Nitrogen biotransformation in anaerobic treatment of phenolic wastewater

Effect of nitrogen on methanogenesis of phenol has been evaluated. Methane generation rate constant (k) has been found to vary from 0.12 to 0.21 d− 1. The process was not impaired due to reduction of COD:N from 300:10 to 300:1. However, a definite decreasing trend in k was noticed at COD:N < 300:1. The µb at 90 days (µb90) was reduced from 0.94 to 0.12. Gas generation completely ceased at COD:N equal to 300:0. The trend of sludge activity was also found to be similar to that of k and µb90. The variation of COD:N from 300:1 to 300:0 in a UASB reactor, did influence the conversion of phenol COD to methane COD i.e. the (i) CH4-COD decreased from 90 to 40%, and (ii) cell yield reduced to 25-50%. The average cell yield was 3.5%. Percent N in cells varied from 10 to 14%. The activity of the sludge assessed as SMA was found in the range from 0.15 to 0.66 g CH4-COD/g VSS/d. The optimum COD:N for phenolic wastewater from both bench-scale batch and continuous reactor study has been estimated to be 300:1.