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BRITISH STANDARD Water quality Ð Determination of biochemical oxygen demand after n days (BODn) Ð Part 1: Dilution and seeding method with allylthiourea addition The European Standard EN 1889-1:1998 has the status of a British Standard ICS 13.060.01; 13.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BS EN 1899-1:1998 BS 6068-2.63: 1998 Confirmed July 2008 BS EN 1899-1:1998 National foreword This British Standard is the English language version of EN 1899-1:1998 It supersedes BS 6068-2.14:1990 which is withdrawn The UK participation in its preparation was entrusted by Technical Committee EH/3, Water quality, to Subcommittee EH/3/2, Physical, chemical and biochemical methods, which has the responsibility to: ± ± ± aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK A list of organizations represented on this subcommittee can be obtained on request to its secretary BS EN 1899-1 is one of a series of standards on water quality, others of which have been, or will be, published as Sections of BS 6068 This standard has therefore been given the secondary identifier BS 6068-2.63 The various Sections of BS 6068 are comprised within Parts to 7, which, together with Part 0, are listed below Part Part Part Part Part Part Part Part Introduction Glossary Physical, chemical and biochemical methods Radiological methods Microbiological methods Biological methods Sampling Precision and accuracy NOTE The tests described in this British Standard should only be carries out by suitably qualified persons with an appropriate level of chemical expertize Standard chemical procedures should be followed throughout Further information Users of this standard are informed that the UK submitted a vote of disapproval on the final voting stage of the draft EN for the following reasons ± Although we are in general technical agreement with the basis of the draft, we are still submitting a negative vote as this standard contains two methods We therefore consider that it should be published as two separate standards, i.e a day one and a day one This would thereby avoid any possible confusion when quoting the standard or reporting the results of analysis ± We also strongly recommend deletion of the reference to ISO 5815:1989 in the title as it serves no purpose and could be misleading The ISO standard is for days only and it is thus wrong to claim in the Foreword that it has been approved with common modifications with no reference to the major change in test conditions Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled `International Standards Correspondence Index', or by using the `Find' facility of the BSI Standards Electronic Catalogue A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This British Standard, having been prepared under the direction of the Health and Environment Sector Committee was published under the authority of the Standards Committee and comes into effect on 15 November 1998 This document comprises a front cover, an inside front cover, page to 12, an inside back cover and a back cover Amendments issued since publication Amd No BSI 1998 ISBN 580 29680 Date Text affected EN 1899-1 EUROPEAN STANDARD NORME EUROPÊENNE EUROPẰISCHE NORM March 1998 ICS 13.060.01 Descriptors: water tests, water, chemical analysis, determination of content, biochemical oxygen demand, dilution English version Water quality Ð Determination of biochemical oxygen demand after n days (BODn) Ð Part 1: Dilution and seeding method with allylthiourea addition (ISO 5815:1989, modified) Qualite de l'eau Ð DeÂtermination de la demande biochimique en oxygeÁne apreÁs n jours (DOBn) Ð Partie 1: MeÂthode par dilution et ensemencement avec apport d'allyl thio-ureÂe (ISO 5815:1989, modifieÂe) Wasserbeschaffenheit Ð Bestimmung des Biochemischen Sauerstoffbedarfs nach n Tagen (BSBn) Ð Teil 1: VerduÈnnungs- und Impfverfahren nach Zugabe von Allylthioharnstoff (ISO 5815:1989, modifiziert) This European Standard was approved by CEN on 13 February 1998 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 Central Secretariat 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 Central Secretariat has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comite EuropeÂen de Normalisation EuropaÈisches Komitee fuÈr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 1899-1:1998 E Page EN 1899-1:1998 Foreword This European Standard has been prepared by 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 September 1998, and conflicting national standards shall be withdrawn at the latest by September 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, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom This European Standard consists of the following parts: EN 1899-1, Water quality Ð Determination of biochemical oxygen demand after n days (BODn) Ð Part 1: Dilution and seeding method with allylthiourea addition EN 1899-2, Water quality Ð Determination of biochemical oxygen demand after n days (BODn) Ð Part 2: Method for undiluted samples Annex A, which is normative, concerns alternative incubation periods Annex B, which is informative, concerns multitesting, which may be used to obtain enhanced precision, or if the presence of substances toxic to microorganisms is suspected Endorsement notice The text of the International Standard ISO 5815:1989 was approved by CEN as a European Standard with agreed common modifications as given below: ± change in setup (splitting into two parts) ± addition of annexes Contents Foreword Introduction Scope Normative references Definition Principle Reagents Apparatus Storage of the sample Procedure Calculation and expression of results 10 Trueness and precision 11 Special cases 12 Test report Annex A Ð (normative) Alternative incubation periods Annex B Ð (informative) Multitesting Page 3 4 5 8 11 12 BSI 1998 Page EN 1899-1:1998 Introduction This European Standard EN 1899-1 is a modified version of ISO 5815:1989, Water quality Ð Determination of biochemical oxygen demand after days (BOD5) Ð Dilution and seeding method The times of incubation specified in the proposal are days - as in ISO 5815 and as has been applied in many European countries - or days as has been applied in several Nordic countries through the past many years The day incubation will typically give higher BOD results than days incubation time With an incubation time of days, weekend work can only be avoided if samples are collected Wednesdays, Thursdays to Fridays With an incubation time of days, samples collected on the first five weekdays can be analysed without implying weekend work For this reason a day incubation can be considered more convenient than the conventional day incubation A new, modified day incubation is described in a normative annex The first investigations indicate that BOD results obtained by this modified method are identical to results obtained by the day method described in the proposed standard It is hoped that more comparative data on these two incubation methods will be obtained during the coming years, so that the modified day incubation method can be included fully at the time of review and revision of this standard The results obtained are the product of a combination of biochemical and chemical reactions They 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 artificially high results It is absolutely essential that tests conducted according to this standard are carried out by suitably qualified staff Annex A describes alternative incubation periods Annex B describes multitesting, which can be used to obtain enhanced precision or to demonstrate the presence of substances toxic to microorganisms Normative references This European Standard incorporates by dated or undated reference provisions from other publications These normative references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only Scope when incorporated in it by amendment or revision For undated references the latest edition of the publication This European Standard specifies a determination of referred to applies the biochemical oxygen demand of waters by dilution and seeding with suppression of nitrification EN ISO 3696, Water for analytical laboratory use Ð Specification and test methods (ISO 3696:1987) This standard is applicable to all waters having biochemical oxygen demands greater than or equal to EN 25813, Water quality Ð Determination of dissolved the limit of determination mg/l of oxygen and not oxygen Ð Iodometric method (ISO 5813:1983) exceeding 000 mg/l of oxygen For biochemical EN 25814, Water quality Ð Determination of dissolved oxygen demands greater than 000 mg of oxygen/l, the oxygen Ð Electrochemical probe method method is still applicable, but the errors caused by the (ISO 5814:1990) necessary dilutions can influence the analytical quality of the test method and the results are to be interpreted EN ISO 8467, Water quality Ð Determination of permanganate index (ISO 8467:1993) with circumspection In this standard the limit of ISO 6060:1989, Water quality Ð Determination of detection, DL, is defined as chemical oxygen demand DL = t0,95(f) ´ ´ sB ´ + (1) ISO 6107-2:1997, Water quality Ð Vocabulary Ð n Part where sB is the within series standard deviation,t0,95(f) ISO 7393-1:1985, Water quality Ð Determination of is the student t-value, with f is the degrees of freedom free chlorine and total chlorine Ð Part 1: Titrimetric for the determination of sB and n is the number of method using N,N-diethyl-1,4-phenylenediamine analysis for determination of the blank in an analytical ISO 7393-2:1985, Water quality Ð Determination of series sB is calculated from determinations of real free chlorine and total chlorine Ð Part 2: Colorimetric samples with a BOD content near the estimated DL method using N,N-diethyl-1,4-phenylenediamine, for In cases where the analytical method does not require routine control purposes any blank correction the term ISO 8245:1987, Water quality Ð Guidelines for the (2) determination of total organic carbon (TOC) 1+ n is omitted √ √ BSI 1998 Page EN 1899-1:1998 Definition For the purposes of this European Standard, the following definition applies: biochemical oxygen demand after n days (BODn) the mass concentration of dissolved oxygen consumed under specified conditions by the biochemical oxidation of organic and/or inorganic matter in water n is the incubation time; it is equal to or NOTE This definition is similar to the definition of ISO 6107-2 For the purpose of this European Standard, ``biochemical oxidation'' is taken to mean ªbiological oxidationº Principle Pre-treatment of the sample of water to be analysed and dilution with varying amounts of a dilution water rich in dissolved oxygen and containing a seed of aerobic microorganisms, with suppression of nitrification Incubation at 20 8C for a defined period, or days, in the dark, in a completely filled and stoppered bottle Determination of the dissolved oxygen concentration before and after incubation Calculation of the mass of oxygen consumed per litre of sample Reagents 5.1 General Throughout the text, use only reagents of recognized analytical quality 5.2 Water Use only grade water (in accordance with EN ISO 3696) However, the water shall not contain more than 0,01 mg/l of copper, nor chlorine or chloramines 5.3 Seeding water If the test sample does not contain, by itself, sufficient adapted microorganisms, seeding water, obtained in one of the following ways, shall be used: a) Urban waste water of maximum COD (chemical oxygen demand measured in accordance with ISO 6060) 300 mg/l or TOC (total organic carbon measured in accordance with ISO 8245) 100 mg/l, collected from a main sewer or from a sewer of a residential zone free from significant industrial contamination Decant or filter the water through a coarse filter; b) River or lake water containing urban 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 adapted to the water to be analysed and cultivated in the laboratory (in the case of industrial effluents containing substances which degrade with difficulty); e) Commercially available seeding material 5.4 Salt solutions 5.4.1 General The following solutions are stable for months and shall be stored in glass bottles at 8C to 8C in the dark They shall be discarded at the first sign of precipitation or biological growth 5.4.2 Phosphate, buffer solution, pH 7,2 Dissolve 8,5 g of potassium dihydrogen phosphate (KH2PO4), 21,75 g of dipotassium hydrogen phosphate (K2HPO4), 33,4 g of disodium hydrogen phosphate heptahydrate (Na2HPO4´7H2O) and 1,7 g of ammonium chloride (NH4Cl) in about 500 ml of water Dilute to 000 ml and mix NOTE The pH of this buffer solution should be 7.2 without further adjustment 5.4.3 Magnesium sulfate heptahydrate, 22,5 g/l solution Dissolve 22,5 g of magnesium sulfate heptahydrate (MgSO4´7H2O) in water Dilute to 000 ml and mix 5.4.4 Calcium chloride, 27,5 g/l solution Dissolve 27,5 g of anhydrous calcium chloride (CaCl2) (or equivalent, if hydrated calcium chloride is used (for example 36,4 g CaCl2´2H2O)) in water Dilute to 000 ml and mix 5.4.5 Iron(III) chloride hexahydrate, 0,25 g/l solution Dissolve 0,25 g of iron(III) chloride hexahydrate (FeCl3´6H2O) in water Dilute to 000 ml and mix 5.5 Dilution water Add to about 500 ml of water ml of each of the salt solutions (5.4.2, 5.4.3, 5.4.4 and 5.4.5) Dilute to 000 ml and mix Bring the solution thus obtained to a temperature of 20 8C ± 8C and keep at this temperature; aerate for at least h using a suitable equipment Take every precaution not to contaminate it (see 6.7), in particular by the addition of organic matter, metals, oxidizing or reducing substances, to ensure that the dissolved oxygen concentration is at least mg/l The water shall not be supersaturated with oxygen - let it stand h in an unstoppered container before use Use this solution within 24 h of preparation and discard any remaining solution, unless laboratory experience and/or the control values show that the water is acceptable for a longer time period 5.6 Seeded dilution water Add, according to its source, ml to 20 ml of the seeding water (see 5.3) per litre of dilution water (see 5.5) Store the seeded dilution water thus obtained at about 20 8C Prepare immediately before use and discard any remaining solution at the end of the working day, unless the laboratory experience and/or the control values (see 8.5) show that the seeded dilution water is acceptable for a longer time period The oxygen consumed over n days, at 20 8C of the seeded dilution water, which is the blank value (see 8.3), shall not exceed 1,5 mg/l of oxygen BSI 1998 Page EN 1899-1:1998 5.7 Hydrochloric acid (HCl) or sulfuric acid, (H2SO4), solution, c(H2SO4) ≈ 0,25 mol/l, c(HCl) ≈ 0,50 mol/l, or as appropriate 6.4 Incubator, capable of being maintained at (20 ± 1) 8C 5.8 Sodium hydroxide (NaOH), solution Approximately 20 g/l or as appropriate 6.5 Equipment for determining dissolved oxygen concentration, in accordance with EN 25813 or EN 25814 5.9 Sodium sulfite (Na2SO3), solution Approximately 50 g/l or as appropriate 6.6 Means of refrigeration, (0 to 4) 8C, for transport and storage of the sample 5.10 Glucose-glutamic acid, control solution Dry some anhydrous D-glucose (C6H12O6) and some L-glutamic acid (C5H9NO4) at (105 ± 5) 8C for h Weigh (150 ± 1) mg of each, dissolve in water, dilute to 000 ml and mix The theoretical oxygen demand of this solution is 307 mg/l oxygen (the empirical BOD5 is (210 ± 20) mg/l of oxygen and the BOD7 is (225 ± 20) mg/l of oxygen) Prepare the solution immediately before use and discard any remaining solution at the end of the working day The solution may also be frozen in small amounts The thawed solution shall be used immediately after thawing 6.7 Dilution vessel, a stoppered glass flask of a capacity dependent on the volume of the diluted sample used with graduation of between 2,5 ml and 10 ml or any appropriate vessel allowing for dilution 5.11 Allylthiourea (ATU), solution, 1,0 g/l Dissolve 200 mg of allylthiourea (C4H8N2S) in water, dilute to 200 ml and mix Store the solution at 8C The solution is stable for at least two weeks This compound is toxic and should therefore be handled with care Apparatus 6.1 General The glassware used shall be clean, i.e free of adsorbed toxic or biodegradable compounds, and shall be protected from contamination 6.2 Incubation bottles, BOD bottles, with stoppers, for example preferably 250 ml to 300 ml or 100 ml to 125 ml with stoppers and preferably with straight shoulders, or any equivalent bottles It is important that the bottles are thoroughly cleaned before use If the iodometric method (EN 25813) for determining dissolved oxygen is used, it is for example normally sufficient to rinse the bottle several times with tap water then deionized water If the electrode method EN 25814 is used, a more stringent cleaning procedure, for example, as follows, is required Add to the empty bottle ml to 10 ml of a wash solution (for example 2,5 g of iodine plus 12,5 g of potassium iodide per litre of % (V/V) sulfuric acid shaking well to coat the bottle walls Let stand for 15 min, pour off the solution and rinse thoroughly with tap water and finally deionized water 6.3 Dilution water vessel, glass or plastics Measures shall be taken to ensure the vessel is kept clean and free from microorganism growths Check that plastic vessels not cause elevated blank values (see 8.3) BSI 1998 6.8 Aeration equipment, a bottle of compressed air or a compressor The air quality shall be such that the aeration does not lead to any contamination, especially by the addition of organic matter, oxidizing of reducing materials, or metals If a contamination is suspected, the air shall be filtered and washed Storage of the sample Store the sample at a temperature (0 to 4) 8C in a filled and hermetically stoppered bottle immediately after sample collection and until the analysis is performed Begin the determination of the BODn as soon as possible and within 24 h of completion of sample collection Regarding freezing of samples, see special cases in clause 11 Ensure that the sample bottles not give rise to elevated blank values Procedure 8.1 Pretreatment 8.1.1 Neutralization of sample If the pH of the sample after dilution is not between and 8, neutralize it after having performed any necessary predilution and after having determined by a separate test the volume of hydrochloric acid solution (5.7) or of sodium hydroxide solution (5.8) necessary to be added Ignore any precipitate which is formed 8.1.2 Presence of free and/or combined chlorine Remove any free and combined chlorine in the sample by adding the required volume of sodium sulfite solution (5.9) Take care to avoid adding an excess NOTE For free and combined chlorine see ISO 7393-1 and ISO 7393-2 8.1.3 Homogenization Homogenization by disruption of particles with for example a laboratory blender is not recommended for routine use but consider its use when testing a sample containing large particles and requiring a high dilution factor When samples have been frozen (see clause 11), homogenization shall take place after thawing of the samples Page EN 1899-1:1998 8.1.4 Presence of algae Consider filtering samples containing algae to avoid producing unusually high results A filter pore size of 1,6 mm is appropriate Filtering can change BOD results radically and it shall only be performed if deemed necessary in the evaluation of the quality of the water If filtration was carried out, the filter pore size shall be recorded in the test report 8.2 Preparation of test solutions Bring the sample (or pretreated sample) to a temperature of (20 ± 2) 8C and if necessary (depending on the origin of the sample) shake in a half-filled vessel so as to eliminate any possible supersaturation with oxygen Place a known volume of the sample (or pretreated sample), the test portion, in the dilution vessel (6.7), add ml of allylthiourea solution (5.11) per litre of diluted sample and fill to the mark with seeded dilution water (5.5) If the dilution factor to be used is greater than 100, carry out serial dilutions in two or more steps Mix gently to avoid entrapment of air bubbles NOTE In some samples an inhibition by chlorine is seen even after removal, due to chlorine products that are not removed NOTE The extent of dilution should be such that, after incubation, the residual dissolved oxygen concentration will be between one-third and two-thirds of the initial concentration In view of the difficulty of selecting the right degree of dilution, several different dilutions are recommended, varying according to the dilution factor and encompassing the dilution corresponding to the expected BODn (see Table 1) Determinations of the total organic carbon (TOC) (see ISO 8245), the permanganate index (see ISO 8467), or the chemical oxygen demand (COD) (see ISO 6060) can give useful information in this respect Table shows typical intervals for R, the ratio of TOC or COD to BODn, dependent on the sample type Table Ð Typical dilutions for determination of BODn Dilution factor*) Expected BODn mg/l of oxygen to to 12 10 to 30 20 to 60 40 to 120 100 to 300 200 to 600 400 to 1200 000 to 000 000 to 000 *) Examples of waters**) between 1,1 and 2 10 20 50 100 200 500 000 R R, E R, E E S S, C S, C I, C I I Volume of diluted sample/volume of the test portion **) R: River water; E: Biologically purified municipal sewage; S: Clarified municipal sewage or lightly contaminated industrial effluent; C: Raw municipal sewage; I: Heavily contaminated industrial effluent Table Ð Typical values of dilution ratios R Total organic carbon TOC/BOD (see ISO 8245) Untreated waste water Biologically treated waste water 1,2 to 2,8 0,3 to 1,0 Permanganate index/BOD (see ISO 8467) 1,2 to 1,5 0,5 to 1,2 Chemical oxygen demand (COD)/BOD (see ISO 6060) 0,35 to 0,65 0,20 to 0,35 BSI 1998 Page EN 1899-1:1998 An appropriate R-value should be selected from Table 2, to calculate the expected BODn value: Expected BODn value: R y where: y is the chemical oxygen demand, permanganate index or the TOC value NOTE Care should be taken that the test samples are representative NOTE The suppression of nitrification is not achievable in all cases A significantly increased addition of ATU above mg/l can affect the Winkler titration (see EN 25813) NOTE If the presence of substances toxic to microorganisms is suspected, several different dilutions of the sample should be made If the BOD result depends on the dilution, results can only be reported if a dilution range is found, where there is no dependence on dilution Multitesting (see annex B), may be applied in this situation 8.3 Blank test Carry out a blank test, in parallel with the determination, using the seeded dilution water (5.6) including mg of ATU solution (5.11) per litre 8.4 Determination 8.4.1 Determination via measurement of dissolved oxygen using iodometric method (in accordance with EN 25813) Using each dilution (see 8.2), fill two incubation bottles (6.2) allowing them to overflow slightly During filling operation precautions shall be taken to prevent changing the oxygen content of the medium Allow any air bubbles adhering to the walls to escape Stopper the bottles, taking care to avoid trapping air bubbles Divide the bottles into two series, each containing one bottle of each dilution and at least one bottle of blank solution (see 8.3) Put one series of bottles (the first) with diluted test solutions (see 8.2) in the incubator (6.4) and leave in darkness for n days ±4 h In the second series of bottles with diluted samples measure the dissolved oxygen concentration at time zero, using the method specified in EN 25813 with the addition of azide in the alkaline iodide±azide reagent After the incubation, determine the dissolved oxygen concentration in each of the bottles, using the method specified in EN 25813 8.4.2 Determination via measurement of dissolved oxygen±electrochemical probe method (in accordance with EN 25814) Using each dilution (see 8.2) fill an incubation bottle (6.2) allowing it to overflow slightly Precautions shall be taken to prevent changing the oxygen content of the medium BSI 1998 Allow any air bubbles adhering to the walls to escape Measure the dissolved oxygen concentration in each of the bottles at time zero, using the method specified in EN 25814 Stopper the bottles, taking care to avoid trapping air bubbles Put the bottles with diluted test solutions (see 8.2) in the incubator (6.4) and leave in darkness for n days ±4 h After the incubation, determine the dissolved oxygen concentration in each of the bottles, using the method specified in EN 25814 8.5 Control analysis To check the seeded dilution water, the seeding water and the technique of the analyst, carry out a control in each batch of samples by placing 20,00 ml of the control glucose-glutamic acid control solution (5.10) in the dilution vessel, adding ml of ATU solution (5.11) followed by dilution to 000 ml with the seeded dilution water (5.6) and proceed as described in 8.4 The BODn obtained should be within the range (210 ± 40) mg/l of oxygen for BOD5 and within the range (225 ± 40) mg/l of oxygen for the BOD7, corresponding to the range of mean value ±2 standard deviation (determined from the inter-laboratory data (see clause 10) The precise control limits for each laboratory shall be established by performing a minimum of 25 determinations over a period of at least several weeks The mean and the standard deviations can then be used to calculate control limits for quality control checks If not, check the seeding water and, if necessary, the technique of the analyst The blank test (see 8.3) shall not exceed 1,5 mg/l of oxygen; if so, check possible sources of contamination Calculation and expression of results 9.1 Examination for valid oxygen consumption during test BODn is calculated for the test solutions, where the following condition is fulfilled c1 2c1 # (c1 c2) # (3) 3 where c1 is the dissolved oxygen concentration of one of the test solutions at time zero in milligrams per litre; c2 is the dissolved oxygen concentration of this same test solution after n days, in milligrams per litre Page EN 1899-1:1998 9.2 Calculation of biochemical oxygen demand after n days (BODn) Calculate the biochemical oxygen demand (BODn), expressed in mg/l of oxygen, using the equation: V Ve Vt (4) BODn = (c1 c2) t ´ (c3 c4) ´ Vt Ve where c1 and c2 see 9.1; c3 is the dissolved oxygen concentration of the blank solution at time zero, in milligrams per litre; is the dissolved oxygen concentration of the c4 blank solution after n days, in milligrams per litre; is the volume of sample used for the Ve preparation of the test solution concerned, in millilitres; is the total volume, in millilitres, of this test Vt solution If several dilutions fall within the required range, calculate the average of the results obtained for these dilutions Results shall be expressed in milligrams of oxygen per litre Results less than 10 mg/l of oxygen shall be reported to the nearest mg/l Results between 10 mg/l of oxygen and 000 mg/l of oxygen shall be reported to two significant figures Results above 000 mg/l shall be reported to three significant figures, e.g 240 mg/l of oxygen 11 Special cases If the time between sampling and start of analysis cannot be kept to less than 24 h, due to time of transportation, as a result of geographical circumstances, freezing of samples is permitted Frozen samples shall be homogenized after thawing and seeding water shall be used in all cases It is recommended, wherever possible that local laboratory facilities shall be found to limit the time of transportation 12 Test report The test report shall include the following information: a) a reference to this European Standard; b) specification that the test was carried out with suppression of nitrification; c) the number of days of incubation (n); d) the result in mg/l of oxygen (reported as described in 9.2); e) for results below the working range a documentation for an adequate detection limit; f) any special details which may have been noted during the test; g) details of any operations not specified in this European Standard, or regarded as optional, such as filtration (see 8.1.4), freezing and homogenization (see clause 11), alternative incubation (BOD2+5) (see annex A), and multitesting (see annex B) 10 Trueness and precision The trueness and standard deviation of reproducibility and repeatability of the BODn determinations were determined by an inter-laboratory comparison in 1992 In this exercise three sample pairs were analyzed by 95 laboratories in 11 countries The results are shown in Table It is possible to establish factors for conversion between BOD5 and BOD7 data within a single type of water The value of conversion factors may be obtained from parallel analyses of BOD5 and BOD7 measurements of the same samples If a factor is not available the correlation between BOD5 and BOD7 may be estimated from the results of the above mentioned European inter-laboratory comparison The results are shown in Table The precision of BODn analyses can be improved if required by multitesting (see annex B) BSI 1998 BSI 1998 *) A 213 20 B 193 C D E F BOD7 See annex A Glucose/glutamic acid solution Glucose/glutamic acid solution Mechanically treated waste water Mechanically treated waste water Biologically treated waste water Biologically treated waste water A 199 19 B 180 C D E F BOD2+5*) Glucose/glutamic acid solution Glucose/glutamic acid solution Mechanically treated waste water Mechanically treated waste water Biologically treated waste water Biologically treated waste water 210 190 64,4 51,6 19,3 17,8 201 180 58,0 45,5 18,1 17,2 203 184 58,3 46,0 18,2 17,2 mg/l of oxygen mg/l of oxygen A 199 19 B 180 C D E F Median Calculated value/ difference Glucose/glutamic acid solution Glucose/glutamic acid solution Mechanically treated waste water Mechanically treated waste water Biologically treated waste water Biologically treated waste water BOD5 Sample 22 19 8,6 6,7 5,0 4,3 24 24 8,9 6,0 4,9 4,2 22 19 7,7 5,0 4,5 3,7 mg/l of oxygen Reproducibility standard deviation 19 17 18 mg/l of oxygen Average of differences Table Ð Inter-laboratory comparison ± Results 13 11 11 mg/l of oxygen Repeatability Standard deviation of differences 91 92 91 88 90 95 95 88 Outliners 91 Number of results Page EN 1899-1:1998 Page 10 EN 1899-1:1998 Table Ð Inter-laboratory comparison ± Comparison of BOD5 and BOD7 Sample type BOD5 BOD7 mg/l of oxygen mg/l of oxygen Median Significant difference*) Number of laboratories BOD7/BOD5 Median Glucose/glutamic acid solution A B 203 184 210 190 Yes Yes 90 87 1,04 1,03 Mechanically treated waste water C D 58 46 64 52 Yes Yes 88 88 1,10 1,12 Biologically treated waste water E F 18,2 17,2 19,3 17,8 Yes Yes 87 89 1,06 1,03 *) Level of significance, a= 0,05 BSI 1998 Page 11 EN 1899-1:1998 Annex A (normative) Alternative incubation periods The rate of oxidation of carbon during the first stage of the BOD test is expressed by Phelps' law: L kt log10 L2x where: L x t k is the ultimate BOD at infinite time in milligrams per litre of oxygen; is the BOD at time t days in milligrams per litre of oxygen; is the time, in days; is the rate constant, expressed as the reciprocal day For a given type of organic matter and microbial seed, the effect of temperature on the rate constant k and on the value of L can be predicted to a first approximation and this may be useful when considering the use of the BOD test in warm climates, or in studies of long rivers which traverse a number of climatic regions It is essential that such relationships, however, are used with caution The standard BOD result is obtained after a or day incubation at 20 8C By incubating for days at (0 to 4) 8C followed by days at 20 8C a BOD2+5 result is obtained It has been observed1) that there is no significant difference between BOD5 and BOD2+5 after sample dilution This was also investigated in an European inter-laboratory comparison performed in 1992 with 95 participants from 11 countries The correlation between BOD5 and BOD7 determinations and BOD5 and BOD2+5 determinations was measured The results of the latter are shown in Table A.1 In practice there is no difference between BOD5 and BOD2+5 results When determining BOD2+5, read 8.4.1 as follows: Add 8.4.1 with alteration of paragraph ªPut one series of bottles (the first) with diluted test solutions (see 8.2) in darkness at (0 to 4) 8C for days ±2 h2) and then put them in the incubator (6.4) and leave in darkness with the temperature of the dilution equilibrated at (20 ± 1) 8C for days ±2 h 2)º and read 8.4.2 as follows: Add 8.4.2 with alteration of paragraph ªPut the bottles with diluted test solutions (8.2) in darkness at (0 to 4) 8C for days ±2 h2) and then put them in the incubator (6.4) and leave in darkness with the temperature of the dilutions equilibrated at (20 ± 1) 8C for days ±2 h.'' When BOD5 determinations are substituted by BOD2+5 determinations, it is necessary for the laboratory to verify that their procedure for BOD2+5 determinations give equivalent results to BOD5 determinations Table A.1 Ð Inter-laboratory comparison ± Comparison of BOD5 and BOD2+5 Sample type Glucose/glutamic acid solution Mechanically treated waste water Biologically treated waste water A B C D E F BOD5 Median value mg/l of oxygen 203 184 58 46 18,2 17,2 BOD2+5 Median value mg/l of oxygen Significant difference from BOD5*) Number of laboratories 201 No 91 180 No 85 58 No 89 46 No 86 18,1 No 89 17,2 No 87 *) Level of significance a = 0,05 1) R.G Tyers and R Shaw, J IWEM, 1989 (3), 366-374 When the same incubator is used for storage at both temperature levels, a fan assisted incubator may be necessary to ensure the change in incubation temperature within the required time interval of up to h 2) BSI 1998 Page 12 EN 1899-1:1998 Annex B (informative) Multitesting Multitesting is analysing a sample in two or more different dilutions This may be used if enhanced precision is desired, or the presence of substances toxic to microorganisms is suspected The sample is analysed as in 8.4, with the exception that an extra bottle is filled for each sample dilution, and that two BOD bottles are incubated Oxygen consumption during incubation is determined for each BOD bottle and plotted against the volume of sample in each dilution The oxygen consumption of the blank test is plotted as the zero volume value If the oxygen consumption against the sample volume is linear, the BODn does not contain components that inhibit microorganisms If the oxygen consumption against the sample volume is linear only for low sample concentrations, only sample dilutions within the linear range may be used for determining BODn The BODn is calculated as in clause 9, and is the average value of all determinations within the linear range BSI 1998 blank BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BSI Ð British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 020 8996 9000 Fax: 020 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services Tel: 020 8996 9001 Fax: 020 8996 7001 In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service Various BSI electronic information services are also available which give details on all its products and services Contact the Information Centre Tel: 020 8996 7111 Fax: 020 8996 7048 Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards For details of these and other benefits contact Membership Administration Tel: 020 8996 7002 Fax: 020 8996 7001 Copyright Copyright subsists in all BSI publications BSI also holds the copyright, in the UK, of the publications of the international standardization bodies Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means ± electronic, photocopying, recording or otherwise ± without prior written permission from BSI This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained If permission is granted, the terms may include royalty payments or a licensing agreement Details and advice can be obtained from the Copyright Manager Tel: 020 8996 7070