BS EN 14742-2015

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BSEN14742 2015
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BSI Standards Publication BS EN 14742:2015 Characterization of sludges — Laboratory chemical conditioning procedureBS EN 14742:2015 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 14742:2015. The UK participation in its preparation was entrusted to Technical Committee EH/5, Sludge characterization. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. © The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 77709 7 ICS 13.030.20 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2015. Amendments issued since publication Date Text affectedBS EN 14742:2015EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 14742 April 2015 ICS 13.030.20 Supersedes CEN/TR 14742:2006 English Version Characterization of sludges - Laboratory chemical conditioning procedure Caractérisation des boues - Mode opératoire de conditionnement chimique en laboratoire Charakterisierung von Schlämmen - Laborverfahren zur chemischen Konditionierung This European Standard was approved by CEN on 28 February 2015. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels © 2015 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14742:2015 EBS EN 14742:2015 EN 14742:2015 (E) 2 Contents Page Foreword 3 Introduction .4 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 4 Principle 5 5 Apparatus .6 6 Procedure .7 7 Test report 8 8 Precision .9 Annex A (informative) Results of Validation trials . 10 Annex B (informative) Examples for mixing devices for chemical conditioning procedure . 15 Annex C (informative) Example of table summarizing the operating conditions and the results of the characterization tests 17 Bibliography . 19 BS EN 14742:2015 EN 14742:2015 (E) 3 Foreword This document (EN 14742:2015) has been prepared by Technical Committee CEN/TC 308 “Characterization of sludges”, the secretariat of which is held by AFNOR. 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 October 2015, and conflicting national standards shall be withdrawn at the latest by October 2015. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes CEN/TR 14742:2006. The main changes with respect to CEN/TR 14742 are listed below: a) normative references have been updated; b) terms and definitions have been updated; c) principle has been updated and supplemented with notes on conditioning agents; d) procedure has been updated; e) figures have been updated. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 14742:2015 EN 14742:2015 (E) 4 Introduction This method gives a standardized procedure for the conditioning operation when selecting a conditioning product at laboratory scale and also for the production of flocculated thickened sludge for subsequent dewatering tests. These tests may also provide details regarding energy requirements, provided information on stirring power is available. BS EN 14742:2015 EN 14742:2015 (E) 5 1 Scope The laboratory assessment of sludge dewaterability is sensitive to the operating procedure adopted for the conditioning step. No generalized ranking of products in order of effectiveness can be given since the ranking changes with the sludge type, dosage of conditioning agent, degree of shearing and dewatering device. The scope of this European Standard applies for sludges and suspensions from: — storm water handling; — urban wastewater collecting systems; — urban wastewater treatment plants; — industrial wastewater that has been treated similarly to urban wastewater (as defined in Directive 91/271/EEC); — water supply plants. This method is applicable to sludge and suspensions of other origin. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 12832, Characterization of sludges ― Utilization and disposal of sludges ― Vocabulary EN 12880, Characterization of sludges ― Determination of dry residue and water content EN 14701-4, Characterization of sludges ― Filtration properties ― Part 4: Determination of the drainability of flocculated sludges EN 15933, Sludge, treated biowaste and soil ― Determination of pH ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12832 and the following apply. 3.1 chemical conditioning mixing of a chemical product with the sludge in order to increase its thickenability/dewaterability 4 Principle Sludge conditioned in accordance with this procedure (Clause 6) can subsequently be used in specific characterization tests in order to determine the most suitable operating conditions for each particular sludge or suspension; these tests determine particularly the required nature of the reagent, the dosage, and the sequence of adding the reagent. Each test is performed as a batch process. BS EN 14742:2015 EN 14742:2015 (E) 6 Variables and/or parameters that can have significant effects on the conditioned sludge are either chemical or physical. Chemical parameters: — characteristics of the sludge, e.g. pH, dry residue, loss on ignition; — characteristics of the conditioning product, e.g. charge density, molecular weight, chemical structure; — concentration and dosage of the chemical product; — water used for on-site product preparation when polyelectrolytes are added. Physical parameters: — method of preparing the solution and its storage; — intensity and duration of stirring; — characteristics of the stirrer, i.e. type, dimensions, position; — method of injecting the conditioning product into the sludge; — (separation-) time between the end of mixing and the dewatering procedure itself. The method of mixing the conditioning product into the sludge is particularly important since inadequate mixing, leading to poor initial dispersion or strong floc shearing, can result in very poor test performances: a large portion of the product may react instantly with particles upon first contact, without dispersing throughout the mixture. Inorganic coagulants are generally injected into a reactor with a short residence time (1 min to 5 min) in a high shearing condition. For this purpose, the reactor is equipped with a high rotating speed stirrer that enables an instantaneous dispersion of the product and brings the high energy needed (e.g. 80 W/m 3to 100 W/m 3 ). Polyelectrolytes are injected into a reactor with a residence time of a few seconds to a few minutes. As far as mechanical degradation can occur, the shearing rate is 4 to 10 times lower than for coagulants and the energy needed lower (e.g. 40 W/m 3to 50 W/m 3 ). The conditioning procedure may concern the addition of more than one product. In that case, the addition sequence is another parameter that requires careful instructing. 5 Apparatus 5.1 Device with control and measurement of physical parameters (variable stirrer/mixer speed and time, position of mechanical stirrer depending on sludge volume, see Annex B). A magnetic stirrer is not recommended, as it does not ensure homogenous and reproducible mixing. A mechanical stirrer with 4 horizontal perpendicular blades is recommended for proper polymer dispersion and floc maturation. In case the formed flocs are very sensitive to shearing, a tilted 3-blade stirrer (see Annex B) should be used. The characteristics of mechanical stirrer shall be the same in comparative tests. Length of each impeller blade should be between 1/4 and 1/3 of the beaker diameter. 5.2 Beakers, volume 200 ml to 1 000 ml. 5.3 Volumetric pipettes or syringe or automatic polymer injection system at constant flow rate. 5.4 Analytical balance with a precision of at least 0,1 mg. BS EN 14742:2015 EN 14742:2015 (E) 7 5.5 pH-meter 5.6 Chronometer, e.g. stopwatch, computer. 5.7 Apparatus for evaluation of flocculation drainability, e.g. drainage cell (see EN 14701-4). 6 Procedure 6.1 Measure the pH of the sludge to be tested according to EN 15933. If necessary, adjust the pH to meet the requirements of the conditioning agent to be used. 6.2 Measure the dry residue of the sludge to be tested according to EN 12880. NOTE The loss on ignition could be determined for additional information. For details, see EN 15935. 6.3 Put a defined amount of sludge into a beaker. The amount of sludge should be between 25 % and 50 % of the capacity of the beaker to avoid loss of sludge during mixing and sludge height between 0,5 and 1 diameter of the cell to ensure proper mixing. It should be taken into account that the whole flocculated sludge will be transferred in a drainage cell and the quantity of dry matter deposited on the filter cloth should be between 0,25 kg/m 2and 1,5 kg/m 2 . 6.4 Adjust the position of the stirrer to the sludge volume (the stirrer should be positioned from the beaker bottom at 1/3 of the sludge volume). 6.5 Polymer addition and dispersion Add a precise amount of conditioning agent using a volumetric pipette or syringe before stirring. Ensure proper distribution of the polymer, across the level surface of the sludge. If the conditioning agent injection is prepared during the stirring of the sludge, add it in the shortest amount of time possible at a controlled and constant flow rate. It is recommended to report the time of the beginning of the injection (TB1) and the time at the end of the injection (TE1). The solution of conditioning agent should be prepared according to the recommendations of suppliers and should be used the day of preparation within 3 h after preparation. NOTE Rapid pre-selection of conditioning agents can be made by pouring the sludge back and forth between two beakers in order to check if flocs are formed. In case of coagulant use, disperse the product at high speed (1 700 rpm) for 2 min and let the microflocs grow at 700 rpm. In case of polymer use, the mixing speed of the horizontal 4-blade impeller should be kept constant at 700 rpm since polymer dispersion and floc maturation occur simultaneously. In case of highly shear-sensitive flocs, it is recommended to disperse the flocculent in the sludge using an axial impeller (tilted 3-blade impeller) at high speed (1 700 rpm) for a very short time (2 s max), followed by a low speed (700 rpm) to enable floc growing. In this case, it is useful to differentiate: TBB1: Beginning time of polymer dispersion = TE1 TEE1: End of polymer dispersion TBB2: Beginning of polymer maturation BS EN 14742:2015 EN 14742:2015 (E) 8 TEE2: End of polymer maturation 6.6 Floc maturation Continue stirring until polymer maturation (TEE2) is reached. Mixing time is the variable parameter for floc growth, depending on the sludge and conditioning agent characteristics. Preliminary tests are recommended to evaluate this parameter by visual observation of floc formation without shearing or by quantitative measurement (torque measurement, particle size). Then, mixing time will be fixed and kept constant for comparative tests. 6.7 Transfer the whole flocculated sludge into a drainage cell to evaluate flocculation drainability according to EN 14701-4 and produce thickened sludge for further specific dewatering test (e.g. CST, specific resistance to filtration) immediately after the conditioning procedure. An automatic transfer from the flocculation cell in the drainage cell as in the device described in Annex B (Bootest) is recommended to avoid operator’s influence on transfer to drainage cell or on floc sampling. 6.8 Repeat steps 6.3 to 6.8 for a lower stirring speed only if flocculation does not take place. 7 Test report The test report (example in Annex C) shall include at least the following information: a) reference to this European Standard (EN 14742); b) all information necessary for complete identification of the sludge sample; c) details of sample pretreatment, if carried out; d) details of the experimental device; e) nature, dosage and preparation procedure of chemical agent; f) mixing conditions; g) results of the preparation according to 6.7 (see Annex B); h) any detail not specified in this European Standard and any other factor which may have affected the results. BS EN 14742:2015 EN 14742:2015 (E) 9 8 Precision Validation data were obtained through an European ILT based on the “Modified Round Robin Tests” procedure developed by CEN/TC 308/WG 1, and reported in doc. CEN/TC 308 N 822. Data were examined according to ISO 5725-2 statistical
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