Fabrication of anti-algae coatings by using quaternary ammonium compounds for wastewater treatment facilities: Anti-algae performance and mechanisms

In wastewater treatment plants, algae growth due to nitrogen and phosphorus in wastewater is an annoying issue for stable operation and management. Utilization of coatings incorporated with biocide is an effective strategy to mitigate algae attachment and growth. In this study, anti-algae coatings were prepared by blending quaternary ammonium compound (QAC) into waterborne enamel paints. Multiple light scattering spectroscopy demonstrated that addition of QAC led to increased stability of the hybrid coatings, attributed to the interaction of QAC and polymers. The modified coating (1.0 wt.% QAC) exhibited a compelling anti-algae activity, with an inhibition rate of 78.2% compared to the control. The anti-algae behaviours might be initiated by the contact between algae and QAC due to the interaction of positive charged quaternary ammonium groups and negatively charged algae cells. Upon contact, the long-chain alkyl groups could penetrate through the cell membrane. The positively charged nitrogen atoms could also replace divalent cations, causing the decrease of cellular Ca2+ level and increase of intracellular reactive oxygen species in algae cells, further inducing severe damage to algae cells and even cell death. The results highlight the potential of QAC to be incorporated into commercial coatings/paints for fabricating anti-algae coatings for wastewater treatment facilities.