Wastewater - Turning Problem to Solution

Wastewater in the circular economy The fresh water that sustains us makes up only 3 per cent of the water on the planet. It is detrimental to keep degrading this finite resource, and improvements are needed in both the environmental and financial performance of the water sector. Circularity thinking provides a framework to develop comprehensive strategies for water management within a circular economy (figure 2.3). It offers an alternative economic model, whereby natural resources, including water sources, are kept at their highest value for as long as possible (UNEP 2019).

providing long-term resource stability and generating income while also improving environmental outcomes (Byrne et al. 2019). In Dakar, Senegal, circularity is being developed because of the co-location of wastewater treatment plants and faecal sludge treatment plants. This has enabled the recovery of resources for: the sale and reuse of treated wastewater for irrigation purposes (horticulture) around Dakar; the production of energy from biogas, saving 25 per cent of energy costs; and the recovery and sale of treated, dried sludge to farmers and for green areas. All these generate revenue, making services more sustainable, reliable and resilient (World Bank Group and Global Water Security & Sanitation Partnership 2021). Increased freshwater withdrawal can result in reduced water being available to sustain natural waterbodies and wetlands, with detrimental effects for biodiversity and associated ecosystem services. Once treated to remove contaminants of concern, such as elevated nutrients, pharmaceutical compounds, microplastics and hazardous compounds, wastewater can be safely fed back into streams, wetlands and waterbodies to maintain water flow and support environmental and recreational (European Union [EU] 2016; Hamdhani, Eppehimer and Bogan 2020). The estimates and projections on the potential of wastewater for resource recovery are based on the maximum theoretical amounts of water, nutrients and energy that exist in wastewater produced worldwide annually (Qadir et al. 2020). However, achieving full-scale resource recovery from wastewater will need a systematic change in policy, legislation, practices and behaviour. Resource recovery from municipal wastewater can generate new business opportunities while helping improve water supply and sanitation services (Otoo and Drechsel 2018). The European Investment Bank (EIB) has estimated that the world water market was 1 trillion euros in 2020, with between 60–70 per cent of the potential of wastewater still unexploited in Europe, creating significant potential for new jobs in this sector (EIB 2022). This is particularly relevant for women, who remain underrepresented in the formal wastewater treatment and reuse sector. One study that looked at wastewater workers in 15 countries found that only 17 per cent of the workforce were women (IWA 2014). Prevailing water scarcity, energy shortfalls and declining reserves of non-renewable nutrients, such as phosphorus, zinc and copper, underpin the need for greater commitments

The transition to a more circular approach to wastewater treatment is gaining traction to improve resilience, design out waste and restore ecosystems. Efforts to reduce the volumes of wastewater produced, improve collection and treat with a view to increase reuse are central to transforming wastewater from a waste into a resource (International Water Association [IWA] 2016; Voulvoulis 2018). The motivation for circularity in water and wastewater management is being driven by increasing water stress and cost of water and environmental protection (van Rossum 2020; Breitenmoser et al. 2022), with long standing examples of reuse not only in arid and semi-arid countries such as Namibia, Israel and Jordan, but even in countries considered to have plentiful water resources. In Japan, for example, water reuse started in the 1980s in response to severe drought and increased demand from urbanization and economic growth (Takeuchi and Tanaka 2020). Embracing circularity encourages a holistic approach to water management to prevent and/or reduce the generation of wastewater by decreasing consumption to sustainable levels, optimizing reuse, recycling and cascading water, recovering contaminants, thereby minimizing waste and pollution, storing and recovering water for protecting and regenerating waterbodies (Morseletto, Mooren and Munaretto 2022). Recovering nutrients (such as nitrogen and phosphorus) and reducing the volume of released wastewater can reduce eutrophication and avoid development of dead zones (UN-Water 2020). In some cases where wastewater treatment is well developed, treatment plants are no longer just removing contaminants during treatment, but are also recovering resources including energy and nutrients (Guest et al. 2009). Recovery and reuse of water can reduce the pressure on the resource, which may be stressed seasonally or by intermittent droughts. It is a way of

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