68 Activated sludge was used as seed and was collected from WWTP Universiti
Teknologi PETRONAS Malaysia. Incubation was conducted for 5 days in the incubator at a temperature of 20 + 1
⁰C. The BOD
5
value was estimated as follows Equation 3.5:
v.t v.tc
control DO
v.t v.s
sample DO
BOD
5 5
5
3.5
where: BOD
5
= BOD
5
of test compound, DO
5
sample = DO
5
of test compound + DO
5
of seed, DO
5
control = DO
5
of seed v.s = volume of seed = 30 ml,
v.tc = volume of test compound = 65 ml, and v.t = total volume = 95 ml.
3.3.4 Identification of UV Absorption Spectra of MDEA
Direct photolysis of an organic compound by UV light usually occurs when the organic compound absorb UV light. Identification of the UV spectrum region
absorbed by MDEA was conducted using UV-VIS-NIR spectrophotometer SHIMADZU UV-3150, Japan. MDEA solution was prepared and tested at
= 200 to 600 nm regions.
3.3.5 Un-reacted MDEA and Degradation Product Identification using HPLC
An Agilent series 1100 brand of HPLC was used to monitor the degradation products and un-reacted MDEA after UVH
2
O
2
treatment. YMC-Pack PolymerC18 reverse phase column was utilized. A solution consisting of 60 Na
2
HPO
4
100mM and 40 NaOH 100mM at pH = 12 was used for elution.
69 UV light at 215 nm was used as detector. Transgenomic Model ORH801 column
was used for organic acid determination with 0.01 N H
2
SO
4
as mobile phase. Refractive index was used as detector. Degradation product determination was
performed by the comparison of sample with the standard compound. Qualitative analysis was based on the retention time of each compound in the chromatogram,
while quantitative analysis was based on the calibration curve prepared using standard compound. The details of the calibration curves for different compounds tested are
presented in Table 3.3 and the plots of concentration vs. area are presented in Figure 1, 2, 3, and 4 of Appendix.
Table 3. 3 The correlation constants for the calibration curves for MDEA and organic acids.
Compound Column name
Calibration curve R
2
Remark
MDEA YMC-Pack PolymerC18
[MDEA] = 0.5354Area 0.9998 Figure A1 of
Appendix A Oxalic Acid
YMC-Pack PolymerC18 [Oxalic Acid] = 0.8558Area
0.9994 Figure A2 of Appendix A
Formic Acid Transgenomic-ORH801
[Formic Acid] = 0.0236Area 0.9999 Figure A3 of
Appendix A Acetic Acid
Transgenomic-ORH801 [Acetic Acid] = 0.0177Area
0.9999 Figure A4 of Appendix A
3.3.6 Nitrate NO
