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

Automated screening of control potential with spatially explicit results to support dialogue about sewer overflow reduction and beyond

For real-time control to become a standard measure for upgrading urban drainage systems, control potential screenings need to be easily integrated into the early planning processes that already take place. However, current screening methods are either not aligned with the present planning process, unrelatable for water managers or too time-consuming. We therefore developed an automated screening methodology through a co-design process with six Danish utilities. The process started out from a literature review, included interviews and workshops, and resulted in the control potential screening tool COPOTO. In the co-design process, utilities generally responded that indicators based solely on an assessment of static system attributes are insufficient. Thus, COPOTO instead post-processes the results of urban drainage simulation models that are commonly available. The decision context considered in initial planning phases was found to include environmental, economic, social and technical objectives that were highly case-dependent. When presenting CSO reduction potentials, the utilities therefore generally preferred interactive, spatially explicit visualisations that link the CSO reduction at a particular location to the storages and actuators that need to be activated. This enables water managers to discuss, for example, operational constraints of a considered control location. COPOTO provides such assessments with very limited manual and computational effort and thus facilitates the integration of real-time control into standard planning workflows of utilities.

Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.

Green Infrastructures and the Consideration of Their Soil-Related Ecosystem Services in Urban Areas—A Systematic Literature Review

Although urban soils are strongly influenced by human activities, they provide a wide range of Ecosystem Services (ES) as long as they are not sealed off. This is a major sustainability issue as the loss of soil functions directly impacts ES and further on the possibility to adapt to the effects of the climate crisis. Green Infrastructure (GI) measures can be utilized to restore previously covered soil surfaces and compensate for lost soil functions. We conducted a systematic literature review to investigate the extent of peer-reviewed publications on GI measures in (peri-) urban areas covering soil-related ES. After identifying the relevant publications (n = 284), we generated an overview of the annual, spatial, and thematic distribution of the publications. Then, we employed an extended content analysis of the published focus topics to assess the representation of soil-related ES provided by GI. The content analysis revealed that the representation of soil-related ES in GI measures focused heavily on the contribution of soil to stormwater management. Detailed assessment of the interconnection of GI measures with key soil-related ES were missing. So far, the assessment of the loss of soil-related ES is not covered extensively in GI research publications.

Managing flooding: from a problem to an opportunity

The paper argues that the concept and practice of sustainability have proved too difficult to achieve within traditional water management, and there is a lack of political will to move towards truly sustainable water services. Instead, compromised concepts, including resistance, resilience, ecosystem services, natural capital and adaptation are defining approaches; each of which may contribute partially to sustainability. Pressures due to the changing climate, ecological degradation, human demands, urbanization and deteriorating assets are challenging sustainability and compelling changes to water management. Water is now seen less as a problem to be managed than as an opportunity, as wherever situated, water brings many opportunities to contribute to anthropogenic needs. New ideas are helping to frame the way in which water management is being approached: (i) waste is no longer waste, but a potential resource within a circular economy; (ii) the interconnectedness of infrastructure systems and services and circularity of the water cycle mean there is a need to integrate approaches; (iii) nature-based systems should be preferenced for water infrastructure. These issues and ideas are considered here, together with examples of schemes showing that managing flooding can lead to wider benefits, and potential longer-term sustainability. This article is part of the theme issue 'Urban flood resilience'.

Mitigation Life Cycle Assessment: Best Practices from LCA of Energy and Water Infrastructure That Incurs Impacts to Mitigate Harm

Climate change will require societal-scale infrastructural changes. Balancing priorities for water, energy, and climate will demand that approaches to water and energy management deviate from historical practice. Infrastructure designed to mitigate environmental harm, particularly related to climate change, is likely to become increasingly prevalent. Understanding the implications of such infrastructure for environmental quality is thus of interest. Environmental life cycle assessment (LCA) is a common sustainability assessment tool that aims to quantify the total, multicriteria environmental impact caused by a functional unit. Notably, however, LCA quantifies impacts in the form of environmental “costs” of delivering the functional unit. In the case of mitigation infrastructures, LCA results can be confusing because they are generally reported as the harmful impacts of performing mitigation rather than as net impacts that incorporate benefits of successful mitigation. This paper argues for defining mitigation LCA as a subtype of LCA to facilitate better understanding of results and consistency across studies. Our recommendations are informed by existing LCA literature on mitigation infrastructure, focused particularly on stormwater and carbon management. We specifically recommend that analysts: (1) use a performance-based functional unit; (2) be attentive to burden shifting; and (3) assess and define uncertainty, especially related to mitigation performance.