Nitrite as oxidizing power for p-cresol removal using a denitrifying sludge: kinetic study

BackgroundChemical plants, oil refineries and petrochemical plants discharge wastewaters polluted with phenolic and nitrogen compounds. Denitrification is an economical and feasible process, however, metabolic and kinetic information is required in order to know and to control the limitations involved when nitrite is present or accumulated. The goal of this study was to study the kinetic behavior of a denitrifying sludge and to reduce nitrite at several p-cresol-C (p-Cr) concentrations. ResultsOver the 10 to 45 mg p-Cr L-1 concentration range tested, nitrite reduction was linked to p-Cr oxidation and the specific rate increased to 7.02 mg NO2--N g(-1) VSS h, with CO2 and N-2 the products. At higher initial p-Cr concentrations, inhibition was observed, diminishing the specific rate to 1.60 mg NO2--N g(-1) VSS h. Electron balance showed that p-Cr consumption was carried out by two biological processes; denitrification and fermentation. The kinetic profile followed the Haldane model, with inhibition constant (K-i) of 35.75 mg p-Cr L-1, affinity constant (Ks) of 20.32 mg p-Cr L-1 and maximum specific nitrite reduction (q(max)) of 9.48 mg NO2--N g(-1) VSS h. CONCLUSIONSThe results suggest that p-cresol can be removed by denitrification and fermentation. Kinetic information should be considered for designing and operating denitrifying reactors to treat industrial wastewaters containing phenolic compounds and nitrite. (c) 2013 Society of Chemical Industry