Growth and desalination effect of salt-tolerant terrestrial algae in brackish water

Abstract:

[Background] The deterioration of the global eco-environment and the shortage of water resources have severely restricted agricultural and economic development and threatened people’s lives. China has defined the indicator (salinity of 5.0–10.0 g/L) of brackish water, which is mainly distributed in the northwest region and the eastern coastal areas. In some arid areas of the northwest, brackish water is even the only available water resource. Long-term consumption of brackish water is harmful to human health and can cause many problems in the agricultural and industrial sectors. Existing desalination methods have high investment and operation costs. [Objective] To achieve desalination of brackish water for alleviating the shortage of freshwater resources in China and explore eco-friendly, economical, and efficient technologies for brackish water desalination, so as to promote the development of China’s national economy and improve the living standards of the people. [Methods] We selected algal strains from the germplasm bank of terrestrial algal strains of Xinjiang Jinzheng Biotechnology Co., Ltd. The strains with salt tolerance were screened and their desalination effects on brackish water were investigated. The four algal strains (A-12, X-6, X-2, and Y-5) with salt tolerance were inoculated into 10 g/L brackish water at inoculation amounts of 10%, 30%, and 50% and aerobically cultured at room temperature (28±2) ℃, a light-dark ratio of 16 h:8 h, a light intensity of 5 000 lx for 10 days. During this period, the absorbance values, total salt content, and electrical conductivity of the water samples were measured. On the day when the experiment ended, the peroxidase activity was measured, and microscopic structures of the algal cells were photographed. [Results] The salt-tolerant microalgal strains screened out had desalination effects on brackish water. They reduced the salt content of brackish water from 10 g/L to 5.60 g/L and the electrical conductivity from 9.29 ms/cm to 5.27 ms/cm. The algal cells can grow and reproduce normally under the stress of high-concentration salt and showed no obvious difference in the cell morphology from the cells growing in the culture medium. With the increase in the inoculation amount of algal strains, the activities of superoxide dismutase and catalase increased accordingly. [Conclusion] When different amounts of algal liquids are inoculated into brackish water, the algal cells can grow and reproduce normally and reduce the salt content through the adsorption effect, thus desalinating brackish water.