International Journal of Engineering Technology IJET -IJENS Vol:13 No: 06 87 [611835]

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 87
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S A Comparative Study of Anoxic Limestone Drain and
Open Limestone Channel for Acidic Raw Water
Treatment

Faradiella Mohd Kusin , Azmi Aris and Amiza Shayeeda Ahmad Misbah

Abstract – This study presents the performance of an anoxic
limestone drain in comparison to an open limestone channel for
treating acidic water . The anoxic limestone drain wa s designed to
enhance limestone dissolution and alkalinity generation thus
minimizing the potential of armouring which may decrease the
rate of acid neutralizatio n. Actual raw water from two different
locations within Sg. Bekok catchment that is highly acidic with
low pH value (~ pH 2.5) was used in the experimen t. The a noxic
limestone drain was found to perform better than the open
limestone channel with respect t o pH increase, acidicy decrease
and alkality production. Iron was removed at relatively higher
rate in open limestone channel but resulted in the armouring of
limestone surfaces thus limiting further generation of alkalinity.

Index Term – Acidic wate r; Anoxic limestone drain ; Alkalinity
production ; Open limestone channel

I. INTRODUCTION
As experienced at Sg. Bekok, Batu Pahat River catchment in
recent years, intensive agricultural drainage activities in the
riparian lowland between Bekok Dam and the town of Yong
Peng have resulted in the deteriora tion of the river water
quality, especially in term of pH, iron and aluminium content.
The water supply intakes within Batu Pahat district have been
unable to provide sufficient supply of raw water which has
lead to water shortages problem. This is a result of water
quality problems undergone by Sg. Bekok with high
concentration of iron (110 mg/L) and aluminium (290 mg/L)
and pH values as low as 2.5 which exceed the limits set out by
the National Water Quality Sta ndard for Class II rivers [1].
This has significantly caused interruptions in the operation of
Yong Peng 2 & 3, Sri Gading and Parit Raja water treatment
plants in producing sufficient potable water for the district’s
needs. This study was carried out to investigate the viability
of limestone treatment in treating acidic raw water prior to
being used for water supply consumption.

Financial support for this study was partly funded by SAJ
Holdings Sdn. Bhd., and was jointly supported through UPM RUGS/93307 00,
FRGS grant/5524261 and TWAS -Comstech joint research grants.
F. M. Kusin (corresponding author) is a senior lecturer at the
Department of Environmental Sciences, Faculty of Environmental Studies,
Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, M alaysia (e -mail:
[anonimizat] )
A. Aris is with the Department of Environmental Engineering,
Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 Skudai,
Johor, Malaysia

In specific, anoxi c limestone drains (ALD) which operate at
low oxygen concentration level were studied. The study aims to compare the performance of an anoxic limestone drain and
open limestone channel in relation to their respective pH
adjustment, acidity reduction, alkal inity generation, and
removal of iron.
Acid sulphate soil is a frequently encountered soil
type in most of the Sg. Bekok catchment. In some of the sub –
catchments, acid sulphate soils are the only soil type that can
be found. Overall acid sulphate soil cove rs 116.4 km2 of the
total 279 km2 which represents about 41.7% of the whole
catchment area (from the Bekok Dam to Sri Gading) [2]. The
soil is typically formed in low lying portions of the terrain,
where the ocean has recently withdrawn and deposited pyrit e,
which when oxidized releases acid and sulphate. The cause of
the problem is believed to be due to the acidification process
of soil by oxidation of pyrite in the soil within the river [3].
Pyrite exposed to the environment through intensive
agricultural drainage reacts with oxygen and water to form
sulfur ic acid , resulting in acidic water condition.
Dissolution of calcite (CaCO 3) can neutralize acidity
and increase pH and concentration of alkalinity (HCO 3- + OH-
) and Ca2+ in acidic water [4, 15]. As the pH increases to near –
neutral value, concentrations of Fe3+, Al3+ and other metals
can decline owing to their precipitation or adsorption [5, 16,
21, 24]. Metal acidity due to high concentrations of Fe3+, Al3+,
Mn2+ and other solutes in acidic water can be lowered through
limestone t reatment of metal precip itation [17 , 18, 19, 22].
Thus, it is the aim of this study to investigate the conditions
under which acidity decreases, pH increases, and metal is
removed in an anoxic limestone drain.

II. MATERIALS AND METHODS
A. Sampling and Experimental Materials
Water samples from two different sources of Bekok Intake
and Semberong Lagoon were used for the experimental work.
An approximately 8 0 liters of water sample were collected at
the respective sites for the experimental purposes. The
limestone us ed to treat t he acidic water was of 30 mm in size
and were used up to 112 kg (28 kg in each of the anoxic
limestone reactor). The chemical reagent used for the
determination of total iron was FerroMo i ron reagent powder
pillow. The 0.1N NaOH solution for acidity test was prepared
using 4 g of NaOH to be dissolved in 1L of distilled water. As
for alkalinity test , the 0.02N HCl solution was prepared by
diluting 200 mL of 0.1N HCl to 1L of deionized water. The

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 88
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S analyse s of t he raw and treated water were being evaluated
based on their respective pH, acidi ty, alkalinity, iron and
aluminium . Both the alkalinity and acidity for the samples
were titrated with HCl and NaOH to pH 4.5 and 8.3 endpoints,
respectively based on Standard Method s for the Examination
of Water and W astewat er [6]. Iron was measured in the
laboratory using atomic absorption spectroscopy (AAS) .
B. Experimental Procedure s
The anoxic limesto ne drain s were constructed in series to
receive the inflow from a holding tank of 30 liters of acidic
raw water . Water from t he tank flowed through the anoxic
drain via gravity to reach the effluent point at several contact
times i.e. 10 minutes, 20 minutes, 30 minutes and 60 minutes.
Each of the limestone drain wa s of 20 cm in diameter with a
length o f 0.67 m and depth of 14 cm . The drain wa s made of
PVC pipe in a semicircular form and wa s constructed with a
slope of 1:50 -100. A cling wrapper wa s used as the drai n liner
prior to place in the 28 kg of 3 mm limestone. The liner wa s
wrapped over t he top of the limestone to minimize O2 from
taking part in the treatment process. The flow rate was
measured by recording the time to collect a known volume of
water as it reached the drain outlet. pH was monitored at the
inlet and outlet of each drain. Samples were taken at the
outlet of final drain and analyzed for acidity, alkalinity, and
Fe. Prior to experiment, oxygen was displaced from the drain
by nitrogen gas until the O 2 content was < 0.5 mg/L which
was considered anox ic [7] . The open limestone channel was
provided without the purg ing of nitrogen gas and by removing
the cling wrapper so that the water is exposed to the
atmosphere . III. RESULTS AND D ISCUSSION

Performance of anoxic limestone drain and open limestone
channel were compared for a contact time of 30 minutes.
These include the comparison of both systems with respect to
pH rise, acidity reduction, alkalinity generation and removal
of iron.

A. pH Rise

Results of pH increase for both systems are as
presented in Table I . It was discovered that pH rise in open
limestone c hannel was slightly slower as compared to anoxic
limestone drain. However, both systems were capable of
enhancing the initial pH of 4.09 and 3.27 for Bekok Intake and
Sembrong Lagoon, respectively to reach near neutral pH level.
As illustrated in Fig . 1(a), initial pH of Bekok Intake
of 4.09 was increased to 6.58 by the anoxic limestone drain
when first contacted with 28 kg of limestone compared to 5.69
by the open channel. This showed a significant difference
between anoxic limestone drain and open limest one channel in
affecting pH rise of the water at the initial stage of the
treatment. However, final pH achieved by both systems was
almost the same. As the water flowed through the drains, pH
increased with increasing limestone amount to finally reach
7.24 and 7.22 by the anoxic limestone drain and open
limestone channel, respectively. The trend showed that the
open limestone channel was capable of enhancing pH level as
effective as the anoxic limestone drain despite its slower pH
rise.

TABLE I.
pH R ISE IN ANOXIC LIMESTONE DRAIN AND OPEN LIMESTONE CHANNEL

*30 minutes contact time

Source of
sample Treatment
type Initial pH Limestone amount (kg)
28 56 84 112*
Bekok Open Drain 4.09 5.69 6.07 6.78 7.22
Intake Anoxic Drain 4.09 6.58 7.19 7.16 7.24
Sembrong
Open Drain 3.27 5.24 6.29 6.33 6.87
Lagoon Anoxic Drain 3.27 6.48 6.79 7.03 7.16

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 89
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S
012345678
28 56 84 112
Limestone amount (kg)pH
Open Drain
Anoxic Drain
012345678
28 56 84 112
Limestone amount (kg)pH
Open Drain
Anoxic Drain
020406080100
Anoxic Drain Open ChannelAcidity (mg/L as CaCO 3) Initial
30 min
020406080100
Anoxic Drain Open ChannelAcidity (mg/L as CaCO 3) Initial
30 min

Fig. 1. Difference between anoxic drain and open channel pH rise (a) Bekok Intake (b) Sembron g Lagoon

As for Sembrong Lagoon, initial pH of 3.27 was
raised to 6.48 by the anoxic limestone drain and 5.24 by the
open limestone channel at the initial stage after contacted with
28 kg of limestone as shown in Fig. 1 (b). Final pH after 30
minutes con tact time was found as 7.16 and 6.87 by the anoxic
limestone drain and open limestone channel, respectively. The
final pH for both systems was found in the near neutral range
even though the rate of pH rise in open limestone channel was
slightly slower.
As shown in the figure, the anoxic limestone drain
was capable of enhancing a higher pH rise as compared to
open limestone channel. It was because, if CO 2 becomes
trapped within the closed anoxic limestone drain, both the
partial pressure of CO 2 and the Ca2+ concentration will
increase, leading to a net rise in pH [8] . When the closed
system reaches equilibrium, the pH attained will be higher
than that of an equivalent open system [9] .

B. Acidity Reduction

Reduction of acidity for both the anoxic limestone
drain and open limestone channel are as shown in Table II . As observed, the anoxic limestone drain gave a higher percentage
of acidity removal in 30 minutes contact time as compared to
the open limestone channel. Fig. 2. illustrates the difference
between ano xic limestone drain and open limestone channel
with respect to acidity removal after 30 minutes of contact
with the limestone.
The acidity of raw water sample of Bekok Intake was
reduced to 24 mg/L as CaCO 3 by the anoxic drain as
compared to 37 mg/L as Ca CO 3 for the open channel. As for
Sembrong Lagoon, initial acidity of 99 mg/L as CaCO 3 was
reduced to 21 mg/L as CaCO 3 by the anoxic drain, as
compared to 43 mg/L as CaCO 3 by the open limestone
channel. The results demonstrated that anoxic drain had a
bette r neutralization rate which tends to remove higher acidity
as compared to open channel. The effect has also been
observed by Ziemkiewicz [10] that armoured limestone (due
to open channel) to be 2 to 45 % less effective in neutralizing
hydrogen ion acidity compared to unarmoured limestone
(anoxic drain).

Fig. 2. Acidity reduction in anoxic drain and open channel (a) Bekok Intake (b) Sembrong Lagoon

(a)
(a) (b) (a) (b)

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 90
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S
TABLE II.
ACIDITY REDUCTION IN ANOXIC LIMESTONE DRAIN AND OPEN LIMESTONE CHANNE L
Source of sample Treatment type Initial acidity
(mg/L as CaCO 3)
Acidity* % Reduction
Bekok Intake Open Drain 73 37 49
Anoxic Drain 73 24 67
Sembrong
Lagoon
Open Drain 99 43 57
Anoxic Drain 99 21 79
*30 mi nutes contact time

C. Alkalinity Generation

The production of alkalinity in both systems is shown
in Table III . It was found that the anoxic limestone drain
showed a greater increase of alkalinity as compared to the
open limestone channel. Anoxic limestone drain which have
been designed to avoid armouring, are particularly effective
for generation of alkalinity [11]. The rate of alkalinity
production for Bekok Intake was found to be increased up to
64 mg/L as CaCO 3 as the water flowed through t he anoxic
drain in 30 minutes of contact with limestone. In contrast, the alkalinity was only generated to a concentration of 47 mg/L as
CaCO 3 by open limestone channel. Sembrong Lagoon water
sample indicated a production of 54 mg/L as CaCO 3 of
alkalinity for the anoxic drain relative to 43 mg/L as CaCO 3
for open limestone channel.
Retaining CO 2 within an enclosed anoxic limestone
drain can enhance calcite dissolution and alkalinity production
[4, 20, 23 ]. As for an open channel, higher rate of metal ion
precipitation could armoured the limestone surface (Fig. 3.),
decreasing the rate and extent of limestone dissolution and
alkalinity production [12, 13].

Fig. 3. Armouring due to iron precipitation in open limestone channel

TABLE I II.
ALKALINITY GENERATION IN ANOXIC LIMESTONE DRAIN AND OPEN LIMESTONE CHANNEL
Source of sample
Treatment type Initial alkalinity
(mg/L as CaCO 3) Alkalinity*
Bekok Intake Open Drain 0 47
Anoxic Drain 0 64
Sembrong
Lagoon
Open D rain 0 43
Anoxic Drain 0 54
*30 minutes contact time

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 91
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S

D. Iron Removal
Results of iron removal for the anoxic limestone
drain and open limestone channel are given in Table IV . The results showed that the open limestone channel was capable of
removing a higher concentration of iron compared the anoxic
limestone drain.

Fig. 4. Iron removal in anoxic drain a nd open channel (a) Bekok Intake (b) Sembrong Lagoon

TABLE IV.
REMOVAL OF IRON IN ANOXIC LIMESTONE DRAIN AND OPEN LI MESTONE CHANNEL

The iron removal in the anoxic limestone drain and
open limestone channel is shown in Fig. 4 . It was observed
that a relatively lower iron concentration was obtained by the
open limestone channel for Bekok Intake and Sembrong
Lagoon sample of 0.048 mg/L and 0.092 mg/L, respectively
after 30 minutes of contact time. It was probably due to higher
precipitation rate as the water was exposed to the atmosphere,
and solid Fe(OH) 3 was produced b y the oxidation of iron. In
contrast, excluding O2 from contact with the acidic water in
anoxic drain minimizes the potential for precipitation of
Fe(OH) 3 [4, 14, 23]. Statistically, there was a significant
difference between anoxic drain and open channel
performance in affecting the pH rise for Bekok Intake and
Sembrong Lagoon at 90% (p -value ≤ 0.1) and 95% of
confidence level, respectively. As described earlier, the anoxic
limestone drain was capable of enhancing a higher pH rise
compared to open limestone channel due to higher
neutralization rate bet ween the calcite and the acidic water.

IV. CONCLUSION

Generally, it was discovered that the anoxic limestone drain
was capable of reducing acidic condition of the raw water.
The anoxic limestone drain was found to be effective in
generat ing higher pH rise, better acidity reduction and
alkalinity production in comparison to open limestone
channel. Iron removal was relatively greater in open limestone
channel du e to higher precipitation rate. However, given the
greater precipitation rate fo r iron in open limestone channel,
amouring of limestone surfaces clearly limits its capability of
producing more alkalinity and hence slower removal of acidity
in the water. Further work will aim at enhancing the
performance of the anoxic limestone drain b y incorporating
the use of compost media and the limestone to compensate
any limitations of system performance encounte red in this
study.

Source of sample Treatment
type Initial iron
concentration Iron
concentration*
% Removal
Bekok Intake Open Drain 0.433 0.048 89
Anoxic Drain 0.433 0.145 67
Sembrong
Lagoon
Open Drain 0.571 0.092 84
Anoxic Drain 0.571 0.185 68 (a) (b)
00.10.20.30.40.50.6
Open Drain Anoxic DrainTotal Iron (mg/L)Initial
30 min
00.10.20.30.40.50.6
Open Drain Anoxic DrainTotal Iron (mg/L)Initial
30 min
(a) (b)

International Journal of Engineering & Technology IJET -IJENS Vol:13 No: 06 92
133906-8686 -IJET -IJENS © December 2013 IJENS I J E N S ACKNOWLEDGMENT
The authors wish to thank Syarikat Air Johor (SAJ) Holdings
Sdn. Bhd. for providing useful informa tion for the study and
for giving permission to use their water treatment plant
facilities.
REFERENCES

[1] SAJ Holdings Sdn Bhd ., Kronologi Masalah Kualiti Air Mentah (Intake
Sg. Sembrong) di Loji Air Parit Raja 4, Batu Pahat , 2005.
[2] Asia Wa ter & Environment Sdn Bhd., Kerja -kerja Pemulihan Sistem
Saliran Kg.Ngamarto dalam Kawasan Tadahan Sg Bekok: Conceptual
Integrated River Basin Management Plan . Syarikat Air Johor Sd n Bhd. ,
2005.
[3] A. Katimon, M. A. Kassim, J. Sohaili, F. Othman, A. A. A. Latiff and A.
T. A. Karim, “Impact of Agricultural Drainage on Stream Water
Quality ,” Journal Teknologi , vol. 31, pp. 67 -77, 1999.
[4] C. A. Cravotta III and M. K. Trahan, “ Limestone Drains to Increase pH
and Remove Dissolved M etals from Acidic Mine Drainage,” Applied
Geochemist ry, vol. 14, pp. 581 -606, 1999.
[5] D. W. Blowe s and C. J. Ptacek, “Acid -neutralization Mecha nisms in
Inactive Mine Tailings,” in Environmental Geochemistry of Sulfide Mine –
Wastes. Short Course Handbook , vol. 22, J.L Jambor and D.W Blowes,
Eds. Mineralogical A ssociation of Canada, Ottawa, 1994, pp. 271 -292.
[6] APHA , Standard Methods for the Examination of Water and Wastewater .
American Public Health Association/American Water Works
Associati on/Water Environment Federation, Washington DC, USA , 1999.
[7] S. Santomartin o and J. Webb, “An Experimental Study of the Chemistry
of Iron Precipitation Within Anoxic Limestone Drains ,” in Proc. 6th
International Conference on Acid Rock Drainage (ICARD) , Cairns
Queensland, 2003, pp. 1117 -1121 .
[8] A. W. Mann and R. L. Deutscher, “ Solution Geochemistry of Lead and
Zinc in Water Containing Carbonat e, Sulphate, and Chloride Ions,”
Chemical Geology , vol. 29, pp. 293 -311, 1980.
[9] R. Freeze and J. A. Cherry, Groundwater . Prentice Hal l, Englewood
Cliffs, 1979, pp. 101-112.
[10] P. F. Ziemkiewicz, J. G. Skousen, D. L. Brant, P. L. Sterner and R. J.
Lovett , “Acid Mine Drainage Treatment with Arm oured Limestone in
Open Channel,” J. Env. Quality , vol. 26(4), pp.1017 -1024, 1997.
[11] R. S. Hedin and G. R. Watzlaf, The Effects of Anoxic Limestone Drains
on Min e Water Chemistry. U.S. Bureau of Mines, Washington, DC , 1994.
[12] G. R. Watzlaf, K. T. Schroe der and C. L. Kairies, “ Long Term
Perform ance of anoxic Limestone Drains,” Mine Water and the
Environment , 2006.
[13] E. I. Robbins, C. A. Cravotta and C. E. Savela, “ Hydr obiogeochemical
Interactions in Anoxic Limestone Drains for Nuetral ization of Acidic
Mine Drainage,” Journal of Fuel , vol. 78, pp. 259 -270, 1999.
[14] C. A. Cravotta III , “Size and Performance of Anoxic Limestone Drains to
Neutralized Acid Mine D rain,” Journal of Environmental Quality , vol.
32, pp.1277 -1289, 2003.
[15] H. A. Aziz, M. S. Yusoff, M. N. Adlan, N. H. Adnan and S. Alias,
“Physico -Chemical Removal of Iron from Semi -Aerobic Landfil l
Leachate by Limestone filter,” Water Management , vol. 24, pp. 353 -358,
2004.
[16] M. Kalin, A. Fyson and W. N. Wheeler, “The Chemistry of Conventional
and Alternative Treatment System for the Neutr alization of Acid Mine
Drainage,” Science of the Total Environment , 2005.
[17] C. J. Lewis and R. S. Boynton, Acid Neutralization with L ime for
Environmental Control and Manufacturing Processes . Arlington,
Virginia , National Lime Association , 1995.
[18] N. Mokhtar, “Treatment of Acidic Raw Water Using Limestone ,” M.S.
thesis, Dept. Env. Eng., Universiti Teknologi Malaysia, 2006.
[19] C. Nuttal l and P. L. Younger, “ Zinc Removal from Hard, Circum Neutral
Mine Waters Using A Nov el Closed Bed Limestone Reactor,” Wat. Res. ,
vol. 34(4), pp. 1262 -1268, 2000.
[20] L. N. Plummer, T. M. L. Wigley and D. L. Parkhurst, “ The Kineti c of
Calcite Dissolution in CO 2,” American Journal of Science , vol. 22, pp.
179-216, 1978. [21] F. M. Kusin, A. P. Jarvis and C. J. Gandy, “ Hydraulic residence time and
iron removal in a wetland receiving ferruginous mine water over a period
of 4 years since commissioning,” Water Science and Tech nology , vol.
62(8), pp. 1937 -1946 , 2010.
[22] F. M. Kusin , A. P. Jarvis and C. J. Gandy, “ Hydraulic performance
assessment of passive coal mine wa ter treatment systems in the UK,”
Ecological Engineering , vol. 49, pp. 233-243, 2012.
[23] P. C. Singer and W. Stumm, “ Acid Mine Drai nage: The Rate
Determining Step,” Journal of Science , vol.167, pp.1121 -1123, 1970.
[24] F. M. Kusin , “A review of the importance of hydraulic residence time on
improved design of mine water treatment systems . World Applied
Sciences Journal , vol. 26 (10), pp. 1316 -1322, 2013 .