Page 115 - Materials Chemistry, Second Edition

Life Cycle Assessment: Principles, Practice and Prospects
102

Figure 8.7 Energy map for water supply (kWh per ML) (Yarra Valley Water 2005).

usually necessary to undertake some analysis of water and contaminant balance to ensure
that influent loads are appropriate to the treatment systems being considered, and that con-
taminants are assessed throughout the water system. Having undertaken a contaminant
balance and water balance and confirmed that the treatment system of interest will likely
deliver the effluent quality required, it is still important to consider potential changes in the
influent quality.
LCA models are often constructed using fixed ‘per litre’ effluent qualities to determine
treatment system emissions, such as the fixed quantities indicated in Table 8.3. These can lead
to errors if interventions alter effluent qualities. One example would be the addition of a urine
separation system to a household wastewater stream in order to reduce nitrogen loads in the
wastewater. Clearly, in this case, an adjustment in the assumed effluent would be required in
order to model impact reductions accurately. In addition, apart from pumping energy and
operational material consumption, the major impacts of water treatment systems typically
occur under the eutrophication indicator, which shares many of the weaknesses of the water
indicator.

8.4 Discussion: water systems, design and social context
Clearly, to determine the impacts associated with infrastructure and operation requires a dis-
tinctly different approach in each case. Infrastructure impacts tend to be driven by the quantity
and type of material used in construction, whereas operational impacts tend to be associated
with energy consumption of pumps and other transport devices. Although materials are
consumed in operation, energy (electricity derived from liquid fuel) tends to dominate during
this phase. There are also other issues associated with water systems that affect overall envi-

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