1、BRITISH STANDARD BS EN 12255-6:2002 Wastewater treatment plants Part 6: Activated sludge process The European Standard EN 12255-6:2002 has the status of a British Standard ICS 13.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 12255-6:2002 This British Standard, ha
2、ving 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 4 April 2002 BSI 4 April 2002 ISBN 0 580 39427 1 National foreword This British Standard is the offic
3、ial English language version of EN 12255-6:2002. 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-refer
4、ences 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 Catal
5、ogue. 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 the tex
6、t; 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 inside
7、front cover, the EN title page, pages 2 to 13, the annex NA page, 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 EUROPISC
8、HE NORM EN 12255-6 January 2002 ICS 13.060.30 English version Wastewater treatment plants Part 6: Activated sludge process Stations dpuration Partie 6: Procd boues actives Klranlagen Teil 6: Belebungsverfahren This European Standard was approved by CEN on 9 November 2001. CEN members are bound to co
9、mply 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 Managemen
10、t 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 the same status as the offic
11、ial 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 COMMITTEE FOR STANDARDIZATION
12、 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 12255-6:2002 EEN 12255-6:2001 (E) 2 Contents Page Foreword3
13、1 Scope 4 2 Normative references 4 3 Terms and definitions4 4 Requirements .4 4.1 General4 4.2 Planning 5 4.3 Flow-splitting structure .5 4.4 Biological reactor.5 4.4.1 Design .5 4.4.2 Operational parameters.6 4.4.3 Mixing6 4.4.4 Aeration.6 4.4.5 Additional considerations.8 4.5 Clarifiers9 4.5.1 Gen
14、eral9 4.5.2 Design .9 4.6 Return and surplus sludge systems10 Annex A (informative) Design-Technical process characteristics 11 Bibliography 12EN 12255-6:2001 (E) 3 Foreword This European Standard has been prepared by Technical Committee CEN/TC 165, Wastewater engineering, the Secretariat of which i
15、s 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 July 2002, and conflicting national standards shall be withdrawn at the latest by December 2002. In this standard the Annex A is info
16、rmative. It is the sixth part prepared by the Working Groups CEN/TC 165/WG 42 and 43 relating to the general requirements and processes for treatment plants for a total number of inhabitants and population equivalents (PT) over 50. The parts of the series are as follows: Part 1: General construction
17、 principles Part 3: Preliminary treatment Part 4: Primary settlement Part 5: Lagooning processes Part 6: Activated sludge processes Part 7: Biological fixed-film reactors Part 8: Sludge treatment and storage Part 9: Odour control and ventilation Part 10: Safety principles Part 11: General data requi
18、red Part 12: Control and automation Part 13: Chemical treatment Treatment of wastewater by precipitation/flocculation Part 14: Disinfection Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants Part 16: Physical (mechanical) filtration 1 ) NOTE For r
19、equirements 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 Part 6: Pumping installations. EN 12255-1, EN 12255-3 to EN 12255-8 and EN 12255-10 and EN
20、 12255-11 were implemented together as a European package (Resolution BT 152/1998). 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, Fr
21、ance, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.1 )In preparation.EN 12255-6:2001 (E) 4 1 Scope This European Standard specifies the performance requirements for treatment of wastewater using the acti
22、vated sludge process for plants over 50 PT. Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. This standard gives fundamental information about the systems; this standard has not attempted to specify all available systems. Detailed information ad
23、ditional to that contained in this standard may be obtained by referring to the bibliography. 2 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
24、the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (inc
25、luding amendments). EN 1085, Wastewater treatment Vocabulary. EN 12255-1, Wastewater treatment plants Part 1: General construction principles. EN 12255-10, Wastewater treatment plants Part 10: Safety principles. EN 12255-11, Wastewater treatment plants Part 11: General data required. prEN 12255-12,
26、Wastewater treatment plants Part 12: Control and automation. 3 Terms and definitions For the purposes of this European Standard the terms and definitions given in EN 1085 apply. 4 Requirements 4.1 General The biological reactors and the clarifiers connected by the return sludge recirculation form a
27、unit process: the activated sludge process. The performance of the process depends on the biological and chemical reactions in the activated sludge tanks as well as the separation of the activated sludge in the final clarifiers. NOTE Biological treatment and clarification may be combined in the same
28、 tank, e.g. a sequencing batch reactor (SBR). The design shall take account of the requirements specified in EN 12255-1, EN 12255-10, EN 12255-11 and prEN 12255-12.EN 12255-6:2001 (E) 5 4.2 Planning The following factors shall be considered in the design of an activated sludge treatment plant: the c
29、apacity 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 maintenance of required final effluent quality if one or more line/unit is out of operation; the
30、aeration and/or mixing equipment; the surface area, volume and depth of the clarifiers ; sludge removal system within the clarifier; the sludge recirculation and excess sludge wasting equipment; the treatment and final destination of the sludge produced; measurement and control; the head loss to be
31、minimized. The structures shall be designed to allow emptying either by gravity flow or by pumping. Emptying shall not affect the stability of structures, irrespective of the groundwater level. All necessary measures shall be taken such as ballast concrete, floor check valve or provision for tempora
32、ry lowering of the groundwater. It can be useful to design the floor to slightly incline towards the lowest points. When a pump is used for emptying a drain pit may be built into these low points. 4.3 Flow-splitting structure When the process involves multiple lines or parallel units, the incoming f
33、low shall be distributed by an adjustable distribution device (e.g. valve, gate, stop-log) that can also be used to isolate each treatment unit. This device shall provide the required flow distribution over the range of flow rates considered. NOTE The accumulation and removal of floating matter can
34、be considered at this stage. 4.4 Biological reactor 4.4.1 Design The number, shape and capacity of the reactors achieving the main biological reactions can vary considerably according to: the size of plant; the level of treatment to be achieved, e.g. carbonaceous removal, nitrification, denitrificat
35、ion and phosphorus removal; the anoxic stage, with respect to nitrogen removal; the dosage of precipitant and/or the anaerobic stage with respect to phosphate removal. The hydraulic design shall minimize short-circuiting. The reactor flow pattern depends on the process selected. In the case of multi
36、point feed (e.g. step-aeration), appropriate devices (e.g. valves, gates, stop- logs) shall be provided to allow modification of the original flow-splitting arrangement.EN 12255-6:2001 (E) 6 When the plant is designed for one or more reactors to be taken out of service for routine maintenance, the r
37、eactors remaining in operation and their associated pipework, channels, etc., shall have the hydraulic and treatment capacity to accommodate all the incoming flow. A selector where return sludge and wastewater are brought into a short period of contact can reduce the growth of filamentous bacteria a
38、nd improve the growth of flocculant bacteria. Owing to the short contact time, the content shall be mixed efficiently. Where intermittent pumping exist the influent and return sludge shall arrive at the same time. 4.4.2 Operational parameters The following operational parameters shall be considered
39、and should be appropriate for the level of treatment required: the mixed liquor suspended solids concentration (MLSS) or the mixed liquor volatile suspended solids (MLVSS); the sludge age; the sludge loading (F/M); the sludge volume index (SVI) e.g. stirred (SSVI) or diluted. NOTE Further informatio
40、n is available in the references listed in the Bibliography. 4.4.3 Mixing Mixing can be performed by the aeration devices themselves (e.g. surface aerators, air-diffusers), by separate mixing devices or by the two together. Individual mixing devices should be capable of being removed without emptyin
41、g the tank. The contents of the aeration tank shall be mixed to prevent activated sludge from settling or forming detrimental deposits. If aeration is not continuous, the devices shall have the capacity to maintain or resuspend the mixed liquor. Mixers should be designed to minimize fouling by fibro
42、us materials. The choice of device depends on the characteristics of the wastewater to be treated and the mixed liquor concentration required. More powerful devices can be required in cases where the activated sludge process is not preceded by primary settlement. 4.4.4 Aeration In the absence of com
43、plementary mixing devices, aeration devices shall have the capacity to provide sufficient agitation to thoroughly mix the biomass, the pollutants and the dissolved oxygen. The dimensioning of the aeration devices and the tanks should ensure both the adequacy of mixing of the activated sludge mixed l
44、iquor and the energy efficiency of the process. If pure oxygen is used in aeration: all necessary safety precautions shall be taken; explosive gas monitoring and explosion proof equipment shall be provided; specific safety signs shall be displayed. It shall be verified that the power input of the ae
45、ration device, derived from aeration requirements, is not lower than the power required to ensure adequate mixing conditions at all times (unless alternative arrangements are in place for the mixing process). Air diffusers shall be installed to ensure a uniform depth of immersion.EN 12255-6:2001 (E)
46、 7 The aeration system shall have the capacity to supply sufficient oxygen to ensure carbonaceous oxidation, endogenous respiration and oxidation of nitrogen compounds (if these are required) under all operating conditions. The basis of the design is clean water oxygen transfer capacity which shall
47、be calculated for the maximum and minimum oxygen uptake rate, considering the alpha factor which depends on the wastewater characteristics and the type of aeration system. In order to maintain the desired dissolved oxygen level, a variable oxygen supply should be provided where possible, especially
48、where a large variation in oxygen demand is anticipated. NOTE The requirement for the oxygen supply is dependent on the wastewater characteristics and the level of treatment to meet the consent standards. When aeration is not controlled by on-line measurements the operation of the aeration device(s)
49、 may be programmed with settings for rate, interval and duration. For nitrification/denitrification in a single reactor, the power of the aeration devices shall be compatible with their duration of operation. The automatic control system shall be designed to ensure adequate aeration is maintained in case of its failure. Where dissolved oxygen control is achieved by variation of mixed liquor level, using an adjustable weir, the surge flows into the clarifiers shall be tak
