Removal of solids, total coliform, e.coli, uv254, colour and turbidity using limestone filter in riverbank filtration
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Date
2018-06
Authors
Siti Nur Aishah Mohd Yusoff
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Abstract
The rapid urbanization and growth of the population in Malaysia have led to
increase demand for water. It has also caused an elevation of pollution level, especially
in water bodies which acts as a water source. The use of riverbank filtration system (RBF)
as pre-treatment method in the water treatment plant has become a common interest in
recent years. Due to natural attenuation process of filtration and sorption by various
types of filter media, RBF has high potential to filter contaminants. In this study,
limestone was used as a filter media in a laboratory scale RBF system. The physical and
chemical characteristics of limestone were first determined before and after the
experiment by using scanning electron microscopy (SEM) and x-ray fluorescence (XRF)
methods. Two difference ranges of limestone sizes, 1.18 mm-2 mm and 2.36 mm- 4.75
mm were used as a porous media and the sample of water was taken from Sungai Kerian,
Lubok Buntar, Perak as a case study site. The removal efficiencies of selected water
parameters namely suspended solids, total coliform, E. coli, UV254, colour and turbidity
were determined within 15 days of the experiment. The sizes of particles retained and
the morphology of media were also determined by using particle analyzer and SEM
machine, respectively. From the SEM results, it showed that the limestone was made of
rhombohedral cleavage plane and the combination of micron-size crystal along with the
small size of pores. The limestone used in this study was mainly made up of calcium
carbonate (CaCO3) and categorized as calcite. The calcite contains 52.93% of calcium
oxide (CaO) and 0.66% of magnesium oxide (MgO). The result from the column study
showed that the removal of particles and total dissolved solids (TDS) using limestone
could not be determined due to the leaching of limestone which added the impurities into
the water. Limestone with size 1.18mm-2.0mm and 2.36mm-4.75mm did show a
significant difference in the removal efficiencies of total coliform, suspended solid, E.
coli, turbidity, UV254 and colour. The removal efficiencies obtained for the following
parameters suspended solids (SS), total coliform, E. coli, UV254, colour and turbidity
were 91%-97%, 82%-93%, 93%-98%, 28%-40%, 60%-83% and 78-83%, respectively
for both column. No breakthrough was observed within 15 days of the experiment. The
addition of limestone has increased the pH of the water sample from 6.19 before filtration
to 6.53 and 6.57 for the final pH at effluent in column 1 and column 2 respectively.