EN 12255-8:2001

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.MHQMHKläranlagen - Teil 8: Schlammbehandlung und -lagerungStations d'épuration - Partie 8: Stockage et traitement des bouesWastewater treatment plants - Part 8: Sludge treatment and storage13.060.30Odpadna vodaSewage waterICS:Ta slovenski standard je istoveten z:EN 12255-8:2001SIST EN 12255-8:2001en01-december-2001SIST EN 12255-8:2001SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12255-8May 2001ICS 13.060.30English versionWastewater treatment plants - Part 8: Sludge treatment andstorageStations d'épuration - Partie 8: Stockage et traitement desbouesKläranlagen - Teil 8: Schlammbehandlung und -lagerungThis European Standard was approved by CEN on 8 March 2001.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2001 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12255-8:2001 ESIST EN 12255-8:2001

Page 2EN 12255-8:2001ContentsPageForeword.31
Scope.32
Normative references.43
Terms and definitions.44
Planning.55
Process requirements.55.1
General.55.2
Thickening.55.3
Disinfection.65.4
Stabilisation and pseudo-stabilisation.75.5
Sludge dewatering.105.6
Composting.115.7
Handling and storage.126
Construction principles.126.1
Service life.126.2
Pipelines.126.3
Sludge pumps.137
Safety.13Bibliography.14SIST EN 12255-8:2001

Page 3EN 12255-8:2001ForewordThis European Standard has been prepared by Technical Committee CEN/TC 165 "Waste water engineering", thesecretariat 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 byendorsement, at the latest by November 2001, and conflicting national standards shall be withdrawn at the latest byDecember 2001.It is the eighth part prepared by the Working Groups CEN/TC 165/WG 42 and WG 43 relating to the generalrequirements and processes for treatment plants for over 50 PT. The parts of the series are as follows:Part 1:General construction principlesPart 3:Preliminary treatmentPart 4:Primary settlementPart 5:Lagooning processesPart 6:Activated sludge processesPart 7:Biological fixed-film reactorsPart 8:Sludge treatment and storagePart 9:Odour control and ventilationPart 10:Safety principlesPart 11:General data requiredPart 12:Control and automation1)Part 13:Chemical treatmentPart 14:Disinfection1)Part 15:Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plantsPart 16:Physical (mechanical) filtration1)NOTEFor requirements 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 outsidebuildings — Part 6: Pumping installations”.The parts EN 12255-1, EN 12255-3 to EN 12255-8 and EN 12255-10 and EN 12255-11 became implementedtogether as a european package (Resolution BT 152/1998). The date of withdrawl (dow) of all conflicting nationalstandards is 2001-12-31. Until the date of withdrawl is reached the National and the already published Europeanstandards both coexist.This standard includes a Bibliography.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countriesare bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France,Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerlandand the United Kingdom.1
ScopeThis European Standard gives design principles and specifies construction requirements for sludge treatment andstorage facilities in wastewater treatment plants for more than 50 PT.Other sludges and organic wastes may be treated together with the municipal sewage sludge.Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. Thisstandard gives fundamental informations about the systems; this standard has not attempted to specify all availablesystems.Detailed information additional to that contained in this standard may be obtained by referring to the bibliography.
1 ) in preparationSIST EN 12255-8:2001

Page 4EN 12255-8:20012
Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listed hereafter. For datedreferences, subsequent amendments to or revisions of any of these publications apply to this European Standard onlywhen incorporated in it by amendment or revision.
For undated references the latest edition of the publicationreferred to applies (including amendments).EN 1085Wastewater treatment — VocabularyEN 12176Characterization of sludge — Determination of pH-valueprEN 12255-1:1996Wastewater treatment plants — Part 1: General construction principlesprEN 12255-4:1997Wastewater treatment plants — Part 4: Primary settlementEN 12255-5Wastewater treatment plants — Part 5: Lagooning processesprEN 12255-6:1997Wastewater treatment plants — Part 6: Activated sludge processesprEN 12255-9:1999Wastewater treatment plants — Part 9: Odour control and ventilationEN 12255-10Wastewater treatment plants — Part 10: Safety principles for the construction of wastewater treatment plantsEN 12880Characterisation of sludges — Determination of dry residue and water contentEN ISO 5667-13Water quality — Sampling — Part 13: Guidance on sampling of sludges from sewage and water treatmentworks (ISO 5667-13 : 1997)3
Terms and definitionsFor the purposes of this European standard the terms and definitions given in EN 1085 and the following apply.3.1psychrophilicprocess conditions for organisms which are active below 30 C.3.2 mesophilicprocess conditions for organisms which are active at temperatures between 30 C and 45 C, with an optimum of32 C to 37 °C.3.3thermophilicprocess conditions for organisms which are active at temperatures between 45 C and 80 C, and have an optimum of55 C to 65 C.3.4pseudo stabilisationprocess which prevents organic degradation so long as particular conditions (such as pH value or dryness) aremaintained, but for which degradation recommences when the conditions are no longer met.SIST EN 12255-8:2001

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PlanningSludge treatment and storage influences subsequent utilization. It may be subject to a variety of regulationsdependent upon the site of the treatment plant and the proposed routes for use or disposal. For new works or majorupgrading an environmental impact assessment should be carried out.The choice of the sludge treatment process depends on the size of the treatment plant, the type, origin andcharacteristics of the sludge to be treated and the final method of utilization or disposal. Processes which allow formore than one sludge utilization or disposal option are preferable.Consideration should be given to the possibility of centralised sludge treatment facilities which allow a wider range oftreatment techniques. Special care is needed in respect of extra loads e. g. of nitrogen generated from sludge liquorsat centralised facilities.Sufficient storage capacity shall be available on the source site for raw or treated sludge to prevent sludge overflowunder all likely conditions.The following factors shall be considered in planning sludge treatment:— the utilization or disposal route and related quality requirements e. g. nutrients, harmful substances andcalorific value;— sludge characteristics;— import of sludges and other organic wastes;— minimum and maximum daily sludge production (volume and mass);— future sludge production;— range of solids concentrations (total and volatile solids);— physical characteristics (viscosity, temperature);— biological properties (degradability, inhibitors and toxicants);— aggressive or corrosive conditions;— likely emissions including greenhouse gases, and odours (see also prEN 12255-9:1999);— removal or disintegration of gross solids which may cause blockage or malfunction;— effect of abrasive or deposit forming solids such as grit;— effect of additives used in wastewater treatment, such as precipitants, coagulants and flocculants and theirinfluence on utilization;— impact of return liquors on the wastewater treatment process e. g. peak loads of ammonia and phosphorusresolubilisation from sludge processing;— health and safety of operators and the general public (see also EN 12255-10) e. g. the generation of toxic and/or explosive atmospheres;— nuisance e. g. smell and visual intrusion;— environment e. g. effect of leakage.5
Process requirements5.1
GeneralProvision shall be made to allow the sampling of input and output for each unit process (see EN ISO 5667-13).Flow measurement for each unit process should be considered.The design shall take account of any requirements for control of odour, noise, vibration and explosive atmospheres inaccordance with prEN 12255-9:1999 and EN 12255-10.5.2
Thickening5.2.1
GeneralSludge thickening is carried out in a continuous or batch mode of operation, using gravity thickeners, mechanicalthickening equipment such as filters or centrifuges, or dissolved air flotation.The selection of the thickening method and its design shall take account of the following factors:— the sludge solids concentration required by subsequent processes;— the solids recovery from the process;— resolubilisation of phosphorus in gravity thickeners;— retention times, which when exceeding one day can result in anaerobic degradation, causing
odour emission,foaming, bulking and impaired dewaterability;— control of the sludge feed and liquor removal rates;SIST EN 12255-8:2001

Page 6EN 12255-8:2001— the storage and controlled return of sludge liquor where nitrification or nitrogen
removal is required.Due to enhanced viscosity, positive displacement pumps should be used for transferring the thickened sludge.A programme of sludge testing and analysis shall be considered where practicable to assist in the design of gravitythickeners.5.2.2
Gravity thickeningGravity thickeners should have a depth of at least 3 m, have a bottom slope of at least 50o
(conical) or 60o (pyramidal)to the horizontal or be equipped with either an agitator or
a rake which includes a bottom scraper (e.g. picket fence).Other features which shall
be considered include:— retention and
removal of scum;— supernatant withdrawal at different levels (e. g. using a vertically moveable device);— observing the quality
of the supernatant liquor during removal;— ventilation and exhaust air deodorisation if thickeners are covered.Factors which affect the design of gravity thickeners include:— the surface loading rate;— the mass surface loading rate;— the solids detention time;— the total depth of the consolidation zone.5.2.3 Mechanical thickeningWhere thickening equipment is similar to that used for mechanical dewatering the relevant construction principlesapply. The most common machines for mechanical thickening are:— drum filters;— belt filters;— centrifuges.Mechanical sludge thickening equipment should:— normally oper
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