Environmental

Chemistry
Introduction

 Chemistry is the study of the properties and behavior of matter.

Matter is the physical material of the universe; it is anything that has
mass and occupies space.
 Chemistry is often at the heart of environmental issues. The
economic growth of both developed and developing nations
depends critically on chemical processes that range from treatment
of water supplies to industrial processes.
Conventional water treatment
Introduction

Environmental chemistry is an interdisciplinary science that includes

chemistry of the air, water, and soil. Although it may be confused with
green chemistry, which deals with potential pollution reduction,
environmental chemistry is the scientific study of the chemical and
biochemical principles that occur in nature.
Water sources, impurities of water
and chemistry
 Industry is a small participant in the global
water cycle .The finite amount of water on
the planet participates in a very
complicated recycling scheme that
provides for its reuse. This recycling of
water is termed the "Hydrologic Cycle“
Water sources, impurities of water
and chemistry
 Water is simply two atoms of hydrogen and one atom of oxygen bonded
together. Despite its simplicity, water has remarkable properties. Water
expands when it freezes, has high surface tension (because of the polar
nature of the molecules, they tend to stick together), and others. Without
water, life might not be able to exist on Earth and it certainly would not
have the tremendous complexity and diversity that we see.
WATER AS A SOLVENT

 Pure water (H20) is colorless, tasteless, and odorless. It is composed of hydrogen

and oxygen. Because water becomes contaminated by the substances with which
it comes into contact, it is not available for use in its pure state.
 To some degree, water can dissolve every naturally occurring substance on the
earth. Because of this property, water has been termed a "universal solvent.“
 Although beneficial to mankind, the solvency power of water can pose a major
threat to industrial equipment. Corrosion reactions cause the slow dissolution of
metals by water. Deposition reactions, which produce scale on heat transfer
surfaces, represent a change in the solvency power of water as its temperature is
varied. The control of corrosion and scale is a major focus of water treatment
technology.
Impurities in water

 Dirty or unsafe water consists of elements called Total Suspended

Solids (TSS) that are not designed to dissolve. These solids include dust,
sand, clay and rust. They remain suspended in water and cause it to
become muddy o r cloudy. They also lack the two essentials of pure
water: hydrogen and oxygen.
TYPES OF IMPURITIES IN WATER

 BIOLOGICAL IMPURITIES IN WATER

Biological impurities in water are caused by the presence of living
organisms. These include algae, protozoa, pathogens, bacteria, viruses,
microbes, and parasites along with their cysts (eggs) in contaminated water.
The latter are simply called germs, microorganisms that can reproduce at
alarming rates.
TYPES OF IMPURITIES IN WATER

 COLLOIDAL IMPURITIES IN WATER

Colloidal impurities in water include organic waste products and amino acids. This
problem occurs due to contact with suspended matter and elements like sand, rocks and
organic matter flowing in rivers, streams and lakes that renders water undrinkable or non-
pure
 Sources of chemical impurities in water include:
• Gases that are picked up from the atmosphere by rainwater and torrential downpours
• Decomposing animals and plants found near streams, rivers and lakes
• Industrial sewage and wastewater
• High levels of calcium, iron, magnesium, sodium, and chlorides in river water
• Organic compounds stemming from agricultural and domestic industrial waste. These
are known as anthropogenic contaminants, which are found in natural and drinking
water.
• Inorganic compounds stemming from medical wastewater and equipment systems
IMPURE WATER SOLUTIONS

 With so many impurities in natural and drinking water, one of the best
solutions for communities is to have the right municipal water
treatment system in place. Water treatment systems help to eliminate
aluminum, chlorides and other hidden chemical and elements from
drinking water systems.
 Common impurities found in freshwater

Constituents Chemical formula Difficulties caused Means of treatment

Turbidity non-expressed in imparts unsightly appearance coagulation, settling,

analysis as units to water; deposits in water and filtration
lines, process equipment,
etc.; interferes with most
process uses
Hardness calcium and chief source of scale in heat softening;
magnesium salts, exchange equipment, boilers, demineralization;
expressed as CaCO3 pipe lines, etc.; forms curds internal boiler water
with soap, interferes with treatment; surface
dyeing, etc active agents
Carbon CO2 corrosion in water lines, aeration, deaeration,
Dioxide particularly steam and neutralization with
condensate lines alkalies
Physical characteristics

 The water as used should be free from all impurities that are
offensive to the sense of sight, taste, or smell. The physical
characteristics of the water include turbidity, color, taste and odor,
temperature, and foamability.
Physical characteristics
 TURBIDITY
The presence of suspended material, such as clay, silt, finely divided
organic material, plankton, and other inorganic material in water is
known as turbidity.
Turbidity is the measure of relative clarity of a liquid. It is an optical
characteristic of water and is a measurement of the amount of light that is
scattered by material in the water when a light is shined through the water
sample. The higher the intensity of scattered light, the higher the turbidity.
Physical characteristics
 Color
Pure water is colourless but water in nature is often coloured by foreign sub-
stances. Water, whose colour is partly due to suspended matter, is said to
have apparent colour. Colour contributed by dissolved solids that remain
after removal of suspended matter is known as true colour.
The tanning, humic acid etc. present in the organic debris (leaves, wood,
weeds etc.) impart a yellowish brown colour to water as it comes in contact
with them. Iron oxide cause reddish water and manganese oxides cause
brown or blackish water.
Physical characteristics

 Taste and Odor

Many substances with which water comes into contact in nature or during hu-
man use may impart perceptible taste and odour. These include minerals,
metals and salts from the soil, and products from biological reactions and
constituents of wastewater.
Water tastes bitter when contaminated with alkaline impurities and salty
when the impurities are metallic salts. Biological decomposition of organic
debris impart a characteristic taste and odour of rotten eggs which is mainly
due to hydrogen sulphide. Growth of algae, micro-organisms, hydrogen
sulphide and ammonia give an obnoxious odour to water making it unfit for
use.
Physical characteristics

 Temperature
 It is one of the most important parameters in natural surface water
systems I he temperature of surface waters governs to a large extent the
biological species present and then- rate of activity. Temperature has an
effect on most chemical ructions that occur in natural water systems.
 Temperature also has a great effect on the solubilities of gases in water.
The use of water for dissipation of waste heats in industry and the
subsequent discharge of the heated water may result in dramatic
temporary change in receiving streams.
Activity 1

 List down the chemical characteristics of water and their

significance