Natural zeolite pretreatment of anaerobic digestate as efficient and promising detoxification strategy to improve microalgae biomass production

Abstract

This work describes a new detoxification approach for the valorization of anaerobic digestate through microalgal cultivation. In this context, adsorption columns packed with different doses of natural zeolite (clinoptilolite) were used to pretreat liquid digestate and remove recalcitrant compounds such as ammonium nitrogen. After 24 h of treatment with 100 g/L of zeolite, the initial ammonium concentration was successfully reduced from 163.2 to 37.5 mg NH4-N/L, achieving 77.0 % of NH4-N removal efficiency and 1.3 mg NH4-N/g of adsorption capacity. As opposed to the untreated digestate, the zeolite pretreatment showed a significant positive effect on Tetradesmus obliquus microalgae consortium growth, with an average specific growth rate of 0.16 d−1 combined with the removal of 99.1 and 73.3 % of NH4-N and PO4-P, respectively. The experimental findings of this study have the potential to unlock the development of microalgae-based processes for the bioremediation of liquid digestate with the concomitant production of valuable algal biomass.