Enhanced removal of PhACs in RBF supplemented with biofilm coated adsorbent barrier: Experimental and model studies

Abstract

The present study focussed on potential application of river bank filtration (RBF) for the effective removal of pharmaceutically active compounds (PhACs), namely, atenolol, ciprofloxacin and gemfibrozil. Experiments on RBF were performed in a pilot scale reactor (3.0 m × 1.0 m × 0.5 m) in which two dimensional unconfined aquifer flow conditions were induced by pumping to depict realistic field conditions. Initially, experiments were carried out in a reactor filled with natural river bed material. The natural attenuation efficiencies were found to be 21, 35 and 8% for atenolol, ciprofloxacin and gemfibrozil, respectively. Pumping experiments conducted through clean sand in RBF indicated that PhACs were highly mobile with minimal degradation. In order to improve the treatment efficiency of RBF, biofilm coated clay composite adsorbent was synthesized and used in a reactive barrier. The reactive barrier could significantly eliminate PhACs up to 80, 90, 75% for atenolol, ciprofloxacin and gemfibrozil, respectively, at the extracting well (located at 125 cm from the inlet) even after 150 h. Pumping experiments showed that 20 cm thick barrier was able to contain the movement of contaminant plume up to 4 h when water was pumped at a rate of 0.0075 L/s and up to 3.2 h when the pumping rate was 0.01 L/s. Further, a 2D reactive transport model was developed and validated based on the experimental data. The transport model would be useful for developing a management model for the optimal design of reactive barrier for enhancing the performance of RBF.