Experimental and numerical investigation of the breakage of wastewater flocs in orifice flow.

It is well accepted that the breakage of wastewater suspended particles (flocs) can lead to better disinfection of effluent, especially when utilizing ultraviolet irradiation as the disinfection method. In this work, the breakage of wastewater flocs in orifice flow was investigated through numerical simulations. The strain rate along particle paths was estimated using computational fluid dynamics. Assuming that particle breakage occurs if the maximum strain rate experienced by the particle exceeds a critical threshold value, breakage of wastewater particles was predicted. The effectiveness of the model was supported by simple experiments. Based on the numerical simulations, under the same nominal orifice strain rate, particle breakage was higher in single-orifice systems compared to that of multi-orifice systems. This finding was further confirmed through experimentation. Furthermore, simulation results revealed that while single-orifice systems were the preferred choice for the breakage of strong particles, multi-orifice systems might be more effective in breaking ‘weak’ particles.