Effectiveness of Natural Zeolite and Geo-fabric as Single and Dual Media in BAFs for Wastewater Treatment

Abstract

The treatment performance of a dual-media biologically aerated filter (BAF) incorporating natural zeolite and geo-fabric (NZGF-BAF) was investigated and compared with single-media BAF systems using natural zeolite (NZ-BAF) or geo-fabric (GF-BAF). The effect of hydraulic retention time (HRT), carbon-to-nitrogen (C/N) ratio, rate of aeration and depth of filter on the single and dual media BAF system’s performance for removal of contaminants like chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia-nitrogen (NH₃-N), turbidity and total dissolved solids (TDS) was studied. According to the experimental results, under similar conditions, the NZ-BAF and GF-BAF showed comparable results for removal of COD, BOD and turbidity due to larger surface areas, biofilm formation, absorption and adsorption potential. While the removal of NH₃-N was higher for NZ-BAF due to its ion-exchange and GF-BAF showed better removal of TDS due to the permeability, adsorption and bacterial activity. The NZGF-BAF with dual media showed improved performance with respect to removal of all the contaminants. Further, optimization study conducted on NZGF-BAF using Response Surface Methodology (RSM) under optimal conditions, achieved maximum removal rates of COD, BOD, NH₃-N, turbidity and TDS as 93 %, 98 %, 94 %, 93 % and 67 % respectively.