Nutrient recovery from wastewater in India: A perspective from mass and energy balance for a sustainable circular economy

Limited phosphorus availability and increased eutrophication (due to discharge of nitrogen) have pushed everyone to rethink, on how to recover these nutrients. Wastewater (WW) is a potential source to recover N, and P, whereas, in India, it is scarcely explored. In this work, four different nutrient recovery methods were compared from a mass- and energy-balance perspective to understand the overall process flow. From 1000-m³ WW, chemical precipitation yielded 33.8 kg struvite, while micro-algae resulted in 299.1 kg (dry powder). Energy consumption was lowest for the fuel cells at 216.2 kWh/1000 m³, while microalgae used the highest energy at 943.3 kWh/1000 m³. Nonetheless, the cost-saving analysis showed that microalgae (78.6$/1000 m³) as a nutrient recovery choice, had higher savings than any other methods compared. For a country like India, where the two-thirds of urban wastewater is untreated, wastewater-biorefinery options such as nutrient recovery hold the key to a sustainable circular economy.