This European Standard specifies determination of the biochemical oxygen demand of waters of undiluted samples.
This standard is applicable to all waters having biochemical oxygen demands greater than or equal to the limit of determination 0,5 mg/l of oxygen and not exceeding 6 mg/l of oxygen. In this standard, the limit of determination, DL, is defined as
D_L=t_0,95(f) ·2·s_B·√(1+ 1/n) (1)
where sB is the within series deviation, t0,95(f) is the Student t-value, with f is the degree of freedom for the determination of sB and n is the number of analysis for determination of the blank in an analytical series. sB is calculated from determinations of real samples with a BOD concentration near the estimated DL.
In cases where the analytical method does not require any blank correction, the term
√(1+ 1/n) (2)
is omitted.
The results obtained are the product of a combination of biochemical and chemical reactions. They do not have the rigorous and unambiguous character of those resulting from, for example, a single, well-defined, chemical process. Nevertheless, they provide an indication from which the quality of waters can be estimated.
The test can be influenced by the presence of various substances. Those which are toxic to microorganisms, for example bactericides, toxic metals or free chlorine, will inhibit biochemical oxidation. The presence of algae or nitrifying microorganisms can produce high results. In these situations a modification of the method (see annex B or as described in EN 1899-1).
It is absolutely essential that test conducted according to this standard are carried out by suitably qualified staff.
Annex A describes alternative incubation periods.
Annex B describes procedures for modification of the method by addition of seeding material, salts, inhibition of nitrification by allylthiourea (ATU) addition, neutralization, homogenization and/or filtration. These modifications may be found necessary for specific evaluations of the water quality of receiving waters.
Required fields are indicated with *
