(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 4
to measure mono- and dichloramine and nitrogen trichloride is considered important [ 165, EA
UK 2008 ].
{Please TWG provide information.}
Economics
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Example plants
In Germany, regulatory measurements of free chlorine in membrane cell chlor-alkali plants are
carried out according to EN ISO 7393–1 [ 161, Germany 2004 ]. In Austria, EN ISO 7393–1
and –2 are used for the determination of free chlorine [ 160, Austria 1996 ].
{Please TWG provide more information which methods are used to measure free oxidants.}
Reference literature
[ 70, COM 2003 ], [ 160, Austria 1996 ], [ 161, Germany 2004 ], [ 162, CEN 2000 ], [ 163,
CEN 2000 ], [ 164, CEN 2000 ], [ 165, EA UK 2008 ], [ 272, DIN 1984 ], [ 273, ASI 2005 ]
4.3.4.6 Monitoring of halogenated organic compounds in water
Issues of general relevance for all monitoring techniques are described in Section 4.3.4.2.
Description
Halogenated organic compounds in effluents are usually measured as AOX (adsorbable
organically-bound halogens) and EOX (extractable organically-bound halogens). These
parameters are quantitative surrogate parameters as described in the Reference Document on
General Principles of Monitoring [ 70, COM 2003 ].
Technical description
The most commonly used method to measure AOX is the EN ISO 9562 standard. It is based on
the adsorption of halogenated organic compounds on activated carbon, which is subsequently
washed and burnt in pure oxygen. The hydrogen chloride, hydrogen bromide and hydrogen
iodide thus formed are absorbed in a solution and quantified by argentometry (e.g. by using
microcoulometry). The method is applicable to test samples with AOX concentrations higher
than 10 Zg/l and chloride concentrations lower than 1 g/l [ 157, CEN 2004 ]. The use of this
method for the analysis of waste water from chlor-alkali plants is impaired by the usually high
chloride concentrations (see Table 3.11). The standard allows sample dilution but the resulting
AOX concentrations may then be lower than the application limits of the standard.
An alternative method is the EOX which is based on a liquid-liquid extraction of the
halogenated organic compounds with a non-polar solvent such as hexane which is subsequently
burnt in an oxyhydrogen torch. The hydrogen chloride, hydrogen bromide and hydrogen iodide
thus formed are absorbed in a solution and quantified by argentometry (e.g. by using
microcoulometry), photometry or by using ion-selective electrodes. The EOX method is not
WORKING DRAFT IN PROGRESS
standardised on a European or international level, but some national standards in EU Member
States exist such as DIN 38409 – H 4 [ 158, DIN 1984 ] and OENORM M 6614 [ 159, ASI
2001 ].
Another alternative consists in using a modified AOX method which is described in the
informative Annex A of the EN ISO 9562 standard. In this method, the halogenated organic
compounds are first separated from inorganic halides by using solid phase extraction with a
styrene-divinylbenzene copolymer. The resulting extract is subsequently analysed according to
the traditional AOX method. The modified AOX method tolerates chloride concentrations up to
100 g/l [ 157, CEN 2004 ].
216 December 2011 TB/EIPPCB/CAK_Draft_1