Unraveling the cellular response and detoxification efficiency of microalgal systems to naphthalene contamination in water

Abstract

Polycyclic aromatic hydrocarbons (PAHs) contamination in water resources is a significant environmental issue due to its widespread presence and harmful effects on aquatic ecosystems and human health. Although microalgae offer a cost-effective and eco-friendly approach for PAH remediation, their use in this context has been less explored and presents technical challenges. This study focuses on the removal of naphthalene (NAP) from water using Selenastrum capricornutum. The relationship between biomass, photosynthetic activity, oxidative damage, removal rate, and degradation products was analyzed. Results showed that at a NAP concentration of 2.5 mg/L, Selenastrum capricornutum not only exhibited enhanced growth, with increased biomass and photosynthetic pigment content compared to the control group, but also achieved a 80.0 % total removal of NAP after 4 days. However, NAP concentrations between 10.0 and 20.0 mg/L inhibited microalgal growth, with inhibition rates of 14.5 % to 33.8 % after 8 days. The degradation experiments revealed that the removal of NAP by microalgae was mainly through biodegradation and partial adsorption, and the best removal effect was achieved at the appropriate concentration (5.0 mg/L), with the removal rate as high as 88.3 %. The microalgae's growth was notably enhanced during the exponential phase, suggesting that NAP by-products are of low or non-toxicity. The degradation rate constants (k) ranged from 0.03 h⁻¹ to 0.06 h⁻¹, with half-lives (t₁/₂) between 13.19 and 18.75 h. LC-MS analysis confirmed that the by-products of NAP metabolism by microalgae are low or non-toxic. This study demonstrates that Selenastrum capricornutum is highly tolerant to NAP and effective in removing trace amounts of NAP from contaminated wastewater, highlighting its potential for PAH remediation using algae.