary fission and are characterized by their shape, size and structure. The common shape of

bacteria

are spherical (cocci), singular (coccus) and cylindrical or rodlike (bacilli).Most bacteria range in size from 0.5 to

5.0 μm long and 0.3 – 1.5 μm wide. The Cocci is about 0.1 μm in diameter.

Viruses. The smallest biological structure that can be seen only by electron microscope. Its size range from 10 to

250 nm. Viruses are unique in that they contain no internal enzymes and therefore can not grow or metabolize on

their own. They are obligate parasites, infecting the tissues of bacteria, plants and animals, including human

beings. Example of of pathogenic viruses are small fox, infectitis hepatitis and influenza. Viruses are not survive

out side the host. Their reproduction or replicate take place within their specific host cells.

Protozoa. Protozoa may be pathogenic or non pathogenic. It is a complete self-contained organisms that can be

free living, or parasitic organism. Protozoa are widely distributed in natural water. Protozoa infections are usually

gastrointestinal disorder of mild order.