Synergistic effect of sono-photocatalysis with blue LED and natural photosensitizer terpinolene for rapid disinfection of multi-drug resistant coliform bacteria in wastewater

Abstract

To safeguard human health and the environment, thorough disinfection treatment strategies are required due to the prevalence of pathogenic and antibiotic-resistant bacteria in wastewater. In this research, a hybrid strategy to disinfect three common multi-drug resistant (MDR) bacteria (Enterobactor sp., Escherichia coli, and Klebsiella pneumonia) was implemented. Disinfection assisted by terpinolene (a natural photosensitive biocide) was used in combination with photocatalysis and ultrasonication. Photocatalysis was carried out by CdS nanorods (NRs) under blue LED irradiation simultaneously with the physico-chemical method of ultrasonic cavitation. Several reaction parameters were investigated, including light intensity, ultrasonication power, catalyst dosage, and inoculum size. With a catalyst loading of 250 mg/L, effective and complete disinfection was seen within 10 min, eradicating a bacterial concentration of 106 CFU/mL. Due to the synergistic impact of the hybrid method, the catalyst dosage below the ideal (1 × MIC) was also able to offer considerable disinfection. The discharge of intracellular nucleic acids and proteins revealed a breach of cell membrane. Reactive oxygen species (ROS) scavenging studies suggested the importance of diverse ROS species in the decontamination trials. Furthermore, tetrazolium dye reduction experiments revealed impediment of respiratory chain dehydrogenase activity. The photocatalytic efficacy of CdS nanorods remained stable even after 5 cycles, indicating the possibility of nanomaterial recycling for wastewater treatment. The findings of this study reveal that employing terpinolene as a natural photosensitive biocidal additive can substantially enhance sono-photocatalysis and effectively remove harmful MDR bacteria while reducing operational time and expense, making it a viable alternative to the enhanced disinfection of high strength MDR bacteria.