FIELD OF INVENTION
The present invention relates to a water filter candle system for removal of
arsenic (As3+) from arsenic contaminated water. The invention further relates to
a method of manufacturing an arsenic removable water filter candle.
BACKGROUND OF INVENTION
The presence of arsenic in drinking water has been a serious problem in many
parts of the world, particularly in India and Bangladesh. The level of arsenic in
ground water in few geographical locations is found to be as high as few
thousands of parts per billion (ppb) [Smith et al., 2000 and Chatterjee et al.,
1995]. Arsenic is generally present in the nature either in organic or inorganic
form. The organic form of arsenic is present in sea food, which is less harmful
and can be easily discarded by the human body. However, the inorganic arsenic,
which is mainly present as arsenic (As3+) and arsenate (As5+), is very poisonous
for human beings. The World Health Organization (WHO) has limited the safe
maximum contamination level (MCL) for arsenic in drinking water to 10 ppb
[WHO, 2006]. The contamination of ground water by arsenic usually takes place
by the weathering of naturally occurring arsenic-bearing subsurface rocks [Jain
and Ali 2006].
Prior art disclose several techniques for removal of arsenic from arsenic
contaminated ground water. However, the prior art are mainly based on
adsorption [Manning and Goldberg, 1997 and Pattanayak et al., 2000] reverse
osmosis [Ning, 2002], ion-exchange [Kim and Benjamin 2004] and coagulation
sedimentation [Yuan et al., 2003 and Kumar et al., 2004]. Adsorption of arsenic
by activated alumina is an effective technique for removal of arsenate (As5+), but
it is less effective for the removal of aesenite (As3+). Activated alumina is not
amenable to regeneration. As a consequence, the activated alumina filters to be
disposed every time after use. This is one of the major drawbacks of this
technique. In the coagulation precipitation method, arsenic can be removed by
coagulation with ferric salts followed by precipitation. This technique is very
costly and needs trained operators. The disposal of large volume of
contaminated sludge is another drawback of this method. The reverse osmosis
and nano-filtration membrane techniques have their own limitation of higher
operational cost. However, all the above techniques are neither suitable for
actual field application nor economically affordable by the consumers [Hossain et
al., 2005]. A SONO [Hussam et al.,2007] arsenic filter is a much simpler and less
expensive method of arsenic removal system. This system uses at least three
pitchers kept vertically, one above the other. The top pitcher contains cast iron
turnings and sand, while the middle one contains wood activated carbon and
sand. The arsenic contaminated water is poured on the top of the first pitcher
and the potable water is collected from the bottom most pitcher.
Moreover, all the prior art technologies are mainly confined to removal of As5+
but very little data are available for removal of As3+. As3+ is more toxic than As5+
and may cause skin cancer and neurological damage. To reduce the As3+
concentration in water, the pretreatment oxidation of arsenate (As3+) into
arsenate (As5+) have been reported, but such a process involving double
conversion increase the overall cost of the technique. Accordingly, there is an
urgent need to purpose a low-cost system for the purpose of reducing As3+ for
supplying potable water, without pre-treatment of oxidation.
OBJECT OF INVENTION
It is therefore an object of the invention to propose a water filter candle system
for removal of arsenic from arsenic contaminated water which is enabled to
reduce the arsenic concentration to below 5 ppb (less than WHO Standard
(10ppb)).
Another object of the invention is to propose a water filter candle system for
removal of arsenic from arsenic contaminated water which can be easily
manufactured, operated, and maintained.
A still another object of the invention is to propose a water filter candle system
for removal of arsenic from arsenic contaminated water which eliminates the pre-
treatment of oxidation;
A further object of the invention is to propose a water filter candle system for
removal of arsenic from arsenic contaminated water which is effective, efficient
and commercially viable.
A still further object of the invention is to propose a method of manufacturing an
improved arsenic removable water filter candle, which eliminates the
disadvantages of prior art candles.
SUMMARY OF INVENTION
According to the invention in a first aspect, there is provided a water filter candle
system for removal of arsenic from arsenic contaminated water comprising :
at least four chambers; a plurality of arsenic removal candles; and CRM fines:
generated in an integrated steel plant. In a second aspect the invention provides
a method of manufacturing an arsenic removal water filter candle.
In a second aspect of the invention there is provided a method of manufacturing
an improved arsenic removable water filter candle, comprising the steps of :
providing a quantity around 2 to 35 by weight percent of cold rolled mill (CRM)
fines with a particle size distribution of 100-300 mm; mixing a balance quantity
of conventional water filtering materials selected from a group consisting of
china clay, ball clay, quartz, feldspar, calcium carbonate, charcoal; continuously
grinding the mixture with water for about eight hours in a ball mill; moulding the
produced liquid clay in a mould formed of plaster of paris which provides a soft
candle; predrying of the soft candle at room temperature for about eight hours;
post drying the candle shell in a furnace maintained around 1100°C for about
fourteen hours; and normalizing the dried candle shell at environmental
conditions and fitted with a food grade resin seal.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 is a schematic view of an arsenic removal water filter candle system
according to the invention.
DETAIL DESCRIPTION OF THE INVENTION
According to the invention, an arsenic removable water filter candle is
manufactured by collecting iron oxide based fines from different sources of
integrated steel industry. The chemical and size analysis of the collected fines
concludes that Cold Rolled Mill (CRM) fines with particle size - 100-300 mm are
most suitable for configurating a low cost arsenic removal system. The rietveld
analysis of the X-ray diffraction patterns of these fines shows only ferrous oxide
(Fe2O3) peaks.
The arsenic removable water filter candle, which is formed by mixing of CRM
fines with other materials (China clay, Ball clay, Quartz, Feldspar, Calcium
Carbonate (CaCO3), Charcoal, etc.) used in making conventional water filter
candles. For the experimental purpose, the arsenic (As3+) contaminated water
was prepared by dissolving the sodium arsenate (NaAsCk) salt into water. The
arsenic concentration in water was measured and maintained by using Merck
Chemical (Merckoquant 117927) arsenic test kit.
MANUFACTURING OF WATER FILTER CANDLE :
The CRM fines (2-35%) was mixed with conventional water filtering materials
(China clay, Ball clay, Quartz, Feldspar, Calcium Carbonate, Charcoal, etc.) A
continuous grinding of all these raw materials with water is done in a ball mill for
at least eight hours. The grinding operation produces a candle casting slip,
which is subsequently put in a Plaster of Pairs mould for casting. The mould
absorbs water from the liquid clay and provides a soft candle shell. The candle
shell is then dried in environmental conditions for about eight hours. The post
drying of the candle shell is done by firing the candle for atleast 14 hours at
1000°C an oil fired furnace. The candle shell is then finished and joined with the
cap with a food grade rasin seal.
This system(s) contains at least four chamber (1, 2, 3, 4) disposed one above
another. The schematic view of the system is shown in Figure 1. In the top most
chamber (4) a plurality of uniformly distributed holes (101) of diameter ~ 2.0
mm is configured at the bottom except three circular areas (102) of diameter ~
5 cm remain free of holes at three places. The third chamber (3) from the
bottom comprises at least three arsenic removal candles (103a) (manufactured
by aforementioned method), which are exactly below the hole free areas (102)
of the top chamber (4); and CRM fines (104) of about 0.5 to 2.0 kg. The function
of the top most chamber (4) is to distribute water uniformly in the third chamber
(3) and ensure a compete assimilation of the arsenic contaminated water with
the CRM fines. In the third chamber (3) the arsenic present in water get adsorbs
by the CRM fines and then the water filter through the arsenic removal water
filter candles (103a). The arsenic removal candles (103a) serve two purposes;
for example, (i) adsorb arsenic from the arsenic contaminated water and (ii) filter
the CRM fines from water. The second chamber (2) from the bottom is provided
with at least three arsenic removal candles (103b). The position of the candles
(103b) is exactly below the outlet of the candles (103a) of third chamber (3).
The candle (103b) in this chamber (3) serves the same purposes as of the
candles (103a) in the third chamber (3) and provides safe potable water in the
bottom most chamber (1). Further the ~ 100 ppb of arsenic contaminated water
is thus allowed to pass through the filters.
The arsenic concentration in the filtered water is measured by using Merck
chemical (Merckoquant 117927) arsenic test kit, which reveals that the final
concentration of arsenic in water in the bottom most chamber (1) is ~ 0-5 ppb.
This result is then duplicated by Flow- Injection- Hydride- Generation, and
Atomic absorption spectrometry (F 1-HG-AAS). The CRM fine containing water
filter candles system(s) gives the potable water with a rate of 50 litres per day
which is good enough for a single house hold. The life time of the arsenic
removal candles (103a, 103b) is four to six months, which is quite economic
compared to other available systems.
WE CLAIM :
1. A water filter candle system(s) for removal of arsenic (As3+) from
arsenic contaminated water, comprising :
a substantially cylindrically shaped housing (H) with an outlet
configured at a side bottom portion, the outlet provided with a stop
cock (105) for preventing undesired out flow of filtered water; and
at least four chambers (1, 2, 3, 4) formed inside the housing (H) along
the vertical plane at substantially equally spaced-apart levels when
viewed from the bottom of the housing (4), the fourth chamber (4),
provided with a plurality of uniformly distributed holes (101) including
at least three hole-free areas (102), the third chamber (3) having at
least three arsenic removable candles (103a) one each disposed below
the at least three hole free areas (102) of the fourth chamber (4), the
second chamber (2) comprising at least three further arsenic
removable candles (103b) disposed substantially beneath the outlets
of the candles (103a) arranged on the third chamber (3), the first
chamber (1) receiving the arsenic free filtered water from the second
chamber (2) and acting as a storage chamber for the portable water.
2. The system as claimed in claim 1, wherein the diameter of the plurality
of holes (101) configured at the bottom of the fourth chamber (4) is
about 2.00 mm, and wherein the diameter of each of the three hole-
free areas (102) is about 5.00 mm.
3. A method of manufacturing an improved arsenic removable water filter
candle, comprising the steps of:
providing a quantity around 2 to 35 by weight percent of cold rolled
mill (CRM) fines with a particle size distribution of 100-300 mm;
mixing a balance quantity of conventional water filtering materials
selected from a group consisting of china clay, ball clay, quartz,
feldspar, calcium carbonate, charcoal;
continuously grinding the mixture with water for about eight hours in a
ball mill;
moulding the produced liquid clay in a mould formed of plaster of paris
which provides a soft candle;
predrying of the soft candle at room temperature for about eight
hours;
post drying the candle shell in a furnace maintained around 1100°C for
about fourteen hours; and
normalizing the dried candle shell at environmental conditions and
fitted with a food grade resin seal.

4. A water filter candle system(s) for removal of arsenic (As3+) from
arsenic contaminated water, as substantially described and illustrated
herein with reference to the accompanying drawings.
5. A method of manufacturing an improved arsenic removal water filter
candle as substantially described and illustrated herein with reference
to the accompanying drawings.