Wastewater in India: An untapped and under-tapped resource for nutrient recovery towards attaining a sustainable circular economy

Wastewater (WW) contains nitrogen (N) and phosphorus (P), where N oxidizes to nitrate followed by denitrification to release N-2 and P is accumulated in sludge. Higher concentrations of N and P leads to eutrophication and algal blooming, thereby threatening the aquatic life systems. Such nutrients could be potentially recovered avoiding the fertilizer requirements. Distinct nutrient recovery systems have been demonstrated including chemical precipitation, ion-exchange, adsorption, bio-electrochemical systems, and biological assimilation at various scales of volumes. This study focusses on the nutrient recovery possibility from wastewater in India. The resource estimation analysis indicates that at 80% recovery, 1 million liters per day (MLD) of sewage can generate 17.3-kg of struvite using chemical precipitation. When compared with traditional fertilizers, nutrient recovery from sewage has the potential to avoid 0.38-Mt/a in imports. Replacing conventional fertilizer with struvite recovered from WW avoids 663.2 kg CO2eq/ha in emissions (53%). Prevailing WW treatment looks at maintaining the discharging standards while recovering nutrients is an advanced option for a self-reliant and sustainable circular economy. However, more detailed assessments are necessary from techno-economic and environmental perspective in realizing these technologies at an industrial scale.