UASB reactor setup and operation
The 30-L UASB reactor was used to producemethane. An acrylic
material was used to make the reactor. It had dimensions of 14 cm
(diameter) by 165 cm (height). This was large enough to allow a
25-L working volume and 5-L head space. Fig. 2 gives a schematic
of the UASB reactor. The UASB reactor contained UASB granules as
inoculums and acidic effluent as substrate. The acidic effluent from
hydrogen production process was used as the substrate and supplemented
with the optimum Ni and Co concentration obtained
from batch fermentation step (Section 2.3). The reactor was started
up using the optimum S/X ratio obtained from batch
fermentation step (Section 2.3) for 24 h. The reactor was operated
at a temperature of 30 ± 2 C in the continuous mode at the
highest HRT of 6 days (equivalent to the organic loading rate (OLR)
of 3.41 ± 0.35 kg-COD/m3 d) until it reached a steady state. The
steady state of each HRT was reached when the variation in the
MPR and substrate utilization was ±10%. After reaching a steady
state, the HRT was decreased to 5, 4, 3, and 2 days, equivalent to
the OLR of 4.20 ± 0.14, 5.25 ± 0.05 and 7.05 ± 0.13 kg-COD/m3 d,
respectively. Optimal HRT coincided with maximal methane
generation.