SIST EN 12255-15:2004
(Main)Wastewater treatment plants - Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants
Wastewater treatment plants - Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants
This part of this European standard specifies the non-steady state measurement of the oxygen transfer capacity and the oxygen transfer efficiency of aeration tanks (see prEN 12255-6) when filled with clean water. NOTE 1: This is known as the clean water test. NOTE 2: Since the method is based on completely mixed tanks or tanks with evenly distributed aerators or diffusers it may not be applicable for certain aeration installations. NOTE 3: Under process conditions with mixed liquor the oxygen transfer capacity and the oxygen transfer efficiency may be different from the clean water test results.
Kläranlagen - Teil 15: Messung der Sauerstoffzufuhr in Reinwasser in Belüftungsbecken von Belebungsanlagen
Diese Europäische Norm legt die Anforderungen zur Messung der Sauerstoffzufuhr und des Sauerstoffertrages von Belüftungseinrichtungen in Belebungsbecken (vergleiche prEN 12255-6) gefüllt mit Reinwasser nach der Absorptions- oder Desorptionsmethode fest. ANMERKUNG 1: Dies ist als Reinwasserversuch bekannt. ANMERKUNG 2: Weil dieses Verfahren auf total durchmischte Becken oder Becken mit gleichmäßiger Belüfterdichte beruht, kann es für bestimmte Belüftungseinrichtungen nicht anwendbar sein.
Stations d'épuration - Partie 15: Mesurage du transfert d'oxygene en eau claire dans les bassins d'aération des stations d'épuration a boues activées
La présente Norme européenne spécifie le mesurage a l'état non stationnaire de l'apport horaire en oxygene, de l'apport spécifique brut et du rendement d'oxygénation des systemes d'aération équipant les bassins d'aération des stations d'épuration a boues activées (voir l'EN 12255-6) lorsqu'ils sont remplis d'eau claire.
NOTE 1 Cette méthode est connue sous le nom d'essai a l'eau claire.
NOTE 2 Cette méthode n'étant applicable qu'au cas des bassins parfaitement mélangés ou des bassins dans lesquels les aérateurs ou les diffuseurs sont répartis uniformément, il est possible que les résultats d'essais effectués sur certaines installations ne soient pas corrects.
NOTE 3 En conditions réelles de fonctionnement, en présence de boues activées, l'apport horaire en oxygene, l'apport spécifique brut et le rendement d'oxygénation peuvent différer des résultats obtenus lors des essais d'aération en eau claire. Cette différence est exprimée par le facteur a.
Čistilne naprave za odpadno vodo - 15. del: Merjenje vnosa kisika v čisto vodo v aeracijskih bazenih naprav z aktivnim blatom
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kläranlagen - Teil 15: Messung der Sauerstoffzufuhr in Reinwasser in Belüftungsbecken von BelebungsanlagenStations d'épuration - Partie 15: Mesurage du transfert d'oxygene en eau claire dans les bassins d'aération des stations d'épuration a boues activéesWastewater treatment plants - Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants13.060.30Odpadna vodaSewage waterICS:Ta slovenski standard je istoveten z:EN 12255-15:2003SIST EN 12255-15:2004en01-maj-2004SIST EN 12255-15:2004SLOVENSKI
STANDARD
SIST EN 12255-15:2004
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12255-15December 2003ICS 13.060.30English versionWastewater treatment plants - Part 15: Measurement of theoxygen transfer in clean water in aeration tanks of activatedsludge plantsStations d'épuration - Partie 15: Mesure de performancesdes aérateursKläranlagen - Teil 15: Messung der Sauerstoffzufuhr inReinwasser in Belüftungsbecken von BelebungsanlagenThis European Standard was approved by CEN on 3 November 2003.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and UnitedKingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2003 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12255-15:2003 ESIST EN 12255-15:2004
EN 12255-15:2003 (E)2ContentspageForeword.31Scope.42Normative references.43Terms and definitions.44Symbols and abbreviations.55Principle and procedures.66Aeration tanks, test-water, equipment and chemicals.76.1Aeration tanks and aeration installations.76.2Measuring Equipment.76.2.1Dissolved oxygen probes (DO probes).76.2.2Recording of the dissolved oxygen concentration.86.2.3Temperature measurement.86.3Chemicals.86.3.1Sodium sulphite.86.3.2Cobalt catalyst.86.3.3Nitrogen and pure oxygen gas.86.4Test-water.87Procedure.97.1Planning of testing.97.2Advance preparation and responsibilities.97.3Filling of the tank with test-water.107.4Installation of the DO probes.107.5Addition of chemicals.117.5.1Cobalt catalyst.117.5.2Sodium sulphite.117.6Gas injection.127.7Data collection during a test.127.8Data analysis.138Precision and accuracy of results.138.1Standard oxygen transfer rate.138.2Standard aeration efficiency.138.3Specific standard oxygen transfer efficiency.149Presentation and interpretation of the results.14Annex A (normative)
Alternative test and evaluation procedure.15A.1Principle.15A.2Measurement of the oxygen saturation value.15A.3In-situ calibration of the DO probes.15A.4Determination of the oxygen transfer coefficient.15Bibliography.16SIST EN 12255-15:2004
EN 12255-15:2003 (E)3ForewordThis document (EN 12255-15:2003) has been prepared by Technical Committee CEN/TC 165 “Waste waterengineering”, 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 identicaltext or by endorsement, at the latest by June 2004, and conflicting national standards shall be withdrawn atthe latest by June 2004.It is the fifteenth Part prepared by the Working Groups CEN/TC 165/WG 42 and 43 relating to the generalrequirements and processes for treatment plants for a total number of inhabitants and population equivalents(PT) over 50. EN 12255 with the generic title "Wastewater treatment plants" consists of the following Parts:¾ Part 1: General construction principles¾ Part 3: Preliminary treatment¾ Part 4: Primary settlement¾ Part 5: Lagooning processes¾ Part 6: Activated sludge process¾ Part 7: Biological fixed-film reactors¾ Part 8: Sludge treatment and storage¾ Part 9: Odour control and ventilation¾ Part 10: Safety principles¾ Part 11: General data required¾ Part 12: Control and automation¾ Part 13: Chemical treatment — Treatment of wastewater by precipitation/flocculation¾ Part 14: Disinfection¾ Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants¾ Part 16: Physical (mechanical) filtrationNOTEFor requirements on pumping installations at wastewater treatment plants, provided initially as Part 2:Pumping installations for wastewater treatment plants, see EN 752-6 Drain and sewer systems outside buildings — Part6: Pumping installations.The parts EN 12255-1, EN 12255-3 to EN 12255-8 and EN 12255-10 and EN 12255-11 were implementedtogether as a European package (Resolution BT 152/1998).Annex A is normative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark,Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom.SIST EN 12255-15:2004
EN 12255-15:2003 (E)41 ScopeThis European Standard specifies the non-steady state measurement of the oxygen transfer rate and theoxygen transfer efficiency of aeration systems in activated sludge aeration tanks (see EN 12255-6) when filledwith clean water.NOTE 1This is known as the clean water test.NOTE 2Since the method is based on completely mixed tanks or tanks with evenly distributed aerators or diffuserstest results from certain aeration installations can be incorrect.NOTE 3Under process conditions with mixed liquor the oxygen transfer rate and the oxygen transfer efficiency can bedifferent from the clean water test results. This is expressed by the a-factor.2 Normative referencesThis 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 listedhereafter. For dated references, subsequent amendments to or revisions of any of these publications apply tothis European Standard only when incorporated in it by amendment or revision. For undated references thelatest edition of the publication referred to applies (including amendments).EN 1085, Wastewater treatment — Vocabulary.EN 25814, Water quality — Determination of dissolved oxygen — Electrotechnical probe method(ISO 5814:1990).3 Terms and definitionsFor the purposes of this European Standard, the terms and definitions given in EN 1085 and the followingapply.3.1standard oxygen transfer rate (SOTR, kg/h)mass of oxygen transferred per hour at standard conditions (water temperature T = 20 °C, barometricpressure p = 1 013 hPa, zero dissolved oxygen concentration), to an aeration tank filled with clean water(Volume V, m³) equipped with an aeration device or system and operated at a specified aeration setting. It isobtained as:100020,20SLCakVSOTR´´=(1)3.2standard aeration efficiency (SAE, kg/kWh)ratio of standard oxygen transfer rate and total wire power uptake (P, kW) measured during the test3.3specific standard oxygen transfer efficiency (SSOTE, %/m)percent oxygen absorbed per metre diffuser submergence (hD, m). SSOTE may also be expressed ing/(m³·m)1
1 The volume expressed in m3 is applicable to standard conditions (dry air, zero humidity, p=1013 hPa, T=0°C), see also3.9.SIST EN 12255-15:2004
EN 12255-15:2003 (E)5()[]m%299,0100AD´´´=QhSOTRSSOTE(2)or()[]m)g/(mhQSOTRSSOTE3DA×´´=1000(3)3.4oxygen transfer coefficient ( kLaT, h-1)determined by evaluation of an oxygen transfer test in clean water at a certain aeration setting and at a certaintemperature. It is converted to the standard temperature of T = 20 °C as follows:()T-20TL20L024,1´=akak(4)3.5standard oxygen saturation value (CS,St,T, mg/l)as listed in EN 25814 for pSt = 1 013 hPa, e.g.: CS,St,20 = 9,09 mg/l3.6test oxygen saturation value (CS,p*,T, mg/l)oxygen saturation value of an oxygen transfer test in clean water at a specific water temperature (T, °C) and aspecific barometric pressure (p*, hPa). The test oxygen saturation value is converted to standard conditionsas follows:)/()/(,*StTSt,S,St,20S,TpS,S,20*ppCCCC´´=(5)3.7mid-depth oxygen saturation value (CS,md,20, mg/l)for diffused air aeration the mid-depth oxygen saturation value for standard conditions is calculated as follows(10,35 m of water is equivalent to 1 013 hPa):()]10,35)
2(/ 1[DSt,20S,md,20S,´+´=hCC(6)3.8diffuser submergence (hD, m)depth below the water level of air release from the diffuser without aeration operating3.9normal air flow rate (QA, m³/h)air flow rate delivered to the aeration tank, corrected for standard conditions (dry air, zero humidity,p = 1 013 hPa, T = 0 °C)3.10aeration settingfor diffused air aeration: a specified air flow rate at a specified diffuser depth with or without additional mixing;for surface aerators: a specified freeboard or a specified immersion depth at a specified rotary speed and withor without baffles and/or additional mixing4 Symbols and abbreviationshDdiffuser submergence, in metre (m)C0oxygen concentration at t = 0, in milligramme per litre (mg/l)SIST EN 12255-15:2004
EN 12255-15:2003 (E)6Ciinitial concentration of dissolved oxygen in the tank without sodium sulphite, in milligramme per litre(mg/l)CS,20 test oxygen saturation value at standard conditions, in milligramme per litre (mg/l)CS,md,20 mid-depth oxygen saturation value, in milligramme per litre (mg/l)CS,p*,Ttest oxygen saturation value, in milligramme per litre (mg/l)CS,p°,T,°oxygen saturation value after a prolonged aeration period determined by Winkler titration (seeEN 25813), in milligramme per litre (mg/l)CS,St,Tstandard oxygen saturation value, in milligramme per litre (mg/l)CS,St,T,°standard oxygen saturation value at the temperature at which the saturation value has beendetermined by Winkler titration, in milligramme per litre (mg/l)Ctoxygen concentration at time t, in milligramme per litre (mg/l)kLa20oxygen transfer coefficient at T = 20 °C, in 1/hkLaToxygen transfer coefficient at test temperature, in 1/hMSomass of sodium sulphite needed for one test, in kilogrammep°barometric pressure during sampling for Winkler titration, in hectopascal (hPa)p*barometric pressure during a test, in hectopascal (hPa)pSt barometric standard pressure (1 013 hPa), in hectopascal (hPa)QAnormal air flow rate, in cubic metre per hour (m3/h)2tMmixing period at oxygen concentration C = 0, in minutes (min)Vtank volume, in cubic metre3 (m3)5 Principle and proceduresAfter decreasing (absorption test) or increasing (de-sorption test) the dissolved oxygen concentration of anaeration tank at constant mixing and a certain aeration setting the increasing or decreasing dissolved oxygenconcentration is monitored. This is described by the following equation:)(exp)(,takCCCC´-´--=TL0T,pS,TpS,t**(7)By a non-linear regression method equation (7) is fitted to the measured values of Ct. The values for C0, CS,p*,Tand kLaT are obtained. The residues (Ct (measured) - Ct (calculated)) plotted versus time shall be randomlydistributed. If they follow a curve a new evaluation shall be performed at which one or more values of Ct fromthe beginning and/or end of the curve are to be neglected. Any computer program for non-linear parameter
2 The volume expressed in cubic metre
is applicable to standard conditions (dry air, zero humidity, p=1013 hPa, T=0°C),see also 3.9.SIST EN 12255-15:2004
EN 12255-15:2003 (E)7estimation may be used, e.g. Stenstrom et al. [1981]. The disks provided by ASCE [1992], by ATV [1996] orby FUL [1995] may be used as well.The value of kLaT is not affected by the calibration of the DO probes. The exact determination of CS,p*,Trequires accurately calibrated DO probes or Winkler titration, see EN 25813 and EN 25814.Experienced Institutions may apply linear estimation (log deficit method) of kLaT using a measured oxygensaturation value CS,p°,T°, see annex A.The oxygen transfer absorption test is the most common test method by which the dissolved oxygenconcentration of the aeration tank is at first decreased by addition of sodium sulphite or by injection of nitrogengas and then aerated close to oxygen saturation. From the increasing dissolved oxygen concentrationmonitored during the aeration period the oxygen transfer coefficient and the oxygen saturation value aredetermined.Clean water oxygen transfer de-sorption testing is a newer test method. By injection of pure oxygen gas thedissolved oxygen concentration of the aeration tank at first is raised beyond the (air) oxygen saturationconcentration and then aerated close to air oxygen saturation. From the decreasing dissolved oxygenconcentration monitored during the aeration period the oxygen transfer coefficient and the oxygen saturationvalue are to be determined.6 Aeration tanks, test-water, equipment and chemicals6.1 Aeration tanks and aeration installationsThe tanks may be square, circular, rectangular or a closed loop (e.g. oxidation ditch) in plan.The aeration systems mainly used today can be categorised as diffused air systems (e.g. porous diffusers,ejectors), vertical shaft surface aerators (e.g. cone aerators) and horizontal axis surface aerators.Diffused air aeration can be installed in any tank and propellers may be installed to create a horizontal flow incircular tanks and in closed loop tanks.Vertical shaft surface aerators may be installed in square, circular, rectangular and closed loop tanks.Horizontal axis surface aerators today are only installed in closed loop tanks. In closed loop tanks with surfaceaerators propellers may be installed to maintain a sufficient flow velocity. Since for surface aerators the depthof immersion is important, during filling of the tank a mark for zero immersion should be made when half of the(running) aerators touch the water level.6.2 Measuring Equipment6.2.1 Dissolved oxygen probes (DO probes)At least three DO probes shall be installed in the aeration tank. In large aeration tanks (V > 3 000 m³) and intanks with tapered aeration it is advisable to install 6 or more DO probes.Calibration of the DO probes shall be carried out in accordance with EN 25814.The response period of the DO probes shall be less than 1/20 of the response period of the aeration tank,hence the probe kLaT shall be higher than 20 times the aeration tank kLaT.At installations with kLaT > 20 h-1 due to a required probe kLaT > 400 h-1, kLaT may be incorrect.SIST EN 12255-15:2004
EN 12255-15:2003 (E)86.2.2 Recording of the dissolved oxygen concentrationAt least one DO probe shall be connected to a continuously recording display device. The signals of theremaining probes then shall be manually recorded at appropriate time intervals.It is preferable to use a data logger for all DO probes. Also in this case either on a screen or by a strip chartrecorder the course of the oxygen concentration of at least one DO probe shall be shown during the test.The frequency of recording Ct shall be as high as possible. At least 30 pairs of Ct/t shall be used for thedetermination of kLaT.6.2.3 Temperature measurementThe temperature of the water in the aeration tank shall be measured with an accuracy of ± 0,1 °C at thebeginning and the end of each test.6.2.4 Power measurementThe total wire power of the aeration equipment (motors of blowers or surface aerators including frequencycontrollers) and the operating mixing equipment shall be measured either with temporary or installed kWh-meters or kW-instruments with an accuracy of ± 3 %.6.2.5 Air flow measurementIf at diffused air installations the oxygen transfer efficiency is to be determined, the normal air flow rate shallbe measured by appropriate equipment with an accuracy of ± 5 %.If at diffused air installations only a fraction of the air delivered by the blower is used for aeration of the tank tobe tested, the air flow rate to the tank and the total air flow rate of the blower shall be measured byappropriate equipment with an accuracy of ± 5 %.6.3 Chemicals6.3.1 Sodium sulphiteEither technical-grade or photo-grade sodium sulphite (Na2SO3) shall be used for de-oxygenation. To remove1 kg of dissolved oxygen 8 kg of Na2SO3 are required. The dissolved solids are increased by 1,13 kg per kg ofNa2SO3.6.3.2 Cobalt catalystEither reagent or technical-grade cobalt chloride (CoCl2 ´ 6 H2O) or cobalt sulphate (CoSO4 ´ 7 H2O) shall beused to catalyse the de-oxygenation reaction. The amount of cobalt to be added may be determined on site. Aconcentration of 0,5 mg/l Co in any case is sufficient and shall not be exceeded.6.3.3 Nitrogen and pure oxygen gasThe gas is delivered in liquid form or in gas bottles tied up in bundles. Appropriate pressure reducer
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