Effect of Enteromorpha extract on characteristics of flocs formed by aluminum sulfate in Yellow River water treatment under different hydraulic conditions

A new coagulant aid, Enteromorpha extract (Ee), was used together with aluminum sulfate (AS) in Yellow River water treatment to assess its effects on floc characteristics. The dual-coagulant, aluminum sulfate–Enteromorpha extract (AS–Ee), was obtained by dosing Ee 30 s after AS dosed. The growth, breakage and regrowth of flocs formed by AS and AS–Ee was comparatively investigated under different hydraulic conditions. Results showed that flocs sizes and growth rates could be obviously improved by Ee addition, and the growth characteristics of flocs produced by AS–Ee were less affected by mixing speed. Furthermore, flocs formed by AS–Ee could resist stronger shear force and longer breakage time than that of AS. Due to its long chains structure of macromolecules, Ee could produce bridging effect besides precipitate charge neutralization and adsorption effects of AS. Therefore, better floc characteristics of AS–Ee were achieved by a combination of two advantages.

• Ee was used as a new coagulant aid with the aim of “treating waste by waste”.
• Water treatment cost and human health risk can be reduced when Ee was used.
• Characteristics of floc were significantly improved due to Ee addition.
• Floc characteristics were less affected by hydraulic conditions when Ee was used.