136
N. Wid and L. F. Ayut
2.4 Preparation of Food Waste Digested Liquor (FWDL)
for Anaerobic Digestion
The FWDL was prepared by performing 15 days anaerobic digestion (AD) using
200 mL working volume as described by Owen et al. (1979), Hansen et al. (2003) and
Angelidaki et al. (2009). PS was added into the anaerobic reactor (250 mL Duran
bottle with stopcock) at ratio 1.5:1.0 (sample to inoculum). The percentage of total
solids (TS) and volatile solids (VS) were first obtained in order to determine the
amount of sample added into the reactor. The pH value of the mixture on Day 1 was
controlled to be in the range of 6.8–7.2 using 1.0 M hydrochloric acid (HCl) and
1.0 M sodium hydroxide (NaOH). The reactor was placed in a water bath for 15 days
at 37° and was manually shaken once per day. The biogas produced was released
daily to avoid reactor explosion and the pH value and temperature were monitored
every three days. On Day 15 (final day) about 5 mL of digested liquor was taken and
filtered for physicochemical analysis.
2.5 Physical Characterisation of Food Waste
The physical characterisation of the sample was performed based on the method
outlined by APHA (2005). The raw sample of food waste was used to determine the
physical characteristics. The studied parameters including pH, TS, and VS. The pH
was determined using a pH meter which calibrated using standard buffer solutions of
pH 4 and pH 7. The TS and VS were determined by weighing out an empty crucible,
g (A), followed by the loading of wet sample into the crucible. The crucible with
a wet sample, g (B), was placed in an oven for 24 h at 105 °C. A further step was
transferring into desiccator to cool down. The crucible with dried sample, g (C), was
weighed and then placed into a furnace for 4 h at 550 °C. Upon complete, it was
again transferred into the desiccator for the same purpose and the crucible with ash
sample, g (D), was then weighed. The percentage of TS and VS were calculated by
using Eqs. 2 and 3, respectively (APHA 2005).
T S (%) =
(C − A)
(B − A)
× 100%
(2)
V S (%) =
(C − D)
(C − A)
× 100%
(3)
2.6 Chemical Characterisation of Food Waste
The chemical characteristics were determined in terms of the concentrations of magnesium (Mg
2+ ), ammonium (NH 4
+ ) and phosphate (PO 4
3− ) ions. The concentration
N. Wid and L. F. Ayut
2.4 Preparation of Food Waste Digested Liquor (FWDL)
for Anaerobic Digestion
The FWDL was prepared by performing 15 days anaerobic digestion (AD) using
200 mL working volume as described by Owen et al. (1979), Hansen et al. (2003) and
Angelidaki et al. (2009). PS was added into the anaerobic reactor (250 mL Duran
bottle with stopcock) at ratio 1.5:1.0 (sample to inoculum). The percentage of total
solids (TS) and volatile solids (VS) were first obtained in order to determine the
amount of sample added into the reactor. The pH value of the mixture on Day 1 was
controlled to be in the range of 6.8–7.2 using 1.0 M hydrochloric acid (HCl) and
1.0 M sodium hydroxide (NaOH). The reactor was placed in a water bath for 15 days
at 37° and was manually shaken once per day. The biogas produced was released
daily to avoid reactor explosion and the pH value and temperature were monitored
every three days. On Day 15 (final day) about 5 mL of digested liquor was taken and
filtered for physicochemical analysis.
2.5 Physical Characterisation of Food Waste
The physical characterisation of the sample was performed based on the method
outlined by APHA (2005). The raw sample of food waste was used to determine the
physical characteristics. The studied parameters including pH, TS, and VS. The pH
was determined using a pH meter which calibrated using standard buffer solutions of
pH 4 and pH 7. The TS and VS were determined by weighing out an empty crucible,
g (A), followed by the loading of wet sample into the crucible. The crucible with
a wet sample, g (B), was placed in an oven for 24 h at 105 °C. A further step was
transferring into desiccator to cool down. The crucible with dried sample, g (C), was
weighed and then placed into a furnace for 4 h at 550 °C. Upon complete, it was
again transferred into the desiccator for the same purpose and the crucible with ash
sample, g (D), was then weighed. The percentage of TS and VS were calculated by
using Eqs. 2 and 3, respectively (APHA 2005).
T S (%) =
(C − A)
(B − A)
× 100%
(2)
V S (%) =
(C − D)
(C − A)
× 100%
(3)
2.6 Chemical Characterisation of Food Waste
The chemical characteristics were determined in terms of the concentrations of magnesium (Mg
2+ ), ammonium (NH 4
+ ) and phosphate (PO 4
3− ) ions. The concentration