Removal of nitrate in raw water using a vertical roughing filter with an external carbon source

High nitrate concentration in water endangers health to both humans and livestock. The aim of this research was to investigate the efficacy of a roughing filter enhanced by an external carbon source in removing nitrate in raw water. Two upward vertical roughing filters in series were used-a vertical roughing filter with ethanol as a carbon source (VRFwt) and a vertical roughing filter without a carbon source (VRFwo). The average nitrate removal efficiency in a VRFwt was 88%, 70% and 83%, at carbon:nitrogen ratios (C/N ratio) of 1.05, 1.08 and 1.1, respectively. The average chemical oxygen demand (COD) removal efficiency in the VRFwt was 75%, 43% and 46% at C/N ratios of 1.05, 1.08 and 1.1, respectively. The total average reduction of dissolved oxygen (DO) in the VRFwt at C/N ratios of 1.05, 1.08 and 1.1 was 42%, 54% and 51%, respectively, while the drop in the VRFwo was 17%, 18% and 17%. The VRFwt showed a high potential for removing nitrate in raw water. Therefore, when the VRFwt is applied at large scale, it would improve access to water sources that were previously declared unacceptable by many water utilities due to excessive nitrate concentrations.