Treatment of phenolic wastewater in UASB reactor: Effect of nitrogen and phosphorous

Phenolic wastewater representing an industrial wastewater was supplemented with varying amount of nitrogen (N) and phosphorous (P) and treated in upflow anaerobic sludge blanket reactor (UASBR). The variation of COD:N:P from 300:10:1 to 300:1:0.1, did not influence the conversion of phenol COD to methane COD. The concentration of N and P in the influent was reduced from 25.5 mg l−1 to 2.5 mg l−1 and 2.5 to 0.25 mg l−1, respectively. However, on further reducing the nutrients in the feed from 300:1:0.1 to 300:0:0 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 and P in cells varied from 10% to 14% and 0.6% to 2.4%, respectively. The activity of the sludge assessed as specific methanogenic activity (SMA) was found in the range from 0.15 to 0.66 g CH4–COD g−1 VSS d−1. The optimum COD:N:P for phenolic wastewater has been estimated to be 300:1:0.1.