The VBPR in this
experiment was approximately 0.7–1.2 m3/m3, which corresponded to an OLR of 1.5–3.5 kg-COD/m3 d. The methane content
in the resulting biogas was approximately 60–65%. This result is
similar to that achieved when treating poultry wastewater using
UASB (Atuanya and Aigbirior, 2002), but lower than the VBPR of
3 m3/m3 d and COD removal rate of 80% achieved when treating
swine wastewater with an IC reactor and a loading rate of 6–
7 kg-COD/m3 d (Deng et al., 2006). This difference was probably
due to the higher ammonia content of the anaerobically digested
CSTR effluent used in this study and the better biodegradability
of the swine wastewater used in the previous study.