Effect of influent C/N ratio on nitrogen removal using PHB as electron donor in a post‐denitritation SBR

Abstract

AbstractBackgroundThe post‐denitritation sequencing batch reactor (SBR) is widely‐used and can achieve high levels of nitrogen removal. In this study the effect of influent COD/TN (total nitrogen) ratio (i.e. C/N ratio) on nitrogen removal performance was investigated.ResultsThe experimental results showed that polyhydroxybutyrate (PHB) was the internal carbon source for denitritation, so PHB degradation rate following first‐order kinetics was the rate‐limiting step both for simultaneous nitritation–denitritation (SND) in the substrate famine period of the oxic stage and endogenous denitritation in the anoxic stage. Higher influent C/N ratio resulted in more PHB fractions in microorganisms, which facilitated a higher efficiency of SND and a faster endogenous denitritation rate (DNR). Consequently, mean TN removal ratio in oxic stage dropped from 32.81% to 8.61%, and average endogenous DNR in the anoxic stage fell from 1.50 to 0.27 mgN h‐1 gVSS‐1, when influent C/N ratio changed from 6.82 to 1.89. Furthermore, PHB fraction in the biomass did not drop drastically when influent C/N ratio dropped for a short‐term period, which facilitated better resistance to shock loads.ConclusionHigh influent C/N ration benefits nitrogen removal in this process, and an influent C/N ratio of 4.00 was suitable for advanced nitrogen removal. © 2013 Society of Chemical Industry