Nutrient Recovery for Fertilizer Production and Wastewater Treatment for a Circular Economy

Abstract

The recovery of nutrients, particularly nitrogen (N) and phosphorus (P), from wastewater plays a crucial role in mitigating eutrophication and advancing sustainability. This paper introduces a novel approach for recovering these essential elements from municipal wastewater (MWW) using an innovative composite, calcined magnetic layered double hydroxide/ hydroxyapatite (CMLDH-HAP). The adsorbent was synthesized by precipitating hydroxyapatite onto magnetic layered double hydroxides derived from agricultural waste, followed by calcination. The adsorption behaviors, characterized by heterogeneous monolayer chemisorption adsorption, and the underlying mechanisms, including interlayer cation and ligand exchange and surface precipitation, demonstrated sustainable recovery of NH 4 + -N and P from real wastewater treatment plant effluent in column experiments, with a breakthrough time of 15 min. The N-and P-adsorbed CMLDH-HAP was then utilized as an eco-friendly, slowrelease fertilizer to enhance the germination, growth, and blooming of Madagascar periwinkle (Catharanthus roseus). Furthermore, the desorption of N and P using a 0.5 M NaHCO 3 solution enabled the regeneration of CMLDH-HAP, rendering it suitable for recycling N and P from wastewater. Economic viability considerations explored more cost-effective wastewater treatment options, underscoring the potential of CMLDH-HAP. This study thus presents a sustainable solution that integrates the reuse of agricultural waste, effective wastewater treatment, and the recovery of N and P nutrients as fertilizer sources. Implementing the demonstrated technologies can help minimize the environmental impact of wastewater and promote circular economy principles.