Page 226 - Handbook of Materials Failure Analysis

222 CHAPTER 9 Reliability and failure analysis of wastewater systems

In the case of wastewater disposal networks, it can be seen that stoneware pipe-
lines appear to be the dominant solution (about 50% of the network length) in the
period 1992-95. However, PVC conduits have been implemented more and more
often since 1996. At present, almost 90% of newly constructed wastewater disposal
networks are assembled of such conduits.
The present state of the construction materials results from a considerable hetero-
geneity of solutions implemented in cities, towns, villages, and different regions.
There are places, where water supply or wastewater disposal networks are made
of only one or two types of materials. On the other hand, in some towns, especially
bigger cities, these networks were and still are made of practically all available mate-
rials. It can be concluded that the use of these construction materials result from dif-
ferent preferences of different water supply and wastewater disposal enterprises at
the moment of selecting material solutions (Figure 9.5). The preferences are often-
times related to local conditions and habits of network operators that most probably
result from their experience gathered up to now in the domain of system operation.
They are less related to analyses of reliability or failure frequency, based on analyses
of actual incidents.
The presented materials used in water supply and wastewater disposal networks
reflect world-wide tendencies in the technology of production or application of these

40 36.9
34.7
35 27.3 24.9
Pipe length (%) 25 12.7 15.1 12.1 23.9
30
20
15
10
5 3.3 0.4 0.3 1.2 0.9 1.1 0.7 0.5
0
Gray cast iron Nodular cast iron Asbestos cement other: GRP, reinforced concrete Stoneware Reinforced concrete Other: PP, steel
Steel PVC PE Concrete PVC PE Cast iron GRP Brick

Water supply network Wastewater dysposal network
Material
FIGURE 9.5
Materials utilized in water supply and wastewater disposal networks in 2008.