| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系 === 100 === Arsenic contamination in natural waters has become a worldwide issue
since it is a well-known human carcinogen due to its toxicity. The
maximum contaminant level of 10 μg L-1 arsenic for drinking water
standard was established by WHO and USEPA as a strict guideline.
Therefore, research and development on arsenic removal from natural
raw waters has gained a lot of attention. In this study, the removal of
arsenic from groundwater using pre-oxidation with NaOCl and hollow
fiber microfiltration was investigated. The effect of coagulation using
FeCl3 in combination with pre-oxidation and microfiltration on the
removal efficiency of arsenic was also examined.
Results showed that the removal efficiency of arsenic could be
arranged in the following order: oxidation using NaOCl in combination
with coagulation > coagulation alone > oxidation alone. In the sand filter,
a higher dosage of coagulant applied would cause an increase in arsenic
removal. However, this also leads to increase in the frequency of
backwashing. The microfiltration unit provided better arsenic removal
due to floc accumulation on the membrane that enhances arsenic
adsorption. In addition, the microfiltration unit requires a lower dosage of
coagulant and experiences lesser decline in flux in comparison to sand
filtration. Membrane fouling by the microfiltration unit is prevented
through a good tank mixing, which lifts and flushes away the floc film
formed on the membrane.
In general, the hollow fiber microfiltration unit can effectively remove
arsenic from groundwater. However, due to floc formation and
accumulation on the membrane that leads to the deterioration of
membrane performance, replacing the microfiltration membrane is
necessary. In addition, the properties and characteristics of the
groundwater would also affect the frequency of changing the membrane
unit. On the other hand, the microfiltration unit could be used as a tertiary
treatment for drinking water, which could be installed at the end of the
water purification process, in order to control the with arsenic
concentration below the regulatory standards.
|
|---|
