Running Waters - Mathematics and Statistics for the Environment - page 563

19.5.1 d issolved o xygen C orreCtion F aCtor
Because of differences in air pressure caused by air temperature changes and for elevation above
the mean sea level (MSL), the DO saturation concentrations generated by the formula must be cor-
rected. The correction factor ( f ) can be calculated as follows:

2116 8008 0 000115
2116 8

. − ( . − . AE )

f = (19.5)

.

where
f = Correction factor for above MSL.
A = Air temperature (°C).
E = Elevation of the site (feet above MSL).

■ EXAMPLE 19.4
Problem: Find the correction factor for the DO sat value for water at 640 ft above the MSL and air
temperature of 25°C. What is the DO sat at a water temperature of 20°C?
Solution:

2116 8008 0 000115
2116 8
2116 80

. − ( . − . AE )

f =

.

. − ( .08 − 0 000115 . × 25 640 ) 2116 8494

2116 8

. − .

= = = 0 977 .

2116 8 . .

DO sat at T = 20°C = 9.02 mg/L. With an elevation correction factor of 0.977,

DO sat = 9.02 mg/L × 0.977 = 8.81 mg/L

19.6 BIOCHEMICAL OXYGEN DEMAND
Biochemical oxygen demand (BOD) measures the amount of oxygen consumed by microorganisms
in decomposing organic matter in stream water. BOD also measures the chemical oxidation of inor-
ganic matter (i.e., the extraction of oxygen from water via chemical reaction). A test is used to mea-
sure the amount of oxygen consumed by these organisms during a specified period of time (usually
5 days at 20°C). The rate of oxygen consumption in a stream is affected by a number of variables:
temperature, pH, the presence of certain kinds of microorganisms, and the type of organic and
inorganic material in the water. BOD directly affects the amount of dissolved oxygen in running
waters. The greater the BOD, the more rapidly oxygen is depleted in the system. This means less
oxygen is available to higher forms of aquatic life. The consequences of high BOD are the same as
those for low dissolved oxygen: Aquatic organisms become stressed, suffocate, and die. Sources of
BOD include leaves and wood debris; dead plants and animals; animal manure; effluents from pulp
and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic
systems; and urban stormwater runoff.

19.6.1 bod t est p roCedure
Standard BOD test procedures can be found in Standard Methods for the Examination of Water and
Wastewater (Clesceri et al., 1999). When the dilution waste is seeded, oxygen uptake (consumed) is
assumed to be the same as the uptake in the seeded blank. The difference between the sample BOD