Characterization of metabolic activities of waste-activated sludge from the SBR process

The biological activity and sensitivities of volatile suspended solids (VSS) were studied using waste-activated sludge (WAS) from the sequencing batch reactor (SBR) process. We also examined the specific oxygen uptake rate (SOUR) and 2,3,5-triphenyltetrazolium chloride-specific dehydrogenase activity (TTC-SDHA) for both the exogenous metabolism and heavy metal inhibition tests. The inhibiting effects of heavy metals on chemical oxygen demand (COD) removal were also examined. It was found that TTC-SDHA and SOUR were more sensitive than VSS in terms of the characterization of growth curve. The maximum biological activity of the growth curve was calculated by fitting polynomial functions for VSS and SOUR. Linear regression analysis revealed a strong correlation between TTC-SHDA and SOUR, with a correlation coefficient of 0.9117. In the inhibition test, TTC-SDHA and COD removal were inhibited at a similar level, while SOUR was more sensitive than the others to the toxicity of zinc (Zn) and cadmium (Cd). The median inhibitory concentration (IC50) of heavy metal was calculated by linearizing experimental data, and this also suggested that SOUR was the most sensitive to inhibition by heavy metals.