Page 94 - 048

       ☺    

2.5 Analytical methods and low chemical oxygen demand (COD) in SLS, result-

The volume of biogas produced was measured ing in low C/N ratio about 6. In contrast, POME contains
using water displacement method. The hydrogen content C/N ratio about 34, which is much higher than that of SLS.
was measured by gas chromatography (Shimadzu GC O-Thong et al. (8) reported the optimum C/N ratio is 74 for
14A equipped with thermal conductivity detector, TCD) biohydrogen production from palm oil mill effluent (POME).
fitted with a 1.5 m stainless steel column paced with Therefore, adding POME into SLS could definitely have
molecular sieve 58 (80/100 mesh). Argon was used as a more suitable C/N ratio for hydrogen production by using
carrier gas at a flow rate of 30 mL/min. The temperature dark fermentation.
of the injection port, oven and detector were 100, 50 and The optimum pH for hydrogen production was
100ฐC, respectively. 0.5 mL of sampling gas was injected 5.4-5.7 (6, 8, 27). Skim latex serum and palm oil mill
in triplicate. Volatile fatty acid (VFA) was analyzed by effluent have rather low pH of 4.83 and 4.68, respectively.
GC-FID (Shimadzu GC 8A). A column capillary packed Under low pH condition, free VFA can cause weak acid
with nitroterephthalic acid-modified polyethleneglycol inhibition (36). These VFA become more toxic due to an

(DB-FFAP) and with a length of 30 m was used. The increase of their undissociated fraction. The undissociated
chromatography was performed using the following pro- VFA can freely cross the cell membrane and then disso-
gram: 100 C for 5 min, 100-250 C with a ramping of 10 C/ ciate which lowers internal pH and disrupts homeostasis
o
o
o
o
min, 250 C for 12 min. The detector temperature was set (37). Therefore low hydrogen production yield obtained
at 300 C. COD, pH, total solid content (TSC), Volatile was also partly contributed by substrates having low pH.
o
solid content (VSC), alkalinity, total Kjeldahl nitrogen Cumulative hydrogen production under thermophilic con-
(TKN), protein content, total organic nitrogen (TON), dition was obtained from co-digestion of SLS and POME
carbohydrate content and sulfate content were determined is shown in Fig. 1. The result shows less than one day lag

in accordance with the procedures described in the Standard phase of all mixing ratio and hydrogen production rate
Methods (26). However, carbohydrate content in POME increased dramatically from 2 to 4 days of fermentation
has not been determined yet in this preliminary batch time. The stationary phase had been reached in 4 days of
experiments to investigate the effect on hydrogen produc- fermentation when using more than 75% of SLS. While
tion by adding POME into SLS at different mixing ratio. the fermentation broth contained less than 75% of SLS,
POME is found previously that it contains carbohydrate at a giving more POME composition, the stationary phase
concentration range of 8-25 g/L, which is the real substrate occurred after the fourth day of fermentation. Cumulative
for hydrogen production by dark fermentation (6, 8, 24, hydrogen production in this experiment ranged from
27). The exact content in POME will be analyzed later in 10.0±0.1 to 42.8±2.0 mL H . The maximum cumulative
2
consecutive investigation for nutrients optimization by hydrogen production (42.8±2.0 mL H ) was obtained
2
using the optimum mixing ratio obtained from this study. using co-digestion of SLS and POME with mixing ratio of
65:35 (%v/v) with C/N ratio of about 9. The lowest cumu-

3. Results and discussion lative hydrogen production (10.0±0.1 mL H ) was
2
obtained from fermentation of using only POME, having
3.1 Hydrogen potential of co-digestion of SLS and POME C/N ratio of about 34. Individual POME was a concen-
Characteristics of raw SLS and raw POME shown trated substrate with high content of lipid, which could
in the table 1 have high Total Kjeldahl Nitrogen (TKN) potentially inhibit the fermentation process. In Fig. 2 shows