A bactericidal technique (PEC-Br) utilizing in situ photoelectrocatalytically generated photoholes (h(+)), long-lived di-bromide radical anions (Br-2(-)) and active oxygen species (AOS) for instant inactivation and rapid decomposition of Gram-negative bacteria such as Escherichia coil (E. coli) was proposed and experimentally validated. The method is capable of inactivating 99.90% and 100% of 9 x 10(6) CFU/mL E. coli within 0.40 s and 1.57 s. respectively. To achieve the same inactivation effect, the proposed method is 358 and 199 times faster than that of the photoelectrocatalytic method in the absence of Br-, and 2250 and 764 times faster than that of the photocatalytic method in the absence of Br-. The decomposition experimental results obtained from 600-s PEC-Br-treated samples demonstrated that over 90% of E. coli body mass was decomposed and 42% biological carbon contents in the sample was completely mineralized and converted into CO2. The mechanistic pathways of disinfection/decomposition by photocatalysis (PC), photoelectrocatalysis (PEC), and photoelectrocatalysis in presence of Br- (PEC-Br) were also illustrated based on experimental evidence. (C) 2010 Elsevier Inc. All rights reserved.