A review of chemical and bioelectrochemical process of N, P nutrient recovery as struvite (MgNH4 PO4·6H2 O)

Abstract

The recovery of nitrogen (N) and phosphorous (P) from wastewater and its conversion to value-added products serve two purposes: satisfying the stringent N, P discharge threshold and meeting the demand for P fertilizers. The driving force for N, P recovery from an increased quantity of discharged wastewater is its environmental impact, on one hand, and the price of inorganic fertilizer and its judicious use, on the other. The available technology for N, P recovery is its precipitation and crystallization as struvite from diversified wastewater sources in several reactor models designed for the purpose. In addition, the electrochemical method of precipitation of struvite is also found to be very effective and novel. The use of electrogenic microorganisms is furthermore favorable to disintegrate the organic matter through the catalytic reaction and a simultaneous recovery of nutrients and the production of bioelectricity can be achieved. The advantage of the electrogenic microorganism method is a high percentage of recovery with good efficiency without the addition of any additional chemicals for pH adjustments. This review describes different aspects of chemical and electrochemical precipitation and the use of microbial electrolysis cell and microbial fuel cell in struvite precipitation from different sources. The critical factors influencing the efficiency and quality of the product are the technique adopted and the interacting process factors such as time and pH. The key differences in each process technology are described in detail with their pros and cons. To conclude, a robust process technology for quality struvite production facilitates its widespread use as a fertilizer.