Removal of nitrate nitrogen and chemical oxygen demand in upflow fixed bed reactor using heterotrophic microorganisms

This communication deals with the removal of contaminants namely nitrate nitrogen (N-NO3−) and chemical oxygen demand (COD) in the form of acetate using an upflow packed bed anaerobic reactor. Effects of various parameters such as nutrient concentration, time, pH and flow rate were studied. The contaminants removal efficiency increased with the increase of initial concentration while the reaction rate of contaminants decreased with the increase of initial pH beyond 7. The effluent flow rate also showed a positive correlation with the contaminant removal rate up to 24 mL/min and beyond that it showed a negative trend. The reaction followed pseudo first order rate and using the same a unified rate equation was developed for both the contaminants such as N-NO3− and COD. The mass transfer rates for the both the contaminants were calculated. Rate equations were also developed using the sorption model, which showed good agreement with the experimental results. Using Monod equation, maximum specific degradation rate as well as half saturation constant for both the contaminants was calculated. Statistical techniques including principal component analyses and multi linear regression analyses were carried out, which substantiated the analysis of the results further.