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

Where,
Ss = Oxygen consumption for Ss * 100 Eq. 4.4
(1-Y) * CODT
Xs = Oxygen consumption for Xs * 100 Eq. 4.5
(1-Y) * CODT
Oxygen consumption for Ss = Area I
Oxygen consumption for Xs = Area II
Based on the area covered by the curve (area I), readily biodegradable COD, is equal
to 40% of total area while area II, slowly biodegradable COD, is equal to 60% of total area.
Thus, it could be said that among the biodegradation COD, readily degradable components
are just 40% compared to that of the slowly degradable component. This shows the
recalcitrant nature of the leachate and the requirement of a long HRT for complete
degradation of the biodegradable components. Based on the result, the estimated readily
biodegradable COD can be degraded within 12 h.
Though OUR experiments suggest the readily biodegradable and slowly
biodegradable components of the biodegradable COD, it does not actually tell the total
biodegradable content present in the leachate. To further investigate on this aspect, a 20
days BOD was measured. It has suggested by Henze (1992) that the fractions of organic
matter in wastewater which are measured in terms of OUR and BOD5 are similar. Thus,
the relation between the COD fraction and BOD concentration may suggest the
biodegradability of the leachate.
When the 20 days BOD of the raw leachate, stripped leachate, bacterial and the yeast
effluent were measured, the trend of increase in BOD was similar for raw and stripped
leachate. The trend of increase in BOD for the yeast and bacterial effluent for the first 10
days was similar. The trend of the 20 days BOD is given in Figure 4.37 and 4.38. The raw
data is given in Table H-1 of Appendix H.
After first 10 days, the BOD of the bacterial effluent did not vary significantly
compared to that of the yeast effluent. Table 4.14 gives contribution of percent BOD of the
total BOD for leachate influent and effluent ay different time periods.
Table 4.14 Contribution of BOD at 5, 10 and 15 Days to the Total 20 Days BOD
Percent BOD of 20 days BOD
Day Raw Stripped YMBR BMBR
Leachate Leachate Effluent Effluent
BOD5 (mg/L) 67 47 25 38
BOD10 (mg/L) 86 85 44 63
BOD15 (mg/L) 94 100 81 75
BOD20 (mg/L) 100 100 100 100
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