Environmental Engineering Reference
In-Depth Information
There are several ways to
prevent
or
reduce
cul-
tural eutrophication. For example, we can use ad-
vanced (but expensive) waste treatment to remove
nitrates and phosphates before wastewater enters
lakes, ban or limit the use of phosphates in household
detergents and other cleaning agents, and employ soil
conservation and land-use control to reduce nutrient
runoff.
There are also several ways to
clean up
lakes suf-
fering from cultural eutrophication. We can mechani-
cally remove excess weeds, control undesirable plant
growth with herbicides and algicides, and pump air
through lakes and reservoirs to prevent oxygen deple-
tion (an expensive and energy-intensive method).
As usual, pollution prevention is more effective
and usually cheaper in the long run than cleanup. If
excessive inputs of plant nutrients stop, a lake usually
can return to its previous state.
Science: Groundwater Pollution
Groundwater can become contaminated with a
variety of chemicals because it cannot effectively
cleanse itself and dilute and disperse pollutants.
A serious threat to human health is the out-of-sight
pollution of groundwater, a prime source of water for
drinking and irrigation. Groundwater pollution comes
from numerous sources (Figure 11-26). People who
dump or spill gasoline, oil, and paint thinners and
other organic solvents onto the ground also contami-
nate groundwater.
When groundwater becomes contaminated, it
cannot cleanse itself of
degradable wastes
as flowing sur-
face water does (Figure 11-24). Groundwater flows so
slowly—usually less than 0.3 meter (1 foot) per day—
that contaminants are not diluted and dispersed effec-
tively. In addition, groundwater usually has much
Polluted air
Hazardous waste
injection well
Pesticides
and fertilizers
Deicing
road salt
Coal strip
mine runoff
Buried gasoline
and solvent tanks
Cesspool,
septic tank
Gasoline station
Pumping
well
Water
pumping well
Waste lagoon
Sewer
Landfill
Accidental
spills
Leakage
from faulty
casing
Discharge
U
n
c
o
n
fi
n
e
d
f
r
e
s
h
w
a
t
e
r
a
q
u
if
e
r
Confined
aquifer
C
o
n
f
i
n
e
d
f
r
e
s
h
w
a
t
e
r
a
q
u
i
f
e
r
Groundwater
flow
Figure 11-26
Natural capital degradation:
principal sources of groundwater contamination in the
United States.
