Integrating groundwater stress in life-cycle assessments - An evaluation of water abstraction.

Understanding groundwater abstraction effects is vital for holistic impact assessments in areas depending on groundwater resources. The objective of our study was to modify the state-of-the-art AWaRe (available water remaining), freshwater impact assessment specifically for use in LCAs in areas dependent on groundwater resources. The new method, called "AGWaRe" (available groundwater remaining), reflects groundwater availability, based on a fraction of available groundwater remaining locally relative to a reference. Furthermore, our method increases spatial resolution beyond 1770 km2 grid cells and adjusts demarcations in order to improve the representation of the heterogeneity of groundwater catchments. The applicability of AGWaRe was demonstrated on three groundwater systems producing 5 million m3 water for the city of Copenhagen, namely Advanced Treatment of Groundwater, Simple Treatment of Groundwater and Infiltration of Reclaimed water. Results were normalised to compare with other effects of supplying water to an average Danish person. The normalised impacts for drinking water for one person ranged between 0.1 and 39 PE (person equivalent) for the three systems, which indicates that effects on groundwater resources differ substantially between systems. A comparative LCA of these groundwater systems shows that other impact categories range between 0 and 1 PE/person. Advanced Treatment of Groundwater generally has the lowest effect, for example <50% of the other groundwater systems in Global Warming Potential. The AGWaRe results indicate that freshwater impacts from Simple Treatment of Groundwater are up to 100 times greater than for Infiltration of Reclaimed water. Furthermore, AGWaRe exposes differences between the groundwater systems that AWaRe cannot evaluate, because one AWaRe cell covers two of the systems in question. These improvements are crucial for groundwater managers looking to include sustainability considerations in their analysis and decision-making.

Selection of spatial scale for assessing impacts of groundwater-based water supply on freshwater resources.

Indicators of the impact on freshwater resources are becoming increasingly important in the evaluation of urban water systems. To reveal the importance of spatial resolution, we investigated how the choice of catchment scale influenced the freshwater impact assessment. Two different indicators were used in this study: the Withdrawal-To-Availability ratio (WTA) and the Water Stress Index (WSI). Results were calculated for three groundwater based Danish urban water supplies (Esbjerg, Aarhus, and Copenhagen). The assessment was carried out at three spatial levels: (1) the groundwater body level, (2) the river basin level, and (3) the regional level. The assessments showed that Copenhagen's water supply had the highest impact on the freshwater resource per cubic meter of water abstracted, with a WSI of 1.75 at Level 1. The WSI values were 1.64 for Aarhus's and 0.81 for Esbjerg's water supply. Spatial resolution was identified as a major factor determining the outcome of the impact assessment. For the three case studies, WTA and WSI were 27%-583% higher at Level 1 than impacts calculated for the regional scale. The results highlight that freshwater impact assessments based on regional data, rather than sub-river basin data, may dramatically underestimate the actual impact on the water resource. Furthermore, this study discusses the strengths and shortcomings of the applied indicator approaches. A sensitivity analysis demonstrates that although WSI has the highest environmental relevance, it also has the highest uncertainty, as it requires estimations of non-measurable environmental water requirements. Hence, the development of a methodology to obtain more site-specific and relevant estimations of environmental water requirements should be prioritized. Finally, the demarcation of the groundwater resource in aquifers remains a challenge for establishing a consistent method for benchmarking freshwater impacts caused by groundwater abstraction.

Life cycle assessment of central softening of very hard drinking water.

Many consumers prefer softened water due to convenience issues such as avoidance of removing limescale deposits from household appliances and surfaces, and to reduce consumption of cleaning agents and laundry detergents leading to lower household expenses. Even though central softening of drinking water entailed an increased use of energy, sand and chemicals at the waterworks, the distributed and softened drinking water supported a decrease in consumption of energy and chemical agents in the households along with a prolonged service life of household appliances which heat water. This study used Life Cycle Assessment (LCA) to quantify the environmental impacts of central softening of drinking water considering both the negative effects at the waterworks and the positive effects imposed by the changed water quality in the households. The LCA modeling considered central softening of drinking water from the initial hardness of the region of study (Copenhagen, Denmark) which is 362 mg/L as CaCO(3) to a final hardness as CaCO(3) of 254 (a softening depth of 108) mg/L or 145 (a softening depth of 217) mg/L. Our study showed that the consumer preference can be met together with reducing the impact on the environment and the resource consumption. Environmental impacts decreased by up to 3 mPET (milli Personal Equivalent Targeted) and the break-even point from where central softening becomes environmentally beneficial was reached at a softening depth of only 22 mg/L as CaCO(3). Both energy-related and chemically related environmental impacts were reduced as well as the consumption of resources. Based on scarcity criteria, nickel was identified as the most problematic non-renewable resource in the system, and savings of up to 8 mPR (milli Person Reserve) were found.

Life cycle assessment of three water systems in Copenhagen--a management tool of the future.

Environmental life-cycle assessment (LCA) was applied to evaluate three different water systems of the water sector in Copenhagen, Denmark, including technologies within water supply, facilities recycling water and treatment of sewer overflow. In these three water systems LCA was used to evaluate the environmental impacts of each of the processes involved. The overall conclusion was that LCA is suitable as a decision support tool in the water sector as it provides a holistic evaluation platform of the considered alternatives categorised in environmental impact categories. The use of LCA in the water sector of this region has limitations since it does not yet consider impact categories assessing freshwater scarcity and ecological sustainability.

Understanding the impacts of groundwater abstraction through long-term trends in water quality.

It is vital to understand long-term trends in water quality parameters when assessing the sustainability of groundwater abstraction. Withdrawal-to-availability analysis is still used widely in groundwater management considering quantities and utilization rates based on in- and outflows. In this study, we took a step further than the water balance approach and carried out a detailed investigation of trends in long-term time series of groundwater quality, in order to analyze the sustainability of groundwater abstraction. We assessed trends, links, and patterns in abstraction, potentiometric surface, and water quality parameters for 28 well fields around Copenhagen, Denmark. Groundwater monitoring data from 1900 until 2014 were investigated for each well field. During this period, the well fields experienced a 2-14 m decrease in the nearby potentiometric surface compared to the first-or pre-pumping-potentiometric surface recordings. Sulfate concentrations increased in 25 out of 27 well fields after the maximum abstraction period, compared to the earliest water quality measurements. The results indicate that in the 1980s, when water consumption (abstraction) and drawdown were at their highest, water abstraction caused a steady increase in sulfate and calcium, which we consider unsustainable. In contradiction, the abstraction in 24 well fields show almost steady sulfate levels in the aquifer after decreased water consumption since 1995. Only four well fields showed more than a 20 mg/L increase in sulfate concentration, which indicates that the recent abstraction does not interfere with sulfate levels in the aquifer. Our method and results show how long-term water quality trends can support the management of aquifer exploitation and evaluate sustainability on the well field scale.

ASTA - A method for multi-criteria evaluation of water supply technologies to Assess the most SusTainable Alternative for Copenhagen.

Utilities in larger cities have to make complex decisions planning future investments in urban water infrastructure. Changes are driven by physical water stress or political targets for environmental water flows e.g. through the implementation of the European water framework directive. To include these environmental, economic and social sustainability dimensions we introduce a novel multi-criteria assessment method for evaluation of water supply technologies. The method is presented and demonstrated for four alternatives for water supply based on groundwater, rain- & stormwater or seawater developed for augmenting Copenhagen's current groundwater based water supply. To identify the most sustainable technology, we applied rank order distribution weights to a multi-criteria decision analysis to combine the impact assessments of environment, economy and society. The three dimensions were assessed using 1) life-cycle assessment, 2) cost calculations taking operation and maintenance into account and 3) the multi-criteria decision analysis method Analytical hierarchy process. Specialists conducted the life-cycle assessment and cost calculations and the multi-criteria decision analyses were based on a stakeholder workshop gathering stakeholders relevant for the specific case. The workshop reached consensus on three sets of ranked criteria. Each set represented stakeholder perspectives with first priority given to one of the three sustainability dimensions or categories. The workshop reached consensus and when the highest weight was assigned to the environmental dimension of sustainability then the alternative of 'Rain- & stormwater harvesting' was the most sustainable water supply technology; when the highest weight was assigned to the economy or society dimensions then an alternative with 'Groundwater abstraction extended with compensating actions' was considered the most sustainable water supply technology. Across all three sets of ranked weights, the establishment of new well fields is considered the least sustainable alternative.

Holistic assessment of a secondary water supply for a new development in Copenhagen, Denmark.

Increasing stress on water resources is driving urban water utilities to establish new concepts for water supply. This paper presents the consequences of proposed alternative water supply options using a unique combination of quantitative and qualitative methods from different research fields. A former industrial harbor area in Copenhagen, Denmark, is currently under development and all infrastructure will be updated to accommodate 40,000 inhabitants and 40,000 jobs in the future. To reduce stress on water resources it has been proposed to establish a secondary water supply in the area as an alternative to the conventional groundwater-based drinking water supply. Four alternative concepts for a secondary water supply have been considered: 1) slightly polluted groundwater for use in toilets and laundry, 2) desalinated brackish water for use in toilets, laundry, and dishwashers, 3) desalinated brackish water for all uses, including drinking water, and 4) local reclamation of rain and gray water for use in toilets and laundry. The concepts have been evaluated for their technical feasibility, economy, health risks, and public acceptance, while the concepts' environmental sustainability has been assessed using lifecycle assessment and freshwater use impact methods. The holistic assessment method exposes conflicting preference solutions depending on assessment criteria, and reveals multi-faceted consequences for choices in urban water management. Not one concept turns out unambiguously positive based on the evaluation criteria included here, but the systematic evaluation will leave decision-makers informed on the consequences of their choices.

Life-cycle and freshwater withdrawal impact assessment of water supply technologies.

Four alternative cases for water supply were environmentally evaluated and compared based on the standard environmental impact categories from the life-cycle assessment (LCA) methodology extended with a freshwater withdrawal category (FWI). The cases were designed for Copenhagen, a part of Denmark with high population density and relatively low available water resources. FWI was applied at local groundwater catchments based on data from the national implementation of the EU Water Framework Directive. The base case of the study was the current practice of groundwater abstraction from well fields situated near Copenhagen. The 4 cases studied were: Rain & stormwater harvesting from several blocks in the city; Today's groundwater abstraction with compensating actions applied in the affected freshwater environments to ensure sufficient water flow in water courses; Establishment of well fields further away from the city; And seawater desalination. The standard LCA showed that the Rain & stormwater harvesting case had the lowest overall environmental impact (81.9 µPET/m(3)) followed by the cases relying on groundwater abstraction (123.5-137.8 µPET/m(3)), and that desalination had a relatively small but still important increase in environmental impact (204.8 µPET/m(3)). Rain & stormwater harvesting and desalination had a markedly lower environmental impact compared to the base case, due to the reduced water hardness leading to e.g. a decrease in electricity consumption in households. For a relevant comparison, it is therefore essential to include the effects of water hardness when comparing the environmental impacts of water systems of different hardness. This study also emphasizes the necessity of including freshwater withdrawal respecting the relevant affected geographical scale, i.e. by focusing the assessment on the local groundwater catchments rather than on the regional catchments. Our work shows that freshwater withdrawal methods previously used on a regional level can also be applied to local groundwater catchments and integrated into the standard LCA as an impact category. When standard LCA is extended to include impacts of freshwater withdrawal, rain & stormwater and seawater (0.09-0.18 compared to 11.45-17.16 mPET/m(3)) were the resources resulting in least overall environmental impact.

Designing water supplies: Optimizing drinking water composition for maximum economic benefit.

It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management.