1、BRITISH STANDARD BS EN 12255-7:2002 Wastewater treatment plants Part 7: Biological fixed-film reactors The European Standard EN 12255-7:2002 has the status of a British Standard ICS 13.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 12255-7:2002 This British Standa
2、rd, having been prepared under the direction of the Building and Civil Engineering Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 5 April 2002 BSI 5 April 2002 ISBN 0 580 39428 X National foreword This British Standard is the
3、 official English language version of EN 12255-7:2002. The UK participation in its preparation was entrusted to Technical Committee B/505, Wastewater engineering, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross
4、-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
5、 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. aid enquirers to understand t
6、he 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. Summary of pages This document comprises a front cover, an i
7、nside front cover, the EN title page, pages 2 to 14, two annex NA pages, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD NORME EUROPENNE E
8、UROPISCHE NORM EN 12255-7 January 2002 ICS 13.060.30 English version Wastewater treatment plants Part 7: Biological fixed-film reactors Stations dpuration Partie 7: Racteurs biologiques cultures fixes Klranlagen Teil 7: Biofilmreaktoren This European Standard was approved by CEN on 9 November 2001.
9、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 a
10、pplication 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 translation under the responsibility of a CEN member into its own language and notified to the Management Centre has t
11、he 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, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN CO
12、MMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2002 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12255-7:2002 EEN 12255-7:2002 (E)
13、 2 Contents Page Foreword3 1 Scope 4 2 Normative references 4 3 Terms and definitions4 4 Requirements .5 4.1 General5 4.1.1 Biological fixed film processes 5 4.1.2 Trickling filters .5 4.1.3 Rotating biological contactors .5 4.1.4 Submerged bed reactors and biofilters.6 4.2 Planning 6 4.3 Process .7
14、 4.3.1 Design .7 4.3.2 Modes of operation7 4.3.3 Selection of support media.8 4.3.4 Dimensions.9 4.3.5 Flow distribution 9 4.3.6 Oxygen supply .10 4.3.7 Clarification and solid separation 10 4.3.8 Additional considerations.11 4.4 Detailed design.11 4.4.1 Structures .11 4.4.2 Mechanical and electrica
15、l equipment 12 Bibliography 13EN 12255-7:2002 (E) 3 Foreword This European Standard has been prepared by Technical Committee CEN/TC 165, Wastewater engineering, the Secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of
16、an identical text or by endorsement, at the latest by July 2002, and conflicting national standards shall be withdrawn at the latest by December 2002. It is the seventh part prepared by the Working Groups CEN/TC 165/WG 42 and 43 relating to the general requirements and processes for treatment plants
17、 for a total number of inhabitants and population equivalents (PT) over 50. The parts of the series are as follows: Part 1: General construction principles Part 3: Preliminary treatment Part 4: Primary settlement Part 5: Lagooning processes Part 6: Activated sludge processes Part 7: Biological fixed
18、-film reactors Part 8: Sludge treatment and storage Part 9: Odour control and ventilation Part 10: Safety principles Part 11: General data required Part 12: Control and automation Part 13: Chemical treatment Treatment of wastewater by precipitation/flocculation Part 14: Disinfection Part 15: Measure
19、ment of the oxygen transfer in clean water in aeration tanks of activated sludge plants Part 16: Physical (mechanical) filtration 1 ) NOTE For requirements on pumping installations at wastewater treatment plants, provided initially as Part 2, Pumping installations for wastewater treatment plants, se
20、e EN 752-6, Drain and sewer systems outside buildings Part 6: Pumping installations. The parts EN 12255-1, EN 12255-3 to EN 12255-8 and EN 12255-10 and EN 12255-11 were implemented together as a European package (Resolution BT 152/1998). According to the CEN/CENELEC Internal Regulations, the nationa
21、l 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, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdo
22、m.1 )In preparation.EN 12255-7:2002 (E) 4 1 Scope This European Standard specifies the design principles and performance requirements for secondary treatment by biological fixed-film reactors at wastewater treatment plants for more than 50 PT. The primary application is for wastewater treatment plan
23、ts designed for the treatment of domestic and municipal wastewater. Biological fixed film reactors include biological trickling filters, rotating biological contactors, submerged bed reactors and biofilters. Differences in wastewater treatment throughout Europe have led to a variety of systems being
24、 developed. This standard gives fundamental informations about the systems; this standard has not attempted to specify all available systems. Detailed information additional to that contained in this standard may be obtained by referring to the Bibliography. 2 Normative references This European Stan
25、dard 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 t
26、o this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 752-6, Drain and sewer systems outside buildings Part 6: Pumping installations. EN 1085, Wastewater treatment Vo
27、cabulary. EN 12255-1, Wastewater treatment plants Part 1: General construction principles. EN 12255-6, Wastewater treatment plants Part 6: Activated sludge processes. EN 12255-10, Wastewater treatment plants Part 10: Safety principles. EN 12255-11, Wastewater treatment plants Part 11: General data r
28、equired. 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in EN 1085 and the following apply. 3.1 wastewater dose volume of wastewater discharged on to a trickling filter from a single pumping cycle or a single siphoning from a filter dosing chamber
29、 3.2 flushing intensity surface hydraulic loading rate divided by the number of arms of a rotary distributor and divided by the number of revolutions per hour NOTE This value gives information on the hydraulic forces to wash excess sludge out of the bed. 3.3 submerged bed reactor bed of packed or su
30、spended inert media which is typically open structure plastic and is submerged in the flow to allow the active biological film attached to the media to purify the wastewater NOTE A clarifier can be required.EN 12255-7:2002 (E) 5 4 Requirements 4.1 General 4.1.1 Biological fixed film processes Biolog
31、ical fixed film processes may include: trickling filters; rotating biological contactors; submerged bed reactors; biofilters. Biological fixed-film processes can treat the following types of influent: primary treated wastewater; finely-screened or sieved wastewater; effluent from secondary treatment
32、. These are processes in which support media is used to support growth of a film of microorganisms which flocculate and biodegrade soluble, colloidal and suspended matter in wastewater. The processes can operate under aerobic and/or anoxic or anaerobic conditions and provide intimate contact between
33、 influent and the biological film. Solids present in treated effluent should be removed before final discharge. In the case of biofilters the solids are retained within the reactors. 4.1.2 Trickling filters In trickling filters, wastewater is distributed over and percolates down through a bed of sup
34、port media, contacting the biological film growing on the surface of elements of the media. The bed shall contain continuous open spaces between elements of support media to promote natural or induced ventilation. Operating conditions on the bed shall support the growth of larger organisms such as p
35、rotozoa and macro-invertebrates, often termed “grazing organisms”, to control the growth of biological film and reduce surplus sludge. Humus tanks should be used to clarify wastewater discharged from the filter. 4.1.3 Rotating biological contactors A rotating biological contactor consists of discs o
36、r packs of support media, which are arranged along a shaft and are partially immersed in wastewater. The shaft rotates, enabling biological film, which grows on the support media, to alternately contact wastewater and air and bring about treatment. Performance can be improved by adopting the princip
37、le of a plug flow system. Rotating biological contactors may be supplied either as stand-alone biological treatment units or as package plants, incorporating primary and secondary settlement zones. Plant shall be designed to ensure that sludge flows to points that provide practical access for its re
38、moval.EN 12255-7:2002 (E) 6 4.1.4 Submerged bed reactors and biofilters In these reactors, wastewater flow should be uniformly distributed through a submerged bed of support media. Air utilized for aeration should be supplied by a blower and distributed from pipework. The design of the aeration syst
39、ems should distribute the air evenly over the fixed bed. Denitrifying submerged bed reactors shall have a system for controlling deposits of sludge accumulating on the bottom or inside the bed of media. In submerged bed reactors using an open structure media backwashing is not required, as the exces
40、s sludge is removed by aeration. Backwashing is typically required if media of a granular type is used. Carbonaceous oxidation, nitrification and denitrification can be carried out in single or separate stages of biofiltration as well as achieving suspended solids removal. Biofilters may be designed
41、 for upward or downward flow of wastewater. They may be required to be taken out of service for backwashing or may operate continuously with a separate washing system. The media may be single or multi-layer and can have a specific gravity greater or lower than that of water. 4.2 Planning The followi
42、ng factors shall be considered in the design: characteristics of incoming wastewater; the capacity and dimensions of the biological reactors; the prevention of dead zones and detrimental deposition in tanks/channels; the establishment of multiple lines/units or other technical means to ensure mainte
43、nance of required final effluent quality if one or more line/unit is out of operation; the surface area, volume and depth of the clarifiers where used; the treatment and final destination of the sludge produced; the head loss to be minimized; measurement and control; media specification. Reference s
44、hould be made to EN 12255-1, EN 12255-6, EN 12255-10 and EN 12255-11 for further considerations.EN 12255-7:2002 (E) 7 4.3 Process 4.3.1 Design The following operational parameters shall be considered and shall be appropriate for the type of treatment required: volumetric loading rate kg/(m 3d) (as B
45、OD 5 , COD, NH 4 -N or NO 3 -N); mass surface loading rate kg/( m 2 d) (as BOD 5 , COD, NH 4 -N or NO 3 -N); support media specific surface (m 2 / m 3 ); recirculation ratio; surface loading rate m 3 /( m 2 h); flushing intensity (mm); interval between backwashing (biofilters). NOTE The references i
46、n the Bibliography give further information. 4.3.2 Modes of operation The plant may be configured in one of the following modes: single stage treatment in which the wastewater passes through only one reactor followed by clarification; two stage treatment in which the wastewater passes through two re
47、actors in series and which can include clarification after both stages or only after the second stage; NOTE Biofilters do not require intermediate or final clarification. alternating double filtration in which the sequence of flow through trickling filters is alternated so that each set of filters t
48、reat in successive periods either settled wastewater or effluent from the first stage. This limits excessive growths of biological film, which might otherwise develop in the upper layers of the first stage trickling filter when treating a high strength wastewater. The types of treatment that may be
49、provided are as follows: carbonaceous oxidation; nitrification, which occurs after carbonaceous removal and is achieved by operating plant either at a lower loading rate or using a separate stage; denitrification, which is typically established in a two stage step system, where the first stage step is used for denitrification and the second stage for BOD removal and nitrification. These flow schemes need a recycle of nitrified wastewater from th
