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methane production stages was conducted in batch reactor for 7 days and 14 days, respectively.
Subsequently, the enriched sludge was further transferred into a continuously stirred tank reactor
(CSTR) and an up-flow anaerobic sludge blanket (UASB) reactor for continuous processes.

4.3.2 Skim latex serum

The skim latex serum used in this experiment was collected after latex coagulation
process from Chana Latex Co, Ltd., Songkhla Province; Southern Thailand. It had the following
characteristics; light yellow color, pH 5.04±0.01, volatile solid content (VSC) of 40.61±0.06 g/L,
chemical oxygen demand (COD) of 33600±0 mg/L, proteins content of 6417±202 mg/L, and
carbohydrates content of 379±0 mg/L. The physical and chemical characteristics of the SLS are
given in Table 4.1. The SLS was kept at 2±1°C and was used within a month in order to
minimize self-biodegradation and acidification.

4.3.3 Palm oil mill effluent

The palm oil mill effluent used in this experiment was collected from the receiving tank
of Palm Pattana Southern Border Co, Ltd., Pattani Province; Southern Thailand. Palm oil mill
effluent has brown color, pH 4.74±0.01, COD of 76160±0 mg/L, proteins content of 5180±35
mg/L, carbohydrates content of 10340±0 mg/L, and oil and grease content of 12083±86 mg/L.
The physical and chemical characteristics of the POME are summarized in Table 4.1. The raw
POME was kept at 2±1°C and was used within a month.