1、BRITISH STANDARD BS EN 12255-4:2002 Incorporating Corrigendum No. 1 Wastewater treatment plants Part 4: Primary settlement The European Standard EN 12255-4:2002 has the status of a British Standard ICS 13.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 12255-4:2002
2、 This British Standard, 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 3 April 2002 BSI 21 June 2002 ISBN 0 580 39426 3 National foreword This Bri
3、tish Standard is the official English language version of EN 12255-4:2002. 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
4、its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electron
5、ic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users of this publication are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations.
6、 aid enquirers to understand the 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
7、 comprises a front cover, an inside front cover, the EN title page, pages 2 to 8, the annex NA page 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 Comments 13961 Corrigendum No. 1 21 J
8、une 2002 Insertion of clause numbering for Clauses 1, 2, 3EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12255-4 January 2002 ICS 13.060.30 English version Wastewater treatment plants Part 4: Primary settlement Stations dpuration Partie 4: Dcantation primaire Klranlagen Teil 4: Vorklrung This
9、European Standard was approved by CEN on 9 November 2001. 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 referenc
10、es concerning such national standards 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 translation under the responsibility of a CEN member into it
11、s own language and notified to the Management Centre has the 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,
12、Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE 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 natio
13、nal Members. Ref. No. EN 12255-4:2002 EEN 12255-4:2002 (E) 2 Contents Page Foreword .3 1 Scope 4 2 Normative references4 3 Terms and definitions .4 4 Requirements.5 4.1 General5 4.2 Planning5 4.3 Process.6 4.3.1 General6 4.3.2 Required Capacity .6 4.3.3 Upward Flow Tanks (including Imhoff Tanks)6 4.
14、3.4 Horizontal Flow Tanks.6 4.3.5 Lamella Separator7 4.3.6 Sludge Collection and Removal.7 4.3.7 Scum Removal.7 4.4 Maintenance.7 4.5 Health and Safety.7 Bibliography8EN 12255-4:2002 (E) 3 Foreword This European Standard has been prepared by Technical Committee CEN/TC 165, Wastewater engineering, th
15、e Secretariat of which is 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. It is the fo
16、urth 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 principles Part 3:
17、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 required Part 12: Control
18、 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 2 ) NOTE For requirements on pumpi
19、ng 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 12255-11 were imple
20、mented 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, France, Germany, Greec
21、e, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.2 )In preparation.EN 12255-4:2002 (E) 4 1 Scope This European Standard specifies the performance requirements for the primary settlement of wastewater at wastewater treatme
22、nt plants for over 50 PT. The primary application is for wastewater treatment plants designed for the treatment of domestic and municipal wastewater. Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. This standard gives fundamental information ab
23、out 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 Standard incorporates by dated or undated reference, provisions
24、 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 to this European Standard only when incorporated in it by am
25、endment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 1085, Wastewater treatment Vocabulary. EN 12255-1, Wastewater treatment plants Part 1: General construction principles. EN 12255-3, Wastewater treatment plants Part 3: Pre
26、liminary treatment. EN 12255-10, Wastewater treatment plants Part 10: Safety principles. EN 12255-11, Wastewater treatment plants Part 11: General data required. EN 12566-1, Small wastewater treatment systems for up to 50 PT Part 1: Prefabricated septic tanks. 3 Terms and definitions For the purpose
27、s of this European Standard, the following terms and definitions given in EN 1085 and the following apply. 3.1 lamella separator system of regularly spaced, inclined plates or tubes, designed to increase the effective settling area in a settlement tankEN 12255-4:2002 (E) 5 4 Requirements 4.1 General
28、 Primary settlement serves the purpose of separating settleable solids, which are removed on a regular basis in the form of raw sludge. Grease and other floating materials which can cause malfunction of a wastewater treatment plant can also be separated and removed during this process. Where large q
29、uantities of grease are expected a separate grease separation step is recommended prior to primary settlement (see EN 12255-3). The type and size of unit(s) will depend on the overall system, PT, sludge removal and ground conditions prevailing on the construction site. Primary treatment may include
30、the following types of settlement tank: upward flow (including Imhoff) generally square or circular in plan; horizontal flow generally rectangular in plan; lamella separator. Primary settlement may not be required e.g. where biological treatment is by lagooning or by certain activated sludge process
31、es. The consequences for subsequent processes of omitting this step shall be considered. Septic tanks can be used for the function of primary settlement. NOTE The design, construction and operation of septic tanks is specified in EN 12566-1. 4.2 Planning The requirements for the performance of prima
32、ry settlement should be determined after consideration of the following factors: the quality and quantity of sludge produced; the effect of the residual loads on the subsequent treatment processes; the need to limit retention time in order to avoid septicity. Those requirements specific to the perfo
33、rmance of the primary settlement plant that are specified in EN 12255-11 shall be applied. Additional requirements are specified in EN 12255-1 and EN 12255-10.EN 12255-4:2002 (E) 6 4.3 Process 4.3.1 General Solids removal and detention times at maximum and minimum flows shall be in accordance with t
34、he requirements of any downstream process. Where applicable, peak flow shall take into account pumped inflow and/or return flow rates. Wastewater shall enter the tank via a stilling device which shall be capable of dissipating the input energy and ensuring even distribution over the entire settlemen
35、t zone or lamella plate pack. The procedure for effluent draw-off shall be designed to minimize disturbance to the settling zone and allow removal of floating matter. 4.3.2 Required Capacity The total primary settlement tank capacity required shall take into account the PT and the dry weather peak h
36、ourly flow to the plant. 4.3.3 Upward Flow Tanks (including Imhoff Tanks) Upward flow tanks may be square or circular in plan. Tanks without mechanical scrapers shall have a hopper bottom for sludge collection. NOTE Tanks square in plan are not usually employed for populations in excess of 5 000 PT.
37、 The tank should be so designed that the upward flow velocity is restricted to within a typical range of 1,0 m 3 /(m 2 h) to 2,0 m 3 /(m 2 h) surface area at dry weather peak hourly flow. The minimum sidewall height between the top of the hopper and top water level shall be from 0,3 m to 1,5 m for i
38、ndividual tanks serving populations 50 PT to 1 000 PT. 4.3.4 Horizontal Flow Tanks Horizontal flow tanks are typically rectangular in plan with a sludge hopper situated at the inlet end of the tank. They shall conform to the following minimum values: 1,5 m water depth at outlet; 3:1 length to breadt
39、h ratio; 0,3 m freeboard in uncovered tanks. Maximum weir overflow rate shall not exceed 30 m 3 /(mh) at dry weather peak hourly flow.EN 12255-4:2002 (E) 7 4.3.5 Lamella Separator Where these tanks are used they should be equipped with inclined settling plates or tubes, typically forming a counter c
40、urrent system by water circulating from the bottom to top and sludge moving from top to bottom. The lamellae shall be so spaced as to avoid clogging and shall be determined by the effectiveness of upstream screening and grease removal. The angle of plates/tubes shall be within a range between 55 and
41、 65measured from the horizontal. The space between lamellae and the bottom of the tank shall be designed to ensure an even distribution of wastewater and a sufficient space for the settled sludge. Sludge should be collected in one or more hoppers and in larger tanks a scraper mechanism may be used t
42、o move the sludge to hopper(s) at one end of the tank. The design should allow ease of cleaning of settling plates or tubes on a regular basis. 4.3.6 Sludge Collection and Removal 4.3.6.1 Upward Flow Tanks Small tanks typically do not have a scraper mechanism to assist sludge removal, and therefore
43、shall have a hopper with smooth sides. The angle of slope of the sides of the hopper measured from the horizontal, shall not be less than 50 for conical and 60 for pyramidal hoppers. As tank size increases (typically for those serving above 1 000 PT) a hopper with a 50 respectively 60 floor slope be
44、comes impractical due to the depth of excavation required. In these cases a shallow sloping floor is required to collect sludge and allow it to be scraped to the central hopper for removal. The floor slope should be between 3 and 30 measured from the horizontal, depending on the size of tank and the
45、 type of scraper to be used. NOTE Where sludge removal is by suction a floor slope may not be required. 4.3.6.2 Horizontal Flow Tanks Very small tanks without a mechanical scraper to assist sludge removal shall have a floor slope of not less than 1:100 to permit emptying to the sludge hopper at the
46、inlet end of the tank. These tanks should be completely emptied for sludge removal. A minimum of two tanks is required to ensure continuity of treatment. Large tanks should have a scraper and/or suction mechanisms installed and a sloping floor may not be required. 4.3.7 Scum Removal All tanks shall
47、be designed with a baffle (scum board) to retain floating matter. The design of the tank shall enable the retained matter to be removed. 4.4 Maintenance The requirements for access, spare parts and maintenance of plants are given in EN 12255-1. 4.5 Health and Safety The generality of health and safe
48、ty requirements for plants are given in EN 12255-10.EN 12255-4:2002 (E) 8 Bibliography The following documents contain details which can be used within the framework of this standard. This list of documents which are published and used by the members of CEN was correct at the time of publication of
49、this European Standard but should not be considered to be exhaustive. Austria 1 OENorm B 2502-1, Domestic sewage treatment plants for buildings up to 50 inhabitants Appliance, dimensioning, erection and operation. 2 OENorm B 2502-2, Small sewage treatment plants Installations for buildings of 51 to 500 population equivalents Application, dimensions, construction and operation. 3 OENorm B 2505, Subsurface flow constructed wetlands (constructed wetlands) Application, d
