284796797 German ATV DVWK a 168E Corrosion of Wastewater Systems Wastewater 1998 PDF

GERMAN ATV STANDARDS W A S T E W A T E R

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W A S T E

ADVISORY LEAFLET ATV-M 168E

Corrosion of Wastewater Systems Wastewater

July 1998 ISBN 3-34984-46-0

Marketing: Publishing Company of ATV - Wastewater, Waste, and Water Management Theodor-Heuss-Allee 17 D-53773 Hennef Postfach 11 65 . D-53758 Hennef

ATV - M 168 E ATV Working Group 1.1.4 "Corrosion in Sewers" within the ATV Specialist Committee 1.1. "General Questions of Principle", which has elaborated this Advisory Leaflet, has the following members: Prof. Dr.-Ing. C. F. Seyfried, Hannover (Chairman) Dipl.-Ing. D. Bunge, Hamburg Dr. rer. nat. G. Heim, Hilden Dipl.-Ing. D. Kittel, Planegg Prof. Dr.-Ing. M. Lohse, Münster Dipl.-Ing. W. Meiger, Köln Dipl.-Ing. U. Neck, Düsseldorf Dipl.-Ing. G. Niedrée, Bonn (as guest) Prof. Dr.-Ing. H. Polster, Berlin Dr.-Ing. J. Rammelsberg, Gelsenkirchen Dr.-Ing. F. Schmitt, Essen Chem H. Schremmer, Dortmund (to 1994) Prof. Dr.-Ing. R. Taprogge, Hamburg

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 or translated into a language usable in machines, in particular data processing machines, without the written approval of the publisher.  GFA -Publishing Company of ATV - Wastewater, Water and Water Management, Hennef 1998 Original German Edition produced by: JF•CARTHAUS GmbH & Co, Bonn

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ATV - M 168 E Contents Notes for users

5

1

Introduction and determination of terms

5

2 2.1 2.1.1 2.1.2 2.2 2.3

Corrosion processes Soils and groundwater Natural soils Artificial soils Wastewater Sewer atmosphere

6 6 6 7 7 7

3 3.1 3.1.1 3.1.1.1 3.1.1.2 3.1.1.3 3.1.1.4 3.1.1.5 3.1.2 3.1.3 3.1.4 3.2 3.3 3.3.1 3.3.1.1 3.3.1.2 3.3.2 3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2

Construction and other materials Cement bonded materials Concrete and reinforced concrete General Chemical loading due to communal wastewater Loading in the sewer atmosphere Loading through soil and groundwater Information on the avoidance of reinforcement corrosion Mortar Fibre cement Composite pipes Vitrified clay, sewer brick, glass Metallic materials Unalloyed and low alloy iron materials Linings for pipes made from ductile cast iron and steel Sheathing High alloy, stainless steels Plastics (PVC-U, PE-HD, PP, GFRP) Preamble Pipe materials Sealing materials General requirements on sealing materials for wastewater systems Materials for and properties of sealing materials

9 9 10 10 10 14 14 14 15 16 16 16 17 17 17 18 18 21 21 22 24 24 24

4 4.1 4.1.1 4.1.1.1 4.1.1.2 4.1.1.3 4.1.1.4 4.1.1.5 4.1.2 4.1.2.1 4.1.2.2 4.1.2.3

Corrosion protection Compound materials and linings Pipe linings with new constructions Factory produced pipe lining using PVC plasticised films Factory produced pipe lining using unplasticised PVC web sheets Factory produced pipe lining using web or knob HDPE sheets Factory produced pipe lining using vitrified clay shells (ceramic plates) Retrofitted pipe lining using plastic sheets Shaft linings with new constructions Factory produced shaft lining using plastic sheets Shaft lining using GFRP sheets and elements Shaft lining using sewer bricks

25 25 25 25 26 26 26 27 27 27 27 28

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ATV - M 168 E 4.1.3

Pipe linings with renovation

28

4.1.3.1 4.1.3.2 4.1.4 4.2 4.2.1 4.2.2

Renovation of non-man accessible profile sections Renovation of man accessible profile sections Shaft linings with renovation Protective paints and coatings Coatings on iron materials Coatings on concrete surfaces

29 29 29 30 30 30

5 5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1.7 5.1.8 5.2 5.2.1 5.2.2 5.2.3 5.2.4 5.3 5.3.1 5.3.2 5.3.3

Notes for planning and operation Notes on planning Preamble Location of wastewater treatment systems Composition of wastewater Indirect discharger operations Drainage systems Gravity pipelines Pump stations and cross-sectionally filled pipelines Soil and groundwater conditions Addition of chemicals Fundamentally suitable means Addition of compressed air and pneumatic delivery Addition of pure oxygen Hydrogen peroxide Operational measures Cleaning and maintenance Measures with the occurrence of corrosion Measures in pump sumps and pressure pipelines

31 31 31 31 31 32 32 32 34 36 37 37 37 39 40 41 41 41 42

6

Bibliography

42

7

Applicable Standard Specifications

45

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ATV - M 168 E

Notes for Users This ATV Standard is the result of honorary, technical-scientific/economic collaboration which has been achieved in accordance with the principles applicable for this (statutes, rules of procedure of the ATV and ATV Standard ATV-A 400). For this, according to precedents, there exists an actual presumption 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

Introduction and Determination of Terms

It is only recently that wastewater networks have been inspected systematically, whereby corrosion damage has been increasingly found (KEDING et al., 1990; MATTHES, 1992; STEIN and KAUFMANN, 1993). According to a census taken by ATV (German Association for the Water Environment) on the condition of sewer systems in Germany, corrosion was named as the fourth most frequent cause of damage in the Federal Republic of Germany behind the formation of cracks and fragments, leaks and blockages to the flow(KEDING et al., 1990). Until recently there has been extensive uncertainty on the part of planners and wastewater system operators on corrosion questions. Therefore the term "Corrosion" is first to be defined: "In the field of wastewater treatment systems, one understands under "corrosion" all reactions on non-metallic construction materials and materials with their environment which, through chemical, electro-chemical or microbiological processes lead to a prejudicing of the construction material or material. Damage as a result of mechanical effects such as wear, erosion or frost are to be considered separately. It cannot be excluded that such damage which is designated as "corrosion" is caused by a combined loading of chemical, microbiological and chemical effects." Due to a lack of knowledge on corrosion processes and material properties, gravity pipelines, pressure pipelines and pump sumps are today still being incorrectly conceived in the same way as 50 years ago. The taking into consideration of a possible corrosion is not easy in particular due to the numerous materials used in sewerage system construction and the complex processes. It could also be associated with the fact that, previously in Germany, there has been no complete set of rules and standards available for the avoidance of corrosion damage in wastewater systems. This Advisory Leaflet has been elaborated by a group of experienced specialists from research, industry, planning and sewerage system operations. Its objective is: − to compile the status of today's knowledge on materials, operational conditions, in sewers and in corrosion processes,

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ATV - M 168 E − to give information on planning, construction and operation to ensure the durability and functional safety of sewers during their planned useful life of 50 - 80 (100) years (LAWA, 1993), − to assist the practician with the selection of suitable materials if particular and hard to estimate parameters exist. Recommendations for renovation are not part of this Advisory Leaflet, however, these can be taken from ATV Advisory Leaflet ATV-M 143.

2

Corrosion Processes

2.1

Soils and Groundwater

The constitution and thus the possible corrosive properties of a groundwater stand in direct relation to the chemical and physical properties of the soil with which the groundwater or the precipitation water that has percolated into the subsoil comes into contact. The material damaging components can only then take effect if they are dissolved by the soil water and thus come into contact with the structure. 2.1.1

Natural Soils

With natural soils the coherence is not only of significance in combination with the water content but also with regard to the oxygen content. In the porous and loose soils the oxygen content reduces less quickly with increasing soil depth than with highly cohesive soils which, particularly with high water contents, are rather impermeable to air. With the presence of oxygen one talks of aerobic and with the absence of oxygen of anaerobic soils. While oxygen is of great significance with attacks on unprotected metallic materials, with cement bonded materials it only has a role insofar as certain chemical and biological processes, which can lead to the formation of corrosive substances (e.g. sulphur dioxide) are dependent on it. With natural soils only a few inorganic substances, in the first instance sulphates, chlorides and excess free carbon dioxide as well as organic substances, e.g. humic acid, come into consideration as corrosive groundwater content substances. High sulphate contents are to be found in the groundwater of soils which are heavily permeated by gypsum or anhydrite (gypseous marl or shale). Chlorides are frequently found in the vicinity of marshy soils, salt pans or with country roads spread with salt. The excess carbon dioxide found in groundwater, which attacks unprotected metallic and cement bonded pipe materials has its origin primarily in the biological metabolisation of organic substances present in the upper soil layers. If the carbon dioxide manages to penetrate into the subsoil with percolated precipitation water and, depending on the soil type, finds no reaction partner (e.g. calcium, magnesium), then it lowers, as dissolved aggressive carbon dioxide in water, the pH value of the soil water. It behaves in a similar fashion to "acid rain" which, inter alia, is caused by SO2 emissions. This phenomenon is receiving increasing attention in specialist publications and seminars (HANTGE, 1993; WALTHER, 1994). Soil suspensions with pH values < 4 in depths of from 1.5 to 2 m are no rarity.

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ATV - M 168 E 2.1.2

Artificial Soils

With artificial soils, to which belong, for example, accumulations of refuse, construction rubble, industrial slag and rocky material resulting from mining operations, high contents of material corrosive substances can occur in the groundwater. If a soil exchange with such materials is to take place with the backfilling of pipeline trenches, a specialist report on the suitability of the material is to be obtained. However, this may not limit itself to an assessment from the aspect of construction material corrosion alone. It must also contain details on the water soluble substances from which a hazarding of the groundwater can stem. This is to be observed particularly with some of the recycling materials offered today. 2.2

Wastewater

Wastewater is to be designated and classified according to its origin: domestic, commercial and industrial wastewater; contaminated precipitation water. With common discharge of wastewater one talks of communal wastewater (EN 1085/DIN 4045). The basic loading of wastewater with inorganic substances results from the composition of the drinking or service water. Depending on the usage of the water - above all in the commercial and industrial area - wastewater can contain various material corrosive substances. According to communal bylaws no substances may be discharged with the wastewater which can prejudice the stability of public wastewater systems. According to ATV Standard ATV-A 115, discharge limitations exist in particular for pH values (6.5 - 10), for sulphates (600 mg SO4/l) and for the wastewater temperature (35 °C). In general stormwater causes no chemical attack. In special cases in which the stormwater cannot be buffered in natural paths there is a possibility of a corrosive attack. From experience, account must be taken of possibly aggressive wastewater contents, despite the discharge limitations set by bylaw for commercial and industrial discharges, as the operator of public wastewater systems is also liable for subsequent damage, which result from unlawful discharge of wastewater, if the originator cannot be traced. Therefore corrosion resistant materials should be employed in industrial areas (IMHOFF, 1993). 2.3

Sewer Atmosphere

The atmosphere in enclosed wastewater systems is, in general, marked by a high humidity with a tendency to the formation of condensation water. Through this, with unprotected metallic materials, corrosion can occur. The presence of hydrogen sulphide leads, in wet places above the water level to the formation of sulphuric acid with a correspondingly high degree of corrosion with cement bonded and unprotected metallic construction materials. The biogenic sulphuric acid corrosion (BSAC) is induced mainly through the biological conversion of sulphate sulphur into sulphides under anaerobic conditions in the underwater area, rarely also through sulphide (H2S, HS- and S2-), which are discharged by industrial concerns. To avoid conditions which can lead to BSAC see Chap. 5, in which information for practical planning and a technically correct operation are given. In simple terms the mechanism of sulphate conversion and BSAC can be described as follows: − biological reduction of sulphates and other sulphur components to sulphides (H2S, HSand S2-) in the wastewater under anaerobic conditions; July 1998

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ATV - M 168 E − release of hydrogen sulphide gas into the atmosphere which dissolves on the wet sewer wall; − biological oxidation of the H2S dissolved on the construction material surface above the water level to sulphuric acid and elemental sulphur. The degradation processes in a sewer under aerobic conditions are shown in the left-hand side of Fig. 1. The reduction of sulphates and albuminous compounds from the wastewater take place in the sewer film and in deposits. If the dissolved oxygen is assimilated (with sewer films already at a few tenths of a millimetre) the reduction of the sulphate to sulphide due to the strict anaerobic desulphuricants begins. The sulphide diffuses in the direction of the wastewater, whereby it has to pass the upper, aerobic layer of the sewer film or the deposits. Here it is again oxidised to sulphate before it reaches the wastewater. Under aerobic conditions, although a sulphur reduction takes place in the depth of the sewer film and the deposits, the reduced sulphur compounds are nevertheless again oxidised before reaching the wastewater. Under anoxic or anaerobic wastewater conditions a reduction of sulphate already takes place in the upper layers of the sewer film and deposits. The from this resultant sulphides can then diffuse, unhindered, into the wastewater. Depending on the pH value of the wastewater there is a balance between H2S and HS-. With normal pH values in the wastewater between pH 7 and 8, the hydrogen sulphide component can be between 50 and 10 %. The lower the pH value the greater is the share of H2S in the total sulphide and the greater is also the H2S potential that can be released into the atmosphere and which, in addition to corrosion, can lead also to odour problems and endangering of life. With regard to the valuation of the sulphide present in the wastewater it must be taken into account that, only from the dissolved sulphides does a pH dependent part exist as hydrogen sulphide, which can escape in the form of gas and lead to corrosion. The determination of the dissolved sulphide takes place according to DIN 38 405, Part 26. If sulphides are present in the wastewater a part will, however, also exist in undissolved form (bonded on metals). Thus, for example, the black colour of digested wastewater can be traced back to finely distributed iron sulphide. The undissolved sulphides can, with normal wastewater conditions, cannot contribute to the production of hydrogen sulphide. If these are determined by the examination of the wastewater (which is often the case with conserved wastewater samples), a reduction for the undissolved sulphides from the determined total sulphide content must take place. With an extensively digested domestic wastewater one can set the content of undissolved sulphides at some 50 % of the total sulphide contents. Due to diffusion and turbulence the hydrogen sulphide gas is released into the sewer atmosphere and then dissolves on the wet sewer wall. With time it forms into a biofilm in which also the very acid tolerant thiobacilli occur. They are capable of oxidising the hydrogen sulphide into sulphuric acid. Particularly in the warm and low discharge seasons there is an enrichment of the biogenically formed sulphuric acid, mainly in the crowns of the pipe which, with very low pH values, are subjected to heavy chemical attack.

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ATV - M 168 E

Fig. 1:

Sulphate conversion in sewers

3

Construction and Other Materials

3.1

Cement Bonded Materials

The construction material or material concrete, mortar and fibre cement consist in general of the hydraulic bonding means cement, mineral additives and/or fibres and water. Processing and employment characteristics are deliberately influenced using additional concrete agents or concrete additives. Cement bonded construction materials are employed in numerous forms with different structures for wastewater collection, delivery and treatment.

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ATV - M 168 E In addition to the technical usage characteristics of concrete such as stability, impermeability, temperature and dimensional stability, the chemical resistance is of significance with regard to durability. As a rule, with cement bonded construction materials, corrosion processes are long-term. The scope of corrosion is, in the first instance, influenced by the concentration of the attacking substances, the delivery conditions and the reaction time. With wastewater systems, with regard to the chemical attack, the reactions and the loading due to the wastewater on the pipe channel surface (see Sects. 3.1.1.2 and 3.1.1.3) and the loading due to the soil and groundwater on the outside of the component or pipe (see Sect. 3.1.1.4) are to be differentiated. 3.1.1

Concrete and Reinforced Concrete

3.1.1.1 General Concrete can be used as locally produced concrete or in the form of prefabricated components. The concrete components can be reinforced - mild steel reinforcement or prestressed - or unreinforced. The Standard Specification DIN 1045 "Structural Use of Concrete; Design and Construction" applies for the production and dimensioning of the concrete. Concrete for components, which are employed in drainage facilities, is to produced in accordance with the specifically applicable Standard Specification DIN 4281 "Concrete for Drainage Units; Manufacture, Requirements and Testing, (3/1985)". Concrete with special composition, e.g. addition of fine particles or use of special cements, meet higher demands on stability, permeability and chemical resistance (see Sect. 3.1.1.2). The most important standard specifications for prefabricated concrete components for employment in sewerage networks are: DIN 4032

Concrete Pipes and Fittings

DIN 4034

Shafts constructed from Prefabricated Concrete and Reinforced Concrete for Underground Drains and Sewers

DIN 4035

Reinforced Concrete Pipes, Reinforced Concrete Pressure Pipes and Associated Fittings

3.1.1.2 Chemical Loading Due to Communal Wastewater For the chemical loading of concrete due to communal wastewater (see Sect. 2.2) and the possible advance of corrosion through this, in addition to concentration and reaction time, the high flow rate of the wastewater in comparison with the regulations of DIN 4030 and the frequency of cleaning processes with their mechanical influences on the surface of the concrete, play a role. Therefore, the limiting values in Tables 1 and 2 are not identical with the limiting values Table 4 of DIN 4030. The size of the limiting values given in Tables 1 and 2 for the concentration of the aggressive substances is so determined that the pipelines remain, in the long-term, free of damage; with this the longest service life is based according to the LAWA Guidelines (LAWA, 1993). A.

Limiting values with permanent loading (normal case) July 1998

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ATV - M 168 E A sufficient resistance of concrete to corrosion loading in the wastewater area (see Sect 2.2) is ensured if wastewater does not exceed the limiting values given in Table 1 with regard to concrete aggressive content substances. For wastewater content substances for which standard values exist in ATV Standard ATV-A 115 "Discharge of Non-domestic Wastewater into a Public Wastewater System“, October 1994, the limiting values agree in the main with the standard values (Column 4). In Column 3 are listed the amounts of wastewater components (extent of the steady load), which come into question for chemical loading which, from experience, occur with normal communal wastewater. In the normal case the amounts lie clearly below the limiting values. This also applies for stormwater runoffs. In individual cases such as, for example, in mountainous regions with a small buffer capacity of the soil, increased spring water runoffs with increased acid content, e.g. with carbon dioxide or humic acid (Schwarzwald), can occur. In such a case the amount of the loading (concentrate, duration) are to be assessed separately. With the loading through normal communal wastewater a sufficient chemical resistance of the concrete exists if the concrete meets the requirements of Table 1, Column 5. With an increased chemical loading of the concrete through communal wastewater, as can occur according to Sect. 2.2, sufficient resistance exists for concrete pipes and shaft components up to a pH value > 4.5 if the concrete, for example, meets the following additional requirements: − high performance concrete with a strength class ≥ C 75/85 using highly reactive pozzolanic fine grain materials, such as, for example, silicate dust, with at least 5 % of the quantity of the bonding means and/or appropriately constituted special cements; watercement ratio w/c: ≤ 0.45, water ingress depth (DIN 1048): ≤ 2.0 cm) − employment of alumina cement as bonding agent, and the pipes and shaft components are examined and monitored according to the "FBS Quality Guideline - Concrete Pipes, Reinforced Concrete Pipes, Service Pipes and Shaft Components for Underground Drains and Sewers (Published by the "Fachvereinigung Betonrohre und Stahlbetonrohre e.V. [Specialist Association for Concrete Pipes and Reinforced Concrete Pipes], Bonn) (also available in English).

B.

Limiting values for temporary or short-term loading (special case)

From experience, with the discharge of wastewater, the discharge conditions can be so changed through, for example, misuse, mishandling, unforseeable failure (accident) or long-term conversion of technical facilities, that the discharge limiting values cannot always be met. Through this, the limiting values given in Table 1 for long-term loading, can be temporarily exceeded or undercut. Therefore, the limiting values for temporary or shortterm higher permitted loadings are listed in Table 2 for concrete corrosive wastewater content substances, by which no damage to the concrete is to be expected with the fulfilment of the requirements, laid down in Table 2, on the concrete composition during the longest service life in accordance with the LAWA Guidelines (LAWA, 1993). Table 1: Limiting values for a long-term loading of concrete in the sewer network through communal wastewater July 1998

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ATV - M 168 E Type of attack

Attacks through, for example

Loading parameters of normal communal wastewater

Sufficient concrete resistance exists: with a long-term load

with fulfilment of following requirements on the concrete

Limiting values in wastewater 1

2

3

4

Loosening through leaching

Soft water

Not given

Not applicable

Loosening through acid attack

Inorganic and organic acids

pH value: 6.5 to 10

pH value ≥ 6.5

Lime dissolving carbon dioxide (CO2)

< 10 mg/l

≤ 15 mg/l

Magnesium (Mg2+)

< 100 mg/l

≤ 1000 mg/l

Ammonia-nitrate (NH4-N)

< 100 mg/l

≤ 300 mg/l

Sulphate (SO42-)

< 250 mg/l

≤ 600 mg/l

As above without HS cement

< 3000 mg/l

As above with HS cement

Loosening through exchange reaction

Swelling

1)

5

w/c ≤ 0.502) and water ingress depth (DIN 1048) of ≤ 3 cm

1) In normal communal wastewater this value is not achieved. At most, in individual cases, a value in the given order is possible with the discharge of large quantities of groundwater containing carbon dioxide (e.g. drainage water). 2) The resistance of the concrete is considerably enhanced through low w/c values and through the use of cement with special composition.

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ATV - M 168 E Table 2: Limiting values for a temporary or short-term loading of concrete in the sewer network through communal wastewater Attack, for example, through

Sufficient resistance of concrete exists with a loading Temporary1)

Short-term2)

With fulfilment of following

Limiting values in wastewater

Requirements on the concrete

1

2

3

4

Soft water

Not applicable

Not applicable

Inorganic acids, e.g. sulphuric acid, hydrochloric acid, nitric acid

pH value: ≥ 5.5

pH value: ≥ 4

Organic acids

pH value: ≥ 6

pH value: ≥ 4

Lime dissolving carbon dioxide (CO2)

≤ 25 mg/l

≤ 100 mg/l

Magnesium (Mg2+)

≤ 3000 mg/l

Ammonia-nitrate (NH4-N)

≤ 1000 mg/l

Sulphate (SO42-)

≤ 1000 mg/l

As above without HS cement

≤ 5000 mg/l

As above with HS cement

w/c ≤ 0.503) and water ingress depth (DIN 1048) ≤ 3 cm

No limitation

1) Duration up top a maximum of one year per ten years. 2) Unscheduled operational conditions; duration up to a maximum of one hour per week. 3) The resistance of the concrete is considerably enhanced through low w/c values and through the use of cement with special composition.

1. Under "temporary" loading (Column 2) one understands a loading which, during longer periods of time, e.g. between two inspection dates during the course of ten operational years, exercises an effect in the order of a maximum of one year. These special conditions can be scheduled for necessary tasks on technical installations, which unavoidably stretch over a longer period. 2. To cover unscheduled operational conditions, with which higher loading occurs for a short time, the limiting values listed under "short-term (Column 3) apply. Such short events are seen as non-critical if they occur, at the most, once a week for a maximum of one hour.

Note: One-off, surge type discharges of concrete corrosive substances with higher concentrations, which occur over a very short term through misuse or accident (discharge in gushes) is, as a rule, irrelevant with regard to a chemical attack on the concrete.

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ATV - M 168 E 3.1.1.3 Loading in the Sewer Atmosphere If a chemical attack on concrete takes place in the sewer atmosphere then this, as a rule, is a biogenic sulphuric acid attack (see Sect. 2.3). With biogenic sulphuric acid corrosion the sulphuric acid attacks the concrete chemically above the wastewater level causes a loosening attack on the surface of the concrete. The sulphates which result as reaction products simultaneously with the loosening attack on the concrete can, in principle, effect an expanding chemical attack in areas close to the surface (see also Sect. 3.1.1.4). One can, however, assume that with a very low pH value the loosening attack and not the sulphates resulting from the reaction determines the rate for a corrosion of the concrete. With expected biogenic sulphuric acid attack a concrete with special composition in accordance with Sect. 3.1.1.2 should be used. 3.1.1.4 Loading through Soil and Groundwater The chemical loading of concrete components of a wastewater network through soil and groundwater is to be assessed and classified with regard to the degree of attack in accordance with DIN 4030 "Assessment of Soil, Water and Gases for their Aggressiveness to Concrete; Principles and Limiting Values " (6/91). The respective necessary technical requirements and measures for concrete, which ensure a long-term damage-free condition, are contained in the concrete standard specifications. In connection with the information in Sect. 2.1.1 on the corrosion processes in natural soils, which are initiated through sulphates or lime dissolving carbon dioxide, the fundamental reactions occurring with these are described below in more detail. Sulphate Due to solutions containing sulphate the aluminates and aluminate hydrates in the hardened cement paste can, for example, react as follows under the formation of trisulphates (ettringite) containing a great deal of crystal water: 3 CaO . AL2O3 + 3 (CaSO4 . 2 H2O) + 26 H2O → 3 CaO . AL2O3 . 3 CaSO4 . 32 H2O) Through the subsequent crystallisation and the growth of the reaction products a pressure develops in a fixed layer, which leads to swelling effects. Here, the formation of ettringite and gypsum should be mentioned. Lime dissolving carbon dioxide With the chemical attack of lime dissolving carbon dioxide, following an initial compaction through the formation of the slightly soluble calcium carbonate according to Ca(OH)2 + CO2 → CaCO3 + H2O with a further effect of water containing CO2, there is a formation of slightly soluble calcium hydrogencarbonate CaCO3 + CO2 + H2O → Ca(HCO3)2. Ca(HCO3)2 is dissolved by water and is carried away. Aqueous solutions of CO2 react slightly acidic (carbonic acid). The corrosive effect of dissolved carbon dioxide is here dependent on the hardness of the water; the greater this is July 1998

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ATV - M 168 E the more stabilising carbon dioxide is required in order to keep the hydrogen carbonate in solution. This means that, in hard water, there must first be a high content of free carbon dioxide to have a damaging effect as opposed to soft water which, already with slight carbon dioxide content, can be aggressive against concrete. 3.1.1.5 Information on the Avoidance of Reinforcement Corrosion With concrete components for wastewater systems there is a satisfactory corrosion protection for the reinforcement if the requirements for the concrete covering dimensions and the crack width limitation, laid down in DIN 1045 or in DIN 4035, DIN 4034 and DIN 4281, depending on the strength of the concrete, and on the environmental conditions in accordance with DIN 1045, Table 10, Line 3, are met. As a rule, the concretes of components used in wastewater systems are very impervious. Therefore, for example, the possible chloride content of normal communal wastewater does not promote corrosion. The general preconditions for a corrosion of the reinforcement, i.e. the carbonating of concrete and addition of oxygen, do not exist with the permanently wet location conditions for components in the area of the wastewater. Therefore, with impervious concrete, no corrosion of the reinforcement can take place here. 3.1.2

Mortar

In general mortar is employed in wastewater systems as brick and joint mortar, as mortar for the repair of components or for purposes of lining pipes (see also Sect. 3.3.1.1). The composition of the mortar depends on required unset and set mortar properties. As a rule, hydraulic mortars of Mortar Groups IIa, III, IIIa according to the Brickwork Standard Specification DIN 1053, are used for wastewater components. With cement bonded mortars important properties such as impermeability, adhesion as well as mechanical and chemical resistance can be improved with the aid of suitable synthetic additives. Such synthetically modified cement mortars are to be selected and applied according to the DAfStb [Service Instructions for Registrars and Supervisory Authorities] Standard for the Protection and Repair of Concrete Components (8/90). Depending on the type of mechanical loading to be expected in the sewer, mortar of Loading Classes M3 or M4 as listed in the Standard can be considered., The Standard contains requirements on the set mortar and details on the required verification. The specialist technical rules are to be observed with the processing of mortar, so that an as impermeable as possible constitution is produced. The mortar must be processed before the start of setting, full width and thickly applied and protected, e.g. from draughts in the sewer, against rapid drying out. For good bonding between the mortar and the subsurface care is to be taken, for example through careful cleaning of the sub-surface, by the removal of all loose components and by wetting. With the use of mortar systems attention is to be paid to the manufacturer's processing instructions which, as a rule, include the necessary preparation of the sub-surface.

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ATV - M 168 E 3.1.3

Fibre Cement

Fibre cement is produced from cement and water with the addition of synthetic fibres as reinforcement and, for example, of pulp fibres as retention aid. In the hardened condition the fibres firmly embedded in the cement matrix increase the tensile strength of the fibre cement. Due to the dewatering of the cement lime, connected with production, a very impervious cement composition results with very favourable water-cement ratios. Through this, the limiting values in accordance with Tables 1 and 2 can also be applied to fibre cement. In exceptional cases, special cements, in particular sulphate resistant cements, can be employed. The most important standard specifications for prefabricated components made from fibre cement for employment in wastewater networks are: DIN 19 840

DIN 19 850

3.1.4

Faserzementrohre und -Formstücke für Abwasserleitungen [Fibre Cement Pipes and Fittings for Drains] Parts 1 and 2 Faserzementrohre und -Formstücke für Abwasserkanäle [Fibre Cement Pipes and Fittings for Sewers, Parts 1 and 2: Pipes, Joints, Fittings, Part 3: Shafts.

Composite Pipes

So-called composite pipes with improved load bearing capacity result from the concrete envelopment of, for example, vitrified clay pipes or plastic pipes. Such composite pipes are, as a rule, produced in concrete factories. They are used with particularly high static and dynamic loading as well as in cases in which the particular protection of a concrete pipe is necessary for technical wastewater reasons. The thickness of the concrete envelope can be matched to the static loading. According to plan, with such composite pipes, the concrete does not come into contact with the wastewater. The provisions of DIN 4030 "Assessment of Soil, Water and Gases for their Aggressiveness to Concrete" apply with regard to a chemical attack on the outside of the composite pipe due to the soil or groundwater. 3.2

Vitrified Clay, Sewer Brick, Glass

Vitrified clay pipes and fittings in accordance with DIN EN 295, Part 1, are manufactured from suitable clay and fired to vitrification. The material properties are described and defined in their requirements (e.g. annealing loss, water absorption, texture and abrasion resistance) supplementary to DIN EN 295, in Works Standard WN 295. Pipes and fittings can be glazed or unglazed on the inside and/or outside. With the exception of hydrofluoric acid they are not attacked by substances contained in the wastewater or in the groundwater soil. If verification is required in the individual case this takes place in accordance with EN 296. Sewer bricks, in accordance with DIN 4051 are used for structures and, in part, for large dimensioned sewers. Using clays they are formed mechanically and fired to vitrification. As sewer bricks are resistant against chemical attack the quality of the mortar used and its technically correct processing has particular significance (comp Sect. 3.1.2). Until now glass has been employed only in trials in the form of shells as lining material for concrete pipes. It also has a very high chemical resistance which, however, is to be verified in special cases.

July 1998

16

ATV - M 168 E 3.3

Metallic Materials

3.3.1

Unalloyed and Low Alloy Iron Materials

The metallic materials used in the construction of underground sewers and wastewater pressure pipelines are essentially unalloyed and low alloy steels and ductile cast iron. These materials and the thereform produced sewers can, unprotected, suffer corrosive attacks internally due to the flowing medium as well as through the type of the sewer atmosphere and externally through the soil and/or its content substances. Components made from steel and ductile cast iron are therefore to be employed only with satisfactory corrosion protection. Table 3: Limiting parameters of the areas of application of cement mortar linings of ductile cast iron pipes, steel pipes and fittings taking onto account DIN 2614 (permanent loading) Parameters in the flowing medium

pH value*) Mg

2+

Unit

Type of lining according to DIN 2614 I-S (Blast furnace or Portland cement) (HOZ or PZ)

I-T (Alumina cement (TZ))

-

6.5 - 12

4.5 - 12

mg/l

≤ 1000

solubility limit

SO42NH4+ 2+

mg/l

≤ 3000

solubility limit

mg/l

≤ 200

≤ 2000

Ca

mg/l

≥1

≥0 (stormwater)

Lime dissolving carbon dioxide

mg/l

≤7

solubility limit(stormwater)

ppm

< 0.5

0.5 - 10

Parameters in the sewer atmosphere H2S concentration in the free crosssection of the sewer as measure for the BSAC**) *)

Short-term undercutting causes no damage

**)

According to the current status of knowledge, it is generally assumed that below 0.5 ppm H2S in the sewer atmosphere one does not have to reckon with biogenic sulphuric acid corrosion. Already with H2S concentrations upwards from 0.5 ppm in the sewer atmosphere heavy degrees of attack by BSAC can occur (BIELECKI and SCHREMMER, 1987). The correlation between H2S concentration and strength of attack was found using simulation in the pollution gas chamber (SAND, 1987), the same relationship was verified by SEYFRIED (in: BELECKI and SCHRAMMER, 1987) for conditions in practice. With a H2S content of 10 ppm is designated as heavy (BOCK et al., 1990).

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17

ATV - M 168 E 3.3.1.1 Linings for Pipes Made from Ductile Cast iron and Steel Cement mortar linings in ductile cast iron pipes have been used for over 120 years, they were originally employed to prevent corrosion damage in pipelines from aggressive drinking water. According to DIN 2614 there are three procedures for the manufacture of cement mortar linings: − rotary centrifugal casting process (Procedure I) − centrifugal application process (Procedure II) − manual lining (Procedure III) for repairs, completion of lining during pipe construction and partially for the lining of fittings. Wastewater pipes (DIN EN 598) are fundamentally lined using the rotary centrifugal process, whereby the mortar is highly compacted. Through this there is a double corrosion protection effect of the mortar lining: 1. The alkalinity of the pore water with a pH value > 9 passivates the underlying iron surface and thus prevents corrosion (active component). 2. The compact mortar structure (high rotation speed - driving out of batch water - w/c ratio ca. 0.3) hinders the diffusion of the oxygen to the iron (passive component). For cement mortar lining in accordance with DIN 2614, essentially sulphate resistant blast furnace and Portland cements in accordance with DIN 1164 (S in accordance with DIN 2614) as well as alumina cement in accordance with British standard BS 915 (T in accordance with DIN 2614) are used. With concrete aggressive wastewater or with an anticipated biogenic sulphuric acid corrosion (BSAC), the alumina cement (TZ) mortar lining (T) is to be applied. The long-term protective effect on linings using organic substances depends very much on the adhesive ability of these substances on to internal metal surfaces. Many years practical experience has shown that, due to the unavoidable permeation of oxygen, water vapour and carbon dioxide through the organic substances, the adhesive capability can, in the long-term, be lost (e.g. polyurethane, polyurethane tar, polyethylene etc.). 3.3.1.2 Sheathing The corrosion probability of a soil against unalloyed and low alloy steels and ductile cast iron is determined according to DIN 30 672, Part 3. From the sum of various analytically determined assessment figures a division of soils into aggressiveness classes or Soil Classes I to III is possible. For on-site post sheathing of the pipe connections with soil of Soil Class III, sheathings made of anti-corrosion bands, heat shrinkage material in accordance with DIN 30 672, Part 1 or rubber collars are used. DIN 30 675, Parts 1 and 2 give information on corrosion protective measures and the sheathings to be used according to the soil class. 3.3.2

High Alloy, Stainless Steels

High alloy, stainless steels belong to a comprehensive material group and are resistant with many corrosion loads. The resistance is governed by a very thin passive layer. The even surface abrasion with values < 10 µm per year in the passive area is negligibly small. The passivity is essentially determined by the content of chromium which gives this steel its passivity. In addition to the chromium content the other alloying elements of significance are, for example, nickel and molybdenum.

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ATV - M 168 E In the first instance, for employment in wastewater systems, austenitic chromium-nickel steels with and without molybdenum addition come into consideration. In a draft for an European Standard Specification (pr EN 1990) there are three often applied steel qualities, whose most important details are contained in Table 4. According to pr EN 1990, there are thus other comparable steel qualities which are permitted. Pitting - as with other materials with passive layers (e.g. Cu, Al) - can occur with the presence of large quantities of chlorides. With this it is not only the chloride contents of the wastewater which are significant; chloride can also accumulate in fixed deposits on steel surfaces even with wastewater with non-hazardous chloride contents. In these cases, with potentials which are greater than the pitting potential UL, there is a break through of the passive layer with pitting as a result. It is pointed out, that also with atmospheric corrosion loads, corrosion hazardous chloride accumulations can occur in fixed deposits. Table 4:

Characteristics of some important stainless steels

Material designation

Masses %

ISO 683/ 131986

Euronorm SS-71

Material No.

C

Cr

Ni

Mo

-

Effective sum in masse s%

Pitting potential UL in mV1)

a

b

c

d

e

f

g

h

i

j

11

X6 Cr Ni5) 18 10

1.4301 (V2A)2)

≤ 0.07

17 to 19

8 to 11

-

-

18

+ 250

19

X3 Cr Ni Mo 17 12 2

1.4435

≤ 0.03

16 to 18.5

11 to 14

2.0 to 2.5 -

25

+ 600

21

X3 Cr Ni Mo Ti 17 12 2

1.4571 (V4A)2)

≤ 0.08

16 to 18.5

10.5 to 14

2.0 to 2.5 5 % C ≤ Ti ≤ 0.5

25

+ 6003)

-

X3 Cr Ni Mo N 17 13 54)

1.4439

≤ 0.04

16.5 to 18.5

12.5 to 14.5

4.0 to 5.0 N 0.12 32 to 0.2

1) 2) 3) 4) 5)

1200

According to GRÄFEN i.a. all potentials referred to the standard Hildebrand electrode Designation in practice Assumed value German designation Do not use V2A in the sewer atmosphere

Pitting does not depend only on the chloride content but also on other factors given below in abbreviated form: − Material quality: the effective sum W in mass % chromium * 3.3 mass % molybdenum (Column i in Table 4) is relevant. The larger W is, the more positive is the pitting potential UL (Column j of Table 4), i.e. the smaller the danger of pitting is (GRÄFEN et al.). In the Table the steel with the Material Number 1.4439 is used as example for a steel with high W value.

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ATV - M 168 E − Redox potential URedox: if URedox is more positive than UL, which is the case, for example, with the addition or influx of oxidation means such as atmospheric oxygen, ozone, Fe3+ ions etc., pitting occurs - even with relatively low chloride contents. − The greater the flow rate of the wastewater the more positive is UL, i.e. the smaller is the danger of pitting. − With sensitising (see below), the susceptibility against pitting increases. The factors listed show that no generally valid details for chloride concentrations, with which no crevice corrosion occurs, can be given. Analogous details in literature must therefore be considered very critically. Crevice corrosion occurs only in wastewater containing chlorides, whereby crevices (some 0.1 to 0.5 mm width) between steels and non-conductors (e.g. plastics) are particularly dangerous points of occurrence. Crevice corrosion is dependent on the potential USP, which is usually more negative than the pitting potential UL, which underlines the dangerousness of crevice corrosion. The possibility of intercrystalline corrosion as a result of a heat treatment of stainless steels, for example with welding, must be considered. This is a selective type of corrosion with which the depositing of chromium rich carbides occurs at the grain boundaries. The corrosion resistance can reduce so far through the chrome depletion that grain disintegration occurs. This material change is designated as sensitising (DIN 50 930, Part 4, 1993). Stabilisation against this type of corrosion can be achieved using the lowest possible carbon content, which is, for example the case with steel of Material Number 1.4435 (see Table 4). Another possibility lies in the addition by alloying of titanium or niobium/tantalum, which have a high affinity to carbon and thus avoid the formation of chrome carbides (steel Material Number 1.4571). The welding of stainless steels requires particular care and specialist knowledge (STRASSBURGER, 1976). Here attention should be drawn to some important points:

− selection of a procedure which avoids the access of atmospheric oxygen such as, for example, metal arc welding, inert gas shielded arc welding and submerged arc welding; − deliberate, not too high addition of heat; − seam root covering; − taking account of increased contraction strains and thermal stresses.

With welding, oxide films and scale layers can appear, which prejudice the resistance against pitting. According to the draft DIN 50 930, Part 4, (1990), thin oxide films of a straw yellow colour can remain on the surface without prejudicing the corrosion resistance. All other oxide films must be removed either through shot peening using glass beads, through careful grinding (grain size > 100) or, best, through pickling. In the factory complete components are pickled in nitric acid - hydroflouric pickling baths, while pickling pastes, which are to be removed completely after treatment, are used on the construction site.

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ATV - M 168 E With wastewater systems a mixed construction of different materials cannot be completely avoided. Contact corrosion can occur with metal conductive connections (direct electron conductive contact) of stainless steels with electro-chemical base materials, e.g. unalloyed steels (DIN 50 919, 1984). Particularly endangered are small area components made from unalloyed steel (anodes) connected to large areas made from stainless steel (cathodes). With protective measures against contact corrosion consideration must be given that coatings must be applied to the stainless steel to reduce the cathode area. Coatings on unalloyed steel hide the danger that high anodic disintegration of non-alloyed steel occurs at often unavoidable, small faults in the coatings. In summary the most important aspects, which should be observed with the employment of highly alloyed stainless steels, are listed below: − use of stabilised steels if welded seams are planned; − professional weld seams and removal of oxide films; − crevice-free construction and processing, crevices > 0.5 mm are non-critical; − with the employment of bolted constructions gaps between components are unavoidable, therefore welded construction is to be preferred; − use of chloride-free sealants; − metallic bright surfaces; the formation of solid deposits is to be avoided; − the three-phase boundary air/steel/water can be endangered if solid deposits form in which chlorides can accumulate; − a heavily anaerobic sewer atmosphere can lead to pitting even with stainless steels.

3.4

Plastics (PVC-U, PE-HD, PP, GFRP)

3.4.1

Preamble

Plastics are employed in the area of sewers both as load bearing pipe and shaft component materials as well as for corrosion resistant linings and coatings for concrete and cast iron pipes. In the area of the overall sewer system plastics are also extensively used, for example in relining processes through the insertion of plastic pipes into damaged sewer systems and also in the form of subsequent application of linings. Against the wastewater compositions which are permitted and occur in communal and other public drains the pipe materials given in Sect. 3.4.2 are generally to be seen as chemically resistant. The appropriate standard specifications for material quality and material properties are to be observed with the selection of material and tendering. Both the external effects from chemical and static loading as well as various material properties are to be taken into account with the selection of the plastic for the respective application case. With coatings and linings, it must be further checked whether the specific parameters for the plastic processing can be maintained on the construction site and/or in the factory. The decision on the final material selection should be made dependent on this.

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21

ATV - M 168 E 3.4.2

Pipe Materials

Plastics are divided into thermoplastics: e.g. polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA) - thermosetting plastics (resins): e.g. epoxide resin (EP), polyester resin (UP), phenolic resin (PF) - and elastomers: e.g. synthetic rubbers, polyurethane (PUR). Thermoplastics can be plastically worked, baked or welded with high temperatures. Once manufactured, thermosetting plastics cannot be worked further. They can, however, be processed using machine procedures (milling, cutting, drilling) and joined with adhesives. Elastomers can no longer be thermally worked following chemical cross linkage. They can, however, be processed mechanically and glued. For application in sewers, plastic pipes and fittings as well as plastic shaft components and linings, mainly from the following materials, can be employed: Symbols − polyvinyl chloride

PVC

− high density polyethylene

PE-HD

− polypropylene

PP

− glass fibre reinforced plastics (GFRP) on the basis of unsaturated polyester resins

UP-GF

With the employment of the above named polymer materials in sewers, the following DIN Standard Specifications are to be observed with regard to the requirements and quality assurances: PVC-U PE-HD PP

DIN 19 534 DIN 19 537 DIN 8077, 8078

In addition, for pipes with profiled walls made from thermoplastic materials, DIN 16 961 is to be observed and the initial, in draft, standard specification DIN 19 566. DIN 19 565 applies for the employment in sewers of centrifugally formed pipes and fittings made from glass fibre reinforced unsaturated polyester resins. Furthermore, a series of pipes, shaft components and linings made from plastic are used, for which currently there are no application standard specifications, but nevertheless carry the RAL Quality Mark of the "Gütegemeinschaft Kunststoffrohre (GKR)" [German Quality Organisation for Plastic Pipes]: nonascendable lower shaft components

profiled sewer pipes and fittings made from PVC-U sewer pipes and fittings made from modified PVC-U

R 7.1.23 R 7.4.20 R 7.6.8 R 7.1.12 R 7.1.19 R 7.1.15 July 1998

22

ATV - M 168 E sewer pipe lining components made from PVC HI driven pipes and fittings made from PVC-U sewer pipes and fittings made from wound UP-GF

R 7.1.13 R 7.1.16 R 7.8.24

For employment in the area of private properties the components must correspond with the Technical Rules published in the "List of Construction Rules A" (Bauregelliste A) of the German Institute for Construction Engineering (DIBt) or the manufacturer must posses a "General Construction Supervision Authorisation" or a "Test Certificate" from the DIBt. With the employment of pipe materials and the therefrom produced pipes, fittings, shaft assemblies, and pipe lining components in accordance with the above given standard specifications and directives, a sufficient chemical resistance for the normal service life of sewers in the communal area (wastewater in accordance with ATV Standard ATV-A 115, October 1994) can be assumed. The selection of the plastics is based on the specific loadings. Plastics are often employed for special applications, e.g. with the discharge of aggressive industrial wastewater or for product pipelines in chemical operations. With aggressive media the directions and corresponding resistance tables of the supplementary notes to the basic standard specifications of pipes made from PVC-C, PE-HD and PP must be observed and the details given by the pipe manufacturer are to be taken into account (DIN 8061, Suppl. 1, DIN 8075, Suppl. 1, DIN 8078, Suppl. 1). With pressure pipelines both DIN Standard Specifications (DIN 8061/62, DIN 8074/75, DIN 8077/78) and the Standards of the German Association for Welding Technology (DVS Standard 2205, Part 1) are to be observed for permitted loading. As with inorganic or metallic materials, plastics can be attacked not only from the surface but also from inside as small molecules can diffuse internally. Primarily organic solvents and also other low-molecular, gaseous and fluid substances can diffuse into plastics. Through this, with some plastics (see above-named supplements), a swelling and subsequent softening can occur. In particular, thermoplastics and soft rubbers can be attacked, also from inside, through internally diffused substances, while duroplastics and hard rubbers are attacked mainly from the surface (SGK, 1994). With PVC the stabilisers can also be attacked under anaerobic conditions (e.g. in anaerobic tanks). Local, mechanical damage can also be caused to GFRP pipes through incorrect handling during delivery (sudden loading) and in operation (incorrectly operated high pressure cleaning). At the damage sites the medium can penetrate into the bearing layers through micro-cracks in the gel coat and, depending on the structure, also into the bearing layers along the fibres due to capillary forces (when employing long fibres). Through this the bearing capacity can be reduced. Damage to the surface and faces are to be mended using resin in order to avoid a penetration of the medium through capillary forces.

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23

ATV - M 168 E 3.5

Sealing Materials

3.5.1

General Requirements on Sealing Materials for Wastewater Systems

Sealing materials, which have contact with aggressive water, soil or gas, must be so manufactured or protected that they can resist their attacks without prejudice to their functional capability. Accordingly the functional capability of pipe connections must be ensured with influences from − wastewater with pH values of 2 to 12, − commercial wastewater in accordance with ATV Standard ATV-A 115. As far as wastewater (e.g. before a separator/interceptor) occurs with properties deviating from these, the respectively relevant loadings are to be taken into account. In water protection areas the functional capability of the pipe connection must be additionally ensured for five hour effects of heating oil EL and motor fuel No. 2 in accordance with DIN 53 521. Insofar as, in individual cases (in particular in the area of private property drainage systems), one has to reckon with longer-term effects of these substances, appropriately resistant sealing materials are necessary. With light liquids, for sewers, at least on the flow path up to the low density material separator, sealing materials with a separate resistance verification are to be employed in accordance with the German Institute for Construction Engineering, Berlin, "Construction and Test Principles for Seals made from Elastomers with Increased Resistance Capability against Light Fluids for Pipe Connections in Wastewater Systems". 3.5.2

Materials for and Properties of Sealing Materials

For sewers and drains almost exclusively the following come into consideration: − sealants made from elastomers in accordance with DIN EN 861, DIN 4060; − sealants on the basis of polypropylene and polyurethane for vitrified clay pipes in accordance with EN 295; − two component sealing compounds on the basis of polyurethane for internal pipe thrust seals in man accessible sewers and pipelines produced by pipe driving; − cold worked plastic sealing compounds in accordance with DIN 4062 are used only in individual cases. With regard to chemical effects all sealing materials meet the requirements of DIN 4062. The functional capability of the pipe connection remains assured with the effect of wastewater with pH values between 2 and 12 and with commercial wastewater with guidance values in accordance with ATV Standard ATV-A 115 (including the limiting values for substances in accordance with the Indirect Discharger Ordinance of the Federal (German) States. As far as light liquids (hydrocarbons such as benzine (petrol), heating oil and similar) or volatile chlorinated hydrocarbons (CHCs) are discharged temporarily into the public sewerage system as a result of an accident, these should cause no disadvantageous effects on the sealing function of the sealants. July 1998

24

ATV - M 168 E Microbiological attacks on sealants in accordance with DIN 4060 and DIN EN 295 have up until now not be determined with sewers. Biologically conditioned material defects occur only with two component sealants on the basis of polysulphide rubber (Thiokol = US brandname), which are therefore considered as unsuitable for wastewater systems. For the area of the public sewerage system negative effects on sealants due to chlorinated hydrocarbons (CHCs) are not to be feared. Apart from the fact that CHCs have only a relatively slight water solubility, they belong to the water hazarding substances which, according to legal regulations, may only be discharged in quantities which are completely harmless for sealants.

4

Corrosion Protection

4.1

Compound Materials and Linings

They are produced mainly from PE, PVC (free of plasticiser) and UP-GF and have, depending on formulation, a good to very good resistance against acids, alkaline solutions, fuels and oils. Further information can be taken from ATV Advisory Leaflet ATV-M 143. 4.1.1

Pipe Linings with New Constructions

Parallel to the testing of various lining systems there are years of experience available with pipe linings made from plastic widths. They are produced mainly from PE, PVC (free of plasticiser) and UP-GF and have, depending on formulation, a good to very good resistance against acids, alkaline solutions, fuels and oils. 4.1.1.1 Factory Produced Pipe Lining Using PVC Plasticised Films In the eighties internal linings using 2-3 mm thick PVC plasticised films were installed which were anchored in the concrete using ribs. With these, films produced in the USA and in Germany a release of the external water overpressure from the groundwater due to encasing with concrete, is only possible at the upper 300° or at 360° through drainage holes below the water level. The films were installed with success; they had only the disadvantage that they were not stable enough against the cleaning equipment used with later operation. The pipes were so manufactured in the concrete factory that, at the pipe faces, the films overlapped or were flush to each other. In both cases the connection, after laying the pipes, had to be welded on site in order to receive a continuous corrosion protection. Currently the factory produced lining with plastic film is no longer practised in Germany.

July 1998

25

ATV - M 168 E 4.1.1.2 Factory Produced Pipe Linings Using Unplasticised PVC Web Sheets A further, very widely used, solution for pipe lining is provided by lining using PVC hard helical films. The 2 or 3 mm thick PVC hard profile sections are anchored to the concrete using ribs and, with a 360° encasement in concrete, accept the full external water pressure from the groundwater and the diffusion pressure. The sealing of the pipe joints takes place through an external seal by means of a rubber seal and an internal permanently elastic seal on a polyurethane basis which, at the same time, ensures continuous corrosion protection. Due to the cases of damage which occur on the internal permanently elastic seal, precise information on the actual chemical attack, for example as a result of biogenic sulphuric acid, is necessary with regard to the sealing material used. The compatibility of the sealing material with PVC hard sheets is also to be investigated (possible plasticiser migration). Due to negative experience with which the sealing material softens due to biogenic sulphuric acid, joint closure using laminated GFRP is practised in several towns. With this, however, often adhesion problems and also detachment are observed. The cause of the black discoloration of PVC web sheets, determined in many places over recent years, is still not known. 4.1.1.3

Factory Produced Pipe Lining Using Web or Knob HDPE Sheets

In the meantime, due to modern manufacturing processes, several lining systems using PE-HD films with a full-surface overlay anchorage made from webs or knobs. The material thickness (without anchorage system) is 4 - 5 mm. Pipe connection is by means of overlay welding of the pipe joints, in part with the aid of a joint band. To ensure an even welding seam quality, extrusion welding, if possible using control, is to be preferred. As the good welding capability and the corrosion resistance of the material is decisive for the durability of the overall system, precise specifications with regard to the material requirements are required. As an aid the requirements, which already exist for dump/landfill linings, can be enlisted. Aim of these requirements which, for example, are laid down in the BAM (German Federal Office Office for [Chemical and mechanical] Materials) Authorisation Directive for PE-HD, is to ensure the suitable material selection, the manufacture and the installation of a functioning and long-term resistant corrosion protection element within the framework of a quality assured production in accordance with DIN ISO 9000. If water pressure on the reverse side of the linings is to be expected, the lining system should, to avoid long-term deformation, be eased by means of stress relieving drillings in the base. 4.1.1.4 Factory Produced Pipe Lining Using Vitrified Clay Shells (Ceramic Plates) Vitrified clay shells and sole plates are a possibility for corrosion resistant lining of pipes, whereby corrosion resistant mortars are to be used. July 1998

26

ATV - M 168 E 4.1.1.5

Retrofitted Pipe Lining Using Plastic Sheets

A further development with large calibre main sewers has been the installation at the construction site of an internal lining made from PVC hard sheets or from PP sheets of 6 to 8 mm thickness, after laying the pipes. These sheets were subsequently stretched axially in one piece over 300° in the sewer and held at the bottom by rails using pins made from stainless steel. The relief of the water pressure behind the sheets is achieved via openings in the foot rails. The sheets are self-supporting but are not dimensioned for additional static loading. The ends of the sheets are welded together. This solution has proved itself against biogenic sulphuric acid attack in routine wastewater operation. Due to the unlined base, however, other solutions are to be preferred for aggressive wastewater. Due to the small inherent stability of the above mentioned thermoplastics, together with a missing full-surface anchorage in the pipe concrete, however, it is to be noted that, with extreme operational conditions (surge flushing, reflected waves in front of closed gate valves) damage has already occurred on linings, which made an additional subsequent attachment necessary. A retrofitted lining using plastic sheets is currently no longer employed in Germany. 4.1.2

Shaft Linings with New Constructions

4.1.2.1 Factory Produced Shaft Lining Using Plastic Sheets Similar to pipe lining, the employment of full-surface widths of back-anchored plastic is also possible with shaft linings. With the design and also the construction of such systems, however, there are specific parameters to be taken into account. Thus, with PVC hard web sheets, particular attention is to be given to the joint problem. With PE-HD sheets, with reverse side water pressure, the drainage to the bottom must not be hindered by the arrangement of the anchorage elements. The employment of the above named widths of plastic sheet with shafts with numerous fittings, recesses, outlets or sharp angled inlets is not economical and is problematic for absolutely watertight concrete protection. These design elements result in numerous irregularly formed surfaces. Thus there arises a large number of profile pieces to be cut on site and numerous joints between the individual pieces, which are difficult to close. In such cases the solutions in accordance with Sect. 4.1.2.2 are more practical. 4.1.2.2 Shaft Lining Using GFRP Sheets and Elements A further possibility for shaft lining lies in a retrofitted GFRP lining. Here, prefabricated GFRP sheets made from polyester resin and glass fibres, with a thickness of 2 mm, is fixed to the concrete using plastic pegs. Subsequently there is a full surface, two-layer GFRP laminate over the whole surface through which all joints and peg heads are covered. Finally there is a double topcoat of the same polyester resin. With the last topcoat a 5 % paraffin solution is added in order to achieve a adhesive-free and saponification resistant hardening. The total layer thickness of such a polyester resin lining is 5 mm, its average glass content is 20 - 25 %. In order to ensure a full surface bonding of the on-site applied laminate with the prefabricated sheets, the prefabrication of the sheets should not take place too soon before installation (max. 3 to 6 months according to manufacturer's specifications).

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27

ATV - M 168 E The lining should not be dimensioned on water pressure. More important, groundwater which has appeared in the natural spaces between GFRP and concrete is to be drained off and allowed to exit at the bottom. Artificially enlarged spaces have not proved themselves. For better quality control one should avoid the addition of colour pigments into the polyester resin. Attention is to be paid to a careful selection of the resin and glass qualities employed. Resin qualities with moulding properties in accordance with DIN 16 946, at least Type 1130, and corrosion resistant ECR glass in accordance with DIN 61 855 are recommended. With smaller shaft dimensions with regular geometry, a solution using prefabricated GFRP elements is possible. These elements consist of glass fibres and polyester resin whereby, to increase the stiffness, quartz sand is added. The composition of the individual components varies here depending on manufacturing process. The manufacture takes place using the wound or centrifugal procedure. The static dimensioning of the elements takes place either for the full loads or only for the acceptance of the water pressure. In the latter case an outer concrete shell is necessary. 4.1.2.3 Shaft Lining Using Sewer Bricks In some areas of sewerage systems shaft structures are carried out using sewer bricks. In order here to avoid sulphuric acid corrosion to the cement bonded mortar joints, the joints are dug out to a depth of ca. 2 cm and filled with an epoxy resin mortar. 4.1.3

Pipe Linings with Renovation

With the renovation of pipes one must fundamentally differentiate between accessible and non-accessible profile sections. The problem with all sewers in operation lies in the maintenance of the runoff capability. Insofar as a drying out using backing up is not possible, there remains only the solutions of pump-over of the wastewater or piping, which is carried out with sheets stretched over 300 ° in the bottom and, in other cases, laid above ground and operated as siphon pipelines. To limit the terms used these are now defined whereby, in future, the normal international terms of DIN EN 752 should be used [already applied in this translation]. Table 5:

Comparison of previously used and new standardised terms with the repair of sewers

Conceptual content Repair of locally limited damage Re-establishment of damaged sewers maintaining the basic material Production of new sewers by giving up or destroying the basic material

ATV Advisory Leaflet ATVM 143, Pt 1

DIN EN 752

Corrective maintenance

Repair

Rehabilitation

Renovation

Renewal

Renewal

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28

ATV - M 168 E 4.1.3.1 Renovation of Non-Man Accessible Profile Sections Depending on the parameters, various procedures are employed with non-accessible profile sections. Insofar as the acceptance of external loads can still be taken on by the original sewer, the insertion of inliners, which lie against the sewer walls, is suitable and is carried out without the production of an insertion trench. Equally suitable is the insertion of socalled inliners, made from PE-HD, or GFRP pipes. This solution, however, means a reduction of the flow cross-section and requires an insertion trench. The advantage of these solutions exists a) in the possibility of employing material specifications which correspond with the actual requirements and, b) it is possible with these to pass external loads to the inliner by appropriate dimensioning which, with unsatisfactory load bearing sewer pipes, makes a possible renewal unnecessary. A static calculation for relining pipes (with buckling proof for plastic pipes) is necessary for installation and operational conditions. The annular space between the outside surface of the inliner and the inside of the old sewer is dammed up following reconnection of domestic connections. With all the given solutions there is a problem with the reconnection of existing domestic connections with a technically sound corrosion safe sealing to the new inliner. If this problem cannot be solved with the employment of appropriate robot equipment from outside the sewer, as a rule there remains only the reconnection in an open trench. With a large number of domestic connections this can frustrate the economy of an inliner solution. 4.1.3.2 Renovation of Man-Accessible Profile Sections With the renovation of man-accessible profile sections, the same solutions as are described under Sect. 4.1.2.1 are applicable. The reconnection of the lateral inlets is here very simple to solve from the sewer. Further renovation possibilities exist with sewers that remain stable, for example with the installation of prefabricated plastic sheets, e.g. made from GFRP, which are stretched over 300° and pegged in the sewer. With this the closure of joints with the use of the same material as for the sheets, for example overlay laminates with GFRP and welding with thermoplastics. 4.1.4

Shaft Linings with Renovation

With the renovation of operational shafts the lining as described in Sect. 4.1.2.2 is used. Due to the essentially better access of a shaft as compared with the sewer, it is nevertheless a question of economics whether it is also possible to carry out a renovation on the basis of plastic modified cement mortar and possibly to repeat this renovation over a period of operating time. The employment of pure plastic mortar is very problematic due to the parameters (water exercising pressure, wet surfaces).

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29

ATV - M 168 E 4.2

Protective Paints and Coatings

The essential part with protective paints and coatings is the pre-treatment and priming. Information on this is contained in ATV Advisory Leaflet ATV-M 263. One surface protective layer produced from one or more associated layers counts as a coating. A coating serves to hinder extensively the penetration of liquid or gaseous substances into the concrete. Such coatings consist, as a rule of reaction or thermosetting resins. Coatings are particularly endangered through diffusion into or through the coating by small molecules (water, oxygen), which leads to corrosion under the coating and to the formation of blisters. Particularly endangered are the coatings under thermo-diffusion conditions (KLOPFER, 1974), e.g. cold pipe walls, warm attacking medium which, with pipelines in groundwater, as really always the case. Due to the temperature gradients in the coatings connected with this, a gradient for the partial pressure of the water vapour also occurs so that the water molecules are pressed through the coating by the pressure difference. With metallic materials, in particular steel, occurs under the coating. Cement bonded mortars corrode, in general first if the coating has broken and the corrosive medium reaches the unprotected material. Blisters can also occur due to osmotic processes if, for example, water soluble substances, such as solvents from the coating or water soluble salts are present due to faulty pre-treatment of the surfaces between coating and material. Therefore solvent-free coatings only are to be always used on absolutely clean surfaces. 4.2.1

Coatings on Iron Materials

Coatings on iron materials on the basis of epoxy resin or polyurethane, which are applied in the factory under clearly defined parameters, as a rule have good resistance. The problem of such coatings consists of the danger of damage (subsurface rusting) and the therefrom resultant poor chance of repair of the system in running operations. Here, in many cases, there remains only the complete dismantling of the unit and a new coating. Preferred are therefore designs made from corrosion resistant material, e.g. stainless steel. 4.2.2

Coatings on Concrete Surfaces

In general concrete surfaces in sewers do not require to be coated. If the concrete in sewers is to be coated then surface protective systems (SPS) in accordance with the DAfStb (German Service Instruction For Registrars and their Supervisory Authorities) Directive for Protection and Repair of Concrete Components (8/90) are to be applied. The Directive gives information on coating substances, requirements on the substance and on the concrete surface.

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30

ATV - M 168 E Through the moisture effects on both sides in the concrete with underground sewers, the adhesion of the coating on the surface, and with this the durability of the protection is jeopardised. In addition the adhesive ability can, from the very beginning, be prejudiced as a result of moisture in the concrete. The technical problems which result due to this moisture influence are currently not completely solved. Therefore, in general, the subsequent application of a coating with a sewer which has been buried fir a long time must be considered to be more problematic, both with regard to implementation as well as with regard to durability, than a coating which is applied before laying the pipe. Even factory applied coatings often have weak points already after short operating times. To these count, for example, the formation of blisters, which before long always lead to rupture of the coating. Following rupture the pipe material is wide open to the corrosive attack. With biogenic sulphuric acid corrosion, the corrosion can even develop much more intensively under the ruptured blister. Therefore attention is to be paid that coatings with substances containing solvents, as a rule are not sealed against diffusion or against osmosis, so that, for example, as a result of SO42- diffusion, a formation of ettringite under the coating can occur. Particular attention must also be paid to edges, for example at pipe faces, as here the coating can frequently be heavily applied or the coating is damaged during installation

5

Notes for Planning and Operation

5.1

Notes on Planning

5.1.1.

Preamble

Corrosion problems can be extensively avoided already with the planning of wastewater systems by observation of the following information. Planning measures are particularly suitable for the hindering of biogenic sulphuric acid corrosion. If, despite all planning precautions, corrosive conditions cannot be excluded then a material resistant against corrosion is to be selected or non-corrosion resistant material are to be protected. 5.1.2

Location of Wastewater Treatment Systems

With the planning of central wastewater treatment plants, from the aspect of the sulphide problem, catchment area and location are to be so determined that the wastewater reaches the wastewater treatment plant from the source over the shortest distance and in the quickest possible time. With increasing length of collectors and/or increasing flow times and the operation of pressure pipelines the danger of sulphide problems increases. 5.1.3

Composition of Wastewater

Insofar as wastewater is available at the time of planning, so that its properties can be included in the planned conditions, several wastewater analyses are to be carried out and the analytical results attached to the request for tenders for the pipes. As parameters the following, for example can be considered: temperature, pH value, settlable solids, Chemical Oxygen Demand (COD), magnesium, ammonium, sulphate, sulphide. The pipe supplier is to take on the guaranty for the satisfactory corrosion resistance for the sodescribed wastewater composition.

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31

ATV - M 168 E 5.1.4

Indirect Discharger Operations

The indirect dischargers recorded in a catchment area are to be assessed with regard to the discharge of possible corrosively acting wastewater. Experience shows that one has to reckon with the exceeding of the concentration ranges laid down in the communal drainage bylaws. A listing of commercial and industrial branches with possible corrosive wastewaters and their boundary values is contained in ATV Standard ATV-A 115. In addition those operations are to be particularly observed which discharge organic acids with their wastewater; with cement bonded materials heavy acid corrosion from such wastewater can be caused already with p 8.5:4 H2O2 + H2S → H2SO4 + 4 H2O With pH values up to 8.5, that is with normal communal wastewater, the stoichiometric requirement is 1 g hydrogen peroxide per 1 g hydrogen sulphide. In practice, due to side effects, some 1.5 to 2 times the quantity is to be applied. In the presence of iron and other metal ions always contained in communal wastewater, the reaction takes place within a few minutes. The substance makes an overdosing possible, so that an oxygen reserve can be taken from the pressure pipeline into a subsequent gravity pipeline, causes no hydraulic problems and is suitable for doing in the gravity pipelines. Attention is to be paid to the relatively high chemical costs and the safety conditions with handling.

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40

ATV - M 168 E 5.3

Operational Measures

5.3.1

Cleaning and Maintenance

Heavily polluted sewers often have anaerobic wastewater conditions and favour biogenic sulphuric acid corrosion. The most important operational measures for the maintenance of functioning wastewater discharge facilities is therefore cleaning and maintenance. In particular the input of mineral substances into the sewerage system must be kept small, as the mineral components of deposits require very high flow rates in order that they can be flushed out of the sewer bottom. The mineral solids input can be most effectively reduced by frequent monitoring and cleaning of road gullies and dirt traps. The regular cleaning of hydraulic stress points, such as initial sewer sections or sewers with storage capacity, also brings an improvement to the wastewater situation as the oxygen depleting deposits are removed regularly and the flow rate is increased. In accordance with a German Federal Supreme Court (BGH) judgement, the complete sewer network has to be cleaned at least once a year (BGH Judgement of 11 July 1974 Ref. No. III ZR 27/72). Continuous inspections should decide locally the necessity and frequency of cleaning of road gullies. With sewers which are difficult to clean with a tendency to become dirty again a continuous cleaning process is sensible. With a process using travelling balls (beads) in the flow or gush-flushing, a permanent sedimentation of solids is prevented by their regular application (DINKELACKER, 1987). If the cleaning possibilities are exhausted or impossible (e.g. in pressure pipelines), and sulphide forms, then the oxygen balance in the wastewater should be improved through suitable measures in order that no biogenic sulphuric acid occurs in the subsequent gravity sewer. Wastewater systems should not only be systematically and comprehensively investigated but also more intensively and frequently investigated at stress and hazard points to avoid the formation of corrosion. The inspection results should be documented and regulated for all time intervals (date monitoring system). 5.3.2 Measures with the Occurrence of Corrosion If corrosion damage occurs in existing systems, then subsequent protective measures are to be taken. Corroded sole areas of shafts or sulphur deposits on the shaft walls and pipe crowns, in combination with H2S, smell indicate that the discharge system is subject to an attack of corrosion. First, the cause of the corrosion attack should be determined (e.g. discharges containing acids, discharge of organic acids, discharges containing sulphide or biogenic sulphuric acid corrosion as a result of anaerobic wastewater conditions) in order to exclude the corrosion sources by preventing problematic discharges. With biogenic sulphuric acid corrosion one should, under no circumstances, delay renovationmeasures too long that a prejudicing of the stability of structures has occurred.

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ATV - M 168 E The cause of the occurrence of biogenic sulphuric acid corrosion often lies in the planning (comp. Chap. 5.1). A too small a gradient also causes a too small flow rate. Deposits form and there is anaerobic sulphur transfer. At the same time re-aeration only over the surface of the wastewater level is often insufficient. Also long flow paths to the wastewater treatment plant or, in particular, the operation of pressure pipelines with too large retention times have a negative effect on the wastewater quality. An improvement can often be achieved through additional or oxygen feed into the pressure pipeline. 5.3.3 Measures in Pump Sumps and Pressure Pipelines Frequently problems occur at points, for example in pump sumps or in pressure pipelines with too long retention times. Here, the oxygen balance has first to be checked. An oxygen content of 1 mg/l in the wastewater normally suffices to prevent effectively the formation of sulphide. If the mean O2 content is lower, then first consideration is to be given as to whether an improvement through operational measures can be achieved. Individual operational measures are: − empty pump sumps as much as possible; − reduction of pump sump volumes by lowering the switch-in point and thus increase the pumping frequency; − flushing of the pump sump to avoid deposits by circulation of the delivered wastewater at intervals; − emptying of pressure pipelines at the end of the pumping process (only practical with short pressure pipelines or small diameters). If these measures cannot be completely or satisfactorily carried out the dosing of various chemicals or a pressure aeration/pure oxygen gassing are to be considered (comp. Chap. 5.2).

6

Bibliography

[Translator's note: known translations are given in English only. Where there is no known translation into English a courtesy translation of the title is given in square brackets, after the original German titles].

ATV-A 110E

Standards for the Hydraulic Dimensioning and the Performance Verification of Stormwater Overflow Installations in Sewers and Drains, 1988

ATV-A 115E

Discharge of Non-Domestic Wastewater into a Public Wastewater system, 1994

ATV-A 116E

Special Sewer Systems Vacuum Drainage Service - Pressure Drainage Service, 1992

ATV-A 134 (draft)

Planung und Bau von Abwasserpumpanlagen [Planning and Construction of Wastewater Pump Stations], 1998 [An English version dated 1982 exists]

ATV-M 143E

Inspection, Repair, Rehabilitation and Replacement of Drains and sewers, 1998

July 1998

42

ATV - M 168 E ATV-M 263E

Recommendations for Corrosion Protection of Steel Components in Wastewater Treatment Systems Using Coating and Cladding, 1991

BICZOK, I

Betonkorrosion - Betonschutz [Concrete Corrosion - Concrete Protection], Bauverlag Wiesbaden, 1968

BIELECKI, R. SCHREMMER, H.

Biogene Schwefelsäure-Korrosion in teilgefüllten Abwasserkanälen. [Bogenic Sulphuric Acid Corrosion in Partially Filled Sewers] Mitteilungen des Leichtweiß-Instituts für Wasserbau der Technischen Universität Braunschweig.

BOCK, E. SAND, W. KIRSTEN, K. RAMMELSBERG, J.

Untersuchung zur Beständigkeit von Zementmörtelauskleidungen duktiler Gußrohre gegenüber biogener Schwefelsäure-Korrosion. [Investigation into the Resistance of Cement Mortar Linings of Ductile Cast Pipes against Biogenic Sulphuric Acid]. fgr Gußrohrtechnik 25, p. 23-28, 1990

DINKELACKER, A.

Kanalreinigung durch mitlaufende Kugeln hat sich im Zweijahrestest bewährt. [Sewer Cleaning Using Travelling Balls has Proved Itself in a Two-year Test] Korrespondenz Abwasser , No. 2, p. 161-165, 1987

GRÄFEN, H. et al.

Die Praxis des Korrosionsschutzes [Corrosion Protection in Practice], Kontakt Studium, Vol. 64, Expert Verlag 7031 Grafenau, p. 37-63

HANTGE, E. MAINZ

Luftschadstoffe - Vermeidungsmaßnahmen und Auswirkungen auf Boden und Wasser am Beispiel des Bundeslandes Rheinland-Pfalz [Air Pollutants - Measures of Avoidance and Effects on Soil and Water Using the Example of RheinlandPfalz]. New DELIWA-Zeitscrifft, Vol. 11, 1993

HVITVED-JACOBSEN, T. JÜTTE, B. NIELSEN, P. H. JENSEN, N. A.

Hydrogen Sulphide Control in Municipal Sewers. In: Pre treatment in Chemical Water and Wastewater Treatment, Proceedings of the 3rd Gothenburg Symposium, Springer Verlag, Berlin, Heidelberg, 1988

IMHOFF, K. IMHOFF, K. R.

Taschenbuch der Stadtentwässerung [Handbook of Municipal Drainage] 28th Edition, Verlag Oldenbourg, 1993

KEDING, M. VAN RIESEN, S. ESCH, B.

Der Zustand der öffentlichen Kanalisation in der Bundesrep ublik Deutschland - Ergebnisse der ATV-Umfrage 1990 [The Status of the Public Sewerage System in the Federal Republic of Germany - Results of the ATV Poll 1990], Korrespond enz Abwasser, 37th Year, Vol. 10, 1990

KLOPFER, H.

Wassertransport durch Diffusion in Feststoffen [Water Delivery through Diffusion in Solids] Bauverlag GmbH, Wiesbaden and Berlin, 1974

July 1998

43

ATV - M 168 E LAWA

Leitlinien zur Durchführungen von Kostenvergleichsrechnungen [Guidelines for the Carrying Out of Cost Comparison Calculations] Länderarbeitsgemeinschaft Wasser [Federal State Working Group - Water] (LAWA), 1993

LOHSE, M.

Schwefelverbindungen in Abwasserableitungsanlagen unter besonderer Berücksichtigung der biogenen Schwefelsäurekorrosion [Sulphur Compounds in Wastewater Discharge Systems Paying Particular Attention to Biogenic Sulphuric Acid Corrosion], Publication of the Institute for Environmental Engineering, University of Hannover, Vol. 62, 1986

LOHSE, M.

Der anoxische Druckleitungsbetrieb [Anoxic Pressure Pipeline Operation]. Korrespondenz Abwasser, No. 6, p. 631-637, 1987

MATTHES, W.

Schadenshäufigkeitsverteilung bei TV-untersuchten Abwasserkanälen [Distribution of the Frequency of Damage with Sewers Investigated Using TV] Korrespondenz Abwasser No. 39, Vol. 3, p. 363-367, 1992

POMEROY, R. D.

The Problem of Hydrogen Sulphide in Sewers. Clay Pipe Development Association, 1976

SAND, W.

Die Bedeutung der reduzierten Schwefelsäureverbindungen Schwefelwasserstoff, Thiosulfat und Methylmercaptan für die biogene Schwefelsäure-Korrosion durch Thiobacillen [The Significance of the Sulphuric Acid Compounds Hydrogen Sulphide, Thiosulphate and Methymercaptane for Bogenic Sulphuric Acid Corrosion through Thiobacilli]. Wasser und Boden 5, p. 237241, 1987

SGK

Richtlinien zum Korrosionsschutz in Abwasseranlagen C6d, Korrosionskommission der Schweizerischen Gesellschaft für Korrosionsschutz (SGK) [Directive for Corrosion Protection in Wastewater Systems C6d, Corrosion Commission of the Swiss Association for Corrosion Protection], Technopark, Pfingstweid Straße 30, CH-8005, Zürich, 1994

STEIN, D. KAUFMANN, O.

Schadenanalyse an Abwasserkanälen aus Beton- und Steinzeugrohren der Bundesrepublik Deutschlandwest [Damage Analysis on Sewers Made from Concrete and Vitrified Clay Pipes In the Federal Republic of GermanyWest]. Korrespondenz Abwasser No. 40, Vol. 2, p. 168179, 1993

STRASSBURGER, F. W.

Schweißen nichtrostender Stähle [Welding of Stainless Steels] Deutscher Verlag für Schweißtechnik, Düsseldorf, 1976

July 1998

44

ATV - M 168 E THISTLETHWAYTE, D. K. B.

The Control of Sulphides in Sewerage Systems. Butterworths, Sydney, Melbourne, Brisbane, 1972

TÖDT, F.

Korrosion und Korrosionsschutz [Corrosion and Corrosion Protection]. Walter de Gruyter, Berlin, 1961

US EPA

Design Manual. Odor and Corrosion Control in Sanitary Sewerage Systems and Treatment Plants. US Environmental Protection Agency, 1985

WALTHER, W.

Boden- und Gewässerbelastung in Niedersachsen durch Stoffeinträge aus der Atmosphäre [Loading of Soil and Bodies of Water in Niedersachsen Due to the Input of Substances from the Atmosphere]. Wasser & Boden, Vol. 1, 1994

7

Applicable Standard Specifications

[Translator's note: known translations are given in English only. Where there is no known translation into English a courtesy translation of the title is given in square brackets, after the original German titles].

BS 915

Specifications for High Alumina Cement (British Standard Institution), Part 2, 1972

DAfStb Directive

Richtlinie für Schutz-und Instandsetzung von Betonbauteilen [Directive for Protection and Repair of Concrete Components] 1990

DIN EN 196

Methods of Testing Cement, Parts 1 - 9

DIN EN E-197

Cement; Composition, Parts 1-2, 04/98

DIN EN 295

Vitrified Clay Pipes and Fittings and Pipe Joints for Drains and Sewers, 11/91 Requirements, Part 1, 11/96 Methods of Testing, Part 3, 11/91

DIN EN 476

General Requirements on Components for Gravity Drainage Systems, 08/97

DIN EN 496

Plastics Piping Systems; Dimensions, 08/91

DIN EN 512

Fibre Cement Pressure Pipes and Joints, 11/94

DIN EN 578

Plastics Piping Systems; Plastic Pipes and Fittings; Determination of the Opacity, 09/93

DIN EN 579

Plastics Piping Systems; Crosslinked Polyethylene (PE-X) Pipes; Determination of Degree of Crosslinking by Solvent Extraction, 09/93 July 1998

45

ATV - M 168 E DIN EN 580

Plastics Piping Systems; Polyvinyl Chloride (PVC-U); Test Method for the Resistance to Dichloromethane at a Specified temperature (DCMT)

DIN EN 588

Fibre Cement Pipes for Drains and Sewers - Part 1: Pipes Joints and Fittings for Gravity Systems, 11/96

DIN EN 598

Ductile Iron Pipes, Fittings, Accessories and their Joints in Sewerage Applications - Requirements and Test Methods, 11/94

DIN EN 637

Plastics Piping Systems; Components Made from Glass Fibre Reinforced Plastics, 08/94

DIN EN 681-1

Materials Requirements for Elastomeric Pipe Joint Seals Used in Water and Drainage Applications - Vulcanised Rubber, 06/96

DIN EN 698

Plastic Piping and Protective Piping Systems - Thermoplatsics, 10/95

DIN EN 705

Glass Reinforced Thermosetting Plastics (GRP) Pipes and Fittings - Methods for Regression Analyses and their Use, 08/94

DIN EN 727

Thermoplastic Pipes and Fittings - Determination of Vicat Softening temperature (VST), 01/95

DIN EN 728

Plastic Piping and Ducting Systems- Polyofelin Pipes and Fittings - Determination of Oxidation Induction Time, 03/97

DIN EN 752

Drain and Sewer Systems outside Buildings Generalities and Definitions, Part 1, 01/96 Requirements, Part 2, 09/96 Planning, Part 3, 09/96

DIN EN 761

Glass Reinforced Thermosetting Plastics (GRP) Pipes - Determination of the Creep Factor under Dry Conditions, 08/94

DIN EN 762

Plastics Piping Systems, 11/92

DIN EN 763

Injection Moulded Thermo Plastics Pipe Fittings - Test Method for Visually Assessing Effects of Heat, 09/94

DIN EN 773

General Requirements on Components for Hydraulically Driven Wastewater Pressure Pipes, 10/92

DIN EN 845

Festlegung für Hilfsbauteile Für Mauerwerk [Definition of Accesories for Brickwork], Parts 1 - 3, 12/92

DIN 846

Prüfverfahren für Hilfsbauteile für Mauerwerk [Test methods for Accessories for Brickwork], Parts 1 - 10, 12/92

July 1998

46

ATV - M 168 E DIN 1045

Structural Use of Concrete; Design and Construction, 07/88

DIN 1053, Pt 1

Mauerwerk - Berechnung + Ausführung [Masonry - Calculations + Implementation], 11/96

DIN 1053, Pt 2

Mauerwerk - nach Eignungsprüfung [Masonry - Following Qualification], 11/96

DIN 1053, Pt 3

Reinforced Masonry; Design and Construction, 02/90

DIN 1053, Pt 4

Masonry; Buildings of Prefabricated Brickwork Components, 09/78

DIN 1164, Pt 1

Cement - Composition and Requirements, 10/94

DIN 2614

Cement Mortar Linings for Ductile Iron and Steel Pipes and Fittings; Application, Requirements and Testing, 02/90

DIN 4030, Pt 1

Assessment of Soil, Water and Gases for their Aggressiveness to Concrete; Principles and Limiting Values, 06/91

DIN 4030, Pt 2

Assessment of Soil, Water and Gases for their Aggressiveness to Concrete; Collection and Examination of Water and Soil samples, 06/91

DIN 4032

Concrete Pipes and Fittings; Dimensions, Technical Conditions of Delivery, 01/81

DIN 4034, Pt 1

Precast Reinforced and Unreinforced Concrete Components for Manholes over Buried Drains and Sewers; Dimensions and Technical Delivery Conditions, 09/93

DIN 4035

Stahlbetonrohre, Stahlbetondruckrohre und zugehörige Formstücke [Reinforced Concrete Pipes, Reinforced Concrete Pressure Pipes and Associated Fittings], 08/95

DIN 4051

Sewer Clinkers; Requirements, Testing, Control, 08/76 Examples, 07/65

DIN 4060

Elastomer Seals for Pipe Joints in Drains and Sewers; Requirements and Testing, 12/88

DIN 4062

Cold Processable Plastic Jointing Materials for Sewerdrains; Jointing Materials for Prefabricated Parts of Concrete; Requirements, Testing and Processing, 09/78

DIN 4281

Concrete for Drainage Units; Manufacture, Requirements and Testing, 03/85

DIN 8061

Unplasticised Polyvinyl Chloride Pipes - General Quality Requirements and Testing, 08/94

July 1998

47

ATV - M 168 E DIN 8062

Unplasticised Polyvinyl Chloride (PVC-U, PVC-Hl) Pipes - Dimensions, 11/88

DIN 8063, Pts 1 - 12

Pipe Joints and Pipe Fittings for Unplasticised Polyvinyl Chloride (Rigid PVC)

DIN 8074

High Density Polyethylene (HDPE) Pipes; Dimensions, 09/87

DIN 8075 (Draft)

High Density Polyethylene (HDPE) Pipes; General Quality Requirements, Testing, 08/97

DIN 8077

Rohre aus Polypropylen, Maße [Polypropylene Pipes, Dimensions],12/97

DIN 8078

Rohre aus Polypropylen Typ I + II, Allgemeine Anforderungen [Polypropylene Pipes Type I + II, General Requirements], 04/96

DIN 16 961, Pt 1

Thermoplastics Pipes and Fittings with Profiled Outer and Smooth Inner Surfaces, Dimensions, 02/89

DIN 16 961, Pt 2

Thermoplastics Pipes and Fittings with Profiled Outer and Smooth Inner Surfaces, Technical Delivery Conditions, 02/89

DIN 19 962, Pts 1 - 13

Pipe Joint Assemblies and Fittings for Polypropylene (PP) Pressure Pipes (Pts 1,3,6-8,11,12, 08/80; Pt 2, 02/83; Pt 4, 11/88; Pt 5, 05/94; Pt 9, 06/83; Pt 10, 10/89; Pt 13, 06/87)

DIN 16 965

Wound Glass Fibre Reinforced Polyester Resin (UP-GF) Pipes: Pt 1: Type A, 07/82 Pt 2: Type B, 07/82 Pt 4: Type D, 07/82 Pt 5: Type E, 07/82

DIN 16 968

Rohre aus Polybuten; Güteanforderungen [Polybutene Pipes; Quality Requirements], 12/96

DIN 16 969

Rohre aus Polybuten; Maße [Polybutene Pipes; Dimensions], 12/97

DIN 19 537, Pt 1

High Density Polyethylene (HDPE) Pipes and Fittings for Drains and Sewers; Dimensions, 10/83

DIN 19 537, Pt 2

High Density Polyethylene (HDPE) Pipes and Fittings for Drains and Sewers; Technical Delivery Conditions, 01/88

DIN 19 537, Pt 3

Prefabricated High Density Polyethylene (HDPE) Manholes for Use in Sewerage Systems; Dimensions and technical Delivery Conditions, 11/90

DIN 19 565, Pt 1

Centrifugally Cast and Filled Polyester Resin Glass Fibre Reinforced Plastic (UP-GF) Pipes and Fitting for Buried Drains and Sewers; Dimensions and Technical Delivery Conditions, 03/89

July 1998

48

ATV - M 168 E DIN 19 565, Pt 5

Prefabricated Glass Reinforced Plastic (UP-GF) Manholes for Use in Sewerage Systems; Dimensions and Technical Delivery Conditions, 11/90

DIN 19 850, Pt 1

Faserzementrohre und -Formstücke für Abwasserkanäle; Maße für Rohren, Abzweigen und Bogen [Fibre Cement Pipes and Fittings; Dimensions for Pipes, Branches and Bends], 11/96

DIN 19 850, Pt 2

Faserzementrohre und -Formstücke für Abwasserkanäle; Verbindungen, Maße [Fibre Cement Pipes and Fittings; Joints, Dimensions], 11/96

DIN 30 672, Pt 1

Corrosion Protection Wrapping Tape and Heat Shrinkable Material for Pipes Designed for Service Temperatures up to 50° C, 09/91

DIN 30 675, Pt 1

External Corrosion Protection for Buried Pipes; Corrosion Protection Systems for Steel Pipes, 09/92

DIN 30 675, Pt 2

External Corrosion Protection for Buried Pipes; Corrosion Protection Systems for Ductile Iron Pipes, 04/93

DIN 38 405, Pt 26

German Standard Methods for the Examination of Water, Wastewater and Sludge; Anions (Group D); Determination of Dissolved Sulphide by Spectrometry (D 26), 04/89

DIN 50 919

Korrosion der Metalle, Korrosionsuntersuchungen bei Kontaktkorrosion in Elektrolytlösungen [Corrosion of Metals, Corrosion Investigations with Contact Corrosion in Electrolyte Solutions], 02/84

DIN 50 929, Pt 3

Corrosion of Metals; Probability of Corrosion of Metallic Materials when Subject to Corrosion from the Outside ; Buried and Underwater Pipelines and Structural Components, 09/85

DIN 50 930, Pt 4

Korrosion metallischer Werkstoffe bei innerer Korrosionsbelastung durch Wässer, Beurteilung der Korrosionswahrscheinlichkeit nichtrostender Stähle [Corrosion of Metallic Materials with Inner Corrosion Loading through Water, Assessment of the Probability of Corrosion of Stainless Steels], 02/93

DIN 53 521

Determination of the Behaviour of Rubber and Elastomers when Exposed to Fluids and Vapours, 11/87

DIN 61 855, Pt 1

Textile Glass; Glass Roving for Plastics Reinforcements; Woven Glass Filament Fabric and Woven Roving; Types, 04/87

DVS 2205, Pt 1 [German Association for Welding Technology]

Berechnung von Behältern und Apparaten aus Thermoplasten, Kennwerte [Calculation of Containers and Apparatus Made from Thermoplastics, Parameters, 06/87

July 1998

49

ATV - M 168 E GKR*) R 7.1.12

Rohre und Formstücke aus PVC-U (weichmacherfreies Polyvinylchlorid) mit gerippter Außenoberfläche und glatter Innenfläche mit Steckmuffen für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [Nonplasticised Polyvinyl Chloride (PVC-U) Pipes and Fittings with Ribbed Outer Surfaces and Smooth Inner Surfaces with Spigot and Socket for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.1.13

Bauteile aus PVC-Hl Typ I (Polyvinylchlorid schlagzäh) mit profilierte Wandung und glatter Innenfläche - zur Auskleidung von Abwasserrohren - mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [PVC-Hl (Polyvinyl Chloride - Impact Resistant) Type I Components with profiled Walls and Smooth Inner Surfaces - for the Lining of Wastewater Pipes - with Spigot and Socket for Sewers and Drains

GKR*) R 7.1.15

Coextrudierte, kerngeschäumte Rohre und Formstücke aus modifiziertem PVC-U mit Steckmuffe für Abwasserkanäle und leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [PVC-U Co-extruded, Foam-filled Pipes and Fittings with Spigot and Socket for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.1.16

Vortriebsrohre und aus Rohren hergestellte Formstücke aus PVC-U mit Steck Verbindungen ohne äußere erhabene Konturen für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [PVC-U Driven Pipes and Fittings Made from Pipes without Outer Raised Profiles for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.1.19

Rohre mit profilierter Wandung und glatter Innenoberfläche aus weichmacherfreie, Polyvinylchlorid (PVC-U) mit Steckmuffe für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [PVC-U Pipes with Profiled Walls and Smoother Inner Surfaces for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.1.23

Nichtbegebare Schachtunterteile und Regenrohrsandfänge aus PVC-U für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [Non-man Accessible Lower Shaft Components and Stormwater Pipe Grit Chambers for Sewers and Drains Made from PVC-U with the Quality Mark of the Quality Association for Plastic Pipes]

_________________ *)

GKR = Gütegemeinschaft Kunststoffrohre = Quality Association for Plastic Pipes

July 1998

50

ATV - M 168 E GKR*) R 7.4.20

Nichtbesteigbare Schachtunterteile aus PP Typ 3 (Polypropylen Copolymerisat) für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [Non-mansized Shaft Lower Components Made from PP Type 3 (Polypropylene Mixed polymer) for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.6.8

Nichtbesteigbare Schachtunterteile aus PE-M (Polyethylen mittlerer Dichte) für Abwasserkanäle und -leitungen mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [Non-man-sized Shaft Lower Components Made from PE-M (Medium Density Polyethylene) for Sewers and Drains with the Quality Mark of the Quality Association for Plastic Pipes]

GKR*) R 7.8.24

Kanalrohre und Formstücke aus UP-GF, gewickelt, mit dem Gütezeichen der Gütegemeinschaft Kunststoffrohre [Wound UP-GF Wastewater Pipes and Fittings with Quality Mark of the Quality Association for Plastic Pipes]

pr EN 1124

Pipes and Fittings of Longitudinally Welded Stainless Steel Pipes with Spigot and Socket for Wastewater Systems, 12/93

_________________ *)

GKR = Gütegemeinschaft Kunststoffrohre = Quality Association for Plastic Pipes

July 1998

51