Zeolitic Tuff for Ammonium Recovery from Anaerobic Digestates: Efficiency, Optimization, and Large Scale Potential Application

The increasing production of wastewater from livestock farming, industrial activities, and domestic sources poses significant environmental and economic challenges [1]. Excessive nutrient discharge into water bodies contributes to eutrophication, while the loss of valuable elements, such as nitrogen (N), represents a missed opportunity for agricultural reuse [2]. In this context, the development of sustainable and cost-effective strategies for nutrient recovery is crucial to promoting circular economy principles and reducing dependence on synthetic fertilizers. Implementing such approaches aligns with the European Green Deal and global sustainability goals, which advocate for resource efficiency and environmental protection [3,4]. This study explores the use of a zeolitic tuff for nitrogen recovery from various anaerobic digestates, including those from livestock (swine and cattle) and organic solid waste. The aim is to assess the feasibility of integrating this process into farm-scale treatment systems for nutrient recycling. The influence of digestate pre-treatment methods (e.g., microfiltration, clarification) on ammonium adsorption efficiency was also examined. A comprehensive set of experiments evaluated ammonium removal under varying conditions, considering (i) contact time, (ii) initial NH₄⁺ concentration, (iii) ionic competition, and (iv) total solids. Adsorption isotherms and kinetic models were applied to understand the process mechanisms and optimize operational parameters. Preliminary findings suggest that the ammonium removal efficiency is closely linked to digestate composition and physicochemical properties. Notably, livestock-derived digestates exhibited a higher nitrogen recovery potential compared to other sources. Moreover, pre-treatment methods, such as microfiltration and clarification, were found to enhance adsorption performance by reducing solid content and potential interferences. Considering the widespread availability of zeolite-rich tuffs and the substantial daily production of livestock digested, the proposed method is valuable for large-scale implementation. The method allows the recovery of several tons of nitrogen per year for agronomic applications without relying on chemical additives and offers both environmental and economic benefits. Following this approach two patents were presented producing NH4-enriched zeolite as soil amendment, and struvite as fertilizer. This latter allowing also to recover P together with N. References: [1] Kim D. et al. (2017) Environ Eng Res 22: 12-18 [2] Ferretti G. et al. (2020) Water 12: 310 [3] Galamini G. et al. (2020) Braz. J. Plant. Physiol 12: 2944 [4] Martinez J. et al. (2009) Boresour. Technol. 100: 5527-5536