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Understanding Water
Quality Issues and
Pollution
By CWanamaker
More than 10% of our nations (USA) waterways are impaired. This means
that they are too polluted for humans or animals to use.
Source: Morgue File
It wasn't until the early 20th century that people began to care
about what was in the water. Prior to this new awakening, it was
believed that water could dilute any substance. As often would be
the case, industrial effluent, raw sewage, and even animal waste
would be dumped into the nearest river for disposal. Most people
(and companies) at that time didn't really think about the damage
that they were actually causing.
Today, we live in a much different world. There are a multitude of
agencies that exist for the sole purpose of ensuring that our
nation's water is clean. These agencies are charged with the duty
to ensure that water pollution is minimized to the maximum
practicable extent possible. In addition to this, the public is also
more aware of the issues associated with water pollution then they
were in the past. So what exactly constitutes water pollution
anyways? Where does this pollution come from? And finally, how
is it measured and detected?
Top 4 Pollutants in Our Water
1.
Hydrocarbons (petroleum)
2.
Raw Sewage
3.
Toxic Chemicals
4.
Heavy Metals
Water Pollution Defined
Essentially, water pollution is any substance that contaminates it
and alters its natural life-supporting ability. Additionally, water
pollution is anything that can cause harm to humans, plants, and
animals when consumed, touched, or inhaled. The list of
substances that fit the description is nearly endless. Pollutants are
divided into five general categories:
Disease Causing Agents - Things that can cause illness and
disease fit into this category. This includes such things as Bacteria,
Viruses, and various types of parasites.
Oxygen Demanding Substances - These substances are
essentially the things that bacteria can consume. Bacteria require
a lot of oxygen when they are breaking down organic matter. The
main problems with these substances are that they remove
dissolved oxygen from the water and encourage the growth of
bacteria. When the oxygen is removed, the fish begin to literally
suffocate.
Inorganic Substances - Many toxic chemicals and heavy metals
are located in this category. These substances can cause birth
defects, brain damage, and even cancer. Some of these
substances are fat-soluble as well. This makes them good
candidates for bioaccumulation and biomagnification, further
damaging the environment.
Nutrient Chemicals - If excess nitrates and phosphates are
introduced into a body of water, it could cause eutrophication. An
overabundance of these nutrients will allow algae to eventually
become overgrown in a body of water. This overgrowth causes the
oxygen supply in the water to disappear causing the fish to die.
The algal blooms also block out the sun, which prevents
photosynthesis in other plants from occurring.
Sediments - Excessive sediments suspended in water can be
considered a pollutant. The problem with sediments is twofold.
First, sediments tend to block sunlight, which can change the
water's temperature as well as prevent photosynthesis from
occurring. Second, sediments can carry pesticides and other
chemicals into a body of water. Sediment is one of the main
reasons water can have high turbidity.
Map showing the percentage of impaired waterways in the USA
Source: US Environmental Protection Agency
Where Does Water Pollution Come From?
Almost all pollutants found in our water are from anthropogenic
sources. These include such things as transportation, mining,
manufacturing, and even recreational activities. However, some
pollution can come from mother nature. For instance, volcanic
eruptions have been a major source of water pollution for millions
of years.
Most pollution found in our water today also comes from nonpoint
sources rather than specific companies and individuals. These
mean that the source of the contaminants is not directly
attributable to any one single action or entity. An example of a
nonpoint source of pollution is the exhaust generated the millions
of cars on our roads. Pretty much everything that we do on a daily
basis is contributing or has the potential to contribute to water
pollution to some degree. Even the humble electric car still
produces brake dust that can reduce the quality of storm water
runoff. Fortunately, the days where point sources dominated the
water pollution market are long gone.
Fortunately, the days where point sources dominated the water
pollution market are long gone. However, many point sources still
exist. In today's society, farming facilities and wastewater
treatment plants make up most of the point sources of water
pollution.
Detecting and Measuring Water Pollution
There are a number of parameters and indicators that are used to
assess the quality of a specific sample or body of water. These
include such things as coliform bacteria, nutrient content, dissolved
oxygen, pH, turbidity, and temperature.
Coliform Bacteria - If coliform bacteria are found in a sample of
water, it usually means that it is contaminated with raw sewage.
When testing a body of water, the amount of coliform bacteria,
they are measured by running a standard total coliform test at
112F (44.5C). The results of these tests are reported as a Most
Probable Number (MPN) index rather than a percentage or total
count of bacteria. Just one coliform colony per 100ml of water is a
major cause for concern.
Dissolved Oxygen (DO) - This parameter is used to assess the
overall suitability of a water sample to support life. For example,
fish typically require a minimum of 5mg of dissolved oxygen per
liter of water to survive. However, it is recommended that DO
levels be kept between 8-15mg/l to support all forms of life in the
water. Measuring dissolved oxygen is accomplished by either
using a standard DO probe and meter or the Azide-Winkler titration
method. The former can be performed in the field and latter is
typical done in the laboratory.
pH - The pH (or percent hydrogen) level of the water will indicate
how acidic or alkaline it is. A healthy range for pH is between 6.5
and 8.0. If the pH gets too low toxic chemicals become easier to
consume by aquatic plants and animals. Slight changes in pH can
cause a significant loss of plant and animal life in a very short
amount of time. Acid rain is one of the biggest contributors to pH
changes in our nation's rivers, lakes, and streams. Testing the pH
of water is very simple and can be done with some litmus paper.
When dipped in water, the paper changes color to correspond to a
specific level of acidity or alkalinity.
Turbidity - This is an indicator of the clarity or transparency of the
water. High levels of turbidly can block sunlight and allow the
water's temperature to change. Visible contaminants in the water
can also hinder a fish’s ability to breath. In addition to this, when
the floating particles settle out they can smother plants growing at
the bottom of a lake. Testing for turbidity is sometimes
accomplished by performing a visual assessment in the field.
However, more often then not turbidity is measured by placing a
sample of the water in a turbidimeter, which measures the
percentage of light that shines through it.
Temperature - Temperature is a measure of the amount of heat
energy that is in the water. Temperature is important because it is
a key variable in many of the natural chemical and biological
processes that occur in water. There is also a direct and
proportional relationship between water temperature and the rate
that photosynthesis in plants can occur. Temperature affects the
amount of oxygen that can be dissolved in the water as well as an
animal's sensitivity to toxic chemicals. The temperature is
measured using a simple thermometer.
Nutrient Content - Nutrients found in water will typically be
composed of nitrates and phosphates. Although these compounds
are required for plants and animals to grow, too much of them can
cause eutrophication. Under normal conditions, nitrate
concentrations are usually less than 1 mg/L. For comparison,
treated wastewater sometimes has a nitrate concentration of more
than 30 mg/L. Phosphorus is a major chemical of concern. It only
takes a miniscule amount of phosphorus to cause a water body to
begin to eutrophy. Sources of phosphorus include wastewater
treatment, stormwater runoff from farm fields, and cleaning
chemicals. There are a number of laboratory-based methods to
test for the concentrations of these compounds. The preferred
method is the use of nutrient test strips because they are easy to
use and can be used in the field.