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Keywords:

  • Sustainable water management;
  • Life cycle assessment;
  • Life cycle costing;
  • Streamlined sustainability assessment tool;
  • Multicriteria analysis

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

Water supply is a key consideration in sustainable urban planning. Ideally, detailed quantitative sustainability assessments are undertaken during the planning stage to inform the decision-making process. In reality, however, the significant time and cost associated with undertaking such detailed environmental and economic assessments is often cited as a barrier to wider implementation of these key decision support tools, particularly for decisions made at the local or regional government level. In an attempt to overcome this barrier of complexity, 4 water service providers in Melbourne, Australia, funded the development of a publicly available streamlined Environmental Sustainability Assessment Tool, which is aimed at a wide range of decision makers to assist them in broadening the type and number of water servicing options that can be considered for greenfield or backlog developments. The Environmental Sustainability Assessment Tool consists of a simple user interface and draws on life cycle inventory data to allow for rapid estimation of the environmental and economic performance of different water servicing scenarios. Scenario options can then be further prioritized by means of an interactive multicriteria analysis. The intent of this article is to identify the key issues to be considered in a streamlined sustainability assessment tool for the urban water industry, and to demonstrate the feasibility of generating accurate life cycle assessments and life cycle costings, using such a tool. We use a real-life case study example consisting of 3 separate scenarios for a planned urban development to show that this kind of tool can emulate life cycle assessments and life cycle costings outcomes obtained through more detailed studies. This simplified approach is aimed at supporting “sustainability thinking” early in the decision-making process, thereby encouraging more sustainable water and sewerage infrastructure solutions. Integr Environ Assess Manag 2012;8:183–193. © 2011 SETAC


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

There is an increasing recognition of the need to improve the sustainability of our cities. In particular, there is ongoing interest from both industry and government bodies in meeting specific water service provision objectives at minimal environmental and economic cost. Water is often at the forefront of urban sustainability considerations, because it frequently constitutes a large fraction of all material flows through urban systems (Decker et al. 2000). Urban water service provision is most commonly achieved by centralized mechanisms, involving large-scale water and wastewater treatment facilities and distribution networks. Population pressure continues to increase the production of wastes and the demand for water, whereas climate change has the potential to further reduce water availability from conventional sources (Cohen 2006). As a result, innovative and diverse approaches to urban water supply, such as blackwater recycling, graywater reuse, rainwater tanks, stormwater harvesting, dual pipe systems, and desalination, have received increased attention.

Sustainability assessment tools such as life cycle assessment (LCA), life cycle costing (LCC), and multicriteria analysis (MCA) allow for more holistic assessments of infrastructure alternatives, allowing decision makers to consider both the economic and environmental consequences associated with a given water service delivery strategy. Because of their holistic and comprehensive scope, these techniques are also recognized as being both time- and resource-intensive and require a high degree of expert knowledge. Unfortunately, these factors are often cited as a barrier for the more widespread application of approaches such as LCA in the industry and policy-making sectors (Bala et al. 2010). Consequently, there has been significant recent interest across a number of industrial sectors in the development of so-called “streamlined” approaches and tools to reduce the burden of these more detailed assessment processes.

The water sector has been at the forefront of the development and application of LCA, with some of the first reported LCA studies in this area conducted prior to the publication of the original ISO 14040 Standard in 1997 (e.g., Emmerson et al. 1995; Roeleveld et al. 1997). Australia has played a significant role in these developments (Peters 2009) and an extensive body of literature is now available on LCA studies in the area of water cycle management, both in Australia and internationally (Friedrich et al. 2007). The most comprehensive of this work was performed by Lundie et al. (2004) and covered the total operations of Australia's largest water utility (Sydney Water), including bulk water supplies, water filtration plants, reticulation, and wastewater treatment. Another detailed study by Friedrich et al. (2009) included both water supply and wastewater treatment services for a South African municipality. Other studies have addressed specific aspects of either wastewater systems (Emmerson et al. 1995; Tillman et al. 1998; Lundin et al. 2000; Beavis and Lundie 2002; Lim and Park 2009; Pasqualin et al. 2009), different biosolids management options (Dennison et al. 1998; Peters and Lundie 2001; Peters and Rowley 2009), or potable water supply systems (Crettaz et al. 1999; Friedrich 2002; Tangsubkul et al. 2005; Landu and Brent 2006). Additional studies investigating both environmental and economic impacts of different aspects of the urban water cycle also exist (Nogueira et al. 2007; Høibye et al. 2008; Lim et al. 2008; Sharma et al. 2009). All of the aforementioned research has been carried out using the traditional and more detailed methodologies, and published reports detailing the application of “streamlined” sustainability assessment tools in the water industry are rare (Friedrich et al. 2007).

Simplified or “streamlined” sustainability assessment tools have the capacity to provide similar results to more detailed assessment approaches but at lower cost and with reduced requirements for operator time and expertise (Hochschorner and Finnveden 2003; Bala et al. 2010). This is particularly relevant in the context of industry and policy-making sectors, where decisions with potentially large environmental and economic consequences are often made with limited time and financial resources, and where the decision-making process often cannot wait for the results of full LCAs (Bala et al. 2010). In the context of the urban water sector, the development and application of a streamlined Environmental Sustainability Assessment Tool (ESAT) would enable assessment of the relative sustainability of alternative water and sewage servicing (infrastructure) options and, therefore, would better position industry decision makers to ultimately select the most environmentally and economically sustainable approach.

This article demonstrates the feasibility of creating such a tool. ESAT was developed by researchers at the University of New South Wales, Australia, in partnership with the Smart Water Fund and can be downloaded from the Smart Water homepage (Schulz and Peters 2008b). ESAT enables quantitative LCA and LCC to be carried out in a user-friendly Microsoft Excel® environment. Locally, water service providers have indicated a desire to be able to quantify financial and environmental performance indicators and then contrast and prioritize decision options by means of an MCA. ESAT facilitates this by allowing the user to measure 1 economic and 5 environmental performance indicators, with a built-in MCA utility that provides a mechanism for weighting and combining the results from the individual performance indicators. Our model is intended to support and encourage “sustainability” or “life cycle thinking,” as described by Elshof (2009), by identifying and measuring key variables to inform and promote sustainable decision making in the area of water and sewerage infrastructure provision and asset management. In this article, some of the capabilities of ESAT are demonstrated through a case study assessment of the environmental and economic sustainability of 3 different water servicing options for Kalkallo, a greenfield development area northwest of Melbourne, Australia. The robustness of results generated by the simplified ESAT tool was then assessed by comparing these results with those of a detailed LCA and LCC study undertaken by an independent group of researchers during 2005 and 2006.

METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

Here, we describe the general principles for the construction of a simplified tool for sustainability assessment of water systems in any city, with Melbourne used as an example. The key to accelerating the application of “life cycle thinking” in water service provision is to simplify the creation of complex life cycle inventories (LCIs) for alternative servicing options. Achieving this requires a balance to be struck between the future extent of software tool application (i.e., tool universality) and the need for a simple user interface. The dialogue in which we engaged water industry representatives taught us that a simplified tool should make a range of information available that is broader in scope than what water engineers are likely to encounter during a “normal” week, without attempting to match the level of comprehensiveness (data input types, modeling methods, or environmental performance indicators) offered by commercial LCA and LCC software packages such as GaBi (PE International 2011) or SimaPro (PRe Consultants 2008). In the following sections, the main types of information and adjustable design features needed in such a simplified tool are described. For more detail on the features, input variables required, relevant LCI data, and modeling principles of ESAT, please refer to the online manual (Schulz and Peters 2008a).

End-use water balance

An end-use water balance is an essential first step in the planning of any water infrastructure. To accurately estimate the levels of water demand and wastewater generation for a particular development, the user should be able to specify the number of households and/or buildings in the development, the number of people per household and/or building, an additional water demand for nonhousehold use (i.e., municipal irrigation or industrial and/or commercial use) and the expected level of efficiency of various household appliances (e.g., washing machines, shower heads, and so forth). ESAT assumes an initial individual water demand of 207 L/person/d (L/p/d), which represents the consolidated average daily residential water consumption for Melbourne (Wilkenfeld and Associates 2003; WSAA 2006; WELS 2008). At present, the user can select the location of the proposed urban development from 5 subregions of Greater Melbourne. This function draws on a 30-y daily time-step historical rainfall record for each subregion to enable spatially relevant estimations of rainwater and stormwater runoff to be made. Prior research has shown that rainfall records of this length and interval are appropriate for facilitating accurate simulations of future rainfall (Mitchell et al. 2008). For further details on the assumptions incorporated into ESAT regarding the end-use water balance, rainwater, and stormwater modeling calculations, the reader is again referred to the online ESAT manual (Schulz and Peters 2008a).

Reticulation options

Three different sewage reticulation systems may be of interest in a simplified tool: conventional gravity systems, low pressure sewage systems, and vacuum systems. Naturally, the topography and scale of urban developments directly influences their associated environmental impacts and cost. As a consequence, the inclusion of additional input fields allows the user to perform detailed modeling of different parts of the reticulation system, including the selection of different piping materials, diameters, and lengths; the number of installed pumping stations combined with rising mains and gravity mains; and the incorporation of maintenance holes. Within the reticulation modeling component of ESAT, particular attention was given to the pumping energy calculations, because earlier work had shown that the environmental impacts associated with pumping energy requirements are significant in situations where there is a heavy reliance on coal-fired electricity generation, such as in Australia (Lundie et al. 2005). ESAT calculates the energy requirements for pumping wastewater through the rising mains, based on the approach of Coulson and Richardson (1985). It is also possible to model the connection to an existing sewer network and to enter the respective energy consumption involved. Again, further details on reticulation assumption and pumping energy calculations can be found in the online ESAT manual (Schulz and Peters 2008a).

Wastewater treatment options

Many different treatment technologies might be considered in a simplified sustainability assessment tool, some of which are more relevant at particular geographic scales. We think the analyst also needs the option of including industrial or commercial wastewater inputs into the normal domestic wastewater stream. This option may be appropriate if the planned development includes some commercial facilities that produce wastewater, or if nearby existing businesses want to connect to the wastewater treatment system of the proposed development. ESAT allows the user some degree of flexibility in terms of how wastewater is treated. A household-scale graywater treatment system and 8 different household- and neighborhood-scale blackwater treatment systems with different treatment technology configurations may be selected. The respective LCI data was obtained directly from manufacturers or from the relevant literature; for details, see Schulz and Peters (2008a). The environmental and economic performance of these systems can be compared to that of a conventional centralized sewage treatment plant (STP) if desired. ESAT also is capable of modeling the reuse of treated wastewater in the event there is a demand for recycled water within the development. If treatment at a conventional STP is required, the location of the development determines whether the sewerage goes to Melbourne's Eastern or Western treatment plants (Melbourne Water 2006a, 2006b), both of which have different operating conditions.

Water supply options

Six common water supply options are noteworthy among the urban water LCA studies mentioned earlier in this article: surface water, groundwater, seawater desalination, rainwater tanks, stormwater, and recycled water supplies. In addition to these water supply choices, questions of scale may play a role and necessitate the software user's detailed definition, for example, the choice of rainwater tank volume. Depending on this, and given the connected roof area, the chosen rainwater end uses, and the modeled rainfall for the selected region, ESAT calculates the relative contribution to the household water balance made by rainwater yield. Further details on LCI data and rainwater modeling assumptions can be found in Schulz and Peters (2008a).

In ESAT, stormwater may be treated by 2 different treatment options: a rain garden or a surface wetland. The main focus is on the nutrient removal capabilities of both systems. The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) software (eWater 2005) was used to estimate treatment performance in terms of the key water quality parameters of interest (total suspended solids, total N, and total P) and the capital and operating expenditures for different sizes of both stormwater treatment systems. In addition, a stormwater reuse option is available based on the collection of stormwater runoff from impervious surfaces around the house. Recycled water for nonpotable purposes can be made available to households by connecting to a water recycling plant via a centralized “3rd pipe” option (also called “dual reticulation scheme”) or from local supplies sourced from some of the decentralised wastewater treatment options. A range of end-uses for the recycled water or stormwater can then be selected. Further details on the assumptions underlying water recycling in ESAT are available elsewhere (Schulz and Peters 2008a).

Cost analysis

The industrial partners of the Smart Water Fund wanted any simplified tool to include an evaluation of cost in a manner that reflects widespread industry practice. ESAT takes into consideration capital expenditure, energy cost–related operating expenditure, and other operating expenditure (e.g., maintenance, chemicals, and so forth) for all water servicing infrastructure items and calculates a LCC expressed as the net present value (NPV) as described in Equation 1:

  • equation image(1)

where C0 = initial investment, N = total time of the project (assumed as 50 y), t = time of the cash flow, Ct = net cash flow, and r = adjusted discount rate (Huppes et al. 2004).

Life cycle impact indicators

The selection of indicators will necessarily reflect the needs of the urban water industry and the preferences of environmental managers in water companies that wish to benefit from using such simplified tools. Following dialogue with industry, we selected a suite of regional and global performance indicators for incorporation into ESAT (Table 1). These impact indicators are common among many detailed LCA studies, both within and outside the water field. In ESAT, the results of these indicator calculations are displayed alongside the environmental impacts resulting from the household water balance as well as the detailed impacts associated with the LCI data such as electricity and materials associated with the scenarios chosen. For the calculation of impact indicator results, the most appropriate available cradle-to-gate LCI data sets were used (e.g., greenhouse gas [GHG] emissions for 1 kWh of electricity produced in Victoria). For further details on the presentation of results in ESAT, please refer to the online ESAT manual (Schulz and Peters 2008a).

Table 1. Description of the environmental life cycle impact indicators used during this study
Impact categoriesUnitsDescription
  1. ESAT = Environmental Sustainability Assessment Tool; GHG = greenhouse gas; IPCC = Intergovernmental Panel on Climate Change.

Primary energy useMJGross calorific value of all fossil energy use associated with the production of materials, generation of electricity, and consumption of transport fuels.
GHG emissionst CO2-eq

Accounts for all GHG emissions linked to the manufacture of water infrastructure, the provision of operating materials, including electricity generation and emissions from transport. The IPCC (2007)

equivalence factors were applied.
Water useML H2O

Reflects both the water used during material production or electricity generation as well as the remaining potable water demand. For the first component of the water use, the characterization method EDIP 97 has been used (Wenzel et al. 1997)

.
Eutrophication potentialkg PO4-eq

The impact indicator called “Nutrients” in ESAT refers to eutrophication potential and describes the nutrient discharge in connection with the full life cycle of the water servicing options included in ESAT. This impact indicator is based on CML (2001)

methodology.
Physical footprintHa

Describes the land area physically occupied by infrastructure necessary for the chosen water service scenario. It follows a simple land use approach as described by Heijungs et al. (1997)

and is not to be confused with the “ecological footprint.”

ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

Kalkallo is a planned greenfield development area for 86 000 people located north of Craigieburn, approximately 30 km northwest of the city center of Melbourne, Australia. The development will convert a total area of 3062 ha of predominantly agricultural land into residential, industrial, commercial, and community areas. A detailed LCA and LCC comparing different water and sewerage servicing options for the area has already been undertaken by another research group during 2005 and 2006 (Grant and Opray 2005; Sharma et al. 2005; Sharma et al. 2006).

In order to critically assess the accuracy of our streamlined tool, 3 of the scenarios described in the detailed LCA and LCC study are analyzed and compared with the results obtained from ESAT. In the first 2 scenarios, labeled “1A UDM” and “1A WPDM” in the original detailed studies, potable water and sewerage services are provided by conventional means. The only difference between these 2 scenarios is the water demand management assumptions. The usual demand management (UDM) scenario refers to water end-use figures corresponding to a lower standard of water-saving appliances than the so-called “white paper” demand management (WPDM) scenario (DSE 2004), both of which have been calculated using Yarra Valley Water data and the Australian/New Zealand Standard for Water Efficient Products (AS/NZS 2003). Hence, WPDM assumes a reduction in the usual residential water demand from approximately 223 L/p/d (in the UDM scenario) to approximately 188 L/p/d, or a 15.6% reduction (Sharma et al. 2005). In the 3rd scenario, “1B.1 WPDM,” the wastewater from residential, commercial, industrial, and community sectors is treated at a local STP and returned to the development via a 3rd pipe system for reuse in toilets and outdoor areas across all sectors. For ease of interpretation, these 3 original scenarios “1A UDM,” “1A WPDM,” and “1B.1 WPDM” are hereafter relabeled scenarios A, B, and C, respectively, in our analysis. An overview of these 3 scenarios is given in Table 2.

Table 2. Description of the investigated water servicing scenario options for the proposed Kalkallo developmenta
ScenariosbWater supplyWater useSewerage system
  • a

    Scenario configurations adopted from detailed LCA study of Grant and Opray (2005) and Sharma et al. (2005).

  • b

    Scenario labels provided alongside original scenario names from the detailed LCA and LCC study (given in parentheses).

Scenario A (1A UDM)Reticulated, centralized bulk water supply systemUsual demand management (UDM)Reticulated, centralized treatment at Werribee STP
Scenario B (1A WPDM)Reticulated, centralized bulk water supply systemReduced water demand by using White Paper demand management (WPDM)Reticulated, centralized treatment at Werribee STP
Scenario C (1B.1 WPDM)Reticulated, centralized bulk water supply systemReduced water demand by using White Paper demand management (WPDM)Decentralized treatment plant at Kalkallo
 Treated wastewater via 3rd pipeRecycled water for toilets and outdoor areas 

Comparative LCA goal and scope

The goal of this comparative LCA is to evaluate different water and sewerage servicing options for the Kalkallo development using ESAT and to verify the accuracy of these results by comparison with parallel results from a detailed LCA and LCC of the same options. The functional unit was defined as the supply of potable water and water sewerage services to the Kalkallo development for 1 y. The system boundary encompassed all processes from the source of potable water to the treatment of wastewater and wastewater reuse. For these processes, environmental burdens associated with different materials and energy use were included in both the detailed LCA and in ESAT. The environmental and economic LCI data was taken from the respective detailed LCA report (Grant and Opray 2005; Sharma et al. 2005) and LCC report (Sharma et al. 2006). The GHG emissions, water use, eutrophication potential, and LCC are common indicators to both the detailed LCA/LCC and ESAT, and were therefore considered to be an appropriate basis for comparing the 2 approaches.

Life cycle inventory data

Household and/or building water balance

The residential area consists of 28 695 lots with 3 people living in each lot; both of these input variables can be set in ESAT. ESAT assumes a default city-wide average water demand of 207 L/p/d, based on Greater Melbourne average data (WSAA 2006). In order to match the assumed 223 L/p/d for the Kalkallo development scenario A and the 196 L/p/d for scenarios B and C, plus an assumed leakage rate of 4% (Sharma et al. 2005), appropriate water-saving appliances were selected in ESAT. The potable water demand and wastewater generation rates of the commercial, industrial, and community areas were taken from the detailed LCA report and were entered into ESAT as an additional “nonhousehold water demand” (scenario A: 7133 ML/y; scenarios B and C: 5756 ML/y). In the same way, the amount of wastewater produced in these 3 sectors is captured in ESAT as an “industrial/commercial wastewater input” (scenario A: 6206 ML/y; scenarios B and C: 4893 ML/y). The average annual rainfall in the proposed Kalkallo development area is 601 mm. This value is close to the default value of the “central development region” as defined in ESAT, which is based on the Melbourne Regional Office rainfall station records of a median yearly average of 610 mm.

Potable water supply

In all scenarios, it is assumed that the potable water supply comes from a reservoir and undergoes water filtration. The electricity demand for potable water treatment and potable reticulation was estimated to be 0.28 kWh/kL and 415 kWh/ML, respectively, based on the work of Grant and Opray (2005). These values were used as default values in ESAT.

Decentralized wastewater treatment

Scenario C would require the construction of a local STP at the Kalkallo development site. Because the development was in the early planning phase and no detailed infrastructure plans were available at the time of study, the detailed LCA based its assumptions regarding a local wastewater treatment facility on the existing Whittlesea STP and up-scaled the infrastructure to suit the service requirements for the planned Kalkallo development. The Kalkallo STP would be approximately 20 times larger than the Whittlesea STP. The modeling approach taken in ESAT was based on connecting Kalkallo to a centralized STP (scenario A and B) but also to provide recycled water via a water recycling plant (scenario C). Considering the large volume of wastewater produced in Kalkallo and the comparatively small volumetric capacity (300 kL/d) of the most suitable neighborhood-scale decentralized wastewater treatment system incorporated in ESAT, this approach was considered to be most realistic. The wastewater and recycled water treatment processes are modeled from generic technology descriptions and process performance data; for further details, please refer to Grant and Opray (2005) and Schulz and Peters (2008a). Regarding the electricity consumption for wastewater and reclaimed wastewater treatment, values of 0.73 and 0.95 kWh/kL, respectively, were entered into ESAT, based on the assumptions of the previous detailed LCA report (Grant and Opray 2005).

Reticulation

The detailed LCA and LCC reports list LCI data for more than 20 different pipe diameters and their respective lengths, materials, and total construction cost per meter for all reticulation requirements for all scenarios (Sharma et al. 2005; Sharma et al. 2006). Because ESAT is designed for use at a reduced level of data complexity, several simplifying assumptions had to be made to allow the more detailed data to be compressed for inclusion in the ESAT platform. To estimate the total pipe material requirements, a length-weighted average cross-sectional area of the detailed reticulation data was calculated to determine an equivalent average pipe diameter and then multiplied by the total length of the reticulation network. Because ESAT only caters for 2 different pipe materials—unplasticized polyvinyl chloride (uPVC) and ductile iron cement-lined (DICL) pipes—the pipe materials listed in the detailed LCA report had to be associated with these 2 pipe material categories. To achieve this, all polyethylene, uPVC, and glass-reinforced plastic pipes were treated as uPVC pipes, and all DICL, mild steel cement-lined, and vitrified clay pipes were treated as DICL pipes. Although the physical properties and attributes of some pipe materials are not readily interchangeable with the default uPVC and DICL materials (e.g., glass-reinforced plastic and vitrified clay pipes), the lengths of these materials were relatively insignificant in terms of the total reticulation network, and the overall consequences of this assumed substitution on the results were considered negligible.

The detailed LCA report assumes an identical electricity demand for supplying 1 ML of potable water to Kalkallo in all modeled scenarios. According to Yarra Valley Water energy maps, the electricity demand for potable water reticulation is 415 kWh/ML (Grant and Opray 2005). The electricity demand for the reticulated sewer network of 451 kWh/ML was based on the values of Grant and Opray (2005) and was used in ESAT. Because the physical location of a proposed “local and/or decentralized” Kalkallo STP (scenario C) would not be expected to be significantly different to that of a “centralized” STP (scenarios A and B), it was considered appropriate to adopt the same value for sewerage reticulation electricity demand. In addition to sewerage energy considerations, the electricity demand for supplying recycled water in scenario C also needed to be considered. Because no specific data was available, it was assumed that the source of recycled water supply was similar in both distance and elevation to the potable water supply. The relevant energy requirements for pumping wastewater and recycled water are calculated in ESAT by means of an incorporated formula (Coulson and Richardson 1985; Schulz and Peters 2008a).

To estimate the total construction cost of different pipe connections, the cost data for the various pipe materials and diameters was drawn from the detailed LCC report and used to calculate a total construction cost function in ESAT. In contrast to the pipe material calculations, a length-weighted average diameter was calculated for both uPVC-type and DICL-type pipes and combined with the calculated cost function in ESAT.

Additional modeling parameters

For most water treatment facilities, energy consumption dominates overall environmental performance, particularly when GHG emissions are considered. Therefore, it is necessary to enter specific energy consumption data for all water servicing options when applying ESAT to real-life scenarios. In order to increase the flexibility of ESAT to be able to handle as many different circumstances as possible, the user has the option of entering defined energy consumption values for their particular treatment processes. In the detailed LCA study, the water balance model “Aquacycle” (Mitchell 2005) was used to calculate the water balance outcomes for the different scenarios. One assumption in Aquacycle is that there is no stormwater inflow or infiltration into the wastewater reticulation system; consequently, the relevant input variable in ESAT is set to a default 0%. It should be noted, however, that adjustment of inflow and infiltration parameters is a feature of ESAT such that users can easily choose to set inflow and infiltration variables according to site-specific preferences.

The detailed LCA did not include any estimates of material reprocessing or recycling. ESAT, however, has the capacity to take into account that some materials (i.e., steel and polyethylene) are recycled and reprocessed to produce new materials. From an environmental perspective, reprocessing of these materials represents a material and/or energy saving or an environmental credit. For the purposes of this case study, the recycling rates were set to 0% to reflect the input variables of the comparative detailed LCA. If available, life spans used for different infrastructure items in the detailed LCA were matched accordingly in ESAT. ESAT also accounts for environmental burdens in relation to transport distances for various materials, i.e., truck and ship transport for materials and preinstalled systems. In the detailed LCA, only transport burdens associated with pipe installation were considered.

Biosolids, a byproduct of wastewater treatment, can be applied during agriculture as a substitute for conventional nitrogenous and phosphorous fertilizers. Results from a recent study of various biosolids management systems suggest that for each dry kilogram of biosolids applied to fields, 0.011 kg of N-fertilizer and 0.037 kg of P-fertilizer can be avoided (Peters and Rowley 2009). Once again, ESAT has the capacity to incorporate this environmental credit based on biosolids production for each scenario, whereas the detailed LCA did not include any information on biosolids management. To ensure consistency for the purposes of this validation study, biosolids management aspects were also omitted from the comparative assessment in ESAT.

In both the detailed LCC and ESAT, relevant cost data included capital expenditure for water supply reservoirs and all reticulation infrastructure, as well as wastewater treatment and recycling facilities, operating expenditure separated by annual maintenance costs for different infrastructure items, and electricity costs for water and wastewater treatment and pumping. For further information on detailed cost data, references, and further assumptions, please refer to the ESAT manual and the detailed LCC report (Sharma et al. 2006; Schulz and Peters 2008a). Because reticulation is often a large proportion of the LCC of a water supply network and because pipe cost data may vary significantly, the LCC component of ESAT allows the user to enter specific construction cost functions for uPVC and DICL pipes. For the LCC modeling, ESAT assumes an adjusted annual discount rate of 6.5% and an electricity cost of A$0.16/kWh, based on the prior assumptions of the detailed LCC study (Sharma et al. 2006). An analysis period of 50 y was chosen for LCC modeling in ESAT, and it was assumed that both the remaining useful life of all components and the salvage value of any infrastructure after the analysis period were zero. These assumptions reflected those made for the LCC component of Sharma et al. (2006).

RESULTS AND DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

Overall, results from the comparative assessment of ESAT outputs versus those from more detailed prior LCA and LCC research for the same development site (Grant and Opray 2005; Sharma et al. 2005; Sharma et al. 2006) showed a striking similarity for many indicator categories across the LCA and LCC components. The water balance results for the Kalkallo development are shown in Tables 3 and 4, with an overall summary of the absolute results provided in Table 5. A breakdown of these results for each investigated scenario and across each of the chosen life cycle impact indicators is presented in Figures 1 to 4, with scenario results shown relative to the “base case” scenario A.

Table 3. Scenario A water balance for the Kalkallo development area comparing values from the detailed LCA study (Grant and Opray 2005; Sharma et al. 2005) with ESAT-derived values
 UnitsSectorTotal
ResidentialCommercialIndustrialCommunity
  • a

    Slight discrepancy in total water demand due to an inexact match of residential water demand values stemming from small differences in assumed efficiency ratings for water-saving appliances.

  • b

    Discrepancy relates to differing assumptions surrounding residential wastewater generation, i.e., proportion of residential water demand used for irrigation assumed in ESAT (24.6%) was different to that assumed in the detailed LCA study (30.9%).

    ESAT = Environmental Sustainability Assessment Tool; LCA = life cycle assessment.

Number of lots 28 695454475 
Potable demand(detailed LCA)L/lot/d67085 89032 42584 658 
ML/y73061468550416114 439
Potable demand(ESAT)ML/y72971468550416114 430
Discrepancy potable demand%0.10000.1a
Wastewater produced(detailed LCA)ML/y52141322474014411 420
Wastewater produced(ESAT)ML/y56971322474014411 903
Discrepancy wastewater%−9.3000−4.2b
Table 4. Scenarios B and C water balance for the Kalkallo development area comparing values from the detailed LCA study (Grant and Opray 2005, Sharma et al. 2005) with ESAT-derived values
 UnitsSectorTotal
ResidentialCommercialIndustrialCommunity
  • a

    Slight discrepancy in total water demand due to an inexact match of residential water demand values stemming from small differences in assumed efficiency ratings for water-saving appliances

  • b

    Discrepancy relates to differing assumptions surrounding residential wastewater generation, i.e., proportion of residential water demand used for irrigation assumed in ESAT (24.6%) was different to that assumed in the detailed LCA study (30.9%).

    ESAT = Environmental Sustainability Assessment Tool; LCA = life cycle assessment.

Number of lots 28 695454475 
Potable demand(detailed LCA)ML/y3499100136801108290
Reclaimed water use(detailed LCA)ML/y2432161713183324
Total water demand (potable plus reclaimed)(detailed LCA)L/lot/d56568 88626 28167 898 
 ML/y59311162439312811 614
Total water demand(ESAT)ML/y61441162439312811 827
Discrepancy: total water demand%−3.6000−1.8a
Wastewater(detailed LCA)ML/y4113104237371149006
Wastewater(ESAT)ML/y4544104237371149437
Discrepancy: wastewater%−10.5000−4.8b
Table 5. Summary of absolute ESAT results versus those of the detailed LCA study (Grant and Opray 2005; Sharma et al. 2005; Sharma et al. 2006) for the proposed Kalkallo development water servicing scenariosa
IndicatorUnitScenario AScenario BScenario C
ESATdetailed LCAESATdetailed LCAESATDetailed LCA
  • a

    ESAT = Environmental Sustainability Assessment Tool; GHG = greenhouse gas; LCA = life cycle assessment; LCC = life cycle costing.

GHGt CO2-eq25 08626 29020 29321 52022 37621 560
Water useML14 53914 00011 91611 58086018084
Eutrophication potentialkg PO4-eq403 50896 570323 71481 050277 17360 790
LCCNPV ($M)518526485509604601
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Figure 1. Comparative greenhouse gas (GHG) emissions for the 3 Kalkallo development water servicing scenarios shown as a percentage of scenario A values. Data calculated by ESAT (dark gray bars) provided alongside original data of the detailed LCA study (light gray bars) (Grant and Opray 2005; Sharma et al. 2005).

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Figure 2. Comparative water use for the 3 Kalkallo development water servicing scenarios shown as a percentage of scenario A values. Data calculated by ESAT (dark gray bars) provided alongside data of the detailed LCA study (light gray bars) (Grant and Opray 2005; Sharma et al. 2005).

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Figure 3. Comparative eutrophication potential for the 3 Kalkallo development water servicing scenarios shown as a percentage of scenario A values. Data calculated by ESAT (dark gray bars) provided alongside data of the detailed LCA study (light gray bars) (Grant and Opray 2005; Sharma et al. 2005).

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Figure 4. Comparative life cycle cost of the 3 Kalkallo development water servicing scenarios shown as a percentage of scenario A values. Data calculated by ESAT (dark gray bars) provided alongside data of the detailed LCA study (light gray bars) (Grant and Opray 2005; Sharma et al. 2005).

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With both the streamlined and the detailed approaches to LCA and across all life cycle impact indicators, the reduced water demand of scenario B was responsible for a superior environmental performance compared to the base case scenario A (Figure 2). Scenario C scored better again than scenario B with regard to water use (Figure 2) and eutrophication potential (Figure 3); however, slightly higher GHG emissions (Figure 1) resulted from the higher electricity requirement for treating wastewater to a level suitable for reuse (0.95 kWh/kL) relative to electricity required to produce potable water from a dam (0.28 kWh/kL).

Results from the LCC assessment are presented as both absolute (Table 5) and relative cost (Figure 4). From a purely economic standpoint, scenario B was the most preferable option followed by scenario A. Scenario C was shown to have the highest LCC mainly due to the additional reticulation infrastructure requirements of the 3rd pipe reuse system. Notably, the capital expenditure required for installation of the reticulation network made the biggest single contribution to the total LCC in all scenarios, and this trend was reflected in both the outputs of ESAT and also the detailed LCC study.

After comparison of the relative environmental and economic performance for each life cycle impact indicator across all investigated scenarios, Figures 1 to 4 demonstrate that the 2 modeling approaches are able to produce consistent outputs for the purposes of strategic environmental analysis, in that the relative environmental and economic performance metrics differed by less than 10%, with the greatest difference being 7.2% for scenario C GHG emissions.

Although relative differences between measured performance indicators for ESAT and the detailed LCA and LCC study were small, there were some more notable differences in terms of the absolute magnitude of these indicators. In the case of eutrophication potential, for example, the absolute values calculated by ESAT were, on average, approximately 4 times higher than those from the detailed LCA report (Table 5). The basis for such a large discrepancy in this instance was attributed to the different primary reference sources having been used for water quality metrics (i.e., biochemical oxygen demand, total N, and total P [TP]) in different kinds of water. The main source of the apparent difference was found to be the much lower TP concentration assumed for treated wastewater and recycled water in the detailed LCA study. Whereas the detailed LCA assumed a TP concentration of 0.5 mg/L for both types of water, ESAT assumed TP levels that were orders of magnitude higher, at 8.8 mg/L and 4 mg/L for treated wastewater and recycled water, respectively. Because the reference sources used in the detailed LCA were considered to be either outdated or poorly defined, values for ESAT were drawn from more recent (2005–2006) Melbourne Water Data (Melbourne Water 2006b), because these were considered to provide a more accurate reflection of the true eutrophication potential.

With regard to the outcomes of the comparative economic assessment, ESAT was shown to calculate slightly lower absolute LCCs for scenarios A and B and a slightly higher LCC for scenario C, although the relative magnitude difference between outputs from ESAT and the detailed LCC study was less than 5% across all scenarios. Reasons for these discrepancies were thought to be related to a combination of the relatively simple total pipe construction cost calculation in ESAT, different data assumptions having been made for annual maintenance costs of water servicing options, and the use of different data sources for the capital expenditure component of the water supply and treatment infrastructure.

The capital expenditure associated with reticulation infrastructure dominates the LCC for each of the chosen water servicing scenarios for the Kalkallo development, yet the vast majority of the environmental burdens come from the operation and maintenance phase. For example, ESAT results for scenario A show that this phase accounts for 97.4% of the total environmental burden in GHG emissions and 96.8% and 96.7% in scenarios B and C, respectively. Within the operation and maintenance phase itself, the GHG emissions relating to electricity production and consumption (e.g., from pumping and/or treating water) account for 92% of the total emissions in the scenarios without water recycling and 93% in scenario C. This shows that pumping and treatment energy requirements predominate in terms of the environmental impact of urban water service provision, and this observation reflects the findings of prior research (e.g., Lundie et al. 2005).

Calculated GHG emissions relating to the production of water servicing infrastructure were slightly higher (≈4%–6%) in the results of the detailed LCA compared with those obtained using ESAT. The reasons for this small difference in results between the 2 approaches were thought to be related to the simple pipe materials estimation process, the way in which treatment plant infrastructure is accounted for, and/or the omission of other minor infrastructure works in the ESAT model. Unfortunately, lack of access to the raw LCI data of the detailed study means that no further insights as to the sources of this variation can be provided. ESAT also provides the user with an analysis of the GHG emissions resulting from transport activities; however, the contribution of transport to all 3 investigated scenarios was negligible (<0.2%). The GHG credits that can be realized from avoided fertilizer use due to biosolids application were equally minor, at approximately 0.2% of the total figure. Figure 5 shows the contribution of each of the different life cycle phases to the total GHG emissions for each of the 3 Kalkallo development scenarios.

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Figure 5. Relative process contributions to total greenhouse gas emissions for the 3 Kalkallo development water servicing scenarios (solid bar area shows “transport” contribution; transparent bar area shows “manufacturing and infrastructure” contribution; light gray bar area depicts contribution from “operation and maintenance”). Data calculated by ESAT provided alongside original data of the detailed LCA study (det. LCA) (Grant and Opray 2005; Sharma et al. 2005).

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It should be noted that because the main goal of this article was to compare the accuracy of results obtained through ESAT with those from detailed LCA and LCC studies, no sensitivity analysis was performed. If the main goal had been to compare the environmental and economic impacts of different water servicing scenarios for the Kalkallo development by using ESAT, then a sensitivity analysis that tested different assumptions about infrastructure items, their operation, or climatic conditions would obviously have been an essential element. Compared with the utility of detailed LCA and LCC investigations, we believe that ESAT offers enhanced opportunities for scenario testing, because alternative scenarios, including their respective LCI data, are already inbuilt and hence would be readily available for such investigations.

CONCLUSIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

In this article, we outlined the key adjustable input parameters and performance indicator results we believe are necessary for a simplified sustainability assessment tool suitable for use in the urban water industry. With regard to the 3 scenarios assessed in the case study, it has been demonstrated that analyses performed with a streamlined sustainability tool such as ESAT can produce results consistent with those from more detailed LCA and LCC studies. Relative differences between the results of ESAT and the full LCA and LCC study were considered small enough that they would be unlikely to change the outcomes of a robust MCA, such that both approaches would ultimately be expected to yield a similar decision outcome. Considering the significant time and resource investments necessary to undertake detailed LCA and LCC studies, ESAT can effectively serve as a rapid and easy alternative for informing sustainable decision-making processes. Admittedly, only 3 scenarios served as the test case for comparing ESAT outputs against those of more detailed LCA and LCC studies; however, because of the striking similarity of results shown in the present example across all indicators and modeled scenarios, it can be expected that ESAT would also deliver a robust basis for decision making in other similar case studies.

Validation of the ESAT tool by use of data from a real-life urban development revealed possible areas for future improvement of such simplified tools. For example, it may be beneficial to further disaggregate the results from the impact indicators, such that GHG emissions from different types of electricity use could be presented separately to allow for more specific life cycle impact interpretation. The LCC component could also be split to show NPV from capital expenditure versus operational expenditure relating to bulk energy use or energy use from maintenance work. The discrepancy in the results of the eutrophication potential indicator between the 2 LCA approaches also suggests that further data entry requirements may be required; in particular, nutrient removal performance data for specific water and wastewater treatment processes would improve the utility of such tools.

Despite these suggested improvements, one of the specific goals during the development of ESAT was to strike a balance between specificity and generality and also between complexity and simplicity. Modifications such as additional data input requirements and extra analytical capacity, although they may enhance the accuracy of ESAT outputs, could also compromise the tool's user-friendliness and ease in which results can be obtained and interpreted by decision makers. The application of ESAT to a real-life scenario here has also shown that creative ways of using ESAT can be applied by the user to best represent specific scenarios (e.g., 2 separate scenarios were used to model scenario C in ESAT). Because ESAT was designed primarily for residential developments, the reuse options for recycled water are limited when it comes to commercial or industrial recycled water reuse. In order to account for the proposed recycled water demand, the residential reuse for toilet flushing was modeled first in 1 scenario and then the remaining recycled water demand for outdoor use and toilet use in the other 3 sectors was accounted for in a separate scenario. Following this, the results from both disaggregated scenarios were combined to yield the total scenario C output. This capacity for a “tiered” modeling approach in ESAT may be considered advantageous in certain situations.

Another potential limitation of ESAT at present is the restriction of its geographical scope. Although ESAT's scope is currently limited to the Greater Melbourne area, we emphasize that the tool could easily be expanded to consider other geographical regions in Australia or, indeed, the world. The 2 main adaptations necessary to achieve this would involve obtaining and importing the respective local rainfall records and remodeling the stormwater treatment scenarios on the basis of the new rainfall data. The updating of transport distances and cost data (if appropriate) would be expected to require only minor additional effort. Also, the default option of using 1 of the 2 major Melbourne STPs could easily be expanded to consider other locations and treatment plants. Furthermore, the market for decentralized water and wastewater treatment systems is developing rapidly, which may lead to the requirement of updating LCI data for this component of ESAT as well. The fact that ESAT has been developed using the commonly available Microsoft Excel® software platform should make the implementation of these updates comparatively straightforward.

Simplified sustainability assessment tools such as ESAT will be most useful in early phases of infrastructure planning, when detailed information is not yet available and rough guidance about the environmental and economic consequences of certain water servicing options is required. This initial screening assessment can probably be achieved by a tool such as ESAT for a cost that is an order of magnitude or lower relative to that of a full LCA and LCC. In addition to the likely cost benefits, an added benefit is avoidance of potentially lengthy time delays in acquiring detailed results from specialist LCA and LCC analysts. Future development and enhancement of ESAT could involve adding additional climate data to allow for application of the tool to other cities and towns while allowing for the incorporation of changes to local rainfall forecasts based on regional climate change impacts. In addition, and as a detailed process modeling tool, it may be worthwhile combining ESAT with one of the input/output–based modeling tools to populate the lower production orders and generate hybrid process and input/output LCA results for a more thorough environmental assessment.

Acknowledgements

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES

We acknowledge the Smart Water Fund for providing financial support as well as for supplying relevant data and reports.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. ESAT VALIDATION: A CASE STUDY OF 3 SCENARIOS
  6. RESULTS AND DISCUSSION
  7. CONCLUSIONS
  8. Acknowledgements
  9. REFERENCES
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