Geology Reference
In-Depth Information
Exercise 13 • Water Quality Data and Pollution Sources
213
TABLE 13.6 Summary of Sources and Their Contaminants in Ground- and Surface-Water Pollution
Source
Principal Contaminants (groundwater contaminants in italics)
Domestic
Undecomposed organic matter (garbage, grease) that increases BOD (Biochemical Oxygen Demand)
Partially degraded organics (raw wastes and nitrates from humans) from combined sewers
Combination of above after limited sewage treatment in municipal sewage plants
Parasites, bacteria, and viruses (pathogens)
Grit from washings, eggshells, ground bone
Miscellaneous organics (paper, rags, plastics, synthetics)
Detergents
Inorganics from organic decay (nitrate, sulfate)
from septic tank systems
Salts and ions in public water supply
Soluble organic compounds
Industrial
Biodegradable organics
Inorganic solids, mineral residues
Chemical residues (acids, alkalies, complex molecules)
Metal ions
Soluble salts from industrial waste ponds and spills
Agriculture
Increased concentration of salts and ions from animal feedlots
Fertilizer residues including sewage sludge on land.
Pesticide residues
Silt and soil particles
Concentrated salts in water applied to land
from irrigation and sewage sludge
Landfill
Hardness-producing leachate
Soluble chemical and gaseous products
(Modified from McGauhey, 1968)
The pollution load that a stream carries can be
calculated if the stream discharge and the concentra-
tion of the specific contaminants are known.
QUESTIONS 13, PART B
1.
Determine the daily load of iron (tons/day) going over Nia-
gara's Horseshoe Falls (approximate discharge = 200,000 cfs)
if the iron concentration is 0.1 mg/L.
Load (tons/day) = Q X C X 0.0027
2.
Biodegradable organic matter promotes oxygen demand in
streams. What water quality parameter would be expected to
change with increased oxygen demand?
where Q = stream discharge (cfs),
C = concentration of specific contaminant
(mg/L), 0.0027 = constant to convert seconds
and mg/L to days and tons
To determine if a stream is being contami-
nated, it is necessary to acquire data that were col-
lected before the apparent contamination or to
determine the concentrations of selected constituents
in uncontaminated reaches of the stream. Com-
monly, water-quality data reflecting natural condi-
tions prior to contamination, sometimes called
background data, are not available. Background
information may be obtained, however, by sampling
the water course and its tributaries in reaches
upstream from the suspected source of pollution.
The quality at any sampling station represents all of
the upstream input.
3.
Why are silt and clay particles considered to be contaminants?
4.
From Table 13.6, what differences in stream-water quality
upstream and downstream from a sewage treatment plant
should be expected? Explain.
5. a.
What is meant by "background" concentrations of chem-
icals in a watershed?
