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

Removal of phytotoxins in filter sand used for drinking water treatment

Phytotoxins - toxins produced by plants - are contaminants with the potential to impair drinking water quality. They encompass a large group of toxic, partially persistent compounds that have been detected in seepage waters and in shallow wells used for drinking water production. If phytotoxins enter wells used for drinking water production, it is essential to know if the drinking water treatment processes will remove them from the water phase. However, it is currently unknown whether phytotoxins remain stable during traditional groundwater treatment using sand filters as the main treatment process. The objective of this study is to investigate removal potential of phytotoxins in biological sand filters and to asses if the removal potential is similar at different waterworks. Microcosms were set up with filter sand and drinking water collected at different groundwater-based waterworks. To be able to monitor phytotoxin removal ptaquiloside, caudatoside, gramine, sparteine, jacobine N-oxide, senecionine N-oxide and caffeine were applied at initial concentrations of 300 µg L-1, which is approx. two orders of magnitude higher than currently detected in environment, but expected to cover extreme environmental conditions. Removal was monitored over a period of 14 days. Despite the high initial concentration, all filter sands removed ptaquiloside and caudatoside completely from the water phase and at waterworks where pellet softening was implemented (pH 8.4) prior to rapid sand filtration, complete removal occurred within the first 30 min. All filter sands removed gramine and sparteine, primarily by a biological process, while jacobine N-oxide, senecionine N-oxide and caffeine were recalcitrant in the filter sands. During degradation of ptaquiloside and caudatoside we observed formation and subsequent removal of degradation products pterosin B and A. Filter sands with the highest removal potential were characterised by high contents of deposited iron and manganese oxides and hence large specific surface areas. Difference between bacterial communities investigated by 16S rRNA gene analyses did not explain different removal in the filter sands. All five investigated filter sands showed similar degradation patterns regardless of water chemistry and waterworks of origin. In drinking water treatment systems biological sand filters might therefore remove phytotoxin contaminants such as ptaquiloside, caudatoside, gramine, sparteine, while for other compounds e.g. jacobine N-oxide, senecionine N-oxide further investigations involving more advanced treatment options are needed.

Environmental assessment of domestic water supply options for remote communities

Access to clean water is one of the targets in the UN Sustainable Development Goals. However, millions of people are still without basic water services, predominantly in rural areas in developing nations. Previous studies have investigated the environmental impacts of water provision, but they mostly focused on large-scale urban systems. This paper considers for the first time the life cycle environmental impacts of different water supply options applicable to remote communities in developing countries. Focusing on the Southeast Asia-Pacific (SEAP) context, a cradle-to-grave approach is followed to estimate the impacts of locally-sourced groundwater, surface water and desalinated seawater as well as externally-sourced bottled water. The results reveal that surface water is environmentally the most sustainable alternative. Locally desalinated water, powered by diesel electricity, has two orders of magnitude higher impacts than surface water. However, externally-sourced water in plastic bottles is the worst option with 4-155 times higher impacts than desalinated water and up to three orders of magnitude higher impacts than surface water. This is largely due to the impacts related to the production of bottles. Doubling their recycling would reduce the impacts by 7-23% but bottled water would still be environmentally the least sustainable option. Although water in single-use bottles currently provides only 3% of the water supply of a representative remote community in the SEAP region considered in this study, it accounts on average for more than 50% of the total impacts from water consumption. By 2030, population increase could lead to greater reliance of remote communities on bottled water and 60-73% higher impacts of water consumption per household. Relying solely on local surface, ground and water desalinated using solar power and avoiding bottled water would reduce the impacts by 33-99% relative to the current situation. This would also improve considerably water availability and security in remote communities. The findings of this study will be of interest to national and local governments developing future policies aimed at increasing access of remote communities to clean water.

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.

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.

Decoration of Cotton Fibers with a Water-Stable Metal-Organic Framework (UiO-66) for the Decomposition and Enhanced Adsorption of Micropollutants in Water

We report on the successful functionalization of cotton fabrics with a water-stable metal-organic framework (MOF), UiO-66, under mild solvothermal conditions (80 °C) and its ability to adsorb and degrade water micropollutants. The functionalized cotton samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). UiO-66 crystals grew in a uniform and conformal manner over the surface of the cotton fibers. The cotton fabrics functionalized with UiO-66 frameworks exhibited an enhanced uptake capacity for methylchlorophenoxypropionic acid (MCPP), a commonly used herbicide. The functionalized fabrics also showed photocatalytic activity, demonstrated by the degradation of acetaminophen, a common pharmaceutical compound, under simulated sunlight irradiation. These results indicate that UiO-66 can be supported on textile substrates for filtration and photocatalytic purposes and that these substrates can find applications in wastewater decontamination and micropollutant degradation.

LCA Methodology for the Quantification of the Carbon Footprint of the Integrated Urban Water System

In integrated urban water systems, energy consumption, and consequently the amount of produced CO2, depends on many environmental, infrastructural, and management factors such as supply water quality, on which treatment complexity depends, urban area orography, water systems efficiency, and maintenance levels. An important factor is related to the presence of significant water losses, which result in an increase in the supply volume and therefore a higher energy consumption for treatment and pumping, without effectively supplying users. The current European environmental strategy is committed to sustainable development by generating action plans to improve the environmental performance of products and services. The analysis of carbon footprints is considered one such improvement, allowing for the evaluation of the environmental impact of single production phases. Using this framework, the aim of the study is to apply a Life Cycle Assessment (LCA) methodology to quantify the carbon footprint of an overall integrated urban water system referring to ISO/TS 14067 (2013). This methodology uses an approach known as “cradle to grave” and presumes to conduct an objective assessment of product units, balancing energy, and matter flows along the production process. The methodology was applied to a real case study, i.e., the integrated urban water system of the Palermo metropolitan area in Sicily (Italy). Each process in the system was characterized and globally evaluated from the point of view of water loss, energy consumption, and CO2 production, and some mitigation strategies are proposed and evaluated to reduce the energy consumption and, consequently, the environmental impact of the system.

Carbon footprint assessment of Western Australian Groundwater Recycling Scheme

This research has determined the carbon footprint or the carbon dioxide equivalent (CO₂ eq) of potable water production from a groundwater recycling scheme, consisting of the Beenyup wastewater treatment plant, the Beenyup groundwater replenishment trial plant and the Wanneroo groundwater treatment plant in Western Australia, using a life cycle assessment approach. It was found that the scheme produces 1300 tonnes of CO₂ eq per gigalitre (GL) of water produced, which is 933 tonnes of CO₂ eq higher than the desalination plant at Binningup in Western Australia powered by 100% renewable energy generated electricity. A Monte Carlo Simulation uncertainty analysis calculated a Coefficient of Variation value of 5.4%, thus confirming the accuracy of the simulation. Electricity input accounts for 83% of the carbon dioxide equivalent produced during the production of potable water. The chosen mitigation strategy was to consider the use of renewable energy to generate electricity for carbon intensive groundwater replenishment trial plant. Depending on the local situation, a maximum of 93% and a minimum of 21% greenhouse gas saving from electricity use can be attained at groundwater replenishment trial plant by replacing grid electricity with renewable electricity. In addition, the consideration of vibrational separation (V-Sep) that helps reduce wastes generation and chemical use resulted in a 4.03 tonne of CO₂ eq saving per GL of water produced by the plant.

Life cycle assessments of urban water systems: a comparative analysis of selected peer-reviewed literature

Water is a growing concern in cities, and its sustainable management is very complex. Life cycle assessment (LCA) has been increasingly used to assess the environmental impacts of water technologies during the last 20 years. This review aims at compiling all LCA papers related to water technologies, out of which 18 LCA studies deals with whole urban water systems (UWS). A focus is carried out on these 18 case studies which are analyzed according to criteria derived from the four phases of LCA international standards. The results show that whereas the case studies share a common goal, i.e., providing quantitative information to policy makers on the environmental impacts of urban water systems and their forecasting scenarios, they are based on different scopes, resulting in the selection of different functional units and system boundaries. A quantitative comparison of life cycle inventory and life cycle impact assessment data is provided, and the results are discussed. It shows the superiority of information offered by multi-criteria approaches for decision making compared to that derived from mono-criterion. From this review, recommendations on the way to conduct the environmental assessment of urban water systems are given, e.g., the need to provide consistent mass balances in terms of emissions and water flows. Remaining challenges for urban water system LCAs are identified, such as a better consideration of water users and resources and the inclusion of recent LCA developments (territorial approaches and water-related impacts).

Mecoprop (MCPP) removal in full-scale rapid sand filters at a groundwater-based waterworks

Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at Kerteminde Waterworks in concentrations up to 0.08μg/L. MCPP was removed to below detection limit in a simple treatment line where anaerobic groundwater was aerated and subsequently filtered by primary and secondary rapid sand filters. Water quality parameters were measured throughout the waterworks, and they behaved as designed for. MCPP was removed in secondary rapid sand filters--removal was the greatest in the sand filters in the filter line with the highest contact time (63 min). In these secondary sand filters, MCPP concentration decreased from 0.037 μg/L to below the detection limit of 0.01 μg/L. MCPP was removed continuously at different filter depths (0.80 m). Additionally, biodegradation, mineralisation and adsorption were investigated in the laboratory in order to elucidate removal mechanisms in the full-scale system. Therefore, microcosms were set up with filter sand, water and (14)C-labelled MCPP at an initial concentration of 0.2 μg/L. After 24 h, 79-86% of the initial concentration of MCPP was removed. Sorption removed 11-15%, while the remaining part was removed by microbial processes, leading to a complete mineralisation of 13-18%. Microbial removal in the filter sand was similar at different depths of the rapid sand filter, while the amount of MCPP which adsorbed to the filter sand after 48 h decreased with depth from 21% of the initial MCPP in the top layer to 7% in the bottom layer. It was concluded that MCPP was removed in secondary rapid sand filters at Kerteminde Waterworks, to which both adsorption and microbial degradation contributed.

How environmentally significant is water consumption during wastewater treatment? Application of recent developments in LCA to WWT technologies used at 3 contrasted geographical locations

Environmental impact assessment models are readily available for the assessment of pollution-related impacts in life cycle assessment (LCA). These models have led to an increased focus on water pollution issues resulting in numerous LCA studies. Recently, there have been significant developments in methods assessing freshwater use. These improvements widen the scope for the assessment of wastewater treatment (WWT) technologies, now allowing us to apprehend, for the first time, a combination of operational (energy and chemicals use), qualitative (environmental pollution) and quantitative (water deprivation) issues in wastewater treatment. This enables us to address the following question: Is water consumption during wastewater treatment environmentally significant compared to other impacts? To answer this question, a standard life cycle inventory (LCI) was performed with a focus on consumptive water uses at plant level, where several WWT technologies were operating, in different climatic conditions. The impacts of water consumption were assessed by integrating regionalized characterization factors for water deprivation within an existing life cycle impact assessment (LCIA) method. Results at the midpoint level, show that water deprivation impacts are highly variable in relation to the chosen WWT technology (water volume used) and of WWTP location (local water scarcity). At the endpoint level, water deprivation impacts on ecosystem quality and on the resource damage categories are significant for WWT technologies with great water uses in water-scarce areas. Therefore, our study shows the consideration of water consumption-related impacts is essential and underlines the need for a greater understanding of the water consumption impacts caused by WWT systems. This knowledge will help water managers better mitigate local water deprivation impacts, especially in selecting WWT technologies suitable for arid and semi-arid areas.

Life cycle and human health risk assessments as tools for decision making in the design and implementation of nanofiltration in drinking water treatment plants

A combined methodology using life cycle assessment (LCA) and human health risk assessment (HHR) is proposed in order to select the percentage of water in drinking water treatment plants (DWTP) that should be nanofiltered (NF). The methodological approach presented here takes into account environmental and social benefit criteria evaluating the implementation of new processes into conventional ones. The inclusion of NF process improves drinking water quality, reduces HHR but, in turn, increases environmental impacts as a result of energy and material demand. Results from this study lead to balance the increase of the impact in various environmental categories with the reduction in human health risk as a consequence of the respective drinking water production and consumption. From an environmental point of view, the inclusion of NF and recommended pretreatments to produce 43% of the final drinking water means that the environmental impact is nearly doubled in comparison with conventional plant in impact categories severely related with electricity production, like climate change. On the other hand, the carcinogenic risk (HHR) associated to trihalomethane formation potential (THMFP) decreases with the increase in NF percentage use. Results show a reduction of one order of magnitude for the carcinogenic risk index when 100% of drinking water is produced by NF.

Water loss control using pressure management: life-cycle energy and air emission effects

Pressure management is one cost-effective and efficient strategy for controlling water distribution losses. This paper evaluates the life-cycle energy use and emissions for pressure management zones in Philadelphia, Pennsylvania, and Halifax, Nova Scotia. It compares water savings using fixed-outlet and flow-modulated pressure control to performance without pressure control, considering the embedded electricity and chemical consumption in the lost water, manufacture of pipe and fittings to repair breaks caused by excess pressure, and pressure management. The resulting energy and emissions savings are significant. The Philadelphia and Halifax utilities both avoid approximately 130 million liters in water losses annually using flow-modulated pressure management. The conserved energy was 780 GJ and 1900 GJ while avoided greenhouse gas emissions were 50 Mg and 170 Mg a year by Philadelphia and Halifax, respectively. The life-cycle financial and environmental performance of pressure management systems compares favorably to the traditional demand management strategy of installing low-flow toilets. The energy savings may also translate to cost-effective greenhouse gas emission reductions depending on the energy mix used, an important advantage in areas where water and energy are constrained and/or expensive and greenhouse gas emissions are regulated as in California, for example.

Measuring environmental sustainability of water in watersheds

Environmental sustainability assessment is a rapidly growing field where measures of sustainability are used within an assessment framework to evaluate and compare alternative actions. Here we argue for the importance of evaluating environmental sustainability of water at the watershed scale. We review existing frameworks in brief before reviewing watershed-relevant measures in more detail. While existing measures are diverse, overlapping, and interdependent, certain attributes that are important for watersheds are poorly represented, including spatial explicitness and the effect of natural watershed components, such as rivers. Most studies focus on one or a few measures, but a complete assessment will require use of many existing measures, as well as, perhaps, new ones. Increased awareness of the broad dimensions of environmental sustainability as applied to water management should encourage integration of existing approaches into a unified assessment framework appropriate for watersheds.

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.

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.

Embodied energy comparison of surface water and groundwater supply options

The embodied energy associated with water provision comprises an important part of water management, and is important when considering sustainability. In this study, an input-output based hybrid analysis integrated with structural path analysis was used to develop an embodied energy model. The model was applied to a groundwater supply system (Kalamazoo, Michigan) and a surface water supply system (Tampa, Florida). The two systems evaluated have comparable total energy embodiments based on unit water production. However, the onsite energy use of the groundwater supply system is approximately 27% greater than the surface water supply system. This was primarily due to more extensive pumping requirements. On the other hand, the groundwater system uses approximately 31% less indirect energy than the surface water system, mainly because of fewer chemicals used for treatment. The results from this and other studies were also compiled to provide a relative comparison of embodied energy for major water supply options.