At first, the raw wastewater was pretreated with IL at optimumassay
conditions prior to anaerobic treatability test. Diluted
wastewater (5% v/v)was taken in 4–1 L flasks and IL beads were
added at a rate of 0.04 g beads/g oil. The initial pH was adjusted
with NaHCO3 to 6.8 and kept in an orbital shaker at 150 rpm for 30 min at a temperature of 37 ◦C. Then the pretreated wastewater
was left to settle for 10 min. Two distinct phases (supernatant
and bottom sludge) were observed and the settled beads were
removed from the flasks. A mixture of supernatant and bottom
sludge (1:1, v/v) was used for anaerobic respirometry.
The respirometric experiments were conducted using 250mL
serum bottles capped with natural rubber sleeve stoppers
(AER208 system, Challenge Environmental System, AR). Volumes
of 70mL of IL pretreated wastewater and 50mL of seed
sludge were filled in flasks. The acclimatized seed sludge used
in this experiment was obtained from a laboratory-scale UASB
reactor treating pet food wastewater [27]. Blanks were also prepared
with raw wastewater and/or seed sludge. The pH of all
samples was adjusted to neutral with NaHCO3. The flasks were
then kept in the temperature-controlled respirometer at 35 ◦C
and mixed with magnetic stirrers. Each flask was connected to
the bubble counter through aKOHtrap, and methane gas productionwas
recorded by a computer. The experimentwas concluded
when the biogas production stabilized. Initial and final samples
were taken for analysis