Separation performance of ultrafiltration during the treatment of algae-laden water in the presence of an anionic surfactant

Ultrafiltration was demonstrated to be an effective and efficient method to treat algae-laden water. However, the presence of compounds such as surfactants can act as a stimulus for algae outbreak and change the characteristics of algae cells and derived organics. Therefore, it is necessary to investigate the filtration and separation performance of ultrafiltration during the treatment of algae-laden water in the presence of anionic surfactants (the most widely used surfactant type). In this study, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (LAS) were employed respectively to simulate the presence of a low concentration of an anionic surfactant in eutrophicated water. It was found that surfactants present in natural waters could enhance the hydrophilicity of the algae interface and the stability of the algae-laden water system with mitigated algae aggregation. During the initial filtration process, membrane fouling was aggravated related to the more serious pore blocking induced by the present SDS or LAS; however, during the next stage, membrane fouling was alleviated due to the formation of a looser cake layer in the presence of SDS or LAS. The pore blocking at the earlier stage contributes more to the decrease of total flux when surfactants are involved. Furthermore, the disinfection byproduct formation potential was reduced with SDS or LAS mainly due to the degradation of free available chlorine by the surfactants. While the concentration of algal toxins was ascended in the ultrafiltration effluent, which indicates that the separation performance was highly impacted by the presence of anionic surfactant.

Automated summary

The study demonstrated that natural surfactants can enhance the hydrophilicity of algae interface and stability of algae-laden water, reducing algae aggregation. While SDS or LAS aggravated membrane fouling in the initial filtration process, it alleviated fouling later on due to a looser cake layer formation. Surfactants led to more pore blocking in the early stage, resulting in a significant decrease in total flux. Additionally, SDS or LAS reduced disinfection byproduct formation potential by degrading free available chlorine, but increased algal toxins concentration in ultrafiltration effluent, indicating a high impact on separation performance.