BS EN ISO 5815-1:2019 pdf free.Water quality – Determination of biochemical oxygen demand after n days (BODn).
The BODn, with inhibition of nitrification is determined, using the dilution method. A batch series with different dilutions of a sample is prepared and examined. The dilution water is enriched with oxygen and seeded with adapted aerobic microorganisms. The sample is incubated at (20土1)。C for a specified period (n), 5d or 7 d, in the dark, in a completely filled and stoppered bottle. The dissolved oxygen concentration is determined before and after incubation. The mass of consumed oxygen per litre sample is calculated.Use seeding water with a COD of about 300 mg/l or a TOC of about 100 mg/l (see 5.5]. If the COD or TOC are higher, adapt to these concentrations with dilution water (5.4) before preparing the seeded dilution water (5.5) or use a correspondingly changed volume of the seeding waters for seeding the dilution water (5.4). If the sample comes from a process that has been subjected to disinfection treatment (chlorination, UV, ozone or other), use inoculum, even when there is no residual disinfectant present. For commercially available seeding material consider respective application recommendations. Determine the total volume of dilution water required for the actual test. Pour about half the required volume of water (5.1) into the feed vessel [6.3) for the dilution water and add 1 ml of each of the salt solutions (5.3.2, 5..3, 5.3.4 and 5.3.5) for each litre of the total volume. Then fill to the required total  volume with water (5.1) and mix by stirring, aeration or shaking. Bring the dilution water obtained in this way to a temperature of (20土2) °C, keep at this temperature and aerate slightly by mixing. If, for example, specially adapted seeding water or seeding material is necessary, the procedure according to Annex C can be followed. EXAMPLE If 20 l of dilution water are required, prepare 10 l of water (5.1). Stirring continuously, add 20 ml of each of the salt solutions individually and fill up with water (5.1) to 20 l. The preparation of a seeded dilution water is needed when the test solutions are prepared according to 9.3 The mass concentration of oxygen consumed over 5 d [or 7 d) at (20土1) °C by the seeded dilution water with the addition of allylthiourea (ATU) solution to inhibit nitrification [blank value (see 9.5)], shall be between 0,2 mg/l and 1,5 mg/l. The volume increase of the dilution water by seeding water should be as low as possible.BS EN ISO 5815-1 pdf download.