Recovery of struvite from wastewaters as an eco-friendly fertilizer: Review of the art and perspective for a sustainable agriculture practice in India

The limited rock phosphate deposits present in the earth’s crust are being used at a fast rate and therefore phosphate fertilizers use will be restricted in the future. Hence, there is an urgent need of conserving the use of phosphorous (P) and recover/reuse of P from wastewaters to the maximum extent. Struvite (MgNH4PO4) is a crystalline mineral composed of magnesium, ammonium, and phosphate, and is considered as an adequate source of nutrients especially P. Struvite can be used as raw material for fertilizer production or as slow-release fertilizer. Recently, there were a lot of researches carried out to explore the possibility of recovering the struvite from wastewater streams. This paper reviews the potential sources of P in wastewater streams and the techniques of struvite recovery available in the literature for practical applications. Anaerobic digester supernatant, urine from livestock and humans are identified as potential wastewater sources of P in India. Continuous stirred tank reactor technique can be easily adopted to recover P, which is known to recover 80–90% P in wastewater. Currently, India is the second largest consumer of P due to the low P in soil and depends on imported sources for meeting her demand on fertilizers. Therefore, the work presented in this review would help India to formulate suitable policy guidelines to meet a part of the P demand by recovering struvite from wastewater streams and apply in agricultural field as an eco-friendly fertilizer. Such an effort significantly contributes to promote circular economy and sustainable agriculture.