Removal of starch from starch dispersions by tangential flow filtration
Absence of systematic wastewater treatment in sago industries in Sarawak has resulted in improper discharge of effluent into our rivers. Tangential flow filtration (TFF) is an attractive alternative for treatment of sago effluent. The main aim of this study was to employ TFF for sago starch separ...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2015
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| Subjects: | |
| Online Access: | http://ir.unimas.my/id/eprint/30033/1/Samantha%20ft.pdf |
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| Summary: | Absence of systematic wastewater treatment in sago industries in Sarawak has resulted in
improper discharge of effluent into our rivers. Tangential flow filtration (TFF) is an
attractive alternative for treatment of sago effluent. The main aim of this study was to
employ TFF for sago starch separation from two model dispersions (1% and 3% w/v). The
laboratory-scale studies used polysulfone membrane filter cassettes (0.45 µm) with
membrane area of 0.1 m2
, 0.2 m2
and 0.3 m2
. This study is essential for next in-situ sago
effluent treatment in order to have good filtration efficiency with low fouling rate. Each
model dispersion was filtered and concentrated to a minimum factor of 3.33 with a final
volume of less than 15 L. High concentration of starch caused high degree and rates of
fouling in the filtration membrane. Consequently, it deteriorates the performance of
membrane filtration. Membrane backflushing is a way to reduce fouling of membrane
during filtration process. By this, the time of operation for treatment of 3% starch
dispersion had been successfully reduced by 5 hours. In treatment of 1% starch dispersion,
expanding the filtration area (0.1 m2
to 0.2 m2
, and to 0.3 m2
) have improved the filtration
efficiency by shortening the filtration time from 1 hour to 30 minutes and also increased
the removal of water by 4%, from 81% to 85.4%. In contrast, the normalized permeate flux
(NPF), specific volume (SV), normalized retentate flux (NRF), normalized instantaneous
specific flux (NISF), transmembrane pressure (TMP) and water recovery (WR) decreased
with filtration area at fixed feed flow of 4.5 LPM. These parameters except TMP decreased
with operational time due to membrane fouling. However, the parameters were improved
when the TMP was reduced after backwashing the membrane and thus increases the
filtration efficiency of membrane. Meanwhile, total suspended solids (TSS), turbidity and
chemical oxygen demand (COD) were not detected in the permeate generated unless overfouling of membrane, and all showed significant differences (p < 0.05) between before and
after treatments. Based on the laboratory study, it is suggested to use 0.3 m2 membrane and
employ backflush in TFF for in-situ study. In treatment of actual sago effluent, similar
results were obtained where most of turbidity, TSS, COD and biochemical oxygen demand
(BOD) were successfully eliminated after the TFF process. The main problem faced in this
in-situ study was the sago fibres in sago effluent which will greatly reduce the filtration
efficiency of TFF process. This has caused the TMP to increase drastically and decrease of
NPF, SV as well as NISF within 10 minutes. However, further investigations regarding the
pre-removal of all sago fibres prior to treatment using TFF system is necessary. In terms of
membrane cleaning, soaking membrane in 0.2 M NaOH solution is found to be the most
effective method to recover the membrane permeability (up to 91%) within the shortest
time (within 72 hours). |
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