Introduction to water

pollution and quality

control

Dr. Pabasari Koliyabandara

• From ancient times, people have chosen to live
near water, settling in river valleys, beside lakes,
or along Coastlines

• Clean water is a crucial resource for drinking,

irrigation, industry, transportation, recreation,
fishing, hunting, support of biodiversity, and
sheer esthetic enjoyment.
 • Substances that show the presence of pollution sources

• These include herbicides indicative of agricultural runoff,

fecal coliform bacteria that are characteristic of pollution
from sewage, and pharmaceuticals, pharmaceutical

Markers of metabolites, and even caffeine that show contamination

by domestic wastewater

Water • Biomarkers of water pollution are organisms that live in

Pollution or are closely associated with bodies of water and
provide evidence of pollution either from accumulation
of water pollutants or their metabolites or from effects
on the organism due to pollutant exposure.
• Fish are the most common bioindicators of water
pollution, and fish lipid (fat) tissue is commonly analyzed
for persistent organic water pollutants.
Surface water

• The water in rivers, lakes,

and ice and snow—are vitally
important to the everyday
life of not only people, but to
all life on, in, and above the
Earth.
• And, of course, surface
water is an intricate part of
the water cycle, on which all
life depends.
• Some part of the precipitation that lands on the ground

surface infiltrates into the subsurface. The part that

continues downward through the soil until it reaches

rock material that is saturated is groundwater recharge.

• Water in the saturated groundwater system moves

slowly and may eventually discharge into streams,

lakes, and oceans.

 Water
Polluatants
Elemental
Pollutants
• Inorganic chemicals’ manufacture has the
potential to contaminate water with trace
elements.
• Among the industries regulated for potential
trace element pollution of water are those
producing chloroalkali, hydrofluoric acid,
sodium dichromate(sulfate process and
chloride ilmenite process), aluminum fluoride,
chrome pigments, copper sulfate, nickel
sulfate, sodium bisulfate, sodium
hydrosulfate, sodium bisulfite, titanium
dioxide, and hydrogen cyanide
Metalloids

• The most significant water pollutant metalloid element is arsenic, a toxic

element that has been the chemical villain of more than a few murder
plots. Acute arsenic poisoning can result from the ingestion of more than
about 100 mg of the element.

• Chronic poisoning occurs with the ingestion of small amounts of arsenic

over a long period of time.

• There is some evidence that this element is also carcinogenic.

 Excessive levels of ammoniacal nitrogen cause water-
quality problems.

Ammonia is the initial product of the decay of

nitrogenous organic wastes, and its presence frequently

Ammonia and Other indicates the presence of such wastes.

Inorganic Pollutants
It is a normal constituent of low-pE groundwaters and is
sometimes added to drinking water as an aid to
disinfection, where it reacts with chlorine to provide
residual chlorine.
ALGAL NUTRIENTS AND EUTROPHICATION

• The term eutrophication, derived from the Greek word meaning “well-nourished,”
describes a condition of lakes or reservoirs involving excess algal growth.
• Although some algal productivity is necessary to support the food chain in an aquatic
ecosystem, excess growth under eutrophic conditions may eventually lead to severe
deterioration of the body of water.

• The first step in eutrophication of a body of water is an input of plant nutrients from
watershed runoff or sewage.
• The nutrient-rich body of water then produces a great deal of plant biomass by
photosynthesis, along
• with a smaller amount of animal biomass. Dead biomass accumulates in the bottom
• Eutrophication is often a natural phenomenon; for instance, it is basically
responsible for the formation of huge deposits of coal and peat.
• However, human activity can greatly accelerate the process.

• In most cases in freshwaters, the single plant nutrient most likely to be limiting
is phosphorus, and it is generally regarded as the culprit in excessive
eutrophication.

• Household detergents were once a common source of phosphate in

wastewater, and eutrophication control has concentrated on eliminating
phosphates from detergents, removing phosphate at the sewage treatment
plant, and preventing phosphate-laden sewage effluents from entering bodies
of water enabling the excessive growth of algae that can cause eutrophication.
 Nutrients in manure
and fertilizers are
transported to lakes,
rivers, and oceans.
Excessive nutrient
inputs
result in degradation of
water quality, causing
the disruption of
aquatic ecosystems.
ACIDITY, ALKALINITY, AND SALINITY
• Aquatic biota are sensitive to extremes of pH. Largely because of osmotic effects, they cannot live
in a medium having a salinity to which they are not adapted. Thus, a freshwater fish soon
succumbs in the ocean, and sea fish normally cannot live in freshwater.

• Excess salinity soon kills plants not adapted to it. There are, of course, ranges in salinity and pH in
which organisms live.

• Excess alkalinity, and frequently accompanying high pH, generally are not introduced directly into
water from anthropogenic sources. However, in many geographic areas, the soil and mineral
strata are alkaline and impart a high alkalinity to water.
• Human activity can aggravate the situation, for example, by exposure of alkaline overburden from
strip mining to surface water or groundwater.

• Excess alkalinity in water is manifested by a characteristic fringe of white salts at the edges of a
body of water or on the banks of a stream

• Water salinity may be increased by a number of human activities. Water passing through a
municipal water system inevitably picks up salt from sources such as recharging water softeners
with sodium chloride.
OXYGEN, OXIDANTS, AND
REDUCTANTS
• oxygen is consumed rapidly by the oxidation of organic matter,

• Unless the water is reaerated efficiently, as by turbulent flow in a

shallow stream, it rapidly loses oxygen and will not support higher
forms of aquatic life.
• In addition to the microorganism-mediated oxidation of organic
matter, oxygen in water may be consumed by the biooxidation of
nitrogenous material:

• The degree of oxygen consumption by microbially mediated oxidation

of contaminants in water is called the BOD (biochemical or biological
oxygen demand).
Oxygen sag curve resulting from the addition of oxidizable pollutant material
to a stream.
 • An important characteristic of organic water
pollutants, especially those that have an
affinity for lipid (fat) tissue and that resist
biodegradation, is the bioconcentration
ORGANIC
factor (BCF), which is defined as the ratio of a
POLLUTANTS substance’s concentration in the tissue of an
aquatic organism to the concentration of the
substance in the water where the organism
lives.
Sewage
 • Bacteria and protozoa in water can produce toxins

that can cause illness or even death.

• Toxins produced in rivers, lakes, and reservoirs by

Microbial Toxins cyanobacteria including Anabaena, Microcystis, and

Nodularia have caused adverse health effects in

Australia, Brazil, England, and elsewhere in the

world.
 • Several classes of pesticides and other chemicals are of particular
concern as water pollutants because of their potential effects.

• These are
• (1) highly biodegradation-resistant compounds
• (2) known or probable carcinogens
PESTICIDES IN
• (3) toxicants with adverse reproductive or developmental effects
WATER • (4) neurotoxins including cholinesterase inhibitors
• (5) substances with high acute toxicities
• (6) known groundwater contaminants.
 • The continued development of new products used
for various purposes has led to interest in emerging
pollutants of various kinds which may be of
concern in water.
EMERGING WATER
POLLUTANTS, • Prominent among these are nanomaterials
consisting of very small entities in the 1–100 nm
PHARMACEUTICALS, size range.
AND HOUSEHOLD
• Nanomaterials of various kinds have unique
WASTES properties of high thermal stability, low
permeability, high strength, and high conductivity.
• These and other properties are leading to uses in
electronics, automobiles, apparel, sunscreens,
cosmetics, water purification, and other products.
It is anticipated that the use of nanomaterials in drug delivery will
increase rapidly in the future. The commercial uses of
nanomaterials are in their infancy, but very rapid growth is
underway.

Little is known about the potential pollution effects and toxicities of

nanomaterials, so their potential effects as water pollutants are of

significant concern
 Purification for domestic use

Water Treatment for specialized

industrial applications
Treatment
Treatment of wastewater to make
it acceptable for release or reuse
Drinking water
quality
standards
 GENERAL STANDARDS AND CRITERIA
FOR THE DISCHARGE OF
INDUSTRIAL EFFLUENTS INTO INLAND
SURFACE WATERS