Wastewater - Turning Problem to Solution

Nature-based solutions for wastewater management and reuse NBS have been identified as a low-tech, lower-cost set of solutions that can be used to manage and treat wastewater, including for resource recovery and reuse, supporting climate change adaptation and mitigation as well as enhancing biodiversity. In 2022, the United Nations Environment Assembly agreed to define NBS as: “actions to protect, conserve, restore, sustainably use and manage natural or modified terrestrial, freshwater, coastal and marine ecosystems which address social, economic and environmental challenges effectively and adaptively, while simultaneously providing human well being, ecosystem services, resilience and biodiversity benefits, and recognizes that nature-based solutions: (a) Respect social and environmental safeguards, in line with the three “Rio conventions” (the Convention on Biological Diversity, the United Nations Convention to Combat Desertification and the United Nations Framework Convention on Climate Change), including such safeguards for local communities and indigenous peoples; (b) Can be implemented in accordance with local, national and regional circumstances, consistent with the 2030 Agenda for Sustainable Development, and can be managed adaptively; (c) Are one of the actions that play an essential role in the overall global effort to achieve the Sustainable Development Goals, including by effectively and efficiently addressing major social, economic and environmental challenges, such as biodiversity loss, climate change, land degradation, desertification, food security, disaster risks, urban development, water availability, poverty eradication, inequality and unemployment, as well as social development, sustainable economic development, human health and a broad range of ecosystem services; (d) Can help to stimulate sustainable innovation and scientific research” (UNEP/EA.5/Res.5). NBS have been employed to treat wastewater for year round reuse in irrigation, fish farming and enhancing biodiversity (for example through urban greening). NBS that promote plant growth can increase carbon dioxide sequestration, provide flood protection and improve human well-being. There is a wide range of NBS approaches being used for wastewater treatment (figure 3.9). The type of NBS selected depends on the source of the water,

existing or functioning centralized sewer and wastewater treatment facilities (Capodaglio 2017). They have high capital investment costs and high demand for constant energy supply, financial resources and human capacity to operate and maintain. Decentralized treatment solutions are implemented at the site level, at the scale of the household, business, municipal service (e.g. a hospital) or small community. There are different types of decentralized solutions using chemical, biological and ecological mechanisms that can be used independently or combined depending on the source and intended reuse, including advanced wastewater treatment to be able to meet regulatory standards for irrigation. Decentralized systems can also be combined with centralized systems to create hybrid systems. The decentralized wastewater treatment approach DEWATS is a wastewater recycling approach designed to be part of a comprehensive wastewater strategy. It is designed to treat wastewater where it is generated for either reuse or disposal. The approach is adaptable to the specific socioeconomic conditions and is scalable. The approach allows for locally adapted infrastructure and capitalizes on natural physical and biological processes, keeping energy requirements low and ensuring there is local capacity for sustainable management. The systems can produce water for irrigation or toilet flushing, produce biofuel and soil conditioner (Gutterer et al. 2009). A case study has been provided for the implementation of this approach for a maternity hospital in Dar es Salaam in Tanzania to provide sustainable wastewater treatment, irrigation water and biogas production. Combining centralized and decentralized solutions Combining centralized and decentralized systems can be most advantageous to address issues of scale. In large urban areas, combining solutions for on-site and off-site sanitation systems as well as centralized and decentralized wastewater management facilities can be suitable to address the issue of infrastructure and service expansion, while offering benefits of decentralization such as reduced investment, low operation and maintenance costs, and customizability to local conditions (Zandaryaa and Brdjanovic 2017). An example is distributed systems, which represent a flexible, localized and highly networked approach, where the central infrastructure plays an arterial role, while smaller, tailored systems operate and interact with users at a more localized level.

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