Publication: Treatment of stabilised anaerobic landfill leachate by ozonation process with zirconium and tin tetrachlorides
Loading...
Date
2020-04-01
Authors
Zakaria, Siti Nor Farhana
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Leachate is a crucial problem in sanitary landfills which threatens the
environment due to hazardous pollutants. However, most of the current results are
unable to comply with the discharge limit of effluent. Therefore, an advanced
oxidation process (AOP) using ozone and coagulation was applied during
stabilised anaerobic landfill leachate (SAL) treatment in this study since this
method promises high degradation of pollutants. Stabilised anaerobic leachate
containing high concentrations of colour (14,984 PtCo), COD (3852 mg/L), and
NH3-N (1241 mg/L). The sample was taken from Alor Pongsu Landfill Site
(APLS), Kerian Perak for a duration of 1 year. Colour, COD and NH3-N were
investigated as a target parameter to see the performance of each method in
removing pollutant. Whilst, 3 critical factors such as dosage, pH and reaction
time were studied their influences on performance of all batch studies and RSM
tests. The experiment started with a batch study of zirconium tetrachloride (ZrCl4)
and tin tetrachloride (SnCl4) as coagulants in the coagulation-flocculation process.
Results for both coagulants were recorded and compared. Next, the performance
of ozonation (O3) in a semi-batch ozone reactor was also examined. Based on the
results, O3 alone could only remove 85.4%, 50% and 15% of colour, COD and
NH3-N, respectively. However, these concentrations still exceeded the standard
discharge limits. To improve the results, O3 was combined with two chemicals
which are ZrCl4 and SnCl4. An optimisation process was designed for both
(O3/ZrCl4 and O3/SnCl4) using the response surface methodology software (RSM).
O3/ZrCl4 improved reduction in colour, COD and NH3-N by 99.8%, 93.5% and
46%, respectively. Meanwhile, O3/SnCl4 removed 98.8%, 85.5% and 26% of
colour, COD and NH3-N accordingly. An integrated treatment method consisting
of ozonation and a jar test (as ZrCl4 and SnCl4 function as coagulants) was
studied. Treatment using ozonation followed a jar test yielded good results
compared to the treatment which started with a jar test and ended with ozonation.
However, there was only a small improvement in the biodegradability
(BOD5/COD) of the sample compared to other methods. On the other hand, the
improvement of BOD5/COD ratio by O3/ZrCl4 from 0.02 (raw) up to 0.43 was
significant. The kinetic constant reaction rate (k’) of O3/ZrCl4 was calculated and
this resulted in a value of 0.1173 min-1 based on the pseudo first-order kinetic
model. Another oxidation method involving O3 and O3/SnCl4 also fit the pseudo
first-order kinetic model. It can be concluded from the research that, the
combination of O3 and ZrCl4 presents an effective treatment method for
remediating high concentrations of containing high concentrations of colour,
COD, and NH3-N in SAL.