2.4. Experiments
2.4.1. Microbial process
As a preliminary study, batch experiment was performed for
background information to see if any substances were released
from the rice husks that could interfere with the spectrofotometric
analyses. The retention time was higher in the batch system when
compared to the continuous systems and hence it was observed
more clearly that the microorganisms were capable of degrading
the compounds which might be released.
In the two parallel continuous systems the experiments were
performed to investigate the effect of the following parameters
explained below.
2.4.1.1. Continuous system 1. In this system effect of the wastewater
composition, the residence time, the amount of yeast extract,
and the wastewater flow rate was tested. In order to investigate the
effect of wastewater composition two different synthetic wastewaters
were prepared as explained in Section 2.3.1. The flowrate
of the synthetic wastewater was adjusted as 0.351 mL/min. The
experiments were lasted until the system reached the steady state
conditions. In the experimental set in which the residence time
effect on the performance was investigated, the number of reactors
was increased from two to four to ensure a longer residence
time and the feed flow rate was 0.351 mL/min. The system was also
inoculated with a rinse solution from the forest residues (50.5 g
wood chips of forest residues rinsed with 400mL 0.9% NaCl) in
order to add new microorganisms which had different capability
for degradation of organic compounds. In order to investigate the
effect of the yeast extract addition, the amount of yeast extract was
increased from 1 g/L to 2 g/L in the synthetic dye mixture. The effect
of the wastewater flow rate was also tested by increasing the rate
from 0.351 mL/min to 0.803 mL/min.
2.4.1.2. Continuous system 2. Parallel to the experiments in continuous
system 1, other experiments in continuous system 2 were
performed to investigate addition of solution from forest residues
and the effect of wastewater flowrate. The system had two reactors
connected in series. The system was inoculated with a rinse
solution from the forest residue so different kinds of microorganisms
were added to the system in order to investigate the effect of
the wood chips solution. The purpose was to add different kind of
bacteria and fungi, which support themselves on complex organic polymers and aromatic molecules. The flow rate of the wastewater
(ww II) was 0.311 mL/min.
Finally, the flow rate of wastewater was increased from
0.311 mL/min to 0.637 mL/min to investigate the effect of increasing
the flow rate and hence residence time.