USE OF CHLORELLA (CHLORELLA SPP.) FOR THE REMEDIATION OF AQUATIC SYSTEMS AND IMPROVEMENT OF THEIR ECOLOGICAL STATUS

Abstract

This article presents a systematic synthesis of contemporary scientific evidence on the use of microalgae of the genus Chlorella as an effective biotechnological tool for treating various types of water bodies (municipal, agro-industrial and industrial effluents, small rivers and ponds) and restoring their ecological status. Based on a critical review of peer-reviewed literature (2018–2025), the main mechanisms of phycoremediation are analyzed – assimilation of dissolved nitrogen and phosphorus species, biosorption and bioaccumulation of heavy metals, adsorption and biotransformation of pharmaceutical micropollutants – as well as the environmental and operational drivers of process efficiency (temperature, irradiance, C:N:P ratio, hydraulic retention time, gas supply regime). Consolidated efficacy ranges are reported for key pollutant classes: total nitrogen (TN) ≈ 50–93%, total phosphorus (TP) ≈ 60–97%, and COD/BOD ≈ 50–85%, with variability depending on system configuration and operating conditions. The suitability of open (HRAP, ponds) and closed (photobioreactors – PBR) technological configurations is discussed with respect to temperate climates, alongside innovations (immobilization, bioflocculation, micro/nanobubbles, algal-bacterial consortia) that increase productivity and facilitate biomass recovery. Risks associated with contaminant accumulation in biomass (heavy metals, residual pharmaceuticals) are assessed, and a safe-handling algorithm is proposed, including monitoring by ICP-MS and LC-MS/MS and decision criteria for biomass valorization routes (agronomic use, material or energy recovery). Practical recommendations are provided for adapting Chlorella systems to Ukrainian conditions: hybrid schemes (PBR in cold seasons + HRAP in warm seasons), selection of local tolerant strains, and pilot programs with explicit performance metrics (TN, TP, COD, energy consumption per m³). Priorities for future research are outlined: standardization of protocols, tabular data synthesis, preliminary TEA/LCA, and long-term field trials in temperate climates. The article’s practical value lies in its integrated approach, combining biological remediation with managerial, technical and regulatory measures to enhance the viability of Chlorella-based phycoremediation in Ukraine.