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Goal definition
Goal and scope definition is the starting point of conducting any ISO-standardized LCA study. It may be define as a preliminary description about the context and layout of the study. The goal definition specifies the context of the study by defining the purpose of conducting the study and rationale behind it, intended areas of application of the results and potential audience, to whom the results of the study are intended to be communicated(ISO, 1997).
Purpose of the study
The current waterworks at Norrvatten in 2020 is unable to satisfy the future water quantity and quality requirements as per Norrvatten future predictions for 2050. So Norrvatten has developed nine future WTP process alternatives (see Table 1) that need to be analysed from an environmental perspective.
The rationale behind conducting this study is based on the fact that due to increasing urbanization, population (increase in number of connected people) and climate change (risk associated with raw water quality deterioration) the use of chemicals along with energy in drinking water production and distribution is continuously increasing. This is transforming the existing WTP from a simple small scale to a complex large scale water production unit. As a result, the role of drinking water production has become more and more prominent in the Swedish society along with its environmental impacts, turning it into a potential environmental hotspot that need to be analyzed and optimized from a life cycle perspective to minimize its potential environmental impacts. The research objectives associated with this study are given in detail in section 1.2. 3.1.2 Intended applications and potential audience of the study.
The direct application of the study is to provide Norrvatten the potential environmental impacts of their future WTP process alternatives for the year 2050 during operational phase. It is expected that the results of the study may be considered in their internal decision making process while selecting their future WTP process alternative based on a life cycle perspective. Moreover, the results are also intended to be applied in reducing Norrvatten’s future environmental impacts by identifying the potential areas of improvements. In future, the study may also be useful to develop Norrvatten’s environmental footprint model to evaluate their real time environmental impacts.
In a narrow perceptive, the direct beneficiary of the study is Norrvatten since they requested the study and govern the research questions as per their organizational needs. Along with that, Norrvatten’s member municipalities may also be interested to know the environmental impacts of their future water production units as the awareness and consensus among the Swedish people is relatively high to reduce their environmental impacts. On a broad perspective, as this is not a commercial study but a voluntary contribution of the author to conduct an LCA based research on waterworks (objective and unbiased assessment of the waterworks) with Norrvatten alternatives as a case study, so the results may also be useful to stakeholders working in the field of sustainability of Swedish drinking water sector especially including the water producers and researchers working in the field of environmental assessment of existing and future water treatment processes. These stakeholders may include the Swedish Agency for Marine and Water Management (SwAM), Svenskt Vatten (The Swedish Water and Wastewater Association), Stockholm International Water Institute (SIWI), and many more.
Type of LCA study
It is nearly impossible to answer all the research questions adequately by focusing only on a particular type of LCA, so this study consists of a combination of both stand-alone and comparative attributional LCA as given in Table 4 to access and compare the total potential environmental impacts that the proposed alternatives may cause in 2050 during their operational phase. An attributional LCA is defined by its aim to describe the environmentally relevant physical flows to and from a life cycle and its subsystems(Ekvall et al., 2016; Finnveden, 2008). It is a system modeling approach in which inputs and outputs are attributed to the functional unit of a product system by linking and/or partitioning the unit processes of the system according to a normative rule(Ekvall et al., 2016; Sonnemann and Vigon, 2011). However, the consequential LCA may also be relevant to perform for some alternatives that involve advanced and new treatment technologies such as Suspended ion exchange (SIX) process, direct precipitation on ultrafiltration membranes (dF/UF) and direct filtration of surface water on Nanofilters. These alternatives have the potential to significantly change the current tradeoff between energy and chemical use in drinking water production which may result in consequences (change in environmental burdens) that need to be considered while evaluating their impacts. For example, nanofiltration has a potential to improve the quality of water significantly relative to conventional WTP along with reducing the chemical use but may significantly increase the energy use. As the Swedish electricity mix is more renewable so this transition may reduce the overall environmental impacts of WTP, which may motivate other water producers to adopt NF based treatment technologies to improve their water quality along with reducing their environmental impacts. This may result in higher energy demand which may change the environmental burden of the energy sector. So the impacts due to increased energy demand need to be considered while evaluating the impacts of NF. However, this study only focuses on attributional part of LCA due to resource constraints but it is highly recommended to conduct a consequential LCA in future to understand the consequences of selecting an advanced water treatment process.
Description of the studied system
The scope of this study is limited to nine future WTP alternatives formulated by Norrvatten with the function to treat the raw water extracted from Lake Mälaren up to the drinking water standard satisfying the Norrvatten predicted future quality and quantity requirements of 2050. A detailed description of the treatment scheme of different alternatives is given in Appendix 2. The studied system comprises of raw water extraction, raw water treatment and pumping of treated water from storage reservoir to main distribution pipeline network along with sludge treatment. The drinking water distribution network and its subsequent processes along with other processes that are essential for the proper functioning of the WTP (employees travel, heating and energy requirements at the workplace, offices solid waste generation, etc.) but not directly related to raw water treatment within WTP are out of the scope of the study. Moreover, the operational phase is considered more specifically in this study based on the literature review as given in Appendix 3, which concluded that the construction and demolition phases of WTP have relatively insignificant environmental impacts in comparison to the operational phase.
Functional unit
The function of the studied system is to treat the raw water extracted from Lake Mälaren up to the drinking water standard satisfying the Norrvatten predicted future quality and quantity requirements of 2050. As a result the functional unit (FU) adopted in this study is the production of 1 m3 of drinking water from raw water extracted from Lake Mälaren that will be pumped into the main distribution pipeline network from the WTP storage reservoir. This also correspond to the most commonly used FU (production of 1 m3 of drinking water) in drinking water sector as per literature review given in section 2.2.2. However, this functional unit doesn’t include any quality aspect of the produced drinking water which is the major limitation as different alternatives may produce different quality of drinking water. Hence while comparing the potential environmental impacts of different future WTP alternatives, the quality of the treated water and its cost of production as given in Appendix 6 need to be considered simultaneously to understand the tradeoff such that the misunderstanding and potential abuse of the LCA results can be avoided.
Simplified flow chart
The detailed flow charts of all the alternatives have been given in Appendix 2. However, as all the alternatives have almost similar inputs and outputs (some exceptions exist) with differences only in the quantity used in different alternative, so a general simplified flow chart is given in Figure 4.
System boundaries
In general, the system boundaries specify the life cycle stages to be included, inflows and outflows to be considered, classification of the significant and insignificant processes (Cut-off criteria), specification of the geographical and temporal scope of the input-output flows of the studied system, and many more. The system boundaries associated with this study are given in the subsequent sections.
Life cycle stages
The studied system doesnot consider all the life cycle stages that the raw water extracted from a water body (Lake Mälaren) may undergo before reaching back to a water body. The entire cradle-to-grave life cycle stages may include raw water extraction, raw water treatment, pumping to main distribution pipeline network, flow through drinking water distribution network, drinking water use by the consumers (wastewater generation), wastewater collection, wastewater treatment and treated wastewater discharge to a water body. The scope of this study is limited to raw water extraction, raw water treatment and pumping of the treated water to main distribution pipeline network, so only these stages have been considered in this study.
Table of contents :
ACKNOWLEDGEMENTS
ABSTRACT
Sammanfattning
List of Tables
List of Figures
Abbreviations
1. Introduction
1.1 Introduction
1.2 Research objectives
1.3 Norrvatten future drinking water treatment alternatives
2. Literature review
2.1 Drinking Water industry Impacts on the Environment
2.2 The Environmental Life Cycle Assessment as a Holistic Sustainability Tool
2.2.1 Overview of the LCA Methodology
2.2.2 Applications of LCA in Drinking Water Sector
3. Study Methodology
3.1 Goal definition
3.1.1 Purpose of the study
3.2 Scope definition
3.2.1 Description of the studied system
3.2.2 Functional unit
3.2.3 Simplified flow chart
3.2.4 System boundaries
3.2.5 Allocation procedures
3.2.6 Scope of emissions
3.2.7 LCA software
3.2.8 Scope of Impact Assessment Analysis
3.2.9 Data and data quality requirements
3.2.10 Critical review considerations
3.2.11 Assumptions and limitations
3.2.12 Sensitivity analysis
4. Life Cycle Inventory Analysis (LCI)
4.1 Scope of the inventory data
4.2 Detailed flow charts
4.3 Classification of inventory data
4.3.1 Chemical consumption
4.3.2 Transportation
4.3.3 Energy consumption
4.3.4 Miscellaneous processes
5. LCIA Results
5.1 Scope of the impact assessment analysis
5.2 Life cycle impact assessment (LCIA) results
5.2.1 Research objective 1 results
5.2.2 Research objective 2 results
5.2.3 Research objective 3 results
5.2.4 Research objective 4 results
5.2.5 Research objective 5 results
6. LCA results and discussion
6.1 Scope of the interpretation phase
6.2 Discussion of LCA results
6.3 Improvement opportunities in future WTP
6.4 Conclusions
6.5 Recommendations
6.6 Future scope of the study
6.7 Quality assessment
6.8 LCA limitations and problems associated with Swedish drinking water sector
References
