Adsorbent supplemented treatment of landfill leachate in sequencing batch reactor
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Date
2006
Authors
Lim, Suat Ping
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Abstract
The objective of this study is to evaluate the performance of the
sequencing batch reactor (SBR) with and without the addition of adsorbent in
the removal of oxygen demand (COD) and ammoniacal nitrogen (AN) from
landfill leachate. Two identical plexiglass SBRs were operated with FILL,
REACT, SETTLE, DRAW and IDLE periods in the ratio of 2:12:2:1:7 for a cycle
time of 24 h. Reactor R-PAC was fed with a mixture of synthetic wastewater
and increasing strength of leachate (115-170 mg/L AN) as well as increasing
dosage of powdered activated carbon (PAC) (0.5-1.5 g/cycle). Whilst reactor RMRH
received a mixture of the same synthetic wastewater and increasing
strength of leachate (115-215 mg/L AN) as well as increasing dosage of
ethylenediamine-modified rice husk (MRH) (0.5-1.0 g/cycle).
The results showed that after the introduction of leachate, the COD
removal efficiency was reduced from 90% for both reactors to 72% for reactor
R-PAC and 79% for reactor R-MRH. Treatment of leachate at higher strength
was sustainable only if PAC or MRH was added. The beneficial effect of MRH
was seen in its ability to sustain the COD removal in R-MRH of above 70% at
the leachate strength of 215 mg/L AN with the dosage of 0.5 g/cycle. In
comparison, the COD removal in R-PAC above 70% at the leachate strength of
170 mg/L AN was sustainable if higher PAC dosage of 1.5 g/cycle was added.
The AN removal efficiency for both reactors was almost 100% before and
after the introduction of leachate at the strength of 115 mg/L AN but
deteriorated when the leachate strength was increased. At the leachate strength
of 170 mg/L AN, the AN removal efficiency in reactor R-PAC was sustained at
almost 100% with PAC addition of 1.5 g/cycle. The same AN removal efficiency
was achieved in reactor R-MRH at a lower MRH dosage of 0.5 g/cycle for the
leachate strength of 215 mg/L AN.
The results of kinetic study showed that the rates of COD and AN
removal during the REACT period can be described by first-order kinetics. The
addition of leachate resulted in the effective inhibition of the conversion of nitrite
nitrogen (NO2
- -N) to nitrate nitrogen (NO3
- -N). The addition of PAC and MRH,
respectively, helped to sustain the rates of COD and AN removal at higher
leachate strength of up to 170 and 215 mg/L AN. This indicates that the addition
of adsorbents had minimized the toxic effect of leachate with MRH showing
more effectiveness than PAC.
Description
Master
Keywords
Science Chemistry , Adsorbent supplemented , landfill leachate , batch reactor