A novel insight into energy conservation and efficiency enhancement in wastewater treatment process: Low-frequency mechanical vibration induced

Abstract

One important way to break the bottleneck of energy conservation and consumption reduction in sewage treatment process is to attenuate the mass transfer resistance, which is thought as one of key factors to determine the efficiency of activated sludge treatment system. Thus, in this study, two independent Anacrobic/Oxic reactors were operated under low dissolved oxygen (DO) condition to evaluate the effects of low-frequency mechanical vibrations on the removal efficiency of pollutants. Results indicate that 40 Hz low-frequency mechanical vibration could greatly strengthen the efficiency of pollutants removal. Microelectrode-mass transfer efficiency test platform revealed that 40 Hz low-frequency mechanical vibration could increase the oxygen transfer coefficient from gas to liquid by approximately 145.19 %, and oxygen diffusion coefficient from liquid to solid by 75.2 %. Fractal dimension of flocs, particle size and zeta potential analyses jointly suggested that low-frequency mechanical vibrations treatment can form more adsorption points and mass transfer channels to enhance mass transfer efficiency of oxygen in floc. In addition, low-frequency mechanical vibrations treatment further stimulated the biological activities associated with nitrogen metabolism (i.e., specific metabolism rate, metabolism enzyme activities), but slightly alerted the overall microbial community. The findings in this study suggest that low-frequency mechanical vibrations could effectively accelerate the pollutants removal under low-DO condition by enhancing oxygen transfer coefficient and stimulating the associated biological activities. Collectively, this study provides a new technical strategy for efficiency enhancement and energy conservation in the global sewage treatment industry.