2.8. Water quality analysis
The concentrations of organic substrates and products (i.e. acetate,
ethanol, propionate, butyrate) were measured using a gas
chromatograph (Agilent 6890N, CA) equipped with a double
bonded fused silica capillary column (Agilent DB-FFAP, CA). The
glucose concentration was measured using phenol–sulfuric acid
assay (Dubois et al., 1956). The sample was diluted in the range
of 10–80 mg/L. One milliliter of sample was mixed with 1 mL of
5% phenol and 3 mL of sulfuric acid and was analyzed with a UVspectrophotometer
(Varian Inc., CA). The absorption wavelength
was compared to a standard curve to obtain the concentration of
the sample.