Application of a biosorbent based on Chlorella and nitrifying bacteria for phosphate removal from water systems

Abstract

Excessive phosphate concentrations in aquatic systems are a primary driver of eutrophication, which triggers ecosystem instability and the deterioration of water resources. The development of highly efficient and sustainable methods of phosphate removal remains an important area for both academic research and industrial application. This study is devoted to the investigation of biosorbents based on microalgae biomass and nitrifying bacteria for phosphate removal from aqueous systems. Two biosorbent formulations were evaluated: a Chlorella-based Biosorbent 1 and a composite Biosorbent 2 consisting of Chlorella vulgaris, nitrifying bacteria, and kaolin. The kinetic analysis demonstrated that phosphate uptake is a complex, multi-stage process. By applying the Weber–Morris intraparticle diffusion model to the experimental data, it was established that the adsorption rate is determined by the interplay between internal pore diffusion and boundary layer mass transfer. The composite Biosorbent 2 exhibited slower but more stable and reproducible adsorption behavior over time. In contrast, Biosorbent 1 showed significant instability during the initial stages, suggesting a susceptibility to desorption or competing reactions. These findings demonstrate that the incorporation of nitrifying bacteria and kaolin significantly enhances the kinetic stability and overall performance of the biosorbent.