Page 112 - Materials Chemistry, Second Edition

Will the well run dry? Developments in water resource planning and impact assessment

Table 8.1 Main components and mass requirements of 600 and 2250 litre water tank assemblies 99
(Hallmann et al. 2003).
Material 600 L 2250 L
Tank body Coloured LLDPE powder 35 kg 55 kg
Brass overflow Copper (prim) 0.2 kg 0.2 kg
protection
Brass outlet Copper (prim) 0.35 kg 0.5 kg
Inlet strainer LLDPE AU 0.35 kg 0.5 kg
Coloured LLDPE LLDPE AU and pigment 35 kg 55 kg
powder 35 kg 55 kg
Pigment TiO 0.35 kg 0.55 kg
2
AU, Australian; LLDPE, linear low-density polyethylene; TiO , titanium oxide.
2

rather than to assist in creating one, so alternative supply or disposal systems need to have
been designed before an LCA can be undertaken to compare them. Furthermore, if two con-
trasting designs are developed as in Figure 8.4, then implications flow for the definition of the
system boundary and the functional unit, and for materials specifications.
The wide variety of materials and components necessitates an extensive range of back-
ground information. An inventory of common materials such as polyethylene, polyvinyl
chloride, ductile iron, concrete and steel needs to be created in order to calculate the infra-
structure impact of the system based on quantities identified in the design. Where good inven-
tory data already exists for materials, the bulk of the research effort is associated with estimating
design-specific quantities. For example, in Table 8.1 some component mass requirements for
two domestic water tanks are illustrated.
Energy is invariably also required to run infrastructure. Pumps are often used in water
systems and can be challenging items to inventory. Useful sources for materials used in
pumping devices can be environmental declaration statements published by manufacturers.
Figure 8.5 illustrates the major elements of a pump inventory where ‘global warming’ is the
environmental indicator.
Installation and construction aspects of systems may also be important. Many LCAs do not
include the impacts of energy and fuel used in the assembly of a mechanical plant used to
produce infrastructure elements because they are typically minor compared to the impact of
manufacturing the materials. Measurable impacts of water systems are often associated with
energy and fuel for on-site excavation to embed pipes and tanks. Estimation of excavation
impacts can be difficult and requires a detailed study of the process. A recent study of excava-
tion practice associated with water infrastructure in Melbourne used data such as pipe diam-
eters and trench widths as well as existing inventory data for transport and gravel extraction to
estimate excavation impacts for pipework installation.
In water infrastructure models, it is also important to address system durability
and lifespan, and likely disposal at end-of-life. Generally in a water LCA, a different opera-
tional ‘design’ life should be defined for each subsystem. An example of the lifetime assumed
in a suburban water servicing model is shown in Table 8.2. Unfortunately, there is no
generically applicable rule for the length of a system’s life, which depends on the unique
circumstances of the LCA being undertaken. It can be difficult to determine a new system’s
life, so a sensitivity analysis should be used to check the influence of ‘life time’ on the LCA
results and conclusions.
Having defined the infrastructure aspects of the water system, it is possible to assess the
operational impacts of the system, which for many LCAs will drive the total system impact.

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