Environmental sustainability in water supply planning – an LCA approach for the Eyre Peninsula, South Australia Gregory Peters (corresponding author) Australian Water Technologies, Sydney Water, L17, 123 Bathurst St, Sydney 2000
[email protected] Karen Rouse South Australian Water, GPO Box 1751, Adelaide SA 5001
ABSTRACT In response to the declining quality and quantity of water resources on the Eyre Peninsula, South Australian Water developed a Master Plan in consultation with key stakeholders to deliver an economical and environmentally sustainable water supply to the Eyre Peninsula in the short to medium term.
Three water supply options were considered in detail: extension of the Morgan-Whyalla pipeline to bring water from the River Murray, desalination of seawater and desalination of water from the Tod River. Extension of the pipeline would have the advantages of relatively simple infrastructure, but require water to be pumped over 700 km from its source to reach Ceduna in South Australia. Desalination technologies are promising, but they also demand large quantities of electrical energy. The Master Plan concluded that desalination of brackish water from the Tod Reservoir was the most appropriate option.
As part of a subsequent policy initiative to undertake environmental life cycle assessment (LCA) on all major capital works projects, SA Water sought the supply of LCA expertise from Australian Water Technologies. This paper discusses the alternatives considered by the LCA, the results of the analysis, and their utilisation within SA Water’s planning process.
Keywords: water supply, desalination, pipeline, LCA, options assessment 1.
INTRODUCTION
1.1
Alignment of planning and reporting indicators
The need to improve the sustainability of the water industry has invoked a variety of responses. In addition to efforts made towards the identification and solution of some of the most obvious local environmental problems, indicated by directly demonstrated negative ecological responses, effort has been made to improve corporate planning through the inclusion of regional and global environmental issues. This has fostered the development of new ways of describing the problems and the rate of progress being made towards their solution. Key developments in water industry sustainability information in the last 10 years have included:
•
development of standards for corporate environmental reporting including: o
the Global Reporting Initiative (GRI), a multi-stakeholder process and independent institution under the United Nations Environment Program whose mission is to develop and promote globally applicable Sustainability Reporting Guidelines [1];
o
The “Sustainability Metrics” of the Institution of Chemical Engineers, similar to the GRI but focussed on the characteristics of the process industries [2];
•
development of public communication tools like ecological footprint calculation (eg.: [3]);
•
improvement of predictive impact assessment models for local environmental effects, for example:
•
o
the Ausplume model for prediction of odour migration and dispersion from point sources, commonly used in environmental assessments for sewage treatment plant upgrades (eg.: [4]);
o
quantitative ecological and human risk assessment for sewage-borne chemicals discharged from sewage treatment plants (eg.: [5]); and
development of predictive impact assessment models for global and regional effects, principally life cycle assessment (LCA) and its application to strategic planning and options selection (eg.: [6] ; [7]).
These different informational developments should be understood in terms of an overall approach to sustainability. They all have a role to play in ensuring that environmental considerations are included at different stages of the planning process. Some are easier to communicate with a wide audience (eg.: ecological footprint), some are ideal for detailed assessment of local environmental effects (eg.: ecological risk assessment). LCA is a holistic approach to environmental assessment which examines the environmental burdens of a product or service from the production of raw materials, their processing, delivery, use and management of wastes. LCA has been successively applied to many industries through the 1990s, including the water and wastewater industries. Major studies by Swedish authorities (eg.: [6]; [8]) and Sydney Water [9] have examined entire water systems. Smaller studies have been performed on particular aspects of water and wastewater systems by these and many other organisations. These studies have been useful in broadening our understanding of the overall environmental performance of technology choices, helping to broaden decision-making beyond consideration of cost effectiveness. One issue faced by many organisations is the alignment of long and short-term environmental planning information. An organisation may have the long term goal of reducing its greenhouse gas impacts and decide to set a goal of reducing energy-sourced greenhouse-gas emissions by some percentage, while at the options assessment stage of business planning, only cost and feasibility of the alternatives might be considered by the relevant decision-makers. Introduction of LCA methodology as the basis for protocols for the calculation of annual environmental performance indicators at the corporate level would ensure that decisions regarding energy sources, efficiency measures, materials selection and any tradeoffs between capital works and operating costs are reflected in these corporate environmental performance indicators. At the other end of the planning process, the application of LCA methodology at the options assessment stage has the advantages of not only ensuring that environmental matters are considered, but also that the indicator used at the project level is compatible with the indicator used at the corporate level. In this way project goals can be aligned with the overall corporate goals. The need for this alignment, and the need to broaden the scope of corporate environmental reporting has been generally recognised in recent times. The leading proponents of corporate sustainability take the view that the LCA perspective of environmental performance assessment should be included in annual environmental reporting and strategic planning. In other words, the environmental impacts associated with the production of materials and energy, whether produced outside the reporting organisation or purchased by it, are included in the indicators they propose (eg.: [1]; [2]; [10]). As environmental planning and performance reporting arrangements develop, we can expect to see increasing alignment between the two processes and the protocols which support them.
1.2
Water supply in the Eyre Peninsula
SA Water is a statutory corporation which owns South Australia's water supply and wastewater treatment systems, and serves nearly 1.4 million people including those living on the Eyre Peninsula. As part of its commitment to improving its sustainability, SA Water has a policy of undertaking LCA on all major capital works projects. SA Water approached AWT Pty Ltd to assess the environmental impacts of alternative water supply augmentation options for the Eyre Peninsula. The Peninsula has some surface water but the volume available for use is highly variable and the water is often highly saline. SA Water taps into several groundwater basins, but these are reaching their ultimate capacity to supply additional water. To meet the growing demands of the Peninsula, SA Water is currently assessing options for augmenting the water supply. This LCA was performed to develop an understanding of the relative environmental performance of the alternative options. Three alternatives were examined using the LCA methodology: desalination of brackish surface water from the Tod Reservoir; desalination of seawater from the Spencer
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Gulf at Louth Bay and the extension of the Morgan-Whyalla water reticulation system, which obtains water from the Murray River. Operating some parts of these options requires significant supplies of energy and materials. In some options a large amount of building materials is initially required. In others there is an ongoing demand for replacement parts such as membrane componentry. SA Water sought an LCA perspective on these options to ensure that potential tradeoffs between material and energy consumption do not prevent holistic environmental comparison of the alternatives.
2.
APPROACH
SA Water’s objective was to compare future water supply alternatives based on delivery of 7.5 ML/d of potable water. The technology used to deliver water by each of these approaches requires the production of energy, chemicals and materials for construction and operation. The three alternatives are illustrative of a range of options.
2.1
Tod River desalination scenario
In the “Tod scenario”, water is obtained from a dam on the Tod River and desalted locally. A reverse osmosis desalination plant capable of producing 7.5 ML/d of treated water is constructed near the reservoir using a three-step membrane filtration process. The dam wall has to be upgraded to ensure its continued safe operability. A 24 km polyvinylchloride (PVC) pipeline carries the brine waste from the plant to a hypothetical discharge location in the Spencer Gulf near Red Cliff.
2.2
Louth Bay desalination scenario
Instead of using reservoir water, the desalination plant in the “Louth scenario” would obtain its raw water from a suction line in the waters of Spencer Gulf. A reverse osmosis plant producing 7.5 ML/d of treated water is built at Louth Bay. An additional raw water supply line is constructed to permit the use of Tod River water instead of seawater, however, the recurrent energy and material consumption data for this plant are based on the “worst case” – the use of seawater 100% of the time. As a consequence of the use of seawater, much higher rates of raw water demand and brine generation are experienced at this plant. Brine is discharged to the Spencer Gulf via a 9 km pipeline into deep waters in Louth Bay.
2.3
Morgan-Whyalla pipeline scenario
The option of extending the supply of Murray River water from its current terminus near Whyalla to reach the west coast of the Spencer Gulf is examined in the “Murray scenario”. The water is treated at the existing Morgan Water Filtration Plant (WFP) and pumped over the Mt Lofty Ranges to Iron Knob, northwest of Whyalla. Consumption of energy and materials by the plant are considered in this LCA. A booster pump is required to pump the water down a 450 mm diameter, 85 km extension of the pipeline system from Iron Knob to Kimba. As a consequence of the marginal capacity of the pipeline from Kimba to Smeaton, this 300 mm diameter pipeline is duplicated. These locations are shown schematically in Figure 1.
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Figure 1: Location of principle existing infrastructure in the scenarios
Legend: existing pipeline locality 100 km (approx.)
Iron Knob Kimba
Whyalla
Smeaton
Tod Reservoir Louth Bay Port Lincoln
Morgan WFP
Spen cer G ulf
Lock
Gulf o Vince f St nt
Adelaide
Great Australian Bight
2.4
Murray River
Scope
The functional unit of the study is the provision of 7.5 ML/d of treated water to the Eyre Peninsula. The functional unit was defined in this way, rather than on the basis of the water entering the plant for treatment, to take into account the different reject rates associated with desalination of brackish surface water and seawater. The cases under study are all future-oriented. They describe the provision of an additional service which would not exist unless one of the options, or a variation on them, were implemented. Consequently there is no need to consider the construction of infrastructure which already exists.
2.5
System boundaries
All major inputs and outputs from the system are examined in LCA methodology. This means drawing the system boundary wide enough to encompass the sources of raw materials in the environment, and the disposal of wastes and emissions. Figure 2 shows the principle components of the systems modelled for the three scenarios. Existing infrastructure is labelled with an asterisk. The diagram is simplified. For example, under the Morgan-Whyalla scenario, energy is used not just at Iron Knob but at several locations along the pipeline including the Number 1 pump station at Morgan, the Lincoln Gap pump station and Iron Knob. The three systems are functionally equivalent as there are no valuable byproducts from any scenario and all are designed to provide 7.5 ML/d of treated water. Consequently, there are no avoided products to take into account while comparing these scenarios.
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Figure 2 : Diagram of overall LCA system
Tod River scenario
brine waste Louth Bay customers
Tod Reservoir
product tank
desalination plant
raw water tank
Louth Bay scenario
outlet pump
brine waste
Louth Bay
customers
raw water pump
raw water tank
product tank
desalination plant
outlet pump
Morgan-Whyalla scenario customers Murray River
raw water pump*
water filtration plant*
outlet pump*
Morgan to Iron Knob pipelines*
booster pump
Iron Knob to Smeaton pipeline
* existing infrastructure
INVENTORY ANALYSIS
3.
Data were principally obtained from SA Water for the three scenarios ([11]; [12]). Datasets obtained via an Australian inventory data project ([13]; [14]) were used for system components not owned by SA Water, supplemented by data available in the GaBi 3v2 software package [15]. Manufacturers’ data was used to develop the inventory for pipelines ([16]; [17]) and filtration equipment ([18]; [19]; [20]; [21]; [22]). Additional data support was found in [7] and [23]. The inventory data is summarised in the Appendix to this report. Several key assumptions and approaches were used in developing the inventory: •
The useable lifespans of plant and equipment were based on standard assumptions used by Sydney Water [24]. Pipelines and buildings are assumed to last 100 years, concrete tanks last 150 years and reservoirs have life spans of 200 years.
•
It was assumed that there are no significant leaks in the trunk water delivery system. In practice, overall leakage rates of greater than 10% are common in the water industry. This includes leaks within the local reticulation system and the trunk mains. If a leakage rate per kilometre is applied to the scenarios under study, they would have the effect of reducing the performance of the Morgan scenario. Nevertheless, as the trunk main in this case is to be laid above ground, facilitating easy checking and maintenance, the assumption is considered valid.
•
Hazardous waste from membrane cleaning was assumed to never be returned to the environment. This mixture of sodium hypochlorite, sodium hydroxide and citric acid solutions did not constitute a significant material flow (
