Download Water Quality

I. Water Quality-Overview
D. Types of Water Pollution
Objectives - students should:
Distinguish among major sources
and types of potential contaminants
of drinking and recreational waters.
 List and describe problems
associated with contaminated
drinking water worldwide.

Water Pollution:

Water pollutants can be divided into
several categories:
– Disease-causing microorganisms.
– Oxygen-demanding wastes.
– Inorganic chemicals.
– Organic chemicals.
– Sediments.
– Alien species.
Disease-causing microorganisms:

A variety of microorganisms found in
water are capable of causing disease in
humans (pathogens to be discussed later)
– The primary source of these microorganisms
is animal and human fecal contamination
(e.g., feedlot runoff, natural animal wastes, or
sewage contamination, combined sewer
overflow).
Combined Sewer Overflow
Oxygen-demanding wastes:

Organic matter in water may be used as a
nutrient source by aerobic microorganisms
and deplete oxygen in water.
– Biochemical Oxygen Demand (BOD) measures
changes in oxygen over time due to microbes.
– Chemical Oxygen Demand (COD) measures
the oxidation of organic compounds by a
chemical oxidant.
Inorganic chemicals:
Inorganic chemicals like acids, salts,
and toxic metals can make water unfit
for drinking, decrease crop production,
or corrode metal machinery.
 Inorganic plant nutrients like nitrates
and phosphates can cause
eutrophication, and oxygen depletion
of water (e.g., in lakes).

Organic chemicals:

A variety of carbon-containing
chemicals can threaten human or
aquatic life.
– Volatile Organic Compounds (VOC’s),
like oil, gasoline, cleaning solvents, etc.
– pesticides, plastics, other Synthetic
Organic Compounds (SOC’s),
Sediments or suspended matter:

Insoluble particles of soil and other solids
become suspended in water
(primarily due to erosion).
– Suspended solids can reduce photosynthesis
in plants, and carry other contaminants,
– Settleable solids (sediment) can destroy
feeding and spawning grounds of fish, and
clog lakes, harbors, streams, etc.
Alien species:
Artificially introduced species (whether
accidentally or intentionally
introduced), can outcompete native
species.
 This reduces the biodiversity of the
aquatic system and can cause severe
economic losses.

Types of water pollution:

Sources of pollution can be point
(PS) or nonpoint (NPS).
– Point sources discharge pollutants at
specific locations and are easier to
locate, regulate, and remediate.
– Nonpoint sources cannot be traced to a
single discharge point, and are difficult
to monitor, regulate, and remediate.
River and stream pollution:
Flowing water recovers relatively quickly
from oxygen-demanding wastes due to
microbial action, dilution, and aeration.
 BOD rises quickly, but decreases
downstream from the discharge point.
 Water quality in 60% of stream length in
the U.S. has never been measured.

Lake pollution:
Lakes are more susceptible to contamination because of slower flow rates.
 Stratification (layering) of lakes results
in a lack of mixing.
 Eutrophication.

– Oligotrophic
– Mesotrophic
– Eutrophic
Groundwater pollution:
Groundwater flow generally slow & nonturbulent, so contaminants are not
degraded quickly.
 50% of U.S. groundwater systems are
contaminated with organic chemicals.
 25 to 75% of groundwater contaminated.
 There are an estimated 1 million leaking
underground storage tanks in the U.S.

Ocean pollution:
Ocean is the ultimate sink for all water.
 Coastal estuarine areas (where rivers
meet the sea) are especially vulnerable
to runoff pollution.
 The Chesapeake Bay is an example of
how an estuarine area can be damaged
by pollution from inland runoff.

Contaminated drinking water:




The World Health Organization (WHO)
estimates that 1.5 billion people lack safe
drinking water supplies.
1.7 billion people lack adequate sanitation
facilities.
5 million people die each year from waterborne disease, primarily transmitted by oralfecal route.
Most of the 13,700 people who die each day
from waterborne diseases prevent-able by
proper sanitation and clean drinking water are
children under age 5.
Solutions to water pollution:

Prevention of contamination is a more
economical and sensible approach:
– Control disposal of hazardous waste.
– Limit application of pesticides, fertilizers.
– Above-ground storage of chemicals, etc.

Physical, chemical, and biological
treatments can reduce water pollution
(e.g., in natural and municipal systems).
Summary:
Sources of water pollution include
chemical, physical, and biological
contaminants.
 Contaminated drinking and bathing
waters may transmit infectious
diseases through pathogens.
