dwa-a_116-1e
DESCRIPTION
Vacuum Sewerage SystemsTRANSCRIPT
Teile 1 und 2
Standard DWA-A 116-1E
Special Sewerage Systems
Part 1: Vacuum Sewerage Systems
Outside Buildings
March 2005
G E R M A N
DWA-Rules and Standards
Standard DWA-A 116-1E
Special Sewerage Systems
Part 1: Vacuum Sewerage Systems
Outside Buildings
March 2005
G E R M A N
DWA-Rules and Standards
DWA-A 116-1E
2 March 2005
The German Association for Water, Wastewater and Waste, DWA (former ATV-DVWK), is the spokesman in Germany for all universal questions on water and is involved intensely with the development of reliable and sustainable water management. As politically and economically independent organisation it operates specifically in the areas of water management, wastewater, waste and soil protection.
In Europe the DWA is the association in this field with the greatest number of members and, due to its spe-cialist competence it holds a special position with regard to standardisation, professional training and infor-mation of the public. The ca. 14,000 members represent the experts and executive personnel from munici-palities, universities, engineer offices, authorities and businesses.
The emphasis of its activities is on the elaboration and updating of a common set of technical rules and standards and with collaboration with the creation of technical standard specifications at the national and in-ternational levels. To this belong not only the technical-scientific subjects but also economical and legal demands of environmental protection and protection of bodies of waters.
Imprint
Publisher and marketing: DWA German Association for Water, Wastewater and Waste Theodor-Heuss-Allee 17 D-53773 Hennef, Germany Tel.: Fax: E-Mail: Internet:
+49 2242 872-333 +49 2242 872-100 [email protected] www.dwa.de
Translation: Dr. M. Roediger, Stuttgart Richard Brown, Wachtberg Printing (English version): DWA ISBN-13: 978-3-939057-46-8 ISBN-10: 3-939057-46-0
The translation was sponsored by the German Federal Environmental Foundation (DBU).
Printed on 100 % Recycling paper.
© DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V., Hennef 2006 (German Association for Water, Wastewater and Waste)
All rights, in particular those of translation into other languages, are reserved. No part of this Standard may be reproduced in any form - by photocopy, microfilm or any other process - or transferred into a language usable in machines, in particular data processing ma-chines, without the written approval of the publisher.
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Foreword
The European Committee for Standardisation (CEN) has, on the basis of its Mandate dated 24 May 1991 from the Commission of the European Union (CEU) and, identically, from the European Free Trade Asso-ciation (EFTA), assumed the task of harmonizing all technical regulations in the field of wastewater engi-neering and generating European Standards the specified areas and products.
After lengthy negotiations with active German participation, and after discussion of numerous objections, EN 1091 “Vacuum Sewerage Systems Outside Buildings” and EN 1671 “Pressure Sewerage Systems Out-side Buildings” were published in 1997.
Both standards contain, in addition to special requirements on the products to be used, general require-ments on the performance of the systems as well as specifications for testing. They do not contain sufficient information for the dimensioning of the systems.
In order to provide necessary national content that is not, or only insufficiently, covered by European Stan-dards, it is possible to generate additional national specifications.
The objective of this Standard is to help the designing engineer to recognise and creatively use the latitude given in EN 1091. Its objective is to facilitate the application of EN 1091.
There has been no essential contradiction between the new European Standards and the previous ATV-A 116 Standard from 1992, which essentially contains requirements on the design and dimensioning of the sys-tems and only very few requirements on the products. Moreover, the German delegation had successfully in-troduced the ATV Standard as an important basis for the work on both European Standards. The report by the ATV-DVGW working group ES-1.1 from the year 2000, referenced in Appendix G, provides a comparison of EN 1091 with the previous Standard ATV-A 116 from the year 1992 and may serve for orientation.
Nevertheless, the DWA working Group ES-2.3 has reviewed and updated the Standard ATV-A 116, not only in view of the new European Standards, but also in consideration of more recent technical improvements and experience.
Standard DWA-A 116 now consists of:
• Part 1: Vacuum sewerage systems outside buildings,
• Part 2: Pressure sewerage systems outside buildings (in preparation),
• Part 3: Pneumatically flushed wastewater transport pipelines (in preparation).
Parts 1 and 2 are covered by European standards. Concerning Part 3 there is a report of the ATV Working Group 1.1.6 from the year 1987 (referenced in Appendix H).
This Standard is directed in particular to consulting engineers, system suppliers, regulators, contractors and operators.
This Part 1 follows the organisational structure of the European Standard EN 1091 in order to facilitate si-multaneous working with both documents. The additional Appendix M provides information about expected service lives. The additional Appendix N specifies requirements on qualification and training of construction and operating personnel.
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Authors This Standard has been elaborated by the DWA Working Group ES-2.3 “Special Drainage Systems” within the DWA Committee ES-2 “System-related Design”.
The DWA Working Group ES-2.3 “Special Drainage Systems” has the following members:
BIEBER, Helmut Baudirektor Dipl.-Ing., Kiel
DIPPOLD, Walter Dipl.-Ing., Germering
ECKSTÄDT, Hartmut Prof. Dr.-Ing. habil., Rostock
FLICK, Karl-Heinz Bauassessor Dipl.-Ing., Köln
HOWE, Harald O. Dr.-Ing., Köln (until 2000)
JEDLITSCHKA, Jens MinisterialRat Dipl.-Ing., München (Chairman)
KLEINSCHROTH, Adolf Prof. Dr.-Ing., München (†)
KLIPPEL, Angela Dipl.-Ing., Berlin
PETERSOHN, Thomas Dipl.-Ing., Aurich
ROEDIGER, Markus Dr.-Ing., Charlotte (NC, USA)
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Contents Foreword .................................................................................................................................................. 3
Authors .................................................................................................................................................. 4 List of Figures .......................................................................................................................................... 6 List of Tables ........................................................................................................................................... 6 User Notes................................................................................................................................................ 7 1 Area of Application ................................................................................................................. 7 2 Normative References ........................................................................................................... 7 3 Definitions................................................................................................................................ 7
4 Description of the System...................................................................................................... 7 4.0 General ..................................................................................................................................... 7 4.1 Collection Chamber and Vacuum Pipeline ............................................................................... 8 4.2 Vacuum Station......................................................................................................................... 9
5 Requirements .......................................................................................................................... 9 5.0 Bylaw Issues ............................................................................................................................. 9 5.1 General Requirements.............................................................................................................. 9 5.2 Performance and Quantitative Requirements (Special Requirements on Components) ......... 9 5.2.1 Gravity Drains ........................................................................................................................... 9 5.2.2 Flows from Interceptor Sewers and Commercial Developments.............................................. 9 5.2.3 Collection Chambers................................................................................................................. 9 5.2.4 Collection Sumps ...................................................................................................................... 10 5.2.5 Interface Valve .......................................................................................................................... 10 5.2.6 Level Sensor ............................................................................................................................. 10 5.2.7 Interface Valve Controller.......................................................................................................... 10 5.2.8 Explosion Proof (Collection Chamber)..................................................................................... 10 5.2.9 Life of Membranes and Seals ................................................................................................... 10 5.2.10 Vacuum Pipeline Components.................................................................................................. 10 5.2.11 Pipe Size ................................................................................................................................... 10 5.2.12 Service Connections ................................................................................................................. 10 5.2.13 Branch Connection.................................................................................................................... 10 5.2.14 Isolation Means ......................................................................................................................... 10 5.2.15 Vacuum Tanks .......................................................................................................................... 12 5.2.16 Control of the Vacuum Station .................................................................................................. 12 5.2.17 Level Control ............................................................................................................................. 12 5.2.18 Equipment (Vacuum Generator) ............................................................................................... 12 5.2.19 Capacity of Forwarding Equipment........................................................................................... 12 5.2.20 Design of Forwarding Pumps.................................................................................................... 12 5.2.21 Replacement of Forwarding Pumps.......................................................................................... 12 5.2.22 Explosion Proof Electrical Equipment (Vacuum Station) .......................................................... 12 5.2.23 Non-Return Valves.................................................................................................................... 12 5.2.24 Ejector Pumps........................................................................................................................... 12 5.2.25 Odour Control............................................................................................................................ 12 5.2.26 Noise Control ............................................................................................................................ 13 5.2.27 Emergency Power Generation.................................................................................................. 13 5.3 Design Requirements................................................................................................................ 13 5.3.0 General ..................................................................................................................................... 13
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5.3.1 Pipeline Design ........................................................................................................................ 13 5.3.2 Pipeline Profiles........................................................................................................................ 13 5.3.3 Hydro-Pneumatic Design ......................................................................................................... 15 5.3.4 Basis of Design ........................................................................................................................ 16 5.3.5 Vacuum Station ........................................................................................................................ 16 5.3.6 Sources of Additional Information ............................................................................................ 17 5.3.7 Application of Vacuum Sewerage .............................................................................................. 17
6 Installation (of Pipelines)....................................................................................................... 17 6.1 Installation (Pipe Laying) .......................................................................................................... 17 6.2 Tolerances................................................................................................................................ 18 6.3 Warning and Location System ................................................................................................. 18
7 Testing and Verification......................................................................................................... 18 8 Commissioning (and Start-up).............................................................................................. 18 9 Economic Aspects ................................................................................................................. 18 Appendices A to E .................................................................................................................................. 19 Appendix F: Operational and Maintenance Information..................................................................... 19 Appendix G: Sources of Additional Information ................................................................................. 19 Appendix H: Bibliography...................................................................................................................... 20 Appendix I: Application of Vacuum Sewerage .................................................................................... 22 Appendix K: Dimensioning Example .................................................................................................... 22
Appendix L: Symbols ............................................................................................................................. 27
K.1 Basic Lay-out............................................................................................................................ 22 K.2 Dimensioning of the Pipelines.................................................................................................. 22 K.3 Dimensioning of the Vacuum Station ....................................................................................... 25
Appendix M: Service Lives .................................................................................................................... 29 Appendix N: Qualification / Training of Personnel.............................................................................. 29
List of Figures Fig. 1: Schematic Diagram of a Vacuum Sewer System ................................................................ 8 Fig. 2: Service Connection .............................................................................................................. 11 Fig. 3: Branch Connetion................................................................................................................. 11 Fig. 4: Examples of Height Profiles in Level Terrain ....................................................................... 14 Fig. K.1: Schematic Diagram of the Dimensioning Example.............................................................. 22
List of Tables Table 1: General Estimation of Mean Air/water Ratios ..................................................................... 15 Table 2: General Estimation of Nominal Pipe Diameters................................................................... 16 Table K.1: Example for the Design of a Wave Profile in Level Ground with HDPE Pipes .................... 23 Table K.2: Dimensioning of Vacuum Main (1) to (V) ............................................................................. 24 Table K.3: Example for the Design of a Reformer Pocket / Saw Tooth Profile in Level Ground with
PVC Pipes ............................................................................................................................ 24 Table K.4: Dimensioning of Vacuum Main (A) to (V)............................................................................. 25
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User Notes This Standard is the result of honorary, technical-scientific/economic collaboration which has been achieved in accordance with the principles applicable therefore (statutes, rules of procedure of the DWA and the Standard ATV-DVWK-A 400). For this, according to precedents, there exists an actual presump-tion that it is textually and technically correct and also generally recognised.
The application of this Standard is open to everyone. However, an obligation for application can arise from legal or administrative regulations, a contract or other legal reason.
This Standard is an important, however, not the sole source of information for correct solutions. With its application no one avoids responsibility for his own action or for the correct application in specific cases; this applies in particular for the correct handling of the margins described in the Standard.
1 Area of Application This Standard supplements EN 1091 “Vacuum Sewerage Systems outside Buildings” and applies only in connection with EN 1091. This Standard applies for design, construction and operation of vacuum sewer systems outside buildings and con-tains further guidelines and information.
2 Normative References
See Appendix G: Sources of additional information.
3 Definitions The following definitions apply in addition to the definitions in EN 1091 and EN 1085:
3.3 Collection Sump As defined in EN 1091, but including an emer-gency storage volume.
3.18 Interface Unit (or Interface Valve Unit)
Unit consisting of interface valve, controller and accessories.
3.19 Length-specific Population Density (LID)
Total population (number of inhabitants and popu-lation equivalents) connected to a vacuum main
and its branches, divided by the length of the vac-uum main.
3.20 Vacuum Main
Vacuum sewer from the vacuum station to the fur-thest collection chamber, not including any branches.
3.21 Air/Water Ratio (AWR) Ratio of aspirated air volume or flow, at standard pressure and temperature, to evacuated wastewa-ter volume or flow.
4 Description of the System
4.0 General
Vacuum sewerage systems, also known as vac-uum sewer or vacuum drainage systems, were in-vented by the Dutchman Liernur [1] in the 19th cen-tury and installed in several large cities such as Amsterdam, Paris and Berlin [2,3]. In the early 1950s the system was re-introduced by the Swede Liljendahl. Since the late 1960s vacuum sewer sys-tems have also been successfully used in Ger-many [4,5,6,7]. Their components and design methods have been considerably improved during the last decades.
Vacuum sewers are closed pipelines without man-holes. The high transport velocity of the air/water mixture prevents deposits in the vacuum pipelines.
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Vacuum sewers are generally used for the collec-tion of wastewater in separate sewer system. Due to the negative pressure in the system, ex-filtration of wastewater can not occur. For this reason vac-uum sewers may be laid in a common trench with drinking water pipelines as well as in water protec-tion areas with no need for special leak protection (see also ATV-DVWK-A 142). In deviation from EN 1091 vacuum sewer systems may also be used for the collection of commercial and industrial waste-water.
Preferred conditions for the use of vacuum sewer-age systems are:
• Rural areas (see also ATV-A 200E),
• insufficiently sloped terrain,
• connection of low-level developments and build-ings,
• need for crossing of obstacles (e.g. water courses, ditches, utility lines),
• high groundwater table,
• low population density,
• unfavourable ground conditions,
• water protection areas,
• seasonal or intermittent wastewater production (e.g. camp sites, weekend home developments, resorts),
• where disturbance (e.g. to traffic, structures, soil) by construction is to be kept minimal.
A vacuum sewerage system is a special wastewa-ter collection system that is, under certain condi-tions, considerably less expensive than a gravity sewer system. The investment costs can be much lower than those of other sewer systems. All con-sequential costs of depreciation, interest, operation and maintenance have to be included in cost com-parisons [15]. On the other hand, it has to be con-sidered that vacuum sewers generally do not drain off storm water.
Vacuum sewers form a branched network with a central vacuum station (Fig. 1). The length of vac-uum mains is up to 4 km in level terrain. They have to be shorter where the sewers rise in flow direc-tion, and may be longer where they fall. Large col-lection areas can be divided into several smaller areas with individual vacuum stations which are, for example, connected via pressure mains.
Fig. 1: Schematic Diagram of a Vacuum
Sewer System
Water course
Vacuum main
Collection chamber for house connection
Service connection
4.1 Collection Chamber and Vacuum Pipeline
The transition from the gravity drain of the house installation to the vacuum pipeline takes place in an interface valve that is usually installed in an out-door collection chamber; however, installation of interface valves in basements is also possible. It is also possible to connect vacuum WCs directly and other sanitary items via interface units to vacuum pipelines within a building. In this case EN 12109 “Vacuum drainage systems inside buildings” must also be observed.
In systems with pneumatic interface valve units only the vacuum station needs power connection. If electro-hydraulic interface valves are used, each collection chamber needs power connection.
When an interface valve opens, wastewater and air are drawn into the vacuum pipeline and flow toward the vacuum station. The mean air/water ra-tios of vacuum systems lie, according to current experience, in a range between 3:1 and 15:1. The air/water ratio rises with longer vacuum mains and greater height to overcome. The air/water ratios of interface valve units are generally set higher at the far end of vacuum mains and lower near vacuum stations.
Vacuum station
Wastewater treatment plant
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4.2 Vacuum Station
Vacuum pumps maintain in one or more tanks of the vacuum station a vacuum pressure of 60 to 70 kPa (40 to 30 kPa absolute pressure), or 0.6 to 0.7 bar, which is normally required for the operation. The wastewater is forwarded from the vacuum sta-tion to wastewater treatment e.g. by pumps or pneumatic conveyers (pressurized vessels).
Vacuum stations should generally be located near the centre or near the lowest point of their respec-tive collection areas. Because vacuum stations generate noise or odour, it is recommended to lo-cate them in sufficient distance from buildings. The distance depends not only on the type and use of these buildings, but also on provisions for noise and odour control.
5 Requirements
5.0 Bylaw Issues
It has proven beneficial to charge the operators of vacuum sewer systems also with the procurement, installation, service and maintenance of collection chambers and interface valve units. As such equip-ment is usually installed on private property, an ap-propriate agreement is necessary, preferably under the legal umbrella of municipal bylaws.
The following exemplary verbiage may be incorpo-rated into bylaws:
“Where wastewater from private property is dis-charged into a vacuum sewer system, the owner of the property must allow the installation of equip-ment serving for the collection and transportation of wastewater on his property; he also must allow operation, maintenance, repair, modification and re-newal work that may become necessary. Type and location of the equipment is determined by the mu-nicipality or its representative. Pipelines and cham-bers may not be built over. The property owner has the obligation to report without delay any detected defect or malfunction of the equipment to the opera-tor of the vacuum sewer system. The property owner must allow the operator and his agent ac-cess to the equipment at all times”.
5.1 General Requirements
Provisions are required to prevent flooding of build-ings caused by backpressure from the collection sump (see EN 12056 and DIN 1986-100).
5.2 Performance and Quantitative Requirements (Special Requirements on Components)
5.2.1 Gravity Drains
Gravity drains of buildings must be ventilated in accordance with EN 12056. EN 12056 and EN 752 together with DIN 1986-100 apply for drainage installations of buildings and private property.
It must be ensured that only wastewater is dis-charged into the collection sumps.
5.2.2 Flows from Interceptor Sewers and Commercial Developments
For reasons of operating safety a collection cham-ber with several interface valve units must be in-stalled where more than 20 inhabitants and popu-lation equivalents are connected, and these interface valve units must maintain a constant air/water ratio independent of the wastewater vol-ume in the emergency collection sump.
5.2.3 Collection Chambers
For reasons of liability it is recommended to pro-vide an individual collection chamber for every house. However, it is principally possible to con-nect several dwellings (e.g. terraced houses) to a common collection chamber. Multiple dwelling units are normally drained to a common collection chamber. The requirements of paragraph 5.2.2 apply accordingly.
Collection chambers are usually installed on the property. This has the advantage that the gravity drains can be short, which is particularly important where the house drains are deep.
Depending on specific circumstances, monitoring equipment can be useful, e.g. providing a local or remote signal in case of backpressure and/or when an interface fails to close.
Where necessary, collection chambers must be secured against flotation.
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5.2.4 Collection Sumps
House installations must be made under consid-eration of the maximum backpressure level, which is normally defined by the level of the collection sump cover.
Collection sumps must be easily accessible to facili-tate removal of coarse material. Their evacuation and vacuum cleaning must be possible through a bypass of the interface valve.
Where interface valve units are installed in collec-tion sumps and can become submerged in waste-water, operator health and safety requirements must be taken into account.
All connecting elements and accessories in collec-tion chambers must be made of corrosion resistant material (e.g. plastic or stainless steel according to EN 10088).
5.2.5 Interface Valve
Interface valves must provide free passage of at least 40 mm in their open position.
Interface valve units must be made of suitable, re-sistant materials. EN 681-1 is to be observed for elastomers.
5.2.6 Level Sensor
Sensor pipes must be arranged such that they are cleaned by the flow during evacuation. Floats are not suitable due to their sensitivity to pollution.
5.2.7 Interface Valve Controller
Controllers may open interface valves only if the transmitted negative pressure is at least 15 kPa (0.15 bar). Where the bottom of a collection sump is more than 1.0 m below the interface valve, the con-trol unit may open the valve only with a corre-spondingly stronger negative pressure.
The controller must maintain the air/water ratio vir-tually independent of the applied vacuum strength.
5.2.8 Explosion Proof (Collection Chamber)
Electrical installations in collection chambers must be explosion proof.
5.2.9 Life of Membranes and Seals
See EN 1091.
5.2.10 Vacuum Pipeline Components
Vacuum pipelines must be resistant to:
• chemical and biochemical attack from inside and outside,
• temperatures of up to 35 °C,
• abrasion,
• internal and external pressure (in accordance with EN 1401).
Particular stresses must be taken into account ad-ditionally.
5.2.11 Pipe Size
The minimum nominal diameter of vacuum sewers in Germany is DN/ID 65 as German bylaws do not permit discharge of coarse solids into sewer systems.
5.2.12 Service Connections
To permit service or exchange of interface valves without vacuum being applied, it must be possible to manually isolate service connections.
Service connections must be introduced into the vacuum pipeline with an angle of maximum 55o in flow direction (see Fig. 2).
5.2.13 Branch Connection
Branches must be connected with an angle of maximum 45o to the vacuum main in flow direction (see Fig. 3).
To avoid backflow of wastewater, the upstream in-verts of the high points in the main and branch must be higher than the crown of the downstream low point.
5.2.14 Isolation Means
Isolation means must be corrosion resistant or cor-rosion protected and non-clogging. Isolation valves with rubberised wedge, without groove, and with enamelled housing are commonly used for vacuum
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sewers. Extension spindles must be made of stainless steel.
Inspection pipes should be provided to permit con-necting pressure gauges and accurate locating of leaks by introducing inflatable balls. Inspection pipes should be located at distances not exceeding ca. 100 m, as well as immediately before and after isolation valves.
The position of isolation valves and inspection pipes must be marked with signs and entered in the sewer plans. They must be protected with valve boxes in accordance with DIN 4055 or DIN 4056. Valve box covers shall be marked with the sign used for the identification of sewers (e.g. “S”)
Fig. 2: Service connection
Fig. 3: Branch Connection
45° Connection
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5.2.15 Vacuum Tanks
Vacuum tanks can be buried in the ground or erected in the vacuum station. They are to be se-cured against flotation where necessary. Vacuum tanks must securely withstand a vacuum pressure of 90 kPa. Steel tanks are to be provided with suit-able inside and outside coatings.
Where several vacuum tanks are provided, the in-coming vacuum sewers should be connected through valves and cross connections such that the system can also be operated with one tank being out of service. Where only one vacuum tank is provided, means for its exchange must be considered.
5.2.16 Control of the Vacuum Station
Failures must be signalled. A power-independent signal is required for power failure, forwarding equipment or vacuum generator failure, when a cer-tain continuous running time of a vacuum generator or forwarding unit is exceeded, when the vacuum strength drops below a minimum or when the liquid level exceeds a maximum.
5.2.17 Level Control
Vacuum tanks may be filled with wastewater up to a maximum of 50 %. When the maximum liquid level is exceeded, the vacuum generators must be locked out automatically.
5.2.18 Equipment (Vacuum Generator)
For reliable operation of the system it is necessary to maintain the temperature in the vacuum station between +1 oC and +35 oC. Appropriate thermal in-sulation, ventilation and heating must be provided.
5.2.19 Capacity of Forwarding Equipment
At least two units with the same capacity are re-quired, whereof one serves for redundancy.
5.2.20 Design of Forwarding Pumps
Wet well (submerged) or dry well pumps may be used.
Unless grinder pumps are installed, the free pas-sage through the forwarding equipment must not be smaller than the free passage through the larg-est suction pipe upstream of the interface valves.
Gas accumulation in the pumps must be pre-vented.
5.2.21 Replacement of Forwarding Pumps
See DIN EN 1091.
5.2.22 Explosion Proof Electrical Equipment (Vacuum Station)
Electrical equipment in vacuum tanks and in suc-tion pipes of vacuum generators must be explosion proof. Flame arrestors or detonation guards be-tween vacuum tanks and vacuum generators are not required, as these would tend to become clogged. However, where vacuum pumps are em-ployed which could be an ignition source, means for purging of the vacuum tanks with an inert gas (e.g. carbon dioxide) must be provided. If a system has been out of service for longer than 48 hours, purging with inert gas must be performed before the vacuum pumps are taken into service again. The purging procedure must be described in the operation manual.
5.2.23 Non-Return Valves
See EN 1091.
5.2.24 Ejector Pumps
Unless grinder pumps are installed, the free pas-sage through ejectors must not be smaller than the free passage through the largest suction pipe up-stream of the interface valves.
5.2.25 Odour Control
Exhaust ducts must be located such that odour nui-sance in the neighbourhood is avoided. Exhaust de-odorization (e.g. in a bio-filter) shall be provided where necessary.
Drain water from bio-filters is organically polluted and is to be disposed of with the wastewater.
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5.2.26 Noise Control
The requirements of the TA-Lärm [German Tech-nical Directive for Noise Control] apply. The maxi-mum nocturnal noise immission according to this directive are presently:
• for purely residential zones 35 dB (A)
• for mainly residential zones 40 dB (A)
• for mixed zones 45 dB (A)
• for commercial zones 50 dB (A)
• for industrial zones 70 dB (A)
Where no zoning exists, the actual use of the buildings in the vicinity of the vacuum station has to be investigated.
5.2.27 Emergency Power Generation
See EN 1091.
5.3 Design Requirements
5.3.0 General
EN 752-3 applies for the design of sewerage sys-tems.
The project file, as the result of design considera-tions and calculations, should contain the following parts:
• Explanatory report with general site plan,
• Plans of the vacuum sewer network,
• Height profile plans of all vacuum sewers,
• Hydro-pneumatic calculations,
• Dimensioning calculations of the vacuum sta-tion,
• Process and instrumentation diagram (PID) of the vacuum station,
• Bill of material and cost estimation,
• Cost comparison calculations,
• Properties register.
5.3.1 Pipeline Design
The gradation of the nominal diameters of vacuum sewers is the result of their hydro-pneumatic design (see Section 5.3.3).
Vacuum pipelines made of PVC must be SDR Class 21. For PVC-U pressure pipes DIN 8061, DIN 8062 and DVGW Guideline W 320 apply. The thermal expansion coefficient of 0.08 mm/(m•K) must be observed. Solvent-welded joints or gas-keted sockets with elastomeric seals (according to EN 681) that are suitable for vacuum application may be used. Solvent-welding must be done after careful cleaning of both surfaces, and the manu-facturers’ instructions must be observed.
Vacuum pipelines made of PE must be SDR Class 11. For HDPE pressure pipes DIN 8075, EN 12201 and the DVGW Guideline W 320 apply. The ther-mal expansion coefficient of 0.20 mm/(m•K) must be observed. Gasketed sockets with elastomeric seals (according to DIN 4060) that are suitable for vacuum application or electro-welded couplings may be used. Electro-welding may be done only by trained personnel.
In deviation from EN 1091 all pipes and fittings in vacuum pipelines must have a nominal pressure rating according to DIN 2401-1of at least 1.0 MPa (10 bar).
5.3.2 Pipeline Profiles
The height profile of vacuum pipelines must be such that wastewater collects at low points and is accelerated and pushed over subsequent high points by air streaming toward the vacuum station.
Several essential types of height profiles can be distinguished (see Fig. 4):
• Wave profiles which can be made without fit-tings by bending of the pipes,
• Saw tooth profiles with 45o fittings which are preferably used where the nominal diameter is DN 100 or larger,
• Reformer pocket profiles which are similar to saw tooth profiles, with the difference that addi-tional U-shaped low points are arranged imme-diately upstream of 45o risers. Reformer pocket profiles are preferably used where the nominal diameter is DN 100 or smaller.
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Fig. 4: Examples of Height Profiles in Level Terrain
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The design of the height profile and the dimension-ing of the pipelines must be agreed with the sys-tem supplier.
5.3.3 Hydro-Pneumatic Design
The maximum head difference is calculated under the conservative assumption that all risers are filled with liquid. The maximum static head difference of a riser is the height of the riser H (height difference between high point and preceeding low point) re-duced by the internal pipe diameter di. The sum of the maximum static head differences along a vac-uum main may normally not exceed 4 to 5 m. Greater static head differences require installation of automatic air admission valves that allow air to en-ter into the vacuum pipeline when the vacuum pressure drops below an adjusted minimum, in or-der to prevent that all risers are simultaneously filled with liquid.
Exact hydrodynamic calculation of the transport procedure in vacuum sewers is not possible due to the complexity of the unsteady multi-phase flow conditions. Due to the lack of fundamental theory, vacuum sewer networks are dimensioned with the help of general dimensioning tables that are applica-ble for the described height profiles.
The mean air/water ratio of a vacuum main is es-timated with the help of table 1.
Table 1: General Estimation of Mean Air/Water Ratios
Length-specific population density Length of vacuum main
0.05 I/m 0.1 I/m 0.2 I/m 0.5 I/m
Mean air/water ratio (AWR)
500 m 3.5 - 7 3 - 6 2.5 - 5 2 - 5
1000 m 4 - 8 3.5 - 7 3 - 6 2.5 - 5
1500 m 5 - 9 4 - 8 3.5 - 7 3 - 6
2000 m 6 -10 5 - 9 4 - 8 3.5 - 7
3000 m 7 - 12 6 - 10 5 - 9 4 - 8
4000 m 8 - 15 7 - 12 6 - 10 (5 - 9)*
* Only recommended for exceptional cases
The gradation of the nominal diameter of a vacuum pipeline depends on the total population (number of inhabitants and population equivalents) con-nected upstream. The nominal diameters are esti-mated with the help of the general dimensioning table 2. It has to be taken into account that the mean upstream air/water ratio at the end of a pipe section is normally greater than the mean value determined with table 1 because the mean up-stream air/water ratio decreases toward the vac-uum station.
Most vacuum sewerage projects can be dimen-sioned using the estimation tables. They relate to a design peak flow of 0,005 l/(I•s), to an even distri-bution of the connections and to level terrain.
Of course, projects with exceptional features can not be designed with the help of general dimen-sioning tables. It is recommended to seek the ad-vice from a system supplier. Any deviation from the general dimensioning results must be justified with technical arguments. In particular, functional reli-ability can be ensured by provision of additional technical means, for example with automatic air admission valves or with interface valve units pro-viding for intermittent water and air admission.
Detailed calculations of pressure profiles shall be made for the system at rest, at peak flow and with pulsing flow near the end of vacuum mains, de-pendent on the air/water ratio.
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Table 2: General Estimation of Nominal Pipe Diameters
Nominal pipe diameter Mean upstream
AWR
DN 65 DN 80 DN 100 DN 125 DN 150 DN 200 DN 250*
Total number of inhabitants and population equivalents connected upstream
2 0 -110 0 - 350 250 - 600 350 - 900 500 -1400 750 - 2100 (1100 - 3000)
4 0 - 65 0 - 200 135 - 340 200 - 500 300 - 800 400 -1200 (600 -1650)
6 0 - 45 0 - 140 95 - 240 140 - 350 200 - 550 300 - 820 (400 - 1150)
8 0 - 35 0 - 105 75 - 185 105 - 270 150 - 425 220 - 625 (300 - 850)
10 0 - 30 0 - 85 60 - 150 85 - 220 120 - 340 175 - 500 (250 - 700)
12 0 - 25 0 - 75 50 - 125 75 - 180 100 - 290 150 - 425 (200 - 600)
* Only recommended for exceptional cases
5.3.4 Basis of Design
Usually a design peak flow of 0.005 l/(I•s) is as-sumed. Wastewater flows from trade and industry are converted into flow related population equivalents, whereby a population equivalent corresponds to a flow of 150 l/d. In special cases the design peak flow is assessed and divided by 0.005 l/s.
Infiltration of ground water normally does not need be taken into account.
5.3.5 Vacuum Station
The maximum air flow QA (at standard pressure and temperature) is calculated by multiplication of the design wastewater flow QWW with the mean air/water ratio. QA is then additionally multiplied with a safety factor SF for the dimensioning of the vacuum pumps between 1.2 and 1.5.
The capacity and number of the wastewater pumps ((QWW,p and nWW) and of the vacuum pumps (QA,p and nA) are selected under consideration of redundancy as follows:
QWW,p ≥ QWW / (nWW – 1) [l/s] (1)
and
QA,p ≥ QA • SF / (nA– 1) [l/s] (2)
The suction capacity per vacuum pump is:
QA,p,s ≥ QA,p • paa * 2 / (pmax + pmin) [l/s] (2a)
paa is the ambient air pressure and pmax and pmin are the maximum and minimum absolute pres-sures in the vacuum tank.
The minimum volume of the vacuum tank is calcu-lated taking into account the maximum start fre-quency f = 12/h of the vacuum pumps. The re-quired minimum water volume VW is:
VW = 0.25 • QWW,p / f [ l ] (3)
The required minimum air volume in the tank is:
VA = 0.25 • QA,p,s • ½ • (pmax + pmin) / [(pmax – pmin) • nA • f] [ l ] (4)
The required minimum air volume in the tank be-comes smaller if a greater number of vacuum pumps nA is selected. However, the number of the installed vacuum pumps nA may be used in this calculation only if all vacuum pumps are operated in sequence.
The required air volume in the vacuum tank VA may be reduced by subtracting a portion of the volume in the incoming vacuum sewers VWW. At the most, half the volume of those last sections of the vacuum sewers may be subtracted, along which the maximum hydrostatic pressure differ-ence is smaller than pmax – pmin. For example, if the hysteresis is pmax – pmin = 10 kPa and a riser with a
DWA-A 116-1E
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maximum hydrostatic height difference of over 1 m is installed at the vacuum tank, then no sewer volume may be subtracted.
The required tank volume is:
V = VW + VA – VWW [ l ] (5)
The minimum volume of the vacuum tank is:
V ≥ 3 • VW [ l ] (6)
The power consumption of the vacuum and wastewater pumps can be estimated with the fol-lowing general equations:
PA,p = {κ / (κ -1)} * QA,p,s • ½ • (pmax + pmin) • [1 – (½ • (pmax + pmin) /paa) {(κ -1)/κ} ] / ηA [ W ] (7)
PWW,p = QWW,p • ρ • g • hman / ηWW [ W ] (8)
The adiabatic coefficient of air is κ = 1.4.
The efficiency of liquid ring pumps and sliding vane pumps is in the range 0.3 < ηA < 0.6 (for pmin ≥ 30 kPa) whereby sliding vane pumps have a better effi-ciency than liquid ring pumps. The efficiency of the combination of ejectors and centrifugal pumps is very poor, it is in the range 0.05 < ηA < 0.1. The ef-ficiency of centrifugal wastewater pumps is in the range 0.2 < ηWW < 0.5.
5.3.6 Sources of Additional Information
Additional information can be found in the report of the DWA Working Group ES-1.2 referenced in Ap-pendix G as well as in publications listed in the bib-liography (Appendix H).
5.3.7 Application of Vacuum Sewerage
See Section 4.0 as well as Appendix I of EN 1091.
6 Installation (of Pipelines)
6.1 Installation (Pipe Laying)
It is recommended to charge the system supplier to train the contractor personnel in pipe laying and collection chamber installation when construction work begins.
Vacuum pipelines must be laid precisely to the plans. Any deviation from the height profile must be approved by the design engineer. The owner or his engineer must have inspected the height profile of the laid vacuum pipelines before back-filling may begin.
Because ex-filtration of wastewater from vacuum sewers cannot occur, vacuum drains and drinking water pipelines may be laid in common trenches, unless this should be forbidden by local regulations.
Vacuum pipelines must be laid in frost-free depth and permanently resistant to earth and traffic loads, buoyancy forces, cyclic forces and vacuum pressures during operation and tightness testing. Pipeline sections above-ground must be protected against the effects of extreme temperature, UV ra-diation and mechanical damage as necessary.
PVC pipes may only be laid at temperatures of at least 4 oC. Particularly with PE pipelines, excessive stress due to shrinking with cooling must be avoided.
The position of high and low points as well as of bends must be permanently secured. Securing is particularly important in soft ground (e.g. in swamps and clay). EN 1610 and ATV-DVWK Standard A 139E apply for pipe laying, in particular concerning bedding.
Height profiles and directional changes can be made by pipe bending if the minimum bending radii are safely maintained. The minimum bending ra-dius of PVC-U pipes is R > 300 • de and of HDPE pipes it is R > 50 • de. Manufacturers’ instructions must be observed.
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Connections must be made according to the manufacturers’ instructions. It is recommended to install fittings for future branches and service con-nections while the vacuum sewers are laid. Service of undeveloped properties should be prepared to avoid later expensive installation of fittings.
Trenchless pipe laying methods may be used in accordance with EN 12889, for example jet drilling, drill-boring or ploughing. However, unacceptable deviations from the designed height profile must be prevented. Advice by the system supplier must be sought.
After the pipelines are laid as-installed plans ac-cording to DIN 2425-4 must be made.
6.2 Tolerances
Where the slope of the vacuum sewers is greater than 1:150, the levels of high and low points may deviate by a maximum of ± 2.5 cm from the de-signed height profile, and the gradients in between must be continuous.
6.3 Warning and Location System
See EN 1091.
7 Testing and Verification
Testing of interface valve units, pipelines and col-lection chambers must be done according to Ap-pendices A to C of EN 1091. Tightness tests ac-cording to sections 7.2 and 7.3 of EN 1091 shall be done before the interface valve units are installed. Type and scope of commissioning tests according to Section 7.4 must be specified in the tender documents and performed according to Appendix D of EN 1091.
8 Commissioning (and Start-up)
The system supplier should be charged to optimise the operation during commissioning and to train the operating personnel.
9 Economic Aspects Cost comparisons shall include not only investment costs, but also operating costs. The total costs of vacuum sewerage systems can be considerably lower than those of conventional systems.
The service lives stated in Appendix M shall be used in cost comparisons (See also the ATV Re-port from 1997 referenced in Appendix G).
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Appendices A to E See EN 1091.
Appendix F: Operational and Maintenance Information Supplementary to Appendix F of EN 1091 the fol-lowing requirements apply:
• An operating log book is to be kept.
• A maintenance contract with the system sup-plier is recommended.
• Operators should keep some replacement inter-face valve units on stock.
• In order to minimize the frequency of failures and the time spent for failure detection, a pre-ventive maintenance program in accordance with manufacturers’ recommendations should be implemented.
• Specifications concerning self-monitoring of the respective country or state shall be observed.
Appendix G: Sources of Additional Information Supplementary to the standards referenced in EN 1091 the following standards apply:
DIN 1960: VOB Vergabe- und Vertragsordnung für Bauleistungen – Teil A: Allgemeine Bestimmun-gen für die Vergabe von Bauleistungen. [VOB German contract specifications for engi-neering services – Part A: General specifications for the award of construction contracts]
DIN 198: Entwässerungsanlagen für Gebäude und Grundstücke. [Drainage and sewerage systems for buildings and properties]
DIN 2425-4: Planwerke für die Versorgungswirt-schaft, die Wasserwirtschaft und für Fernleitun-gen – Teil 4: Kanalnetzpläne öffentlicher Abwas-
serleitungen. [Plans for public utilities, water resources and long-distance lines – Part 4: Sewer network drawings of public sewerage systems]
DIN 4055: Wasserleitungen; Straßenkappen für Un-terflurhydranten; Technische Regel des DVGW. [Water pipelines; pipeline valve boxes for under-ground hydrants; Technical Guideline of the DVGW]
DIN 4056: Wasserleitungen, Straßenkappen für Ab-sperrarmaturen; Technische Regel des DVGW. [Water pipelines; valve boxes for isolation valves; Technical Guideline of the DVGW]
DIN 4060: Rohrverbindungen von Abwasserkanälen und -leitungen mit Elastomerdichtungen – Anforde-rungen und Prüfungen an Rohrverbindungen, die Elastomerdichtungen enthalten. [Pipe connections of drains and sewers with e-lastomeric seals - requirements and tests of con-nections containing elastomeric seals]
DIN 8061: Rohrverbindungen aus weichmacher-freiem Polyvvinylchlorid – Allgemeine Qualitäts-anforderungen. [Plasticised polyvinyl chloride pipes – General quality requirements and testing]
DIN 8062: Rohrverbindungen aus weichmacherfrei-em Polyvvinylchlorid (PVC-U, PVC-HI) – Maße. [Unplasticised polyvinyl chloride (PVC-U, PVC-HI) pipes - dimensions]
DIN 8074: Rohre aus Polyethylen (PE) – Maße. [Polyethylene (PE) pipes - dimensions]
DIN 8075: Rohre aus Polyethylen (PE) – Allgemei-ne Güteanforderungen, Prüfungen. [Polyethylene (PE) pipes – General quality re-quirements and testing]
EN 681: Elastomere Dichtungen - Werkstoffanforde-rungen für Rohrleitungsdichtungen für Anwendun-gen in der Wasserversorgung und Entwässerung. [Elastomeric seals – material requirements for pipe joint seals used in water and sewerage ap-plications]
EN 752: Entwässerungssysteme außerhalb von Gebäuden. [Drain and sewer systems outside buildings]
EN 1085: Wörterbuch der Abwasserbehandlung. [Wastewater treatment vocabulary]
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EN 1091: Unterdruckentwässerung außerhalb von Gebäuden. [Vacuum sewerage systems outside buildings]
EN 1401: Weichmacherfreies Polyvinylchlorid (PVC-U) – Anforderungen an Rohre, Formstücke und das Rohrleitungssystem. [Unplasticised polyvinyl chloride (PVC-U) –Speci-fications for pipes, fittings and the system]
EN 1610: Verlegung und Prüfung von Abwasserlei-tungen und -kanälen. [Construction and testing of drains and sewers]
EN 1671: Druckentwässerungssysteme außerhalb von Gebäuden. [Pressure sewerage systems outside buildings]
EN 10088: Nichtrostende Stähle. [Stainless steels]
EN 12056: Schwerkraftentwässerungsanlagen in-nerhalb von Gebäuden. [Gravity drainage systems inside buildings]
EN 12109: Unterduckentwässerungssysteme in-nerhalb von Gebäuden. [Vacuum drainage systems inside buildings]
EN 12201: Kunststoff-Rohrleitungssysteme für die Wasserversorgung – Polyethylen (PE). [Plastic piping systems for water supply - Poly-ethylene (PE)]
EN 12889: Grabenlose Verlegung und Prüfung von Abwasserleitungen und -kanälen. [Trenchless construction and testing of drains and sewers]
ATV-DVWK-A 139E: Einbau und Prüfung von Abwasserleitungen und –kanälen. [Installation and testing of drains and sewers]
ATV-DVWK-A 142E: Abwasserkanäle und -leitungen in Wassergewinnungsgebieten. [Sewers and drains in water catchment areas]
ATV-A 200E: Grundsätze für die Abwasserentsor-gung in ländlich strukturierten Gebieten. [Principles for the disposal of wastewater in rurally structured areas]
DVGW-W 320: Herstellung, Gütesicherung und Prü-fung von Rohren aus PVC hart, PE-HD hart und PE-LD für die Wasserversorgung und Anforde-rungen an Rohrverbindungen und Rohrleitungs-teile. [Production, quality assurance and testing of pipes made from PVC-U, HDPE and LPDE for
water supply and requirements on pipe joints and pipeline components]
RAL-GZ 961: Herstellung und Instandhaltung von Abwasserleitungen und -kanälen – Gütesicherung. [Production and maintenance of drains and se-wers – quality control]
TA-Lärm: Technische Anleitung Lärm [Technical Directive Noise]
ATV-DVWK Report: of the ATV-DVWK Working Group ES-1.2 – Special drainage processes “Questions of operation and service lives of pressure and vacuum sewer systems”. Korres-pondenz Abwasser 5 (1997), p. 921 ff. [Not available in English]
ATV-DVWK Report: of the ATV-DVWK Working Group ES-1.2 – Special drainage processes “Comparison of Standard ATV-A 116 with the European Standard EN 1091 (vacuum sewer-age) and EN 1671 (Pressure sewerage)”. Kor-respondenz Abwasser Water management, wastewater, waste (2/2000), p. 258 ff. [Not available in English]
Appendix H: Bibliography [1] Liernur „Die pneumatische Canalisation in der
Praxis“. [“The pneumatic sewerage system in practice”]. Verlag der Ingenieur-Firma Liernur & De Bruyn-Kops, Frankfurt am Main (1873)
[2] Foreman B. E. „Wastewater Collection by Vacuum“, Proceedings of the International Symposium on Urban Hydrology, Kentucky, USA (1985) S. 37 ff.
[3] Kleinschroth A. „Abfallstoffe und ihre Beseiti-gung – Auszüge aus einer Veröffentlichung des Oberingenieurs Adam Kleinschroth aus dem Jahre 1909. [Waste material and its dis-posal - extracts from a publication by Senior Engineer Adam Kleinschroth 1909]. Informa-tionsberichte des Bayerischen Landesamtes für Wasserwirtschaft, München (1986) Vol. 3, p. 193 ff.
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[4] Dippold W. und Jedlitschka J. „Vakuumsys-tem und Druckentwässerung – Bericht über die Abwasserbeseitigung der Donaugemein-den Fristingen und Kicklingen, Landkreis Dil-lingen/Donau“. [Vacuum and pressure sewer-age - Report of wastewater disposal of the Danube communities of Fristingen and Kick-lingen, County of Dillingen at the Danube river]. Wasser und Boden 28 (1976), Vol. 5, p. 100 ff.
[5] Drebes H. und Ivers H. „Vakuumentwässe-rung Krempel/Dithmarschen“. [Vacuum sewe-rage at Krempel/Dithmarschen]. Wasser und Boden 27 (1975), Vol. 5, p. 115 ff.
[6] Horwitz S. „Abwasserförderung mit Vakuum – eine volkswirtschaftlich günstige Lösung der kommunalen Abwasserprobleme“. [“Waste-water transportation using vacuum – an eco-nomical solution for municipal wastewater problems”]. Wasser und Boden 23 (1971), Vol. 10, p. 291 ff.
[7] Winkelmair G. „Abwasserableitung in gefälle-losen Leitungen kleinen Durchmessers – Das Vakuumsystem“. [Wastewater sewerage in small diameter pipelines without gradient – The vacuum system]. Wasser und Boden 26 (1974), Vol. 8, p. 229 ff.
[8] ATV-Handbuch „Bau und Betrieb der Kanali-sation“. [ATV Manual “Construction and op-eration of sewer systems”]. 4th Edition (1995), Verlag Ernst & Sohn, Berlin, p. 387 ff.
[9] Roediger M. „Unterdruck- und Druckentwäs-serung – alternative Verfahren der Ortsent-wässerung“. [Vacuum and pressure sewerage – alternative methods for municipal wastewater collection]. Abwassertechnik (1995), Vol. 6, p. 11
[10] Pfeiffer W., Roediger M. „Anforderungen an die Kanalisation bei Druck- und Unterdruck-entwässerung“. [“Requirements on pressure and vacuum sewer systems]. Schriftenreihe WAR der TH Darmstadt, Band 82 (1995) S. 211 ff.
[11] Roediger M., Schütte M. „Besondere Entwäs-serungsverfahren – Betriebserfahrungen“. [Special sewerage systems – operating ex-perience]. Korrespondenz Abwasser 6 (1992), p. 865
[12] Goldberg B. „Unterdruckentwässerung – ein sicheres Verfahren für verträgliche Abwas-sergebühren“. [Vacuum sewerage – a reliable system for affordable wastewater fees”]. WWT (1995) Vol. 5, p. 20
[13] Anonym „Vakuumentwässerungstechnologie erstmalig erfolgreich im Bereich der Chemie-industrie eingesetzt“. [Vacuum sewerage technology for the first time successful used in the chemical industry]. Umwelt (1995) Vol. 7 - 8, p. 284
[14] Jedlitschka J. „Druck- und Unterdruckentwäs-serung“ [Pressure and vacuum sewerage]. Berichte der ATV Vol. 37, St. Augustin (1986) p.133 ff.
[15] LAWA (Länderarbeitsgemeinschaft Wasser) „Leitlinien zur Durchführung von Kostenver-gleichsrechnungen“. [(Working Group of German States for Water) Guidelines for cost comparison calculations]. (1998)
[16] Schluff R. „Unterdruckentwässerung – Neue Er-kenntnisse führen zu einem betriebssicheren Fördersystem“. [Vacuum sewerage – new ex-perience leads to a reliable transportation sys-tem]. Abwassertechnik 37 (1986), Vol. 4, p. 37 ff.
[17] Schluff R. „Unterdruckentwässerung – Ab-wasserbeseitigung im ländlichen Raum“. [Vacuum sewerage – wastewater disposal in rural areas]. Eigenverlag, Heikendorf (1991)
[18] Schrieber R. „Vakuum-Kanalisation – Neue Wege führen zu erhöhter Betriebssicherheit“. [Vacuum sewerage system – new ap-proaches lead to improved reliability]. Abwas-sertechnik 40 (1989), Vol. 2, p. 43 ff.
[19] Schinke R. „Die Vakuumkanalisation – ein Verfahren mit vielen, oft ungenutzten Möglich-keiten“. [Vacuum sewerage system – a sys-tem with many often unused advantages]. Korrespondenz Abwasser 4 (1999), p. 506 ff.
[20] Otterpohl R. et al. „Alternative Entwässe-rungskonzepte zum Stoffstrommanagement”. [Alternative sewerage concepts for resource management]. Korrespondenz Abwasser 2 (1999), p. 204 ff.
[21] Hassett A. F. and Starness J. C. „Vacuum Wastewater Collection: The Alternative Se-lected in Queen Ann’s County, Maryland”. Jl. Water Poll. Control 53 (1981), Vol. 1, p. 59 ff.
[22] Hassett A. F. and Pattie D. M. „Old Vacuum Sewer Reaches New Heights”. Proceedings of the Water Environment Federation, 65th Annual Conf. New Orleans (1992)
[23] Hassett A. F. „Vacuum Sewers – An Uplifting Global Future”. Proceedings of the New and Emerging Environmental Technologies and Products Conference for Wastewater Treat-ment and Storm Water Collection, Toronto Canada (1995)
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[24] Averill D. W. and Heinke G. W. „Vacuum Sewer Systems”. Report prepared for Northern Science Research Group of the Canadian Department of Indian Affairs and Northern Development (1974)
[25] „Alternative Sewer Systems”, Manual of Prac-tice, Water Environment Federation, Alexan-dria, Virginia (1986)
[26] „Alternative Wastewater Collection Systems”, Manual of the Environmental Protection Agency, Washington, DC (1991)
[27] Arbeitsbericht der ATV-Arbeitsgruppe 1.1.2: „Druckluftgespülte Abwassertransportleitun-gen – Planungs-, Bau- und Betriebsgrundsät-ze“. [Report of the ATV Working Group 1.1.2: “Pneumatically flushed wastewater transport pipelines – Design, construction and operat-ing principles”]. Korrespondenz Abwasser 1 (1987), p. 70 - 76
Appendix I: Application of Vacuum Sewerage See Section 4.0.
Appendix K: Dimensioning Example K.1 Basic Lay-out
An area with a population of 910 inhabitants is to be connected via a vacuum sewerage system to a wastewater treatment plant (Fig. K.1). The terrain is level. There will be two vacuum mains. For rea-sons of illustration the two vacuum mains have very different characteristics which, in practice, would be unusual for a single system.
A wave profile with HDPE pipes is selected for the main (1) to (V), while for the other main (A) to (V) a combination of reformer pocket profile and saw tooth profile with PVC pipes is chosen.
The height profiles described below serve only as an example. In agreement with the system suppli-ers, they could also be designed differently.
Fig. K.1: Schematic Diagram of the Dimen-sioning Example
K.2 Dimensioning of the Pipelines
The two vacuum mains are dimensioned sepa-rately.
Vacuum main (1) to (V) with wave profile:
Length of the vacuum main: 1900 m Total population connected to the vacuum main: 130 I Length-specific population density: 0.07 I/m Mean air/water ratio from the general estimation table 1: AWR = 6 to 9 Distance between inspection pipes: ≤ 100 m Location of inspection pipes: anywhere Height difference between high and low points: H ≈ di + 5 cm Maximum hydrostatic pressure head difference of each rising section: h = H – di ≈ 5 cm Bending radius for HDPE: R ≥ 50 • de Length of rising sections: L1 ≥ 2•(R•H)1/2 Slope of falling sections: ≥ 0.2 % Length of falling sections: L2 ≤ 500•H
Interpolation of the values in the general estimation Table 1 results in a mean air/water ratio between 5.4 und 9.4. Due to the uneven distribution of the service connections (only 30 I have a distance from the vacuum station < 900 m, 100 I have a dis-tance > 900 m) a value of at least 8 is selected from this range. The chosen local air/water ratios at the service connections fall from 12 at the end of
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the vacuum main to 4 in the vicinity of the vacuum station, which lead to a mean air/water ratio in this vacuum main of at least 8.
The system is divided into individual sections. For each section the total population (inhabitants and population equivalents) that are connected up-stream of and to the respective section are added to Σ PTi. The mean AWR at the end of the sections is calculated as:
Σ (PTi • AWRi) / Σ PTi.
The nominal diameters DN of the sections are taken from the general estimation table 2. The dis-tances Li between subsequent low points are de-pendent on the internal diameter di (see Table K.1). The number of low points in the sections with the lengths li is ni = li /Li.
As each rising section of a wave profile in level ground has a maximum hydrostatic head differ-
ence of ca. 5 cm, the maximum hydrostatic head difference of a section is: hi = ni • 5 cm = li /Li • 5 cm.
In rising terrain the lengths Li would be shorter and/or the height differences H greater. This would result in more low points and/or greater head dif-ferences hi. The opposite would occur in falling ter-rain. For this reason it is possible, at least as an approximation, to add geodetic height differences to the sum of the maximum hydrostatic pressure differences.
The head differences are summed up to Σ hi whereby hi is added to the highest head at the up-stream end of the section. The total maximum hy-drostatic head difference of the vacuum main 1-2-3-4-V in the example is only 1.55 m, which corre-sponds to a maximum hydrostatic pressure differ-ence of 15.2 kPa. However, the maximum hydro-dynamic head loss will certainly be greater.
Table K.1: Example for the Design of a Wave Profile in Level Ground with HDPE Pipes
External diameter de of HDPE pipes
[mm]
Internal diameter di of SDR 11
pipes
[mm]
Selected height difference H
between high and low points
[cm]
Minimum length L1 of rising sections
(rounded up)
[m]
Maximum length L2 of falling sec-
tions
[m]
Selected dis-tance L between subsequent low
points
[m]
75 61 10 1.25 50 50 90 74 12 1.5 60 60 110 90 14 1.75 70 70 125 102 15 2 75 75 140 114 16 2.1 80 80 160 131 18 2.4 90 90 180 147 20 2.7 100 100 200 164 22 3 110 110 225 184 24 3.3 120 120 250 204 26 3.6 130 130 280 229 28 4 140 140
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Table K.2: Dimensioning of Vacuum Main (1) to (V)
1 2 3 4 5 6 7 8 9 10 11 Section PT con-
nected to section
PT con-nected
up to the end of section
Local AWR of service
connections to section
Mean AWR at end of section
DN of section
taken from Table 2
Length of
section
Distance between
low points
Number of low
points in section
Max. static head
difference in section
Max. static head
difference to end of section
i PTi Σ PTi AWRi Σ(PTi • AWRi) / Σ PTi
DNi li Li = f (DNi)
ni = li /Li hi = ni • 5 cm
Σ hi
1-2 15 15 12 12 65 400 m 50 m 8 0.4 m 0.4 m 5-2 10 10 10 10 65 150 m 50 m 3 0.15 m 0.15 m 2-3 30 55 8 9.5 80 600 m 60 m 10 0.5 m 0.9 m 6-7 10 10 10 10 65 200 m 50 m 4 0.2 m 0.2 m 8-7 10 10 10 10 65 150 m 50 m 3 0.15 m 0,15 m 7-3 25 45 8 8.9 80 400 m 60 m 7 0.35 m 0.55 m 3-4 0 100 6 9.2 100 500 m 70 m 7 0.35 m 1.25 m 9-4 10 10 6 6 65 200 m 50 m 4 0.2 m 0.2 m 4-V 20 130 4 8.2 100 400 m 70 m 6 0.3 m 1.55 m
> 8 < 4-5 m Vacuum main (A) to (V) with reformer pocket/ saw tooth profile:
Length of the vacuum main: 3000 m Total population connected To the vacuum main: 780 I Length-specific population density: 0.26 I/m Mean air/water ratio from the general estimation table 1: AWR = 5 to 8 Distance between inspection pipes: ≤ 100 m Location of inspection pipes: right after each
high point Use of reformer pocket profile (R): DN 65 and DN 80
Use of saw tooth profile (S): ≥ DN 100 Height difference between high and low points: H ≥ di + 5 cm Maximum hydrostatic head difference of each riser with reformer pocket profile: h = H Maximum hydrostatic head difference of each riser with saw tooth profile: h = H – di ≥ 5 cm Slope: ≥ 0.2 % Distance between low points: L ≤ 500 • H
Table K.3: Example for the Design of a Reformer Pocket/Saw Tooth Profile in Level Ground with
PVC Pipes
Nominal diame-ters DN of PVC
SDR 21 pipes
Type of height profile
Height difference H between high and low
points
[cm]
Maximum hydrostatic head differences h at
low points
[m]
Distance L between low
points
[m]
65 R 20 0.2 100 80 R 20 0.2 100
100 S 20 0.1 100 125 S 20 0.075 100 150 S 20 0.05 100 200 S 30 0.1 150 250 S 30 0.05 150
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A population of ca. 400 inhabitants, that is ap-proximately half of the population, is connected at a distance of < 1500 m from the vacuum station. Raising the AWR is not necessary. A special case is section L-E due to its particularly low length-specific inhabitant density of only 0.03 I/m. For this section a mean AWR of 6 is selected in accordance with Table 1. The local AWR is chosen between 10 at the end of the vacuum main and 3 in the vicinity
of the vacuum station. This results in a mean AWR of about 6.
The maximum hydrostatic head difference of the vacuum main A-B-C-D-E-V is 2.8 m, which corre-sponds to a hydrostatic pressure difference of 28 kPa. No automatic air admission valves are necessary.
Table K.4: Dimensioning of the pipeline section (A) to (V)
1 2 3 4 5 6 7 8 9 10 11 Section Total
popula-tion PT
con-nected to section
PT up to the end of the
section
Local AWR of service connec-tions to section
Mean AWRat end of section
DN of section
taken from Table 2
Length of
section
Distance between
low points
Number of low
points in section
Max. static head
difference in the
section
Max. static head
difference up to end of section
i PTi Σ PTi AWRi Σ(PTi • AWRi)/ Σ PTi
DNi li Li = f (DNi)
ni = li /Li ni • hi
hi from table K.3
Σ (ni•hI)
A-B 80 80 10 10 80 500 m 100 m 5 1.0 m 1.0 m F-B 20 20 9 9 65 100 m 100 m 1 0.2 m 0.2 m B-C 70 170 8 9.1 100 500 m 100 m 5 0.5 m 1.5 m G-C 50 50 8 8 80 300 m 100 m 3 0.6 m 0.6 m C-D 120 340 6 7.8 150 600 m 100 m 6 0.3 m 1.8 m H-D 40 40 5 5 65 200 m 100 m 2 0.4 m 0.4 m I-D 50 50 5 5 65 300 m 100 m 3 0.6 m 0.6 m D-E 120 550 4 6.5 200 800 m 150 m 6 0.6 m 2.4 m K-E 100 100 4 4 80 500 m 100 m 5 1.0 m 1.0 m L-E 30 30 10 10 65 1000 m 100 m 10 2.0 m 2.0 m E-V 100 780 3 5.9 200 600 m 150 m 4 0.4 m 2.8 m
≈ 6 < 4-5 m K.3 Dimensioning of the Vacuum Station
With a specific wastewater flow wWW,d of 150 litres per total number of inhabitants and day the total daily wastewater volume is:
QWW,d = Σ(PT) • wWW,d QWW,d = (780 I + 130 I) • 0.15 m3/(I•d)
= 136.5 m3/d
The dimensioning flows for the vacuum mains QWW,i are:
QWW,i = Σ PT • 0.005 l/(I•s) QWW,1 = 130 I • 0.005 l/(I•s) = 0.65 l/s QWW,A = 780 I • 0.005 l/(I•s) = 3.9 l/s
The dimensioning flow QWW for the entire vacuum system is:
QWW = Σ QWW,i QWW = 0.65 l/s + 3.9 l/s = 4.6 l/s
The maximum air flows QA,i (at standard pressure and temperature) of the vacuum mains are:
QA,i = QWW,i • AWRi QA,1 = 0.65 l/s • 8.2 = 5.3 l/s QA,A = 3.9 l/s • 5.9 = 23 l/s
The total maximum air flow is:
QA = Σ QA,i QA = 5.3 + 23 = 28.3 l/s = 102 m3/h
The mean AWR of the system is:
AWR = QA / QWW AWR = 28.3 l/s / 4.6 l/s = 6.2
With selected start and stop pressures for the vacuum pumps of pmin= 35 kPa and pmax= 45 kPa, the medium pressure in the vacuum tank is
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pmean= 40 kPa. With an atmospheric pressure paa= 100 kPa, and with a selected safety factor SF of 1.25, the minimum suction capacity QA,s of the vacuum pumps is:
QA,s = SF • QA • paa / pmean QA,s = 1.25 • 102 m3/h * 100 kPa / 40 kPa = 319 m3/h
Selected is a number nA = 3 of sliding vane vac-uum pumps, each with a suction capacity QA,p,s of 200 m3/h (QA,p = 80 m3/h). Selected is also a number nWW = 2 of wastewater pumps, each with a capacity of QWW,p = 10 l/s. With these vacuum and wastewater pumps the requirements of Equations 1 and 2 of Section 5.3.5 are met:
QWW,p ≥ QWW / (nWW – 1) (1)
10 l/s ≥ 4.6 l/s / (2 – 1) = 4.6 l/s
QA,p,s ≥ QA,s / (nA – 1) (2)
200 m3/h ≥ 319 m3/h / (3-1) = 160 m3/h
With sequential operation of the units and a maximum start frequency f = 12/h the minimum required water volume VW and the minimum re-quired air volume VA in the vacuum tank are:
VW = 0.25 • QWW,p / f (3) VW = 0.25 • 10 l/s • 3600 s/h / 12/h = 750 l
= 0.75 m3
VA = 0.25 • QA,p,s • ½ • (pmax + pmin)/ [(pmax – pmin) • f • nA] (4)
VA = 0.25 • 200 m3/h • 40 kPa / (10 kPa • 12/h • 3)
= 5.6 m3
The vacuum station has a vacuum tank installed above ground. The incoming vacuum sewers have risers with a maximum head difference ex-ceeding 1 m. This is the reason why no volume VWW in the incoming vacuum mains is taken into account. The minimum volume V of the vacuum tank is:
V = VW + VA – VWW (5) V = 0.75 m3 + 5.6 m3 – 0 m3 = 6.4 m3
In addition, the following requirement must be met:
V ≥ 3 • VW (6) V ≥ 3 • 0.75 m3 = 2.3 m3
A tank volume of 7 m3 is selected.
The power consumption per vacuum pump is ap-proximately:
PA,p = {κ / (κ -1)} • QA,p,s • ½ • (pmax + pmin) • [1 – (½ • (pmax + pmin) /paa) {(κ -1)/κ} ] / ηA (7)
PA,p = 3.5 • 200 m3/h • 40 kPa • [1 – (40 kPa / 100 kPa) 0.29] / (3600 s/h • 0.4) = 4.5 kW
The wastewater is pumped over a distance of 500 m through a DN 125 pressure main. The ve-locity in the pressure main is ca. 0.8 m/s and the hydraulic pump pressure ∆phydr is approximately 30 kPa (0.3 bar).
With a vacuum pressure to be overcome of ∆pvac = paa – pmin = 70 kPa, and with a geodetic height difference ∆hgeo = 2 m, the manometric pressure difference of the pumps ∆pman is:
∆pman = ∆phydr + ∆hgeo • ρ • g + ∆pvac ∆pman = 30 kPa + 2 m • 1000 kg/m3
• 9.81 m/s2 + 70 kPa = 120 kPa = 1.2 bar
The power consumption of the wastewater pumps is:
PWW,p = QWW,p • ∆pman / ηWW (8) PWW,p = 0.01 m3/s • 120 kPa / 0.48 = 2.5 kW
The mean daily running time tWW (d) of the wastewater pumps is:
tWW (d) = QWW,d / QWW,p
tWW (d) = 136.5 m3/d / (0.01 m3/s • 3600 s/h)
= 3.8 h/d
The mean daily running time tA (d) of the vacuum pumps is:
tA (d) = QWW,d • AWR / QA,p tA (d) = 136.5 m3/d • 6.2 / 80 m3/h
= 10.6 h/d
The expected daily power consumption is:
W(d) = PWW,p • tWW (d) + PA,p • tA(d) W(d) = 2.5 kW • 3.8 h/d + 4.5 kW • 10.6 h/d = 57 kWh/d
The power consumption relative to the wastewa-ter volume is:
W(V) = W(d) / QWW,d W(V) = 57 kWh/d / 136.5 m3/d = 0.42 kWh/m3
The power consumption per total number of in-habitants and population equivalents and year is:
W(PT) = W(V) • wWW,d • 365 d/a W(PT) = 0.42 kWh/m3 • 0.15 m3/(I•d) • 365 d/a = 23 kWh/(I •a)
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Appendix L: Symbols Translator’s note: While the main terms remain unchanged as they are recognised internationally, the indices used reflect the English translation of the individual German parameter. For simplicity and clarity these have been chosen to match as far as possible the German indices. Where this is not possible the original German symbol is placed in square brackets after the English version. This procedure is not intended to create new symbols for the English-speaking engineering community but serves solely to make German symbols/indices com-prehensible to non-German speakers.
Symbol
English German Unit Designation
de [da] [mm] External pipe diameter
di [mm] Internal pipe diameter
DNi [-] Nominal diameter of section i (corresponds approximately to the internal diameter)
LID [EDL]
[I/m] Length-specific population density
PT [EW]
[I] Total population (= number of inhabitants and population equivalents)
PTi [EWi] [I] Total population connected to section i
f [1/h] Maximum start frequency of electrical motors
g [m/s2] Gravity acceleration
H [m] Height of a rise in a vacuum pipeline = height difference be-tween high point and preceeding low point
h [m] Maximum hydrostatic head difference of a rise in a vacuum pipeline
hi [m] Maximum hydrostatic head difference in section i
hman [m] Manometric head
li [m] Length of section i
Li [m] Distance between low points in section i
AWR [LWV]
[-] Air/water ratio (Volume of air under standard condition)
AWRi [LWVi] [-] Local air/water ratio of collection chambers in section i
ni [-] Number of low points in section i
nA [-] Number of vacuum generators (vacuum pumps)
nww [-] Number of wastewater pumps
pmax [kPa] Maximum absolute pressure in vacuum tanks (start of vacuum generators)
pmin [kPa] Minimum absolute pressure in vacuum tanks (stop of vacuum generators)
pmean [pmittel] [kPa] Mean absolute pressure in vacuum tanks
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Symbol English German
Unit Designation
paa [pu] [kPa] Ambient air pressure
PA,p [PL,p] [kW] Power consumption of a vacuum pump
PWW,p [PS,p] [kW] Power consumption of a wastewater pump
QA [QL] [m3/h] Peak air flow at standard pressure and temperature
QA,s [QL,s] [m3/h] Peak suction air flow at operating conditions
QA,p [QL,p] [m3/h] Air flow through a vacuum generator at standard pressure and temperature
QA,p,s [QL,p,s] [m3/h] Suction capacity of a vacuum generator (vacuum pump)
QWW [QS] [l/s] Design wastewater flow
QWW,d [QS,d] [m3/d] Mean daily wastewater flow
QWW,p [QS,p] [l/s] Capacity of a wastewater pump
R [m] Minimum bending radius of pipes
SF [-] Safety factor for the dimensioning of the vacuum generators
tA(d) [h/d] Mean daily running time of vacuum pumps
tWW(d) [tS(d)] [h/d] Mean daily running time of wastewater pumps
V [m3] Minimum vacuum tank volume
VA [VL] [m3] Minimum air volume in vacuum tanks
VWW [VS] [m3] Maximum water volume in vacuum tanks
VW [m3] Minimum volume in the vacuum tank for wastewater
wWW,d [wS,d] [l/(I•d)] Mean daily wastewater flow per inhabitant
W(d) [kWh/d] Mean daily power consumption
W(PT) [W(EW)] [kWh/(I•a)] Mean annual power consumption per total population
W(V) [kWh/m3] Mean power consumption per volume of wastewater
∆phydr [kPa] Hydraulic flow pressure difference
∆hgeo [kPa] Geodetic height difference
∆pman [kPa] Manometric pressure difference
∆pvac [kPa] Highest negative (vacuum) pressure in the vacuum tank
ηA [ηL] [-] Efficiency of a vacuum generator
ηWW [ηS] [-] Efficiency of a wastewater pump
κ [-] Adiabatic exponent of gases (of air)
ρ [kg/m3] Density (of water)
Σhi [m] Maximum hydrostatic head difference to the end of section i
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Appendix M: Service Lives Due to their thick pipe walls the expected service life of vacuum pipelines is not different to that of conven-tional systems. According to the report of the ATV-DVWK Working Group 1.1.2, dated May 1997 (see Ap-pendix G) the service lives to be expected are:
• 50 – 80 years for vacuum pipelines,
• 30 – 55 years for collection chambers
• 30 years for pneumatic interface valve units,
• 25 – 40 years for vacuum tanks,
• 20 years for vacuum pumps
• 12 years for wastewater pumps.
Appendix N: Qualification / Training of Personnel
Construction work
Owners must take appropriate care when awarding construction work contracts and must investigate the required qualifications, i.e. verify that the contractor has these qualifications. Further information is given in DIN 1960 (VOB/A § 8 Sect. 3). RAL Quality Management Guideline GZ 961 specifies requirements on:
• personnel,
• equipment,
• training,
• self-monitoring,
• employment of subcontractors,
• procurement and subcontracting.
The owner can make use of a “System for the Assessment of Suppliers or Contractors” in accordance with the EU Directive dated 17.09.1990 (Appendix C of EN 1610). The German “Güteschutz Kanalbau e. V.” is such a system.
Operation
In order to be able to do their work correctly and safely, operator personnel must be qualified for the rele-vant work and provide certification about successful participation in relevant continuation training programs. Examples for qualifying occupations are: Qualified Wastewater Systems Operator; or Qualified Pipe, Sewer and Industrial Services Technician.