Multicompartment Depletion Factors for Water Consumption on a Global Scale.

Balancing human communities' and ecosystems' need for freshwater is one of the major challenges of the 21st century as population growth and improved living conditions put increasing pressure on freshwater resources. While frameworks to assess the environmental impacts of freshwater consumption have been proposed at the regional scale, an operational method to evaluate the consequences of consumption on different compartments of the water system and account for their interdependence is missing at the global scale. Here, we develop depletion factors that simultaneously quantify the effects of water consumption on streamflow, groundwater storage, soil moisture, and evapotranspiration globally. We estimate freshwater availability and water consumption using the output of a global-scale surface water-groundwater model for the period 1960-2000. The resulting depletion factors are provided for 8,664 river basins, representing 93% of the landmass with significant water consumption, i.e., excluding Greenland, Antarctica, deserts, and permanently frozen areas. Our findings show that water consumption leads to the largest water loss in rivers, followed by aquifers and soil, while simultaneously increasing evapotranspiration. Depletion factors vary regionally with ranges of up to four orders of magnitude depending on the annual consumption level, the type of water used, aridity, and water transfers between compartments. Our depletion factors provide valuable insights into the intertwined effects of surface and groundwater consumption on several hydrological variables over a specified period. The developed depletion factors can be integrated into sustainability assessment tools to quantify the ecological impacts of water consumption and help guide sustainable water management strategies, while accounting for the performance limitations of the underlying model.

Advancing water footprint assessments: Combining the impacts of water pollution and scarcity.

Several water footprint indicators have been developed to curb freshwater stress. Volumetric footprints support water allocation decisions and strive to increase water productivity in all sectors. In contrast, impact-oriented footprints are used to minimize the impacts of water use on human health, ecosystems, and freshwater resources. Efforts to combine both perspectives in a harmonized framework have been undertaken, but common challenges remain, such as pollution and ecosystems impacts modelling. To address these knowledge gaps, we build upon a water footprint assessment framework proposed at conceptual level to expand and operationalize relevant features. We propose two regionalized indicators, namely the water biodiversity footprint and the water resource footprint, that aggregate all impacts from toxic chemicals, nutrients, and water scarcity. The first impact indicator represents the impacts on freshwater ecosystems. The second one models the competition for freshwater resources and its consequences on freshwater availability. As part of the framework, we complement the two indicators with a sustainability assessment representing the levels above which ecological and human freshwater needs are no longer sustained. We test our approach assessing the sustainability of water use in the European Union in 2010. Water stress hampers 15 % of domestic, agricultural and industrial water demand, mainly due to irrigation and pesticide emissions in southern Europe. Moreover, damage to the freshwater ecosystems is widespread and mostly resulting from chemical emissions from industry. Approximately 5 % of the area is exceeding the regional sustainability limits for ecosystems and human water requirements altogether. Concerted efforts from all sectors are needed to reduce the impacts of emissions and water consumption under the sustainability limits. These advances are considered an important step toward the harmonization of volumetric and impact-oriented approaches to achieve consistent and holistic water footprinting as well as contributing to strengthen the policy relevance of water footprint assessments.

Heat recovery and water reuse in micro-distilleries improves eco-efficiency of alcohol production.

The number of micro-scale spirit distilleries worldwide has grown considerably over the past decade. With an onus on the distillery sector to reduce its environmental impact, such as carbon emissions, opportunities for increasing energy efficiency need to be implemented. This study explores the potential environmental benefits and financial gains achievable through heat recovery from different process and by-product streams, exemplified for a Scotch whisky distillery, but transferrable to micro-distilleries worldwide. The eco-efficiency methodology is applied, taking into account both climate change and water scarcity impacts as well as economic performance of alcohol production with and without heat recovery. A Life Cycle Assessment, focusing on climate change and water scarcity, is combined with a financial assessment considering investment costs and the present value of the savings over the 20-year service life of the heat recovery system. The proposed heat recovery systems allow carbon emission reductions of 8-23% and water scarcity savings of 13-55% for energy and water provision for 1 L of pure alcohol (LPA). Financial savings are comparatively smaller, at 5-13%, due to discounting of the future savings - but offer a simple payback of the investment costs in under two years. The eco-efficiency of the distillery operations can be improved through all proposed heat recovery configurations, but best results are obtained when heat is recovered from mashing, distillations and by-products altogether. A sensitivity analysis confirmed that the methodology applied here delivers robust results and can help guide other micro-distilleries on whether to invest in heat recovery systems, and/or the heat recovery configuration. Uptake should be enhanced through increased information and planning support, and in cases where the distillery offers insufficient heat and water sinks to use all pre-warmed water, opportunities to link with a heat sink outside the distillery are encouraged. A 10% reduction in heating fuel use through heat recovery has the potential to save 47 kt of CO2 eq. or £7.4 M per annum in United Kingdom malt whisky production alone, based on current fuel types used and current prices (2021).

Life Cycle Assessment and Cost-Benefit Analysis of Technologies in Water Resource Recovery Facilities: The Case of Sludge Pyrolysis.

In Europe, sewage sludge is mostly used in agriculture (49%) or incinerated (25%). Technologies for sludge management that can support the transformation of wastewater treatment plants (WWTPs) to water resource recovery facilities (WRRFs) are emerging. Sludge pyrolysis is one of them. It can generate two main high-value co-products: heat and biochar. Moreover, biochar can be transformed into activated carbon. The economic and environmental impacts of sludge pyrolysis and its comparison to the direct application of sludge in agriculture and incineration are unknown. Therefore, we applied a life cycle assessment (LCA) and a cost-benefit analysis (CBA) of sludge pyrolysis. We quantified environmental externalities in an LCA and then applied the benefit transfer method to monetize these externalities, which were included in an economic CBA. Pyrolysis reduced impacts in five to nine LCA categories and had a positive economic net present value (NPV) compared to using sludge in agriculture. Pyrolysis with biochar production was not better than incineration, showing increased impacts in nine categories and negative NPVs (-19 to -22 €/t sludge). The factor driving differences between the alternatives was the assumed CO2 externality price (164 €/ton CO2-eq) and the removal rate of pharmaceutical micropollutants of the sludge-based activated carbon. High uncertainty in environmental prices is one of the limitations of our study.

Challenges in carbon footprint evaluations of state-of-the-art municipal wastewater resource recovery facilities.

Wastewater treatment is an important source of direct and indirect greenhouse gas (GHG) emissions, which some wastewater operators report and account for CO2-eq impacts through carbon footprint evaluations. We investigated the challenges with GHG emissions' accounting of three state-of-the-art energy-efficient wastewater resource recovery facilities (WRRFs) and reviewed their CO2 accounting reports. Our study aimed to highlight the major contributors and factors to estimate emissions, including direct N2O and CH4 emissions and propose recommendations for public reporting of CO2 accounting of WRRFs. We categorised emissions as direct (scope 1), background (scope 2), downstream and avoided emissions (scope 3A and 3B) and evaluated how a change in emission factor may affect how close the WRRFs are to reaching CO2 neutrality. The results show that electricity consumption and direct emissions constitute between 20 and 70% of actual CO2-eq emissions and therefore need careful consideration. All three plants have increasingly offset scope 2 emissions over 2014-2019, resulting in a total reduction of approximately 3211 tons CO2-eq, corresponding to 72% of their needed cuts by 2030 set by the Danish government. No standard factors are used across the plants to estimate emissions. We propose some general recommendations that wastewater operators can apply to correctly report and account for CO2-eq emissions. We also recommend that operators move their long-term focus from CO2 neutrality to CO2-eq reduction and make an effort to measure and quantify scope 1 direct emissions properly. A tax on N2O emissions should be introduced in future policies.

From wastewater treatment to water resource recovery: Environmental and economic impacts of full-scale implementation.

To reduce greenhouse gas emissions and promote resource recovery, many wastewater treatment operators are retrofitting existing plants to implement new technologies for energy, nutrient and carbon recovery. In literature, there is a lack of studies that can unfold the potential environmental and economic impacts of the transition that wastewater utilities are undertaking to transform their treatment plants to water resource recovery facilities (WRRFs). When existing, literature studies are mostly based on simulations rather than real plant data and pilot-scale results. This study combines life cycle assessment and economic evaluations to quantify the environmental and economic impacts of retrofitting an existing wastewater treatment plant (WWTP), which already implements energy recovery, into a full-scale WRRF with a series of novel technologies, the majority of which are already implemented full-scale or tested through pilot-scales. We evaluate five technology alternatives against the current performance of the WWTP: real-time N2O control, biological biogas upgrading coupled with power-to-hydrogen, phosphorus recovery, pre-filtration carbon harvest and enhanced nitrogen removal. Our results show that real-time N2O control, biological biogas upgrading and pre-filtration lead to a decrease in climate change and fossil resource depletion impacts. The implementation of the real-time measurement and control of N2O achieved the highest reduction in direct CO2-eq emissions (-35%), with no significant impacts in other environmental categories. Biological biogas upgrading contributed to counterbalancing direct and indirect climate change impacts by substituting natural gas consumption and production. Pre-filtration increased climate change reduction by 13%, while it increased impacts in other categories. Enhanced sidestream nitrogen removal increased climate change impacts by 12%, but decreased marine eutrophication impacts by 14%. The reserve base resource depletion impacts, however, were the highest in the plant configurations implementing biological biogas upgrading coupled with power-to-hydrogen. Environmental improvements generated economic costs for all alternatives except for real-time N2O control. The results expose possible environmental and economic trade-offs and hotspots of the journey that large wastewater treatment plants will undertake in transitioning into resource recovery facilities in the coming years.

Evaluation and comparison of centralized drinking water softening technologies: Effects on water quality indicators.

Drinking water softening is often implemented to increase consumer convenience e.g. by reducing lime scaling and soap use. Softening reduces hardness, but changes also the overall mineral composition of the water, depending on the technology. A broad spectrum of effects from softening has to be considered in relation to e.g. health and corrosion when selecting softening technology and design, otherwise adverse effects may be overlooked in the attempt to increase consumer convenience. We here provided a framework for evaluating softening technologies using water quality indicators for lime scaling, soap use, corrosion, human health, taste and removal of contaminants. None of the evaluated softening technologies scored positive on all the included water quality indicators. Precipitation technologies (lime/soda-ash softening and pellet softening) reduce the predicted copper and lead release, but negatively affect stainless steel corrosion expressed by the Larson Ratio. Pellet softening does not remove magnesium, which may limit the achievable softening depth, but maintains a protective effect against cardio-vascular diseases. Strong-acid cation exchange is not expected to affect the included corrosion indicators, whereas the effects from membrane separation (nanofiltration and reverse osmosis) and weak-acid cation exchange depend on the specific source water and process design. All the evaluated technologies reduce hardness, calcium carbonate precipitation potential (CCPP) and atopic eczema, but have potential adverse effects on dental carries (expressed by DMF-S). Our framework provides a better understanding of softening and can prepare water utility planners and managers for better decisions that balance the positive and adverse effects from drinking water softening.

Life cycle assessment of point source emissions and infrastructure impacts of four types of urban stormwater systems.

The implementation, operation and decommissioning of stormwater management systems causes environmental damage, while at the same time reducing pollutant loads in receiving waters by treating stormwater. The focus in research has been either on assessing impacts caused by stormwater infrastructure, or risks associated with stormwater discharges, but rarely have these two sources of environmental impacts been combined to allow a comprehensive environmental evaluation of stormwater management. We assess the environmental sustainability of four different generic stormwater management systems for a catchment of 260ha by a) modelling the flow of pollutants in stormwater, and resulting point source emissions to freshwater, and b) quantifying emissions and resources for all relevant processes associated with the life cycle of the infrastructure. Using life cycle impact assessment, we quantify the resulting environmental impacts and consequent damage to two areas of protection - ecosystems (expressed in time-integrated species loss) and natural resource availability (expressed in extra costs for future resource extraction). Our assessment shows that combined stormwater management causes the highest damage to both ecosystems (1.4E-03 species.yr/yr) and resource availability (8.8E+03 USD/yr). Separate systems using only green infrastructure were found to avoid damage to resource availability (-3.7 to -5.2 USD/yr) and cause lower ecosystem damage (1.1-1.3E-03 species.yr/yr). Stormwater discharges contribute significantly to the total ecosystem damage of the different systems (36-88%), and the sustainability of separate systems can be further improved by optimizing the removal efficiency of low-tech elements like surface basins and filter soil. The systems are designed according to engineering standards. Choosing different criteria, e.g. identical flood safety levels, would result in substantial changes of the relative performance of the systems. The findings highlight the importance of including point source emissions into the assessment to allow comparative conclusions and minimisation of environmental damage of stormwater management.

Pollution levels of stormwater discharges and resulting environmental impacts.

Stormwater carries pollutants that potentially cause negative environmental impacts to receiving water bodies, which can be quantified using life cycle impact assessment (LCIA). We compiled a list of 20 metals, almost 300 organic compounds, and nutrients potentially present in stormwater, and measured concentrations reported in literature. We calculated mean pollutant concentrations, which we then translated to generic impacts per litre of stormwater discharged, using existing LCIA characterisation factors. Freshwater and marine ecotoxicity impacts were found to be within the same order of magnitude (0.72, and 0.82 CTUe/l respectively), while eutrophication impacts were 3.2E-07 kgP-eq/l for freshwater and 2.0E-06 kgN-eq/l for marine waters. Stormwater discharges potentially have a strong contribution to ecotoxicity impacts compared to other human activities, such as human water consumption and agriculture. Conversely, contribution to aquatic eutrophication impacts was modest. Metals were identified as the main contributor to ecotoxicity impacts, causing >97% of the total impacts. This is in line with conclusions from a legal screening, where metals showed to be problematic when comparing measured concentrations against existing environmental quality standards.

Definitions of event magnitudes, spatial scales, and goals for climate change adaptation and their importance for innovation and implementation.

We examine how core professional and institutional actors in the innovation system conceptualize climate change adaptation in regards to pluvial flooding-and how this influences innovation. We do this through a qualitative case study in Copenhagen with interconnected research rounds, including 32 semi-structured interviews, to strengthen the interpretation and analysis of qualitative data. We find that the term "climate change adaptation" currently has no clearly agreed definition in Copenhagen; instead, different actors use different conceptualizations of climate change adaptation according to the characteristics of their specific innovation and implementation projects. However, there is convergence among actors towards a new cognitive paradigm, whereby economic goals and multifunctionality are linked with cost-benefit analyses for adapting to extreme rain events on a surface water catchment scale. Differences in definitions can lead to both successful innovation and to conflict, and thus they affect the city's capacity for change. Our empirical work suggests that climate change adaptation can be characterized according to three attributes: event magnitudes (everyday, design, and extreme), spatial scales (small/local, medium/urban, and large/national-international), and (a wide range of) goals, thereby resulting in different technology choices.

Life cycle assessment of stormwater management in the context of climate change adaptation.

Expected increases in pluvial flooding, due to climatic changes, require large investments in the retrofitting of cities to keep damage at an acceptable level. Many cities have investigated the possibility of implementing stormwater management (SWM) systems which are multi-functional and consist of different elements interacting to achieve desired safety levels. Typically, an economic assessment is carried out in the planning phase, while environmental sustainability is given little or no attention. In this paper, life cycle assessment is used to quantify environmental impacts of climate change adaptation strategies. The approach is tested using a climate change adaptation strategy for a catchment in Copenhagen, Denmark. A stormwater management system, using green infrastructure and local retention measures in combination with planned routing of stormwater on the surfaces to manage runoff, is compared to a traditional, sub-surface approach. Flood safety levels based on the Three Points Approach are defined as the functional unit to ensure comparability between systems. The adaptation plan has significantly lower impacts (3-18 person equivalents/year) than the traditional alternative (14-103 person equivalents/year) in all analysed impact categories. The main impacts are caused by managing rain events with return periods between 0.2 and 10 years. The impacts of handling smaller events with a return period of up to 0.2 years and extreme events with a return period of up to 100 years are lower in both alternatives. The uncertainty analysis shows the advantages of conducting an environmental assessment in the early stages of the planning process, when the design can still be optimised, but it also highlights the importance of detailed and site-specific data.

Life cycle assessment as development and decision support tool for wastewater resource recovery technology.

Life cycle assessment (LCA) has been increasingly used in the field of wastewater treatment where the focus has been to identify environmental trade-offs of current technologies. In a novel approach, we use LCA to support early stage research and development of a biochemical system for wastewater resource recovery. The freshwater and nutrient content of wastewater are recognized as potential valuable resources that can be recovered for beneficial reuse. Both recovery and reuse are intended to address existing environmental concerns, for example, water scarcity and use of non-renewable phosphorus. However, the resource recovery may come at the cost of unintended environmental impacts. One promising recovery system, referred to as TRENS, consists of an enhanced biological phosphorus removal and recovery system (EBP2R) connected to a photobioreactor. Based on a simulation of a full-scale nutrient and water recovery system in its potential operating environment, we assess the potential environmental impacts of such a system using the EASETECH model. In the simulation, recovered water and nutrients are used in scenarios of agricultural irrigation-fertilization and aquifer recharge. In these scenarios, TRENS reduces global warming up to 15% and marine eutrophication impacts up to 9% compared to conventional treatment. This is due to the recovery and reuse of nutrient resources, primarily nitrogen. The key environmental concerns obtained through the LCA are linked to increased human toxicity impacts from the chosen end use of wastewater recovery products. The toxicity impacts are from both heavy metals release associated with land application of recovered nutrients and production of AlCl3, which is required for advanced wastewater treatment prior to aquifer recharge. Perturbation analysis of the LCA pinpointed nutrient substitution and heavy metals content of algae biofertilizer as critical areas for further research if the performance of nutrient recovery systems such as TRENS is to be better characterized. Our study provides valuable feedback to the TRENS developers and identifies the importance of system expansion to include impacts outside the immediate nutrient recovery system itself. The study also show for the first time the successful evaluation of urban-to-agricultural water systems in EASETECH.

Increasing urban water self-sufficiency: new era, new challenges.

Urban water supplies are traditionally based on limited freshwater resources located outside the cities. However, a range of concepts and techniques to exploit alternative water resources has gained ground as water demands begin to exceed the freshwater available to cities. Based on 113 cases and 15 in-depth case studies, solutions used to increase water self-sufficiency in urban areas are analyzed. The main drivers for increased self-sufficiency were identified to be direct and indirect lack of water, constrained infrastructure, high quality water demands and commercial and institutional pressures. Case studies demonstrate increases in self-sufficiency ratios to as much as 80% with contributions from recycled water, seawater desalination and rainwater collection. The introduction of alternative water resources raises several challenges: energy requirements vary by more than a factor of ten amongst the alternative techniques, wastewater reclamation can lead to the appearance of trace contaminants in drinking water, and changes to the drinking water system can meet tough resistance from the public. Public water-supply managers aim to achieve a high level of reliability and stability. We conclude that despite the challenges, self-sufficiency concepts in combination with conventional water resources are already helping to reach this goal.

The valuation of water quality: effects of mixing different drinking water qualities.

As water supplies increasingly turn to use desalination technologies it becomes relevant to consider the options for remineralization and blending with mineral rich water resources. We present a method for analyzing economic consequences due to changes in drinking water mineral content. Included impacts are cardiovascular diseases, dental caries, atopic eczema, lifetime of dish and clothes washing machines, heat exchangers, distribution systems, bottled water consumption and soap usage. The method includes an uncertainty assessment that ranks the impacts having the highest influence on the result and associated uncertainty. Effects are calculated for a scenario where 50% of Copenhagen's water supply is substituted by desalinated water. Without remineralization the total impact is expected to be negative (euro -0.44+/-0.2/m(3)) and individual impacts expected in the range of euro 0.01-0.51/m(3) delivered water. Health impacts have the highest contribution to impact size and uncertainty. With remineralization it is possible to reduce several negative impacts and the total impact is expected to be positive (euro 0.14+/-0.08/m(3)).