Isolation and performance of ultraviolet tolerant bacterium strain for pretreatment and quorum quenching to control reverse osmosis biofouling.

Conventional biocides and UV disinfection are often ineffective against biofouling in reverse osmosis (RO). This study explores a new approach to combine Staphylococcus sp. SSN, a UV-tolerant quorum quenching (QQ) bacterium isolated from activated sludge and UV treatment to defer the onset of biofouling. Under UV exposure, immobilized Staphylococcus sp. SSN retained QQ activity, reducing biofilm formation (by 81 %), and extracellular polymeric substance production (by 22 %). Within 2 h, the combined UV-QQ treatment achieved 3.5-log bacterial inactivation, outperforming UV alone. The observed enhanced effect is likely due to suppressed quorum sensing and biofilm gene expression, reducing UV shielding and increasing oxidative stress. In real wastewater experiments, UV-QQ pretreatment lowered RO flux decline to 45 % after 6 days, compared to 70 % in the control. These findings demonstrate the potential of integrating QQ bacteria with UV disinfection to slow down biofouling development in RO for water reuse applications.