Thesis - faculty.ait.ac.th - Asian Institute of Technology

1. Obtaining endogenous sludge: 0.9 liter of fresh sludge without the substrate was
obtained in a respirometer and aerated for two hours.
2. Suppressing nitrification: With high ammonia concentration during the organic
oxidation, the oxygen uptake rate of nitrification process was constant. Hence,
NH4Cl of concentration 70 mg/L was added.
3. Recording endogenous oxygen uptake rate (OUR): After suppressing the nitrification
process, the mixture was aerated for half an hour before measuring the endogenous
OUR.
4. Adding substrate: An accurate dose of substrate was injected into the respirometer
and the total OUR was recorded by respirogram. Re-aeration was done once the DO
concentration dropped below 2 mg/L.
3.4.2 Lead Toxicity
The lead toxicity on the bacterial and yeast culture was conducted in the same
manner as described in the section 3.4.1. Lead nitrate (Pb (NO3)2) was used as Lead (Pb)
source. Soluble Pb concentration was varied from 0 to 20 mg/L. At each concentration, the
sample was filtered with 0.45 µm membrane filter and soluble Pb concentration was
analyzed using an atomic absorption spectrophotometer (AAS).
3.5 Ammonia Stripping
The characteristics of leachate used for the experiment are as described in Table 3.1.
The summary of the experiments conducted in order to optimize ammonia stripping is
illustrated in Figure 3.4.
The efficiency of ammonia stripping in ammonia removal was tested varying three
parameters namely- pH, contact time and the velocity gradient.
The experiments conducted are as follows:
1. Optimum pH for air stripping: The pH was varied from 9-12 (9, 10, 11, and 12) using
12 N NaOH solution. The removal efficiency of ammonia at varying pH was
assessed with a velocity gradient of 2,850 s -1 for two hours.
2. Optimum velocity gradient and contact time: After the optimum pH was obtained,
the velocity gradient and the contact time were varied. The velocity gradients at
which the experiment was done were 1,530, 2,850, and 4,330 s -1 . The contact time
was varied from 1 to 6 hours.
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