Herman Helness

Nature-based solutions (NBS) can play a key role in progressing toward achieving the UN Sustainable Development Goals. With NBS, the same solution can, in principle, be used to fulfil multiple management objectives. Their use and sustainability must, therefore, be evaluated in a holistic manner. Results are presented from the Water JPI-funded project EviBAN, where a toolbox for adaptive water management has been developed to assess NBS and compared with traditional solutions for water management, and the Norwegian Research Council-funded project DRENSTEIN, where the stakeholder group contributed with input and data to the development and testing. The toolbox contains tools for NBS and traditional solutions for water management, to model performance, to optimise selection of solutions, and to provide a wider assessment of benefits and co-benefits using a social-ecological system perspective. The overarching tool and the final step of an assessment is a framework for integrated sustainability assessment (ISA) of both NBS and traditional solutions for water management. In this article, the ISA is presented, with a focus on how this can be applied to assess the sustainability of different NBS for managing stormwater or storing runoff to increase water resources.

The present study introduces the SWMMLIDopt tool that aims to optimize the implementation of low-impact development (LID) measures for stormwater management. The developed tool utilizes the capabilities of the stormwater management model (SWMM) and provides a user-friendly interface for conducting multi-objective optimization of the selection and placement of LID measures in urban catchments. The features and capabilities of the developed optimization tool are demonstrated on two urban catchments in Northern Europe, Norway and Finland. The catchments exhibit different catchment sizes and characteristics, complexities and constraints demonstrating the flexibility of the tool. The selection and placement of LID measures within the study catchments were optimized according to two criteria: (1) minimizing the peak flow and (2) minimizing the cost. The generated Pareto-fronts for the study catchments allow for the evaluation of optimal scenarios based on the trade-offs between the two selected criteria. The results obtained using SWMMLIDopt demonstrate its efficacy in optimizing LID measures in urban stormwater management that will aid practitioners in designing cost-effective and climate resilient infrastructure.

Recent climate instability necessitates a fresh approach to water cycle services in the Hessequa municipal region. Attention is drawn to impacts on water storage in this region, and an assessment of the current status is necessary. Land-use change and soil properties are focal points of a runoff assessment. Defining Land Type soils information is necessary to support agricultural needs, concentrating on depth-limiting materials, mechanical limitations and texture. It is evident in the area under study that mountainous regions are not well-described. With most dams located in mountain regions and the land increasingly being used for agroforestry, the demand for better supporting information has increased. Furthermore, the available Land Type polygons for the region are too coarse for the catchment, which is primarily undulated. Enhanced Land Type mapping resolution may be defined through terrain morphological segmentation. The process indicates that the terrain prediction capability is acceptable, with 62% and 74% within 4 and 15 m search windows, respectively. This information has provided a broader platform to enhance our ability to deal with the impacts of climate and land-use change in the Korentepoort mountain catchment.

A novel approach for resource recovery includes forward osmosis (FO) as a concentration step in municipal wastewater treatment. The current study investigates different pre-treatment strategies including biological treatment with a moving-bed bioreactor (MBBR) at different loading rates and particle removal by filtration and sedimentation. Membrane performance and recovery potential for energy and nutrients were investigated in laboratory-scale FO experiments in batch mode using pre-treated municipal wastewater as feed and 35 g/L NaCl as a draw solution. Initial water fluxes were in the range of 6.3 to 8.0 L/(m²·h). The baseline fluxes were modelled to account for flux decline due to concentration effects and to enable the prediction of flux decline due to membrane fouling. Fouling-related flux decline varied from 0 to 31%. Both organic fouling and precipitation of CaCO₃ and CaHPO₄ were identified by using SEM–EDS. High-rate flushing resulted in complete flux recovery under most conditions. Scaling could be avoided by lowering the pH. Two operation strategies were tested to achieve this: (1) applying a bioreactor with a low organic loading rate to achieve high nitrification, and (2) adding a strong acid. A low organic loading rate and the use of additional particle removal were efficient measures that reduced organic/particulate fouling. The recovery potentials for COD and phosphorous in FO concentrate were close to 100%.

Wastewater treatment plants (WWTPs) require an urgent transition from a linear to a circular economy operation/design concept with a consequent resource recovery and more sustainable waste management. Natural resources have to be preserved, and wastes have to become an opportunity for recovering resources and materials (water reuse, energy, sludge reuse). However, the transition toward a circular economy is a complex and long process due to the existence of technical, economic, social and regulatory barriers. These existing barriers are critical challenges for a modern and sustainable WWTP concept. The recovery of resources must be considered a strategic target from the earliest process-design phase. In this context, the European Union’s Horizon 2020 project “Achieving wider uptake of water-smart solutions—WIDER UPTAKE” aims to overcome the existing barriers (technological, regulatory, organizational, social and economic) toward the transition from a linear to a circular economy model for WWTPs. This study is aimed at increasing the awareness of the existing barriers to a circular economy and summarizes the key contributions of the WIDER UPTAKE project in terms of water reuse, sludge reuse and nutrient recovery.

Lined permeable pavements (LPPs) are types of sustainable urban stormwater systems (SUDs) that are suitable for locations with low infiltration capacity or shallow groundwater levels. This study evaluated the hydrological performance of an LPP system in Norway using common detention indicators and flow duration curves (FDCs). Two hydrological models, the Storm Water Management Model (SWMM)-LID module and a reservoir model, were applied to simulate continuous outflows from the LPP system to plot the FDCs. The sensitivity of the parameters of the SWMM-LID module was assessed using the generalized likelihood uncertainty estimation methodology. The LPP system was found to detain the flow effectively based on the median values of the detention indicators (peak reduction = 89%, peak delay = 40 min, centroid delay = 45 min, T50-delay = 86 min). However, these indicators are found to be sensitive to the amount of precipitation and initial conditions. The reservoir model developed in this study was found to yield more accurate simulations (higher NSE) than the SWMM-LID module, and it can be considered a suitable design tool for LPP systems. The FDC offers an informative method to demonstrate the hydrological performance of LPP systems for stormwater engineers and decision-makers.

Combined sewer overflows (CSOs) pollute receiving waters and have a negative impact on ecosystem services. In urban areas rehabilitation of the sewer system to avoid CSOs is associated with high investment costs. Furthermore, not all CSOs can be closed due to the need for hydraulic reliability of the system. Local treatment of CSO with high rate filtration offers an alternative to rehabilitation of the sewer system that is flexible with respect to design and has lower investment cost than separating sewage and storm water runoff. Results from DESSIN, a 4-year EU demonstration project, are presented. The results showed on average 50% removal of particulate matter during CSO events, with higher removal (80%) in the initial first flush period. Other constituents, for example heavy metals, were removed through their association with particles. Potential impacts on ecosystem services in the catchment and the sustainability of the solution were assessed.