CHEMICAL ANALYSIS AND TESTING, CHEMICAL ENGINEERING, CHEMISTRY, EFFLUENTS(SEWAGE), MILLS, PAPER, PAPER PULP, PAPER TECHNOLOGY, TEST EQUIPMENT, TESTING,TRADE EFFLUENTS
适用范围
1.1
This method determines the chemical oxygen demand (COD) of water and wastewater
by reaction with a measured excess of potassium dichromate under reflux
conditions. The COD is defined as the milligrams of oxygen consumed by one
litre of sample under the conditions of the test. 1.2
This method is not to be considered as a replacement for the biochemical oxygen
demand (BOD) test, CAN/CGSB-9.2 No. 2. The conditions of oxidation used in the
COD test procedure are much more severe, with the result that COD test results
will almost invariably be several times higher than BOD test results obtained
on the same sample. 1.3
In general, BOD test results will more closely parallel the conditions
prevailing for natural degradation of dissolved materials in water and
wastewater. However, in the case of waters containing materials which are
toxic towards the micro-organisms essential to the BOD test procedure, the COD
method as described here may provide the only procedure available for
evaluating oxidizable matter in an effluent. 1.4
In general, this method will be used on unfiltered samples. In the case of
these samples, suspended organic solids present will be largely or completely
oxidized during the test and will therefore contribute to the COD result
obtained on the test specimen. it must be recognized that the presence of
suspended solids may impose a significant problem in obtaining representative
aliquots. Where it is desired to measure the COD of the dissolved solids only,
samples must be filtered through a medium retentive filter paper (Note 1). 1.5
This method is used to determine COD levels up to 500 mg/L directly on
undiluted test specimens. This range can be extended upwards by appropriate
dilution of the test specimen. 1.6
It may be desirable or necessary to filter samples which contain gross
heterogeneities which are obviously not representative of the water or
wastewater stream under examination. If the sample has been filtered, this
must be stated in the report.