Analytical methods
The volume of biogas produced in the batch experiment was
measured using a wetted-glass syringe method [15]. The volume
of biogas produced in the reactor experiment was measured using
gas counter (Fig. 2). Hydrogen and methane production were
determined by gas chromatography (GC, Shimadzu 2014, Japan)
equipped with a thermal conductivity detector (TCD) and a 2-m
stainless column packed with Unibeads C (60/80 mesh). The GCTCD
conditions followed those of Saraphirom and Reungsang
[16]. The hydrogen and methane volume in the biogas was
calculated using a mass balance equation [17]. The VFAs were
measured by high performance liquid chromatography (HPLC)
according to the method of Saraphirom and Reungsang [16]. The
COD, VS, and VSS were measured according to the APHA method
[18].
3. Results and discussion
3.1. Batch fermentation of methane
The MY produced in all treatments was within the ranges of
14.94e321.17 mL CH4/g-VS-sub-added, while the biodegradability efficiency
ranged from 4.00 to 86.09% (Table 2). The highest MY and
biodegradability of 321.17 mL CH4/g-VSsub-added, and 86.09%,
respectively, were obtained at an S/X ratio, Ni and Co concentrations
of 0.80 g-VSsub/g-VSinoclum, 0.60 mg/L and 0.06 mg/L,
respectively (Run 2). The lowest MY and biodegradability of
14.94 mL CH4/g-VS-added and 4.00% were obtained at an S/X ratio, Ni
and Co concentrations of 0.47 g-VSsub/g-VSinoclum, 0.90 mg/L, and
0.03 mg/L, respectively (Run 19). The multiple regression analysis of
experimental data (Table 2) resulted in the quadratic equation
shown below (Eqs. (2) and (3)). Our results showed that the microorganisms
in the UASB granules effectively converted the VFAs
in the acidic effluent to produce methane.
MY ¼ 296:08 þ 17:61X1 33:01X2 þ 25:74X3 þ 1:42X1X2
þ 8:36X1X3 25:88X2X3 77:87X22
61:40X23
(2)
Table 1
Composition of the acidic effluent discharged after hydrogen production process at
steady state condition.
Composition Concentration
g/L g-COD/L
Sugarcane juice