Natural flocculant from Durio zibethinus seed starch for municipal solid waste landfill leachate treatment
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Date
2016-09-01
Authors
Mohd Faiz Muaz Ahmad Zamri
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Abstract
The used of polyaluminium chloride (PAC) coagulant is prominent in landfill
leachate treatment. PAC coagulant is proven to be among the effective coagulants for
landfill leachate treatment. However, it was found that PAC coagulant has a toxic
potential of aluminium residual to the aquatic environment. As an alternative, the
combination of natural flocculants with inorganic coagulants could reduce the dosage
and dependence on the PAC coagulant and improved the flocculant properties. In this
study, natural based flocculants from durian seed starch were used for landfill
leachate treatment. The landfill leachate samples were collected from Matang landfill
located at Taiping, Perak. The durian seed starches were extracted using dry milling
and wet milling extraction method. The best starch obtained was further modified by
crosslinking modification method to improve the treatment process. The
experimental condition in removing colour, Chemical Oxygen Demand (COD),
suspended solid and turbidity were further optimized statistically using Response
Surface Method (RSM). The settling velocity values were compared and used for
mixing and settling tanks calculation design. According to the results, the use of wet
milling durian seed starch (WM-DSS) as a flocculants increased the removal
percentage of colour, suspended solids and turbidity by 0.4 %, 2.9 %, and 13.2 %
compared to PAC coagulants alone (88.8%, 90.7 % and 80.5 %). Besides, the sludge
velocity index (SVI) was also improved from 531.3 mL/g to 158.1 mL/g. In contrast,
the use of dry milling durian seed starch (DM-DSS) flocculants had decreased the
removal percentage of chemical oxygen demand (COD), suspended solids and
turbidity by 25 %, 1.6 %, and 2.8 % compared to PAC coagulants alone (59.6 % 97.2
xxi
% and 95.0 %). In this respect, wet milling extraction method was effective to be
used for starch flocculants synthesis. In fact, the crosslinking modification of the wet
milling starch flocculants (CWM-DSS) further increased the removal percentage of
colour, chemical oxygen demand (COD), suspended solids and turbidity by 1.7 %,
5.1 %, 14.8 %, and 14 % compared to PAC alone (94.4 %, 55.8 %, 70.4 % and 81.1
%). Moreover, this starch modification had able to reduce 0.557 g/L concentration of
PAC coagulant for landfill leachate treatment. Besides, the used of CWM-DSS
flocculants able to reduce the number of settling tank from 6 to 3 units and increased
the volume of treated leachate from 2376 m3/day to 2404.08 m3/day. Therefore, it
was clearly observed that the used of CWM-DSS flocculants is effective to be used
for landfill leachate treatment process.