Enhancing domestic wastewater treatment through four chlorophyta strains-based phycoremediation: nutrient removal efficiency and algal physiology

Phycoremediation is a promising solution for environmentally sustainable wastewater treatment. However, its effectiveness depends on the selection of suitable microalgae species. In this study, four algal species (<i>Chlorella sorokiniana</i>, <i>Chlorella vulgaris</i>, <i>Scenedesmus ecornis</i>, and <i>Strombomonas</i> sp.) were evaluated for their ability to remove pollutants from secondary treated domestic wastewater using multi-soil-layering (MSL) technology. Among the four strains tested, <i>Chlorella sorokiniana</i> exhibited the highest algal density (2.832 ± 0.187 × 10⁷ cells/mL) and outperformed other species with phosphorus, nitrogen, and COD removal rates exceeding 82.01%, 63.64%, and 61.09% respectively. In addition, <i>Chlorella sorokiniana</i> had a higher total chlorophyll content of 31.11 µg. L^-1 (Chl a: 15.47 ± 0.148 µg. L^-1; Chl b: 15.642 ± 0.052 µg. L^-1) than other species. Physiological analyses of proline and glycine betaine indicated that the two <i>Chlorella</i> strains experienced lower stress levels, which facilitated an accelerated bioremediation process compared to other Chlorophyta, namely <i>Scenedesmus ecornis</i> and <i>Strombomonas</i> sp. The efficiency of <i>C. sorokiniana</i> in the treatment of secondary treated wastewater from MSL, combined with its maximum biomass production, underlines its potential for industrial application. Consequently, there is a compelling interest in evaluating <i>C. sorokiniana</i> within a prototype as a prelude to industrial development.