Environmental Engineering Reference
In-Depth Information
development of safe drinking water supplies:
quantity
and
quality
. Herein
lies the problem. Quantity may indeed be a major issue (a limiting factor) for
a particular location, often simply because water suitable for consumption
is not evenly distributed throughout the world. Those locations fortunate
to have an ample supply of surface water or groundwater may not have a
quantity problem, as long as the quantity is large enough to fulfill the needs
of all its consumers. But, again, not every geographical location is fortunate
enough to have an adequate water supply—that is, a quantity of water avail-
able to satisfy residents' needs. This is one of the primary reasons, of course,
why major portions of the globe are either uninhabited or sparsely popu-
lated at best. The other key concern (and the main focus of this text) is water
quality. Obviously, having a sufficient quantity of freshwater available does
little good if the water is unsafe for consumption or for other uses.
We began this chapter
by revealing some of the contradictions with water.
At this point, we must bring up another contradiction—one that human
beings bear considerable responsibility for. Consider that most of the early
settlements of the world began along waterways. Waterways were important
primarily because of the ease of transportation they afforded and because of
their industrial value (e.g., water power), in addition to serving as a source
of food for the settlers. And, of course, such waterways provided a natural,
relatively clean, relatively safe source of drinking water. Unfortunately, these
early waterways soon became polluted. When you get right down to it, this
should not be surprising—humans have always been polluters … we can
actually say that pollution is a natural byproduct of civilization. We eat, we
work, we do whatever is necessary to sustain our existence, and in doing so
we pollute.
Are we the only freshwater polluter? No, not exactly. Natural occurrences
also pollute our water sources, especially our surface waters; for example, a
stream that flows through a heavily wooded area (such as a deciduous for-
est) suffers from the effects of natural pollution each year during leaf-fall.
When leaves fall from their lofty perches and make their sinuous descent
into the blue-green phantoms we call surface streams below, they are carried
with the flow, drifting until they sink, are saturated, or become lodged in an
obstruction in the stream.
Leaves are organic and eventually degrade. During this process, the
microbes degrading the leaves take up and use dissolved oxygen in the
water. In some cases, the amount of oxygen used during degradation is of
such quantity (especially in slow-moving or stagnant water areas) that the
natural biota in the stream suffer from a lack of oxygen. When this happens,
they either move on to healthier parts of the stream or succumb because of a
lack of oxygen. Note that other natural water polluters also affect water qual-
ity, including forest fires, earthquakes, and floods.
Remember that Nature understands the contradictions of water … and
because she understands, she is also well suited and equipped to deal with
such problems. When a stream becomes polluted (for whatever reason),
