5010 Introduction

5010 INTRODUCTION
5010 A. General Discussion
Analyses for organic matter in water and wastewater can be
classified into two general types of measurements: those that
quantify an aggregate amount of organic matter comprising
organic constituents with a common characteristic and those that
quantify individual organic compounds. The latter can be found
in Part 6000. The former, described here in Part 5000, have been
grouped into four categories: oxygen-demanding substances,
organically bound elements, classes of compounds, and forma-
tion potentials.
Methods for total organic carbon and chemical oxygen
demand are used to assess the total amount of organics
present. Gross fractions of the organic matter can be identified
analytically, as in the measurement of BOD, which is an index
of the biodegradable organics present, oil and grease, which
represents material extractable from a sample by a nonpolar
solvent, or dissolved organic halide (DOX), which measures
organically bound halogens. Trihalomethane formation
potential is an aggregate measure of the total concentration of
trihalomethanes formed upon chlorination of a water
sample.
Analyses of organics are made to assess the concentration and
general composition of organic matter in raw water supplies,
wastewaters, treated effluents, and receiving waters; and to de-
termine the efficiency of treatment processes.
5010 B. Sample Collection and Preservation
The sampling, field treatment, preservation, and storage of
samples taken for organic matter analysis are covered in detail
in the individual introductions to the methods. If possible,
analyze samples immediately because preservatives often in-
terfere with the tests. Otherwise, store at a low temperature
(4°C) immediately after collection to preserve most samples.
Use chemical preservatives only when they are shown not to
interfere with the examinations to be made (see Section
1060). Never use preservatives for samples to be analyzed for
BOD. When preservatives are used, add them to the sample
bottle initially so that all portions are preserved as soon as
collected. No single method of preservation is entirely satis-
factory; choose the preservative with due regard to the deter-
minations that are to be made. All methods of preservation
may be inadequate when applied to samples containing sig-
nificant amounts of suspended matter.