Taking the water out of “wastewater”: An ineluctable oxymoron for urban water cycle sustainability

Abstract

Water, energy, and food are key resources that could easily limit sustainability of human society development. Water supply requires considerable amounts of energy, and "usedwater" carries considerable amounts of embedded energy and recoverable materials within. Usedwater is increasingly considered as a potential resource, rather than as a waste. Among process technology options that may allow efficient recovery of that energy, anaerobic digestion could be considered the most mature, already sporting countless applications worldwide. However, the present inefficient dilutionbase collection systems paradigm produces rather dilute sewage, preventing to a large degree a more efficient application of this technology. A new collection system paradigm, based on liquid sources segregation and minimal organics dilution, could result in significant energy savings for conveyance and treatment. This could also enhance recovery of nutrients and reclamation of potentially reusable water, with the associated benefit of reduced production of process residuals requiring further disposal. Implications of this model are discussed. © 2020 Water Environment Federation • Practitioner points • The nexus between water, energy, and food is an impending challenge on water cycle sustainability • Current paradigms of urban water management are based on disadvantageous paradigms: high dilution and gravity flow • Taking the water out of wastewater may improve energy and recovery efficiency of urban water systems and water reuse options • Technologies exist (high-rate anaerobic, vacuum sewers) and are mature for more widespread application of new urban sanitation paradigms

Sustainable management of biological solids in small treatment plants: overview of strategies and reuse options for a solar drying facility in Poland

“…UASBs, EGSPs) generate less. It was estimated that the energy required for sludge disposal ranges between 50 and 100 kWh/m 3 wastewater treated in aerobic facilities, compared with 5 kWh/m 3 in anaerobic ones (Bruce and Fisher 1984), and this is one of the many reasons prompting the latter's adoption under new urban sewerage sustainability paradigms (Zeeman et al 2008;Capodaglio et al 2016b;Capodaglio 2020). Other microbially based unconventional processes, such as bioelectrochemical processes, may generate even less waste sludge (Callegari et al 2018a).…”

Editorial: Wastewater management and resource recovery

“…At present, energy is required especially for transferring wastewater with gravity flow that requires frequent pumping and for the treatment of wastewater with EDITOR'S CHOICE-EDITORIAL energy-intensive activated sludge process. According to Capodaglio (2020), efficient harvesting of the energy present in municipal wastewater would enable water industry to become energy self-sufficient. This could be accomplished, for example, by using high-rate anaerobic treatment for source separated wastewater that has high concentrations of organics.…”

“…Phosphorous could be recovered either from the mainstream or via phosphorous precipitation after anaerobic digestion of the sludge originating from EBPR (Guisasola et al, 2019; Roldán et al, 2020). Recovering phosphorous from municipal wastewater with EBPR and mineral precipitation is also considered by Capodaglio (2020) as one of the most efficient methods for phosphorous recovery at present.…”

“…In the perspective article, Capodaglio (2020) reconsiders the whole wastewater collection and treatment infrastructure and suggests transforming the current wastewater collection system that results in diluted wastewaters to source segregation that would enable water reclamation and nutrient recovery. Indeed, technologies for source separation, such as vacuum sewers, already exist.…”

“…Capodaglio (2020) suggests that source segregation would also save energy used currently for transportation and treatment of wastewater. At present, energy is required especially for transferring wastewater with gravity flow that requires frequent pumping and for the treatment of wastewater with energy‐intensive activated sludge process.…”