Batch co-digestion assays
Co-digestion of LSBB and co-substrates WAS and glycerol was
evaluated through biochemical methane potential (BMP). The BMP
assays were carried-out in batch tests, performed in sealed 117 mL
vials. An initial substrate concentration of 5 g/L of volatile solids
(VS) was applied. Anaerobic granular biomass from a full scale
UASB reactor treating brewery wastewater was used as inoculum.
Anaerobic biomass/substrate ratio was 1:1, expressed as VS. Medium
was supplemented with yeast extract (200 mg/L), NH4Cl
(65 mg/L), KH2PO4 (18.5 mg/L), CaCl2*2H2O (4 mg/L) and
MgSO4*7H2O (5.7 mg/L). Sodium bicarbonate was also added (5 g/
L), to provide pH buffer capacity. Temperature was kept constant at
35 C. Co-substrates were used at different proportions. WAS were
added at LSBB/WAS ratios of 1:3, 1:1 and 3:1. Glycerol was mixed
with LSBB at a ratio of 1:9. All previous ratios are expressed in terms
of volatile solids (VS). Endogenous biogas production from anaerobic
biomass was established by blank assays, where no substrate
was provided. BMP tests were performed in triplicates.
Methane production was determined following pressure increase
and biogas composition in the headspace of the vials. Pressure
was measured through pressure transducer (Cole Parmer) and
biogas composition was determined by gas chromatography
coupled to thermal conductivity detector (Clarus 580, Perkin Elmer).
The BMP value was expressed as methane volume per mass of
substrate (mL CH4/g VS). Total solids (TS), VS and chemical oxygen
demand (COD) were determined according to APHA et al. (2005).