Molecular Mechanism of Granulation. II: Proton Translocating Activity

A laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used in this study to produce granular sludge at mesophilic temperatures (35 ± 1°C). After more than 150 days of operation, a COD removal efficiency of 95% was achieved with an organic loading rate of 8.73 gCOD/L/day. At the same time, the sludge granulation process was observed. The mature granules were examined for their stability in terms of the presence of calcium ion, surfactant, pH (buffer and H2SO4/NaOH solution), metabolic inhibitor (iodoacetic acid and sodium fluoride), and proton translocator (carbonyl cyanide m-chlorophenyl-hydrazone). The results showed that bacterial surface dehydration, biological metabolic activity, and proton translocating activity were directly related to the strength of UASB granules. This indicated that the proton translocating activity on bacterial surfaces was the crucial factor in sludge granulation and, as a consequence, supported the proton translocation-dehydration theory. Experimental results from other studies were also used to support this new theory.