Aqualytic OxiDirect BOD-System, Инструкция по эксплуатации

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4. BOD Measurement
4.1 Sample Volume
The sample volume is related to the expected BOD value. The OxiDirect
®
is designed
to operate with the following ranges and sample volumes, allowing BOD measurement
up to 0 - 4000 mg/l, without any dilution.
Note
The expected results should be in the upper half of the range.
For domestic waste it is generally appropriate to consider a BOD
5
value which is ap-
proximately 80 % of the COD value.
Range BOD mg/l Sample volume in ml Dosage ATH
0 – 40 428 10 drops
0 – 80 360 10 drops
0 – 200 244 5 drops
0 – 400 157 5 drops
0 – 800 94 3 drops
0 – 2000 56 3 drops
0 – 4000 21.7 1 drops
4.2 Preparing the Water Sample
1. Check the pH value of the effluent sample. The optimum pH value for biochemical
oxidation is between pH 6.5 and 7.5. If the pH value of the sample is higher or lower, it
should be pre-adjusted. Any significant deviation will result in a lower BOD value. If the
pH value is too high, it can be reduced by adding dilute hydrochloric acid (1 mol/l) or
dilute sulphuric acid (1 mol/l). If the pH value is low, it can be adjusted with a sodium
hydroxide solution (1 mol/l).
2. Mix the water sample well and allow to settle for a short while. It may also be advisable
to filter or homogenise the sample.
3. Measure the sample volume precisely, using the appropriate overflow measurement
flask and pour the sample into the sample bottle (it may be helpful to use a funnel for
this). Ensure that the sample in the bottle contains a representative portion of any solids
in suspension. It is recommended that each sample should be tested twice or three
times.