Curtailing COVID-19 spread in drain pipelines: Using interfacial hydrodynamics for removing Bacterial and Viral Biofilms

Abstract

Drainage systems contains biological contaminants like bacteria and viruses flowing through them. Additionally, these pipelines also have organic matter known as biofilms growing on their walls. These biofilms infact act as incubation zones for further growth of bacteria and coronaviruses. Standard water treatment routines with traditional cleaning agents are known to be not be able to clean or sterilize microbes located in the inner layers of the biofilm. A recent study has identified specialised fluids which are effective in removing biofilms but these need to be used prudently. The present study proposes to use ‘ interfacial hydrodynamics’ to ensure that the cleaner-fluid (CF) is transported effectively to the location of the biofilms at the pipe walls, and allowed to be in contact with the biofilms for a sufficient amount of time so as to ensure its effective removal. The present study has used CFD technique of Multi-fluid VOF and has demonstrated that relative superficial velocities of cleaner- fluids and sewage water can be controlled, so as to achieve flow regimes that ensure delivery of cleaner fluid to the periphery of the tube walls. Our simulations indicate that most effective cleaning can be achieved by using a cleaner-fluid with a high viscosity ( ~5000 cP)). In such cases, a low- medium velocity (~0.05-0.3 m/s) of CF and water would ensure that the cleaner fluids are in constant contact with the pipe walls. Other suitable viscosity and velocity combinations have also been proposed. Flow parameters that can be used to monitor and cross-verify expected flow patterns on-site have also been proposed.