Investigate the role of biofilm and water chemistry on lead deposition onto and release from polyethylene: An implication for potable water pipes.

ABSTRACT

In this study, the influence of biofilm presence and water chemistry conditions on lead (Pb) deposition onto low density polyethylene (LDPE) surface was examined. The results demonstrated that biofilm presence on LDPE surfaces strongly and significantly enhanced Pb uptake, with the 13-fold greater equilibrium Pb surface loading when biofilm was present (1602 µg/m2) compared to the condition when it was absent (124 µg/m2). The kinetics of Pb adsorption onto LDPE surface when biofilm was present is best described by Pseudo 2nd order kinetic model. Pb adsorption onto new LDPE surfaces was significantly reduced from 1101 µg/m2 to 134 µg/m2 with increased aqueous solution's ionic strength from 3 × 10-6 M to 0.0072 M. The presence of chlorine residual (2 mg/L) significantly reduced Pb adsorption onto LDPE surfaces by possible oxidation of Pb2+ to Pb4+ species. The kinetics of Pb release from LDPE surfaces was investigated under static and dynamic conditions through immediate exposure of Pb accumulated LDPE pellets to the synthetic water at pH 5.0 and 7.8. The results demonstrated a greater Pb release (86 %) at pH 5.0 compared to the pH 7.8 (58 %). An enhanced Pb release into the contact water was found under dynamic conditions compared to static conditions.