Characterization of the effects of low power pulsed vibration energy on biofouling inhibition in water piping systems

Low power pulsed vibration energy inhibits biofouling in water piping systems. The precise inhibition mechanisms, however, are unknown. This research focused on low power pipe structural vibrations that inhibit biofouling in flowing water systems. First, the effects of the pulse energy were evaluated. Biofouling inhibition in clear plastic piping was analyzed as a function of the distance from a Pulsed Acoustic Device (PAD) using a novel light absorption technique to approximate biofouling mass. Vibration induced in the PVC pipe wall inhibited biofouling up to 50% out to a distance of 24-pipe diameters from the PAD. Biofouling inhibition decreased with distance from the PAD. Second, pipe wall acceleration power spectrum levels were measured at discrete longitudinal distances from the PAD and evaluated between 0 and 10,000 Hz. Biofouling rate inhibition was observed over approximately four-week durations, however, the experiments were not run long enough to evaluate any long-term effects on total fouling population. Results indicate a potential relationship between biofouling inhibition and bending wave acceleration power spectrum levels at 1 kHz and potentially no relationship at 2 kHz. When the pipe was vibrated at two specific frequencies with equivalent bending wave acceleration power spectrum levels, it was observed that biofouling inhibition occurred at the higher of these frequencies (14,350 Hz) and that it did not occur at the other (700 Hz).; Pipe wall vibration was shown to be a necessary condition for pulsed-induced inhibition; the presence of an acoustic wave in the fluid by itself does not appear to inhibit biofouling. The data suggest that pipe wall vibration at selected frequencies within the critical residence time inhibited the irreversible attachment of microbes causing the fouling.; Experimental data were not sufficient to reach conclusions regarding whether the broadband impulse from the PAD excites many pipe natural frequencies. Nevertheless, the data suggest that some of the excited modes might in turn excite some of the mechanisms that could transfer energy to microbes to break them free from reversible adhesive forces holding them tentatively to the pipe wall and push them away from the wall.