TM 5-814-8
CHAPTER 3
NATURE AND ORIGIN OF WASTEWATERS
also measure a quantity of reduced inroganic
3-1. Introduction
materials such as ammonia or sulfites.
While domestic wastewaters can be consistently
(2) Chemical oxygen demand (COD). COD is
classified as to their strength and constituents,
another indirect measurement of organic material.
industrial wastewaters and domestic/industrial
COD measures the oxygen equivalent of the
discharges may be highly variable. The latter
organic material oxidized by bichromate or
types of wastewaters are usually a complex
permanganate during acid digestion. This parame-
rather than a simple misture of constituents.
ter was developed in order to substitute for the
Characterization of the waste stream by flow
more time-consuming BOD test.
measurement and chemical analysis is used to
(3) Total organic carbon (TOC). The TOC test
identify the undesirable characteristics, to deter-
is an indirect measurement of organic material.
mine the source of these characteristics, and to
The test measures the quantity of carbon dioxide
implement a solution to control them to an
liberated during the combustion of the waste-
acceptable level.
water sample. Thus, TOC is the amount of carbon
present in organic molecules contained in the
3-2. Wastewater characteristics
wastewater sample.
Wastewaters may contain any material which
(4) Total oxygen demand (TOD). TOD is an
may be dissolved or suspended in or on water.
indirect method of measuring organic material
Wastewater constituents are classified into or-
concentration. However, it is the most direct
ganic, inorganic, particulate and pathogenic.
measurement of oxygen demand. TOD is the
Tests serve as a first step in determining the
difference in the oxygen content of a sample
treatment requirements for a particular waste-
before and after combustion. TOD measures the
water to preclude potential negative environmen-
amount of oxygen required to burn the contami-
tal impact.
nants in the wastewater sample.
a. Primary organic parameters. Organic materi-
b. Organic parameter relationships. A prelimi-
als in wastewater have traditionally been the
nary step in developing treatment alternatives for
major concern in the field of water pollution
a specific wastewater should be an analysis of the
control. The decrease in dissolved oxygen due to
organic parameter relationships. This analysis will
the process of biodegradation is detrimental to
provide the designer with a general idea of the
.
the health of the receiving waterways and aquatic
treatment technologies most likely to be effective
life. There are four major tests used to measure
on the wastewater.
organic material in wastewater: the customary
c. Additional organic parameters. As attention
pollutant parameter, Biochemical Oxygen De-
has been focused on the TOD, TOC, COD, and
mand (OBD); the noncustomary pollutant parame-
BOD parameters, it is necessary to recognize
ters Chemical Oxygen Demand (COD), Total Or-
other important organic evaluations, such as oil
ganic Carbon (TOC), and Total Oxygen Demand
and grease content, phenols, organics containing
(TOD).
toxic functional groups, etc. Oil and phenol analy-
(1) Biochemical oxygen demand (BOD). The
ses are particularly significant when evaluating
BOD test is an indirect measurement of biode-
unit processes for the treatment of wastes con-
gradable organic material. The test does not
taining petroleum distillates. Quantities of toxic
measure specific organic materials but indicates
organic compounds, such as pesticides, present in
the amount of oxygen required to stabilize the
wastewaters entering the environment are ex-
biodegradable organic fraction. This test was
tremely significant and require a great deal of
devised to simulate the impact of a particular
effort to control. The need to analyze or treat
wstewaster on the dissolved oxygen level in the
these organic compounds is site specific. If a
receiving waters. Adequate dissolved oxygen
substance is used or manufactured in an indus-
must be provided in order to maintain aquatic
trial activity, then the possibility exists that it is
life. The BOD test measures the oxygen depleted
present in the wastewater.
after a period of five days in a closed system
(1) Oil and grease. Oil and grease in waste-
which contains a mixture of wastewater and an
water is usually a characteristic of petroleum-
acclimated seed of microorganisms. The test may
3-1
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