A novel bio-physical approach for perchlorate contaminated well water treatment

Abstract

A novel bio-physical approach for treating well water contaminated with perchlorate (ClO4¯) at 15 mg/L is reported in this study. In this process, the ClO4¯ was initially treated in an anaerobic fixed-film bioreactor (55 L), followed by a ceramic Micro-Filtration (MF) unit (1.5 μm pore size, 0.12 m2 surface area) and a Reverse Osmosis (RO) unit (0.38 m2 surface area) connected in series. The bioreactor inoculated with a ClO4¯ reducing bacterium Serratia marcescens (Gen bank no. JQ807993) removed ~97% of the ClO4¯ using acetate as substrate (acetate/ClO4¯ ratio = 4). Subsequently, the MF and RO units removed ClO4¯ to <10 μg/L, Total Dissolved Solids (TDS) to <25 mg/L and Total Chemical Oxygen Demand (TCOD) to below detection Limit. The fouling associated with membranes was controlled (88–100%) through hourly manual backwashing with 2 L pure water at 25 L/h, and 60 psi, and forward flushing with 1 L pure water at 30 L/h and 3–5 psi for MF and RO units, respectively. The rejects and membrane wash water were also treated in the bioreactor, resulted in complete removal of ClO4¯ through this approach. This is the first report where biotreatment is adopted as a pre- and post-treatment to membrane process for removing ClO4¯, and this will find field application for treating ClO4¯ contaminated ground as well as surface water sources.