Waterworks sludge-filter sand permeable reactive barrier for removal of toxic lead ions from contaminated groundwater

This study aims to use of inexpensive and available byproduct waterworks sludge resulted in huge quantities from the activities of water supply treatment system in the remediation of groundwater contaminated with lead ions as an application of sustainability principles. Results revealed that this material can be used effectively in the permeable reactive barrier technology. The best operational conditions for initial pH, contact time, and sorbent dosage in the batch tests were 5, 1 h, and 0.3 g/50 mL, respectively at agitation speed of 200 rpm and initial concentration of 50 mg/L to achieve the maximum removal efficiency (97 %). Langmuir isotherm model was introduced a fair description for sorption measurements with maximum capacity of 20.41 mg/g. Also, the precipitation/co-precipitation processes were found the predominant mechanisms in the sorption process under consideration based on Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) images in combination with final pH values. The developed model for continuous tests solved by COMSOL Multiphysics 3.5a to plot the contaminant transport under the effects of initial concentration, flowrate and bed depth. It is recognized that the model predictions can be simulated the experimental values with satisfactory concurrence where the coefficient of determination (R-2) >= 0.983. The breakthrough point in the continuous transport was appeared earlier by decreasing the bed depth, and increasing both the initial concentration as well as the flow rate.