Water quality - Determination of biochemical oxygen demand after n days (BODn) - Part 1: Dilution and seeding method with allylthiourea addition (ISO 5815-1:2019)

This part of ISO 5815 specifies the determination of the biochemical oxygen demand of waters by dilution and seeding with suppression of nitrification after 5 d incubation time.
This part of ISO 5815 is applicable to all waters having biochemical oxygen demands usually between 3 mg/l and 6 000 mg/l. It applies particularly to waste waters. For biochemical oxygen demands greater than 6 000 mg/l of oxygen, the method is still applicable, but the errors caused by the necessary dilutions can influence the analytical quality of the test method. Then the results are to be interpreted
with circumspection.
The results obtained are the product of a combination of biochemical and chemical reactions with participation by living matter which behaves only with occasional reproducibility. 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.

Wasserbeschaffenheit - Bestimmung des biochemischen Sauerstoffbedarfs nach n Tagen (BSBn) - Teil 1: Verdünnungs- und Impfverfahren mit Zugabe von Allylthioharnstoff (ISO 5815-1:2019)

Dieses Dokument legt die Bestimmung des biochemischen Sauerstoffbedarfs in Wässern durch Verdünnung und Impfen mit Nitrifikationshemmung nach 5 d oder 7 d Inkubationsdauer fest.
Es ist für alle Wässer geeignet, deren biochemischer Sauerstoffbedarf in der Regel zwischen 1 mg/l und 6 000 mg/l liegt. Es ist insbesondere für Abwässer anwendbar, ist aber auch für natürliche Wässer geeignet. Für einen biochemischen Sauerstoffbedarf von mehr als 6 000 mg/l Sauerstoff ist das Verfahren zwar noch anwendbar, aber besondere Vorsicht im Hinblick auf die Repräsentativität der Teilproben zur Herstellung der Verdünnungen ist geboten. Die erzielten Ergebnisse beruhen auf einer Kombination von biochemischen und chemischen Reaktionen unter Beteiligung von lebender Materie, welche sich nur selten reproduzierbar verhält. Die erhaltenen Ergebnisse haben daher keinen exakten und eindeutigen Charakter wie z. B. die eines einzelnen gut definierten chemischen Prozesses, liefern aber dennoch einen Hinweis, der auf die Beschaffenheit von Wässern schließen lässt.

Qualité de l'eau - Détermination de la demande biochimique en oxygène après n jours (DBOn) - Partie 1: Méthode par dilution et ensemencement avec apport d'allylthiourée (ISO 5815-1:2019)

Le présent document spécifie la méthode de détermination de la demande biochimique en oxygène dans les eaux, par dilution et ensemencement, avec suppression de la nitrification après une durée d'incubation de 5 jours ou 7 jours.
Cette méthode est applicable à tous les types d'eau dont la demande biochimique en oxygène se situe généralement entre 1 mg/l et 6 000 mg/l. Elle s'applique particulièrement aux eaux usées mais convient également à l'analyse des eaux naturelles. Pour des demandes biochimiques en oxygène de plus de 6 000 mg/l d'oxygène, la méthode est encore applicable, mais une attention particulière est nécessaire concernant la représentativité du sous-échantillonnage pour la préparation des étapes de dilution. Les résultats obtenus sont le produit d'une combinaison de réactions biochimiques et chimiques en présence de matière vivante dont le comportement et les caractéristiques ne sont qu'occasionnellement reproductibles. Les résultats ne possèdent pas le caractère exact et rigoureux de résultats issus par exemple d'un processus chimique unique bien défini. Les résultats fournissent cependant une indication qui permet d'estimer la qualité des eaux.

Kakovost vode - Določevanje biokemijske potrebe po kisiku po n dneh (BPKn) - 1. del: Metoda razredčevanja in cepljenja z dodatkom aliltiosečnine (ISO 5815-1:2019)

Ta del standarda ISO 5815 opredeljuje določevanje biokemijske potrebe po kisiku pri razredčevanju in cepljenju z zaviranjem nitrifikacije po 5-dnevni inkubacijski dobi.
Ta del standarda ISO 5815 se uporablja za vse vode z biokemijsko potrebo po kisiku, ki je običajno med 3 mg/l in 6000 mg/l. Uporablja se predvsem za odpadne vode. Če je biokemijska potreba po kisiku večja od 6000 mg/l kisika, se metoda še vedno uporablja, vendar lahko napake zaradi potrebnega razredčevanja vplivajo na kakovost analize pri tej preskusni metodi. Rezultate je treba razlagati previdno.
Pridobljeni rezultati so posledica kombinacije biokemijskih in kemijskih reakcij, v katerih sodelujejo žive snovi in se odzivajo le z občasno ponovljivostjo. Nimajo strogega in nedvoumnega značaja kot na primer tiste, ki nastanejo z enim natančno določenim kemijskim procesom. Kljub temu služijo kot kazalnik, na podlagi katerega je mogoče oceniti kakovost vode.

General Information

Status
Published
Public Enquiry End Date
01-Feb-2018
Publication Date
29-Sep-2019
Withdrawal Date
12-Nov-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Sep-2019
Due Date
25-Nov-2019
Completion Date
30-Sep-2019

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SLOVENSKI STANDARD
SIST EN ISO 5815-1:2019
01-november-2019
Nadomešča:
SIST EN 1899-1:2000
SIST EN 1899-2:2000
Kakovost vode - Določevanje biokemijske potrebe po kisiku po n dneh (BPKn) - 1.

del: Metoda razredčevanja in cepljenja z dodatkom aliltiosečnine (ISO 5815-1:2019)

Water quality - Determination of biochemical oxygen demand after n days (BODn) - Part

1: Dilution and seeding method with allylthiourea addition (ISO 5815-1:2019)
Wasserbeschaffenheit - Bestimmung des biochemischen Sauerstoffbedarfs nach n

Tagen (BSBn) - Teil 1: Verdünnungs- und Impfverfahren mit Zugabe von Allylthioharnstoff

(ISO 5815-1:2019)

Qualité de l'eau - Détermination de la demande biochimique en oxygène après n jours

(DBOn) - Partie 1: Méthode par dilution et ensemencement avec apport d'allylthiourée

(ISO 5815-1:2019)
Ta slovenski standard je istoveten z: EN ISO 5815-1:2019
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
SIST EN ISO 5815-1:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 5815-1:2019
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SIST EN ISO 5815-1:2019
EN ISO 5815-1
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2019
EUROPÄISCHE NORM
ICS 13.060.50 Supersedes EN 1899-2:1998
English Version
Water quality - Determination of biochemical oxygen
demand after n days (BODn) - Part 1: Dilution and seeding
method with allylthiourea addition (ISO 5815-1:2019)

Qualité de l'eau - Détermination de la demande Wasserbeschaffenheit - Bestimmung des

biochimique en oxygène après n jours (DBOn) - Partie biochemischen Sauerstoffbedarfs nach n Tagen (BSBn)

1: Méthode par dilution et ensemencement avec apport - Teil 1: Verdünnungs- und Impfverfahren mit Zugabe

d'allylthiourée (ISO 5815-1:2019) von Allylthioharnstoff (ISO 5815-1:2019)
This European Standard was approved by CEN on 26 July 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5815-1:2019 E

worldwide for CEN national Members.
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SIST EN ISO 5815-1:2019
EN ISO 5815-1:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 5815-1:2019
EN ISO 5815-1:2019 (E)
European foreword

This document (EN ISO 5815-1:2019) has been prepared by Technical Committee ISO/TC 147 "Water

quality" in collaboration with Technical Committee CEN/TC 230 “Water analysis” the secretariat of

which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by March 2020, and conflicting national standards shall

be withdrawn at the latest by March 2020.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN 1899-2:1998.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 5815-1:2019 has been approved by CEN as EN ISO 5815-1:2019 without any

modification.
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SIST EN ISO 5815-1:2019
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SIST EN ISO 5815-1:2019
INTERNATIONAL ISO
STANDARD 5815-1
Second edition
2019-07
Water quality — Determination of
biochemical oxygen demand after n
days (BOD ) —
Part 1:
Dilution and seeding method with
allylthiourea addition
Qualité de l'eau — Détermination de la demande biochimique en
oxygène après n jours (DBO ) —
Partie 1: Méthode par dilution et ensemencement avec apport
d'allylthiourée
Reference number
ISO 5815-1:2019(E)
ISO 2019
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Principle ........................................................................................................................................................................................................................ 3

5 Reagents ........................................................................................................................................................................................................................ 3

6 Apparatus ..................................................................................................................................................................................................................... 6

7 Sampling and preservation ....................................................................................................................................................................... 6

8 Interferences ............................................................................................................................................................................................................ 7

8.1 General ........................................................................................................................................................................................................... 7

8.2 Presence of free and/or combined chlorine .................................................................................................................. 7

8.3 Presence of algae ................................................................................................................................................................................... 7

8.4 Presence of peroxides and peroxide compounds...................................................................................................... 8

9 Procedure..................................................................................................................................................................................................................... 8

9.1 General ........................................................................................................................................................................................................... 8

9.2 Pretreatment ............................................................................................................................................................................................. 8

9.2.1 Neutralization of the sample ................................................................................................................................. 8

9.2.2 Homogenization ............................................................................................................................................................... 9

9.3 Preparation of test solutions ....................................................................................................................................................... 9

9.4 Calculation of dilutions .................................................................................................................................................................... 9

9.4.1 Empirical determination of the dilutions ................................................................................................... 9

9.4.2 Determination of dilutions via the factors R of the TOC, the permanganate

index or the COD ...........................................................................................................................................................10

9.4.3 Calculation of dilution stages via the COD ..............................................................................................11

9.5 Blank value determination ........................................................................................................................................................11

9.6 Determination of dissolved oxygen ....................................................................................................................................11

9.6.1 Measurement of dissolved oxygen using iodometric method (in

accordance with ISO 5813) ..................................................................................................................................11

9.6.2 Measurement of dissolved oxygen using probes (in accordance with

ISO 5814 or ISO 17289) ..........................................................................................................................................12

9.7 Control analysis ...................................................................................................................................................................................12

10 Calculation and indication of the results .................................................................................................................................13

10.1 Examination of test solutions for valid oxygen consumption during test ........................................13

10.2 Calculation of biochemical oxygen demand after n days (BOD ) .............................................................13

10.3 Validity criteria ....................................................................................................................................................................................14

11 Test report ................................................................................................................................................................................................................14

Annex A (normative) Influence of incubation periods and temperatures .................................................................15

Annex B (informative) Multitesting ....................................................................................................................................................................16

Annex C (informative) Direct seeding of the analysis batches ................................................................................................19

Annex D (informative) Performance data ....................................................................................................................................................20

Bibliography .............................................................................................................................................................................................................................22

© ISO 2019 – All rights reserved iii
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the World

Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL:

www .iso .org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 5,

Biological methods.

This second edition cancels and replaces the first edition (ISO 5815-1:2003), which has been technically

revised. The main changes compared to the previous edition are as follows:
— change of working range: 1 mg/l instead of 3 mg/l as lower limit;
— changes in test procedure;

— in 5.2, option to check seeding water suitability in advance with a CGA control analysis batch;

— in 5.3.2, phosphate buffer solution pH-value: requirement for preparation of a new solution if the pH

value is out of the range pH 7 and pH 8;

— in 5.5, range for oxygen consumption of seeded dilution water 0,2 mg/l to 1,5 mg/l instead of upper

limit 1,5 mg/l;

— in 5.9, allowable range BOD of the CGA control solution changed to (198 ± 40) mg/l and BOD

5 7
(206 ± 40) mg/l;

— in 6.5, electrochemical probe option to measure the dissolved oxygen concentration added;

— in 8.4, interferences: subclause on presence of peroxides and peroxide compounds added;

— in 9.4, options to determinate the dilutions elaborated;
— in 9.7, control analysis: elaborated description of procedure;
— in 10.3, "approval of results/validity criteria” added;
— Annex A: title changed and “normative” instead of “informative”
— Annex C "Direct seeding of the analysis batches" added;
iv © ISO 2019 – All rights reserved
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
— new Annex D "Performance data" included.
A list of all parts in the ISO 5815 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
© ISO 2019 – All rights reserved v
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
Introduction

The incubation time specified in this document is 5 d or 7 d. The latter corresponds to the practice in

several Nordic countries. Annex A describes an incubation time of (2 + 5) d.

ISO 5815-1 specifies the determination of the biochemical oxygen demand (BOD) of waters with an

expected BOD in the range 1 mg/l to 6 000 mg/l using the dilution method. A lower limit of working

range may result from validation data in the laboratory. For samples with an expected low BOD in the

range of 0,5 mg/l to 6 mg/l ISO 5815-2 provides the option of the determination of the (BOD) of waters

using undiluted samples.
vi © ISO 2019 – All rights reserved
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SIST EN ISO 5815-1:2019
INTERNATIONAL STANDARD ISO 5815-1:2019(E)
Water quality — Determination of biochemical oxygen
demand after n days (BOD ) —
Part 1:
Dilution and seeding method with allylthiourea addition

WARNING — Persons using this document should be familiar with normal laboratory practice.

This document does not purport to address all of the safety problems, if any, associated with its

use. It is the responsibility of the user to establish appropriate safety and health practices.

IMPORTANT — It is absolutely essential that tests conducted in accordance with this document

be carried out by suitably qualified staff.
1 Scope

This document specifies the determination of the biochemical oxygen demand of waters by dilution and

seeding with suppression of nitrification after 5 d or 7 d incubation time.

It is applicable to all waters having biochemical oxygen demands usually between 1 mg/l and

6 000 mg/l. It applies particularly to waste waters but also suits for the analysis of natural waters.

For biochemical oxygen demands greater than 6 000 mg/l of oxygen, the method is still applicable, but

special care is needed taking into consideration the representativeness of subsampling for preparation

of the dilution steps. The results obtained are the product of a combination of biochemical and chemical

reactions in presence of living matter which behaves only with occasional reproducibility. The results

do not have the rigorous and unambiguous character of those resulting from, for example, a single,

well-defined, chemical process. Nevertheless, the results provide an indication from which the quality

of waters can be estimated.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 5667-3, Water quality — Preservation and handling of water samples
ISO 5813, Water quality — Determination of dissolved oxygen — Iodometric method

ISO 5814, Water quality — Determination of dissolved oxygen — Electrochemical probe method

ISO 6060, Water quality — Determination of the chemical oxygen demand

ISO 8245, Water quality — Guidelines for the determination of total organic carbon (TOC) and dissolved

organic carbon (DOC)
ISO 8467, Water quality — Determination of permanganate index
ISO 10523, Water quality — Determination of pH

ISO 15705, Water quality — Determination of the chemical oxygen demand index (ST-COD) — Small-scale

sealed-tube method

ISO 17289, Water quality — Determination of dissolved oxygen — Optical sensor method

© ISO 2019 – All rights reserved 1
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
biochemical oxygen demand after n days
BOD

mass concentration of dissolved oxygen consumed under specified conditions by the biochemical

oxidation of organic and/or inorganic matter in water where n is the incubation time equal to 5 d or 7 d

Note 1 to entry: For the purposes of this document “biochemical oxidation” is taken to mean “biological oxidation”.

Note 2 to entry: n is either 5 or 7.
3.2
chemical oxygen demand
COD

mass concentration of oxygen equivalent to the amount of dichromate consumed by dissolved and

suspended matter when a water sample is treated with that oxidant under defined conditions

[SOURCE: ISO 6060:1989, 3]
3.3
total organic carbon
TOC

sum of organically bound carbon present in water, bonded to dissolved or suspended matter, including

cyanate, elemental carbon and thiocyanate
[SOURCE: ISO 8245:1999, 3.3]
3.4
permanganate index (of water)

mass concentration of oxygen equivalent to the amount of permanganate ion consumed when a water

sample is treated with that oxidant under defined conditions
[SOURCE: ISO 8467:1993, 3.1]
3.5
seeding water

water with adapted (aerobic) microorganisms via which the oxidation of the water contents occurs

Note 1 to entry: The seeding water is used for producing the seeded dilution water.

3.6
dilution water
water added to the test sample to prepare a series of defined dilutions
[SOURCE: ISO 20079:2005, 3.7]
3.7
seeded dilution water
dilution water to which a definite amount of seeding water is added
2 © ISO 2019 – All rights reserved
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)
3.8
free chlorine

chlorine present in the form of hypochlorous acid, hypochlorite ion or dissolved elemental chlorine

[SOURCE: ISO 7393-1:1985, 2.1]
3.9
combined chlorine

fraction of total chlorine present in the form of chloramines and organic chloramines

[SOURCE: ISO 7393-1:1985, 2.2]
3.10
nitrification

oxidation of ammonium salts by bacteria where usually the intermediate product is nitrite and the end

product nitrate
[SOURCE: ISO 11733:2004, 3.9]
4 Principle

The BOD , 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 ± 1) °C for a specified period (n), 5 d 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.
5 Reagents
Use only reagents with the degree of purity "for analysis".
5.1 Water, at least grade 3 in accordance with ISO 3696.

The water shall not contain more than 0,01 mg/l of copper, nor chlorine or chloramines.

5.2 Seeding water, which can be obtained in one of the following ways:
a) municipal waste water, decanted or coarsely filtered;
b) surface water containing municipal waste water;
c) settled effluent from a waste water treatment plant;

d) water taken downstream from the discharge of the water to be analysed, or water containing

microorganisms that are adapted to the water to be analysed;
e) commercially available seeding material.

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.

© ISO 2019 – All rights reserved 3
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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)

The selected seeding material can be checked in advance by running the procedure with a control

analysis (9.7) batch only to prove its suitability for the analysis of samples.
5.3 Salt solutions
5.3.1 General

The following solutions can be kept for at least six months in glass bottles in the dark at (5 ± 3) °C.

Discard the solutions at the first signs of precipitation or opaqueness.
5.3.2 Phosphate-buffer solution

Dissolve 8,50 g of potassium dihydrogen phosphate (KH PO ), 21,75 g of dipotassium hydrogen

2 4

phosphate (K HPO ), 33,4 g of disodium hydrogen phosphate-heptahydrate (Na HPO ⋅7H O) and 1,70 g

2 4 2 4 2

of ammonium chloride (NH Cl), in about 500 ml of water (5.1). Dilute with water (5.1) to 1 000 ml and

mix. Measure the pH value. If the pH value is outside the range pH 7 to pH 8, prepare a new solution.

5.3.3 Magnesium sulfate heptahydrate solution, ρ = 22,5 g/l.

Dissolve 22,5 g of magnesium sulfate heptahydrate (MgSO ⋅7H O) in water (5.1). Dilute with water (5.1)

4 2
to 1 000 ml and mix.
5.3.4 Calcium chloride solution, ρ = 27,5 g/l.

Dissolve 27,5 g of anhydrous calcium chloride (CaCl ) (or an equivalent amount, if the hydrate is used

(for example 36,4 g CaCl ⋅2H O) in water (5.1), dilute with water (5.1) to 1 000 ml and mix.

2 2
5.3.5 Iron (III)-chloride-hexahydrate solution, ρ = 0,25 g/l.

Dissolve 0,25 g of iron (III)-chloride-hexahydrate (FeCl ⋅6H O), in water (5.1). Dilute with water (5.1) to

3 2
1 000 ml and mix.
5.4 Dilution water

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, 5.3.3, 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 ± 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.
5.5 Seeded dilution water

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 ± 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.

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SIST EN ISO 5815-1:2019
ISO 5815-1:2019(E)

The amount of the seeding water (5.2) needed to attain a hypothetic COD of 0,6 mg/l to 3,0 mg/l,

corresponding to the aimed oxygen consumption in the blank values (9.5), is calculated with

Formula (1):
COD ⋅V
target dilutionwater
V = (1)
seedingwater
COD
seedingwater
where

V is the volume of the seeding water (5.2) to be added to the dilution water (5.4) in

seeding water
litres, l;

COD is the hypothetic COD (0,6 mg/l O to 3 mg/l O ) in the seeded dilution water (5.5)

target 2 2
in milligrams per litre of oxygen, mg/l O ;
COD is the C
...

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