Significance of hydrodynamic cavitation to enhance reuse of secondary sedimentation tank effluent: a geometrical assessment

Abstract

ABSTRACT Adequate wastewater management is an environmental concern because of the lack of freshwater resources, which brings about the quick augmentation of technologies for complete quantitative and qualitative wastewater recovery. In the cluster of the advanced oxidation process, hydrodynamic cavitation developed as a promising technology to treat wastewater, in the last couple of decades, due to its low-cost energy efficiency without aided and residual chemicals. In the present study, two pilot-scale experimental setups (I and II) of hydrodynamic cavitation reactor have been used to treat the secondary sedimentation tank (SST) effluent of natural six sewage treatment plant (STP) of Surat city for irrigational reuse, using an orifice as a cavitating device. At inception, the inlet pressure has been optimized, which follows the first-order kinetic rate constant. The pump power with respect to the diameter of the main pipeline has differentiated by keeping the constant dimension of the cavitating device to compare the geometrical effect and was analyzed using the number of rotations concerning recirculation time to degrade the chemical oxygen demand (COD). It is found that the maximum COD, total suspended solids (TSS), and most probable number (MPN) were degraded to 79.8%, 63.8%, and 99.5%, respectively, by setup II; also, descent within the permissible limit proclaimed by CPHEEO India to irrigate the non-edible crops.