Community level biological denitrification system for removing nitrate from groundwater

摘要

In the present study an attempt has been made to remove nitrate from sub-surface water using a low cost bench scale treatment system.An anoxic reactor was used for denitrification with cow dung slurry as the seed culture and powdered dried sugarcane bagasse as the sole source of carbon and energy for the denitrifying organisms. From batch studies in an anoxic reactor,it was found that 0.05 g/L of carbon source was more efficient in removing nitrate with very less amount of COD concentration remalned in the water.Since cow dung slurry and powdered sugarcane bagasse was used some amount of microorganisms and solids concentration was observed in the treated water and to remove this.A sand filter unit and a disinfection system was used.After five cycles of operation,the water from anoxic reactor contained 9 mg/L of nitrate-nitrogen while COD concentration was 8 mg/L and most probable number (MPN)Was 11.After filtering the water in sand filter and disinfecting the final treated water contained nitrate-nitrogen concentration of 7.2 mg/L while COD concentration and MPN were not detected.The treated water was found to be potable with respect to various other water quality parameters.Bacterial contamination was reduced using sand filter unit and a disinfection system using combination of bio-coagulants like“Moringa Oleifera”and“Abelmoschus Esculentus”seed powder with chlorine.The nitrate removal rate was found to be 0.30kgN/m3-d with C/N ratio of 0.17.