Thesis - faculty.ait.ac.th - Asian Institute of Technology
Thesis - faculty.ait.ac.th - Asian Institute of Technology
Thesis - faculty.ait.ac.th - Asian Institute of Technology
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COD/TOC, VS/FS and VFA/TOC ratios <strong>of</strong> le<strong>ac</strong>hate are depends greatly on <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e<br />
landfill (Chian and DeWalle, 1976; Kylefors, 1997). Figure 2.3 represents <strong>th</strong>e trend <strong>of</strong><br />
le<strong>ac</strong>hate variation and over <strong>th</strong>e period <strong>of</strong> time in <strong>th</strong>e landfill. During <strong>th</strong>e initial stages, <strong>th</strong>e<br />
landfill is aerobic rich in biodegradable organic content. As <strong>th</strong>e landfill age increases, <strong>th</strong>e<br />
microorganism present in <strong>th</strong>e landfill tend to degrade <strong>th</strong>ese organic compounds into<br />
inorganic components. When anaerobic phase begins, <strong>th</strong>e COD starts increasing causing a<br />
decrease in BOD/COD ratio. This decrease in BOD/COD ratio observed, suggests <strong>th</strong>e<br />
change in biodegradability <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate wi<strong>th</strong> time. For young landfill, <strong>th</strong>e ratio is around<br />
0.5-0.8 while it re<strong>ac</strong>hes almost 0.1 in <strong>th</strong>e old landfill. The reason for low biodegradability<br />
in <strong>th</strong>e old landfill could be due to <strong>th</strong>e presence <strong>of</strong> humic and fluvic <strong>ac</strong>ids.<br />
Figure 2.3 Variation in Significant Pollutant Ratios wi<strong>th</strong> Increase in Age <strong>of</strong> <strong>th</strong>e Landfill<br />
(Chian and DeWalle, 1976)<br />
The ammonium concentration in <strong>th</strong>e le<strong>ac</strong>hate also varies wi<strong>th</strong> age <strong>of</strong> <strong>th</strong>e landfill, wi<strong>th</strong><br />
young le<strong>ac</strong>hate having a high COD (>5,000 mg/L) and low nitrogen content (< 400 mg<br />
N/L) and old le<strong>ac</strong>hate having a high concentrations <strong>of</strong> ammonia (> 400 mg N/L) and<br />
recalcitrant compounds and a low biodegradable organic fr<strong>ac</strong>tion (BOD5/COD = 0.1).<br />
Municipal solid waste landfill in Asia (except Japan) is char<strong>ac</strong>terized by 60 to 90 %<br />
organic waste and 3 to 18 % plastic (Agamu<strong>th</strong>u, 1999). Le<strong>ac</strong>hate char<strong>ac</strong>teristics <strong>of</strong> landfills<br />
surveyed in Asia including Thailand, Europe, and America are presented in Table 2.2. The<br />
char<strong>ac</strong>teristic <strong>of</strong> le<strong>ac</strong>hate from different landfill site as reported show a great variation. It is<br />
dependent on <strong>th</strong>e solid waste composition, landfill site location, and local climate. The<br />
BOD and COD concentrations decrease as <strong>th</strong>e landfill age increases.<br />
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