Environmental Engineering Reference
In-Depth Information
TABLE 1.1. Strength of Various Point and Nonpoint Sources
BoD
5
(mg/l)
Total Suspended
Solids (mg/l)
Total Nitrogen
(mg/l)
Total Phosphorus
(mg/l)
Total Coliforms
(MPN/100 ml)
Source
urban stormwater
10-250 (30)
a
3,000-11,000 (650)
3-10
0.2-1.7 (0.6)
10
3
-10
8
Construction site runoff
NA
b
10,000-40,000
NA
NA
NA
Combined sewer overflows
60-200
100-1100
3-24
1-11
10
5
-10
7
light industrial area
8-12
45-375
0.2-1.1
NA
10
10
2
roof runoff
3-8
12-216
0.5-4
NA
10
7
-10
9
Typical untreated sewage
190-50
210-300
40-50
7-16
Typical PoWT effluent
(20)
(20)
(30)
(10)
10
4
-10
6
a
Number in brackets indicates mean.
b
NA means not available or unreliable; PoWT means publicly owned treatment works with secondary (biological) treatment.
1.2.1.5 Spills.
Spills and accidental or intentional
releases can occur in a variety of ways. Transportation
accidents on highways and rail freight lines can result in
major chemical spills, and accidental releases at petro-
leum product storage installations are another common
source of accidental spills. leaks and spills from under-
ground storage tanks into the groundwater are of special
concern because these releases may remain undetected
for long periods of time.
1.2.2 Nonpoint Sources
Nonpoint sources of contamination generally occur
over large areas, and, because of their diffuse nature, are
more complex and difficult to control than point sources.
Nonpoint source pollution is a direct result of land use
patterns and runoff controls, so many of the solutions
to pollution by nonpoint sources lie in finding more
effective ways to manage land and stormwater runoff.
Much nonpoint source pollution occurs during rain-
storms and snowmelts, resulting in sporadic large flow
rates that make treatment even more difficult. Nonpoint
sources of contamination that must generally be consid-
ered in managing water bodies include agricultural
runoff and urban runoff. runoff from urban and agri-
cultural areas are typically the primary sources of
surface water pollution.
Groundwater contamination originating from septic
tanks, leaking underground storage tanks, and waste
injection wells is quite common and are of particular
concern when groundwater is the source of domestic
drinking water supply. The strengths of various sources
of water pollution are shown in Table 1.1. It is apparent
from these data that pollutants at high concentrations
can enter water bodies from a variety of sources, and
control of these sources is central to effective water-
quality management.
Figure 1.4.
livestock in a stream.
Source
: State of Arkansas
(2005).
activities that influence the quality of both surface and
groundwaters that receive runoff or infiltration from
these areas. The application of fertilizers is of major
concern because dissolved nutrients in surface runoff
accelerate growth of algae and depletion of oxygen in
surface waters. Nitrogen, in the form of nitrates, is a
contaminant commonly found in groundwater underly-
ing agricultural areas and can be harmful to humans,
particularly infants. Erosion caused by improper tilling
techniques is another agricultural activity that can
adversely affect water quality through increased sedi-
ment load, color, and turbidity.
1.2.2.2 Livestock.
Feedlots have been shown to con-
tribute nitrates to groundwater and pathogenic micro-
organisms to surface waters. overgrazing eliminates the
vegetative cover that prevents erosion, increasing the
sediment loading to surface waters. In some extreme
cases, livestock are allowed to wade in and cause direct
contamination of streams, and such a circumstance is
shown in Figure 1.4. This practice should be avoided as
1.2.2.1 Agricultural Runoff.
Application of pesti-
cides, herbicides, and fertilizers are all agricultural
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