1、BSI Standards PublicationPD CEN/TR 16456:2013Characterization of sludges Good practice of sludgedewateringPD CEN/TR 16456:2013 PUBLISHED DOCUMENTNational forewordThis Published Document is the UK implementation of CEN/TR16456:2013.The UK participation in its preparation was entrusted to TechnicalCom
2、mittee EH/5, Sludge characterization.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Instit
3、ution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 77059 3ICS 13.030.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This Published Document was published under the authority of theStandards Policy and Strategy Committee on 31 August 2013.Amendments is
4、sued since publicationDate Text affectedPD CEN/TR 16456:2013TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16456 August 2013 ICS 13.030.20 English Version Characterization of sludges - Good practice of sludge dewatering Caractrisation des boues - Bonnes pratiques pour la dshydratation
5、 des boues Charakterisierung von Schlmmen - Gute fachliche Praxis der Schlammentwsserung This Technical Report was approved by CEN on 6 November 2012. It has been drawn up by the Technical Committee CEN/TC 308. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyp
6、rus, 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 Ki
7、ngdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16456:2013: E
8、PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 2 Contents Page Foreword . 4 Introduction 5 1 Scope 8 2 Normative references . 8 3 Terms and definitions 8 4 Description and features of thickening / dewatering systems . 11 4.1 Thickening devices 11 4.1.1 General . 11 4.1.2 Devices based on natural forces (
9、gravity) 11 4.1.3 Devices based on flotation 13 4.1.4 Devices based on filtration 14 4.1.5 Devices based on centrifugation . 19 4.2 Dewatering devices 20 4.2.1 General . 20 4.2.2 Filter press (plate, membrane) . 20 4.2.3 Belt (filter) press . 22 4.2.4 Centrifuge . 23 4.2.5 Screw press 23 4.2.6 Other
10、s . 24 5 Conditioning . 25 5.1 General . 25 5.2 Conditioning processes . 25 5.2.1 General . 25 5.2.2 Coagulation 25 5.2.3 Flocculation 25 5.2.4 Physical processes 27 5.3 Conditioners . 28 5.3.1 General . 28 5.3.2 Polymers . 28 5.3.3 Inorganic chemicals (multivalent salts, lime) . 29 5.3.4 Other prod
11、ucts . 29 5.4 Technical aspects 30 5.4.1 Storage of conditioner . 30 5.4.2 Selection of conditioner . 30 5.4.3 Preparation of conditioners . 31 5.4.4 Injection, dosing and mixing with sludge . 34 5.4.5 Automation . 37 6 Parameters / Methods for the evaluation of sludge thickenability or dewaterabili
12、ty 37 6.1 General . 37 6.2 Mechanisms description 37 6.2.1 Settling / Flotation 37 6.2.2 Centrifugation 39 6.2.3 Filtration . 39 6.3 Basic theories and parameters 41 6.3.1 Settling / Flotation 41 6.3.2 Centrifugation 42 6.3.3 Filtration . 42 6.4 Methods of evaluation 44 PD CEN/TR 16456:2013CEN/TR 16
13、456:2013 (E) 3 6.4.1 General . 44 6.4.2 Settleability / Thickenability . 44 6.4.3 Centrifugability . 45 6.4.4 Filterability 46 6.4.5 Basic parameters . 48 7 Critical parameters for sizing and optimisation of thickening/dewatering systems . 49 7.1 General . 49 7.2 Gravity thickeners 50 7.3 Belt thick
14、eners 50 7.4 Centrifuges . 50 7.5 Filter-presses 52 7.6 Belt-presses 52 7.7 Screw-presses 53 8 Operational and economic aspects of thickening/dewatering systems 53 8.1 General . 53 8.2 Performances . 53 8.3 Energy consumption 56 8.4 Labour requirements 57 8.5 Water consumption 57 8.6 Maintenance . 5
15、8 8.7 Safety aspects 58 8.8 Automation . 58 8.9 Cost aspects . 59 8.10 Final considerations . 60 9 Conclusions 63 Annex A (informative) Environmental checklist . 65 Bibliography 66 PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 4 Foreword This document (CEN/TR 16456:2013) has been prepared by Technical C
16、ommittee CEN/TC 308 “Characterization of sludges”, the secretariat of which is held by AFNOR. 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
17、rights. PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 5 Introduction Sludge processing train is a major problem in water and wastewater treatment, as it can account for up to 50 % of total operating costs. The effectiveness and cost of sludge treatment and disposal operations are strongly affected by it
18、s volume and, consequently, by its water content or solids concentration. Thickening and dewatering are therefore important steps in the total sludge processing train and have serious impact on subsequent operations. For illustration, Figure 1 shows the existing solutions for sludge water content re
19、duction, and Figure 2 shows the level of dry matter content required for intended utilisation and disposal routes. Figure 1 Principal thickening / dewatering processes PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 6 This guide deals with the dewatering and thickening techniques quoted in Figure 1. Figur
20、e 2 Percentage Dry Solids (DS) usually required after thickening and dewatering for intended routes Sludges management options are developed in a series of CEN Technical Reports to which belong the present report, see Figure 3 below. PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 7 Figure 3 A basic schem
21、e for deciding on sewage sludge use/disposal options and the relevant CEN/TC 308 guidance documents PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 8 1 Scope This Technical Report describes good practice for sludge dewatering and belongs to a series on sludge management options. It gives guidance on techn
22、ical and operational aspects of conditioning, thickening and dewatering processes. Drying, which is another water content reduction process, is not dealt with in this document, but in CEN/TR 15473, Characterization of sludges Good practice for sludges drying. This report is applicable for sludges fr
23、om: urban wastewater treatment plants; treatment plants for industrial wastewater similar to urban wastewater; water supply treatment plants. This document may be applicable to sludges of other origin. 2 Normative references The following documents, in whole or in part, are normatively referenced in
24、 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 12832:1999, Characterization of sludges Utilization and disposal of sludges Voc
25、abulary prEN 16323:2011, Glossary of wastewater engineering terms 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12832:1999, prEN 16323:2011 and the following (taken either from the normative references or from a technical dictionary 1) apply. 3.1 ca
26、ke solid fraction of sludge as resulting from a solid-liquid separation process 3.2 centrate sludge liquor separated by centrifugation 3.3 centrifugation partial separation of solid from liquid under centrifugal forces 3.4 charge density percentage of positive or negative charge 3.5 compressibility
27、ability of a sludge to be compressed under pressure PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 9 3.6 compression point sludge solids concentration at which compression begins in a sedimentation process 3.7 desaturation removal of water due to displacement of water by air 3.8 draining / drainage of sl
28、udge separation of water from sludge liquor by gravity filtration 3.9 dryness ratio of dry solids to sludge mass 3.10 electroosmosis movement of liquid relative to a stationary charged surface as induced by an electrical field 3.11 expression removal of sludge water due to deformation of solids unde
29、r pressure 3.12 filter device for the removal of sludge water whereby solids are retained on a water-permeable filter medium 3.13 filter medium material where through a fluid flows and which retains matter contained in the fluid 3.14 filterability characteristic describing the ability of sludge to b
30、e filtered 3.15 filtrate sludge liquor separated by filtration 3.16 filtration process of retention of the suspended matter by passing through a medium 3.17 floc aggregate of particles that results from a flocculation process 3.18 flotation raising of suspended matter in liquid to the surface by the
31、 entrainment of a gas 3.19 “g“ gravitational acceleration (9,81 m/s2) 3.20 isolelectric point condition in which a substance has a neutral charge PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 10 3.21 mesh interlacing of crossed wires that determines the openings which can be square, triangular or rectan
32、gular 3.22 molecular weight chain length of a polymer 3.23 particle size distribution relative amount of particles classified per size ranges 3.24 polymer class of natural and synthetic materials which are formed by association of structural units (monomers) by covalent bonds 3.25 porosity ratio of
33、the void volume to the total volume of material 3.26 pre-treatment improvement of sludge characteristics by physical or chemical means 3.27 rheology study of flow and deformation properties under the influence of an applied stress 3.28 saturation ratio of the volumes of water and pores in a solid ma
34、trix 3.29 sieve (sludge treatment) device for removing solids from fluids whereby the fluid flows through slots, perforations or a mesh 3.30 settling ability for sludge solids to separate from water by sedimentation under gravity 3.31 sludge liquor liquor separated from sludge. Sludge liquor can be
35、called supernatant, filtrate and centrate 3.32 specific cake resistance property representing the resistance to filtration of a layer of particles, having a unit mass of dry solids deposited on a unit filtering area 3.33 supernatant sludge liquor separated by gravity thickening 3.34 water distributi
36、on different physical states of water associated with sludge solid particles PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 11 3.35 zeta potential electrical potential present at the plane of slip when a particle moves relative to its suspending liquid (or vice versa) 4 Description and features of thicke
37、ning / dewatering systems 4.1 Thickening devices 4.1.1 General Thickening devices enable the removal of free water from sludge. They are based on: natural (static) forces; artificial forces. Thickening presents the following advantages: reduction of sludge volume with low energy consumption; reducti
38、on of storage capacities and volumes for subsequent treatment; reduction of transport costs; improvement of performance of dewatering machines; decrease in quantity of chemicals for dewatering in some cases. This section discusses the most commonly used devices for thickening. 4.1.2 Devices based on
39、 natural forces (gravity) 4.1.2.1 General The principle of gravity thickening relies on sludge settling under the effect of gravitational forces. It enables the raising of the concentration of a suspension through sedimentation to produce a thickened sludge with a relatively clear liquid as overflow
40、. Thickeners can be designed to operate in either the batch or continuous mode. Sludge thickening can be achieved in clarifiers or separate thickeners which provide for a greater sludge storage capacity. 4.1.2.2 Gravity thickener The traditional gravity thickener (Figure 4) comprises a relatively sh
41、allow, open top cylindrical/rectangular tank with either a flat bottom or a bottom shaped in the form of an inverted cone. The feed mixture is gently and continuously introduced to the feedwell. The supernatant is removed via an annular weir at the top of the unit and sludge solids are removed from
42、a well at the bottom. Slowly rotating rakes mounted on a central shaft aid the thickening process by directing thickened solids towards the well for subsequent discharge and by creating channels to release further liquid from the sludge. Tanks with a diameter smaller than 25 m are usually formed fro
43、m steel and have bottoms with an angle usually less than 10 equipped with rake arms. Larger tanks between 25 m and 200 m diameter are normally PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 12 made from a combination of concrete and steel and employ rakes designed to match the angle of the conical bottom
44、. Key 1 feed 6 rake 2 drive head 7 feedwell 3 walkway 8 thickened suspension (underflow) 4 supernantant (overflow) 9 well 5 flocculant Figure 4 Gravity thickener 1 When space is limited, the lamellar separator is used. It is a rectangular tank containing a series of closely spaced rectangular plates
45、 inclined at an angle of higher than 50 to the horizontal. Commercial designs provide three flow patterns, cross-flow, parallel flow and the most common counterflow where the feed and supernatant flows can be most simply arranged. The choice of a lamella separator is mainly related to the concentrat
46、ion of the input sludge. 4.1.2.3 Deep cone thickener A deep cone thickener (Figure 5) has the same operation principle as a conventional circular gravity thickener but the slopes of the bottom are far steeper and have an angle in the region of 37. Units are available with diameters of up 15 m. A rak
47、e rotating at speeds between 0,25 rpm and 2 rpm is usually provided in order to aid the thickening process and increase the underflow concentrations. PD CEN/TR 16456:2013CEN/TR 16456:2013 (E) 13 Key 1 fast acting flocculant 5 supernatant (overflow) 2 feed 6 rake and scraping arms 3 mixing device 7 t
48、hickened suspension (underlow) 4 motor drive Figure 5 Deep cone thickener 1 4.1.3 Devices based on flotation Flotation thickeners are process devices wherein solid particles are separated from the liquid phase by becoming attached to air bubbles. The particles float to the water surface and are remo
49、ved with skimmers. The most common device is dissolved air flotation (Figure 6) which uses pressurised air 300 kPa to 600 kPa and dissolves it in pressurised water. The pressure is then suddenly released to form small bubbles with a diameter of 40 m to 80 m. Bubbles are mixed with sludge (direct flotation) or with sludge diluted by underflow water (indirect flotation). Other systems are also used: vacuum flotation thickeners employ air that is dissolved at atmospheric pressure followed by a pressure drop to allow the formation of
