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2. Materials and methods 2.3 Palm oil mill effluent (POME)

The fresh raw POME was collected from the
2.1 Anaerobic seed sludge receiving tank of Palm Pattana Southern Border Co, Ltd.,
The anaerobic seed sludge used in this experi- Pattani Southern Thailand. Raw POME has brown color,
ment was obtained from lab-scale upflow anaerobic sludge pH 4.68ฑ0.00, a temperature of 70-80 C. The POME
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blanket reactor (UASB) producing hydrogen from SLS. was fully characterized, as presented in Table 1, and kept
The sludge was pretreated at 121 C for 15 minutes to in cold room at 4 C prior experimental conducting.
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remove methanogenic bioactivity. The sludge was 2.4 Batch hydrogen production from SLS and POME
enriched with synthetic medium according to Angelidaki Co-digestion of SLS with POME was tested at
and Sanders (25) with 10 g/L of sucrose and operated different mixing ratios of SLS to POME (95:5, 90:10, 85:15,
under thermophilic conditions (55 C) in 150 mL of serum 80:20, 75:25, 70:30, 65:35, 60:40, 55:45 and 50:50 (%v/
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bottles with 50 mL of working volume. v)). The assay was conducted as batch cultivations in 150
2.2 Skim latex serum (SLS) mL serum bottles. In each bottle, 15 mL of inoculum and
The fresh raw SLS was collected from Chana 35 mL of substrate/water mixture were added. The mixtures
Latex co, Ltd., Songkhla, Southern Thailand. The pH of were then purged with N (100%) to ensure anaerobic
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mild yellow raw SLS was 4.83ฑ0.01. Raw SLS was kept conditions. Afterwards the bottles were closed with butyl
at 4 C prior using in order to minimize self-biodegradation stoppers and placed in a 55 C incubator for 8 days.
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and acidification. Some chemical and physical characteris- Hydrogen production in the headspace of the vials was
tics of SLS are given in table 1. monitored. The headspace gas was collected for hydrogen
determination daily.

Table 1. Chemical and physical characteristics of SLS and POME

Characteristics SLS POME
pH 4.83±0.01 4.68±0.00
TSC (g/L) 49.65±0.01 42.07±0.16

VSC (g/L) 43.46±0.39 32.24±0.89
Alkalinity (mg/L as CaCO 3) 56±1 28±0

COD (mg/L) 29219±5666 42553±6137
TKN (mg/L) 5180±0 1245±11

Protein (mg/L) 7583±505 7781±66
TON (mg/L) 92±6 ND

Carbohydrate (mg/L) 602±0 ND
Sulfate (mg/L) 258±1 ND
ND = Not determined.