Wastewater management is a crucial aspect of urban infrastructure, and as our cities continue to grow, finding sustainable and innovative solutions has become paramount. One intriguing approach that’s gaining traction is the integration of nature-based solutions (NbS) into traditional wastewater treatment systems.
As someone who’s always been fascinated by the power of nature, I’ve been closely following the developments in this field. It’s truly remarkable how we can harness the natural processes and ecosystems to address the challenges of wastewater treatment in a more sustainable and cost-effective manner.
Unlocking the Potential of Nature-Based Solutions
The International Union for the Conservation of Nature defines NbS as “actions to protect, sustainably manage, and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits.” In the context of wastewater treatment, these solutions can take various forms, from treatment wetlands and soil infiltration systems to green roofs and living walls.
One of the key advantages of NbS is their ability to provide multiple benefits beyond just water treatment. These solutions can enhance biodiversity, improve urban microclimates, mitigate flooding, and even generate biomass for energy production. It’s a truly holistic approach that aligns with the principles of sustainable development.
Slow-Rate Soil Infiltration: A Proven Approach
One of the well-established NbS for wastewater treatment is slow-rate soil infiltration. This technique involves the controlled application of wastewater to a vegetated land surface, where the water infiltrates the soil and may percolate to the groundwater or be recovered for reuse.
A fascinating case study is the Lubbock Land Application System in Texas, USA, which has been in operation since the 1930s. As the city of Lubbock grew, this system was expanded to avoid groundwater contamination. The application of municipal wastewater to agricultural lands has been a cost-effective and water-conserving treatment method, reducing the demand on freshwater resources from surface water and groundwater. This approach has helped Lubbock build resilience against the increasing water scarcities caused by climate change and growing demand.
Vertical-Flow Treatment Wetlands: Multifunctional Ecosystems
Another NbS that has gained traction is the vertical-flow treatment wetland, as demonstrated in Shenzhen, China. This system was designed as a polishing step to meet environmental standards, with treated wastewater being intermittently loaded onto the surface to percolate vertically through the filter.
The benefits of this system go beyond just wastewater treatment. The effluent from the treatment wetland serves as an additional source of water for the Pingshan River, improving its water quality. Moreover, the wetlands provide a green recreational area for the residents of Shenzhen and habitat for plants and animals, increasing the local biodiversity. These wetlands also play a role in flood control, stormwater management, and carbon sequestration – a true testament to the multifunctional nature of NbS.
Integrating Green Infrastructure for Urban Wastewater Reuse
In dense urban areas, newer NbS technologies like green walls and green roofs are being used to treat greywater, which can then be reused for irrigation, toilet flushing, and other non-potable purposes. These systems not only provide water-efficient solutions but also offer a range of co-benefits.
A case study from Tilburg, Netherlands, showcases a demonstration project that combined a green roof and a treatment wetland. The aim was to reuse wastewater for toilet flushing, creating a green space for local treatment and promoting water reuse. Interestingly, the system also helped to balance the temperature of the building, reducing air conditioning costs and mitigating the urban heat island effect.
Another example is the living wall system in Marina di Ragusa, Italy, which collected greywater from bathroom showers and treated it through a modular, plant-based filtration and biological treatment process. The treated greywater was successfully reused for irrigation and toilet flushing throughout the tourist season, highlighting the system’s capacity for efficient treatment and reuse. Additionally, the living wall provided habitat for biodiversity and helped reduce the urban heat island effect, making it a valuable addition to the resort’s infrastructure.
Willow Systems: A Closed-Loop Solution
For peri-urban or rural settings, the use of willow systems – treatment wetlands dominated by willow plants – offers a unique and innovative approach. These systems are designed to treat all the inflow water through evapotranspiration, resulting in zero discharge and a fully circular operation.
An exemplary case study is the willow system on Zaeland Island, Denmark, which has been in operation since 2017, treating wastewater for a community of 190-250 people. The system has little to no impact on the surrounding environment, as the nutrients and carbon are absorbed and bound within the willow biomass. This biomass can then be harvested and used for energy purposes or as a soil amendment, further enhancing the system’s sustainability.
Navigating the Complexity of NbS Selection
Integrating NbS into wastewater treatment can be a complex task, as wastewater utility managers and local governments need to weigh various factors, such as the type of NbS, the quantity and quality of water to be treated, and the local climatic conditions.
To help navigate these options, a web-based tool is under development, which includes information on different NbS technologies, their co-benefits, input requirements, and case studies from around the world. This resource can be invaluable in raising awareness and deepening the understanding of viable NbS options for wastewater treatment.
Embracing NbS in Policy and Practice
The growing recognition of the potential of NbS is evident in the policy landscape. Within the European Commission’s Horizon 2020 programme, NbS have been a focal point, aligning biodiversity and ecosystem services with goals of innovation, growth, and job creation.
The World Bank has also integrated NbS into more than 100 projects across 60 countries, developing a strong knowledge base to support the uptake of these solutions for disaster management and water resource stewardship.
As we look to the future, the UN’s recent working paper, “Smart, Sustainable, and Resilient Cities: The Power of Nature-based Solutions,” highlights the significant opportunity presented by the fact that three-quarters of 2050’s infrastructure doesn’t yet exist. This provides an ideal window to incorporate nature-based thinking into the design of our urban landscapes and wastewater systems.
Furthermore, the COVID-19 recovery plans offer a unique chance to generate economic growth in a way that protects and restores the natural environment, addresses climate change, and supports livelihoods. It’s a pivotal moment to “build back better” by embracing the integration of nature into our urban infrastructure.
Conclusion: A Future Rooted in Nature
As we navigate the complex challenges of urban wastewater management, the integration of nature-based solutions presents an exciting and promising pathway. These innovative approaches not only address the primary function of water treatment but also deliver a multitude of co-benefits that enhance the overall sustainability and resilience of our cities.
By leveraging the power of natural processes and ecosystems, we can create wastewater treatment systems that are not only effective but also harmonious with the surrounding environment. This holistic approach aligns with the principles of sustainable development and the growing global commitment to addressing climate change, biodiversity loss, and water scarcity.
As we continue to explore and implement NbS in wastewater infrastructure, I’m filled with a sense of optimism and wonder. The future of urban wastewater management is one where nature and technology work in tandem, creating vibrant, livable, and resilient communities. It’s a future that I’m excited to be a part of, and I encourage you to join me in this journey of embracing the power of nature-based solutions.