Lemna minor reduces contaminants in textile effluent

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online) Volume 5, Issue 3, March (2014), pp. 285-293 © IAEME
285
APPLICATION OF LEMNA MINOR L. ON REDUCTION OF
CONTAMINANTS IN A TEXTILE INDUSTRY EFFLUENT
D. Sivakumar*, A.N. Kandaswamy*, E. Arivoli*, V. Sesha Sayee*
*Department of Civil Engineering,
Vel Tech High Tech Dr.Rangarajan Dr.Sakunthala Engineering College, Chennai.
ABSTRACT
Textile industry processes are among the most environmentally unfriendly industrial
processes, because they produce colour effluent that is heavily polluted the environment. Therefore,
effluent from textile industry has to be treated before being discharged into the environment. In this
study, experiments were performed using different process parameters like nutrient dosage, dilution
ratio, pH and contact time to remove TDS and sulphate from the textile industrial effluent in
constructed wetlands with the help of aquatic macrophytes Lemna minor L. From the experiments it
was found that the maximum percentage reduction of various parameters in a textile industry
wastewater by Lemna minor L. were obtained at an optimum nutrient dosage of 50 g, dilution ratio of
8, pH of 8 and contact time of 4 days. Similarly, the validation experiments results showed that the
experiments were able to reproduce and the maximum removal percentage of sulphate in a textile
industry effluent is 81.31 %, which is lesser than the removal of sulphate in an aqueous solution
(84.62 %). Further, first order kinetic model was well fitted with the experimental data of this
present study. Finally, this study was concluded that Lemna minor L. might be used for removing
various parameters in any type of textile industry effluent.
Keywords: Aquatic Macrophyte, Process Parameters, Textile Industry Wastewater.
1.0 INTRODUCTION
Textile industries consume a large volume of water and chemicals for making various textile
goods and as a result, large volume of effluent discharged on land with or without treatments. The
quantities and characteristics of effluent discharged vary from mill to mill, which depends on the
water consumption and the average daily product [14]. Many approaches have been taken to reduce
water consumption by recycling the effluent comes from the textile industries. The raw materials
particularly dyes used in the textile industry determine the volume of water required for production
as well as wastewater generated [6]. The wastewater generated from the various processing units are
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
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ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 5, Issue 3, March (2014), pp. 285-293
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desizing, scouring, bleaching, mercerizing, dyeing, printing, and packing required huge amount of
organic chemicals of complex structure [2, 11, 12].
The main parameters identified in the textile industry are pH, electrical conductivity (EC),
chloride, sulphate, phenols, total dissolved solids (TDS), biochemical oxygen demand (BOD) and
chemical oxygen demand (COD) and other solution substances [18]. Therefore, wastewaters from
the textile industry have to be treated before being discharged to the environment [16]. Various
methods including aerobic and anaerobic microbial degradation, coagulation, chemical oxidation,
precipitation, filtration, membrane separation, electrochemical treatment [11] filtration, flotation,
hydrogen peroxide catalysis, and reverse osmosis [3], ozonation [10] and biological techniques can
be employed to remove various pollutant forms the textile industry wastewater [5]. However their
costs are high and most of them are difficult to use under field conditions, hence such a condition
there is an urgent need to study natural, simple, and cost-effective techniques for controlling
pollution from industrial effluents and treating such wastewater, such as phytoremedation [7, 8].
Phytoremedation is the utilization of plants accumulation capabilities to remove contamination from
water, wastewater, soil and air [4, 14, 17]. In recent years, considerable attention has been focused
on absorption process using aquatic plants because, it has more advances than over conventional
treatment methods include: low cost; high efficiency; minimization of chemical and biological
sludge [15]. The application of phytoremediation technology by duckweed in wastewater treatment
and management is quite interesting and revealing.
Lemna minor L. known as common duckweed is a small, free floating aquatic plant fast
growing, adapt easily to various aquatic conditions and play an important role in the extraction and
accumulation of pollutants from waters and wastewaters [9, 13]. Thus, this study was conducted to
remove the TDS and sulphate in a textile industrial effluent in constructed wetlands by using aquatic
macrophytes Lemna minor L. using different process parameters. Further, the experiment results of
TDS and sulphate in a textile industrial effluent is verified for their reproducibility with the separate
experiments conducted to remove the same TDS and sulphate in an aqueous solution. Finally,
kinetic model was developed to check the kinetics of experimental investigation of this present
study.
2.0 MATERIALS AND METHODS
2.1 Collection of Lemna minor L.
Lemna minor L. was collected from the local pond, which had no connection with any textile
effluent discharge points. The collected Lemna minor L. (Fig. 1). was washed with deionized water
and weighed. Further, the Lemna minor L. was initially subject to stabilization in small plastic tanks
containing well water and the same were preserved for 15 days period. In addition, these plastic
tanks were filled with gravel and wetland soil (collected from the local pond) up to five inches in
height and maintained at normal temperature.
Fig. 1: Photographic View of Lemna minor L.

287
2.2 Collection of Textile Industry Effluent
For the present study, textile industry effluent samples were collected from the final clarifier
of textile industry effluent treatment plant of Chennai city, Tamil Nadu, India with the help of
airtight sterilized bottles. Then, took the effluent samples to the Environmental Laboratory and then
they were stored in refrigerator at a temperature of 278 K for analyzing total dissolved solid (TDS)
and sulphate in later stages. In order to reduce the various parameters in a textile industry effluent,
wetlands was constructed (plastic tanks) by using Lemna minor L. and conducted the removal study
with various nutrient dosages, dilution ratio and contact time.
2.3 Absorption Experiments
For the experiments, Lemna minor L., which maintained in the plastic tanks were collected,
cleaned and introduced in the experimental tanks (constructed wetland). The experimental tanks also
a plastic tank as similar to the plastic tank for preserving the Lemna minor L. Approximately, 100 g
of Lemna minor L. was used in each experimental tank for this study. These experimental tanks
were filled with textile industry effluent of 1000 ml. Triplicate of each experimental setup was
maintained. In order to reduce the TDS and sulphate in a textile industry effluent, the experimental
setup (constructed wetland) was examined for a period of 7 days by 1 day intervals by using aquatic
macrophytes Lemna minor L. and conducted the removal study with various nutrient dosage (10, 20,
30, 40, 50, 60 and 70 g), dilution ratio (2, 4, 6, 8, 10, 12 and 14) and pH (4, 5, 6, 7, 8, 9 and 10).
The nutrient used in this study was dried Cow dung, collected locally. The dilution ratio was
used such that 1 part of effluent with various numbers of part of well water, thus, the ratio of 2, 4, 6,
8, 10, 12 and 14 represents these parts of well water mixed with raw effluent. The pH was adjusted
by using 0.1 M of NaOH and 0.1 M of HCl. The concentration of TDS and sulphate in a textile
industrial effluent before and after treatment with Lemna minor L. were determined as per the
standard procedure stipulated by APPA, AWWA and WEF [1]. The removal percentage of various
parameters by Lemna minor L. was calculated by using the Equation (1):
Percentage Removal = (1)
in which C1 is the concentration of the parameter before treatment with Lemna minor L. and C2 is the
concentration of the parameter after treatment with Lemna minor L. The initila concentration of TDS
and sulphate in a textile industry wastewater is 2622 mg/l and 758 mg/l respectively.
3.0 RESULTS AND DISCUSSIONS
The different process parameters like nutrient dosage, dilution ratio and contact time were
selected for conducting the constructed wetland absorption study using Lemna minor L. to reduce the
various parameters like TDS and sulphate in a textile industry effluent.
3.1 Effect of Nutrient Dosage
Experimental investigations were conducted by changing the nutrient dosage from 10 g to 70
g with an increment of 10 g using Lemna minor L. and for the different contact time from 1 day to 7
days with an increment of 1 day. Fig. 2 indicates the percentage reduction of various parameters like
TDS and sulphate in a textile industry effluent using Lemna minor L. against nutrient dosage (since,
day 4 is the optimum contact time found from the study, the results obtained on the day 4 was
presented and the results obtained from the day 1, 2, 3, 5, 6 and 7 were not presented in this study)
with a contact time of 4 days, dilution ratio of 6 and pH of 7.
The results revealed that the percentage removal of the selected various parameters is low by
Lemna minor L. at the starting time of the experiment and then increases with contact time. This is

288
because, the supplied nutrient could not be effectively utilized by Lemna minor L. for removing
various parameters and thereafter as contact incrases, Lemna minor L. used nutrients effectively,
results more removal of selected parameters. Up to nutrient dosage 50 g, the removal of various
parameters in a textile industry effluent increased by Lemna minor L. steadily and for the nutrient
dosage of 60 g and 70 g, the percentage removal results showed the resembles of the results obtained
nutrient dosage 50 g. Hence, the optimum nutrient dosage found in this study for the maximum
removal of TDS and sulphate in a textile industry effluent by Lemna minor L. is 50 g. The removal
percentage for TDS and sulphate was not significant even the contact time and nutrient dosages were
higher, it is more likely that an even sufficient contact time available, a significant portion of the
available active sites remains undiscovered, leading to lower specific uptake for the nutrient dosage
of 60 g and 70 g and for the contact time of 5, 6 and 7 days. Thus, the maximum removal percentage
for TDS and sulphate in a textile industry effluent by Lemna minor L. against nutrient dosage is
64.35 and 68.14 % respectively (Fig. 2).
Fig. 2: The Percentage Reduction of TDS and Sulphate in a Textile Industry Effluent using
Lemna minor L. against Nutrient Dosage
3.2 Effect of Dilution Ratio
Experimental investigations were conducted by changing the dilution ratio from 2 to 14
(effluent 1 : well water 2) with an increment of 2 using Lemna minor L. and for the different contact
time from 1 day to 7 days with an increment of 1 day. Fig. 3 indicates the percentage reduction of
TDS and sulphate in a textile industry effluent using Lemna minor L. against dilution ratio (since,
day 4 is the optimum contact time found from the study, the results obtained on the day 4 was
presented and the results obtained from the day 1, 2, 3, 5, 6 and 7 were not presented in this study)
with a contact time of 4 days, the nutrient dosage of 50 g and pH of 7. The results revealed that the
percentage removal of the selected various parameters is low at the beginning of the contact time and
then increases later stages. In other words, the active sites in the Lemna minor L. could not be
utilized effectively by the various parameters for their removal at the beginning and thereafter,
absorbent sites of Lemna minor L. could be effectively utilized in later stages.

289
Fig. 3: The Percentage Reduction of TDS and Sulphate in a Textile Industry Effluent using
Lemna minor L. against Dilution Ratio
Up to dilution ratio of 8, the removal of various parameters in a textile industry effluent by
Lemna minor L. increased steadily and in the dilution ratio 10, 12 and 14, the percentage removal
results showed the resembles of the results obtained for the dilution ratio 8. Hence, the optimum
dilution ratio found in this study for the maximum removal of various parameters in a textile industry
effluent is 8. Further, at low dilution ratio, the removal of TDS and sulphate in a textile industry
effluent were not absorbed easily by the Lemna minor L. and high dilution ratio, the removal of TDS
and sulphate in a textile industry effluent were absorbed more by the Lemna minor L. This is
because, the high dilution ratio, the ions freely move within the solution results easy to absorb more
on to the minor L. active sites. The removal percentage for various parameters was not significant
even the contact time and dilution ratio were higher, it is more likely that an even sufficient contact
time available, a significant portion of the available active sites remains undiscovered, leading to
lower specific uptake for the dilution ratio 10, 12 and 14 and for the contact time of 5, 6 and 7 days.
Thus, the maximum removal percentage for TDS and sulphate in a textile industry effluent by Lemna
minor L. against dilution ratio is 72.53 and 75.22 % respectively (Fig. 3).
3.3 Effect of pH
Experimental investigations were conducted by changing the pH from 4 to 10 with an
increment of 1 using Lemna minor L. and for the different contact time from 1 to 7 days with an
increment of 1 day. Fig. 4 indicates the percentage reduction of TDS and sulphate in a textile
industry effluent using Lemna minor L. against pH (since, day 4 is the optimum contact time found
from the study, the results obtained on the day 4 was presented and the results obtained from the day
1, 2, 3, 5, 6 and 7 were not presented in this study) with a contact time of 4 days, the nutrient dosage
of 50 g and dilution ratio of 8.

290
Fig. 4 The Percentage Reduction of TDS and Sulphate in a Textile Industry Effluent using
Lemna minor L. against pH
The results revealed that the percentage removal of TDS and sulphate is low in acidic pH and
then high with pH increases. This is because, in a slight alkaline to alkaline condition, the active sites
in the Lemna minor L. could be effectively utilized for removing TDS and sulphate in a textile
industry effluent than in acidic condition. Up to pH of 8, the removal of various parameters in a
textile industry effluent by Lemna minor L. increased steadily and for the pH 9 and 10, the
percentage removal results showed the resembles of the results obtained for the pH 8. Hence, the
optimum pH found in this study for the maximum removal of various parameters in a textile industry
effluent is 8. The removal of TDS and sulphate in a textile industry effluent on day 7 and for the pH
9 and 10, the removal percentage for TDS and sulphate was not significant, even contact time and
pH were higher, it is more likely that an even sufficient contact time available, a significant portion
of the available active sites remain undiscovered, leading to lower specific uptake for the pH of 9 and
10 and for the contact time of 5, 6 and 7 days. Thus, the maximum removal percentage of TDS and
sulphate in a textile industry effluent by Lemna minor L. against pH is 78.27 and 81.31 %
respectively (Fig. 4).
3.4 Verification Experiment
In order to validate the above experiments in reducing the various parameters in a textile
industry effluent, a separate experiment has been performed with an optimum nutrient dosage (50 g),
dilution ratio (8), pH (8) and contact time (4 days) for the removal of sulphate in an aqueous
solution. The maximum removal percentage of sulphate in a textile industry effluent and in an
aqueous solution by Lemna minor L. is shown in Fig. 5. The initial concentration of sulphate in an
aqueous solution is similar to the initial concentration of sulphate in a textile industry effluent. The
results (Fig. 5) showed that the maximum removal percentage sulphate in a textile industry effluent
by Lemna minor L. is about 81.31 %, which was lesser than the removal of sulphate in an aqueous
solution, where the removal rate is 84.62 %. The maximum removal rate in an aqueous solution is
due to there were no competitive ions present in an aqueous solution than in a textile industry
effluent. Based on the results, it may be concluded that Lemna minor L. may be used for removing
any other parameters in any type textile industry effluent for an identified optimum values of
selected parameters.

291
Fig. 5: The Percentage Reduction of Sulphate in a Textile Industry Effluent and in an aqueous
solution using Lemna minor L. against Optimum Nutrient Dosage (50 g), Dilution Ratio (8), pH
(8) and Contact Time (4 days)
3.5 Model Development
In this study, the experimental data are fitted with first order kinetic model. The first order
model is given by
(2)
on integration the Eqn.1 becomes
(3)
where C0 is the initial concentration of TDS and sulphate in mg/l, C is the concentration of TDS and
sulphate in mg/l at time ‘t’, ‘t’ is degradation time, days and ‘k1’ is the first order rate constant, days-
1
. The negative sign indicates as time increases the rate constant decreases. The first order rate
constant was calculated from the slope of the straight line by least square fit (Fig.6). The rate
constant k1 and R2
values are presented in Table 1.
Table 1: The kinetic parameter and the regression equation for the parameters TDS and
sulphate in a textile industry effluent at an Optimum Nutrient Dosage (50 g),
Dilution Ratio (8), pH (8) and Contact Time (4 days)
Sl.No. Parameters k1 R2
1 TDS, mg/l -0.2799 0.9699
2 Sulphate, mg/l
-0.3183 0.9811

292
Fig.6: First order Kinetic Model for TDS and Sulphate in a Textile Industry Effluent
for the Optimum Nutrient Dosage (50 g), Dilution Ratio (8), pH (8) and Contact Time (4 days)
The R2
value for TDS and sulphate respectively is 0.9699 and 0.9811 respectively (Table 1)
and indicate that the ability of the first order kinetic model in describing the kinetics of the present
work. In other words, the model is fitted well with the experimental data. Thus, from the kinetic
studies, it was found that the reduction of TDS and sulphate in a textile effluent follows the first
order kinetic model.
4.0 CONCLUSION
In the present study, the experiments were conducted to find out the ability of Lemna minor
L. in removing TDS and sulphate in a textile industry effluent. The ability of Lemna minor L. for
removing TDS and sulphate in a textile industry wastewater by various nutrient dosages, dilution
ratio, pH and contact time were monitored. The maximum percentage reduction of TDS and sulphate
in a textile industry wastewater by Lemna minor L. were obtained at an optimum nutrient dosage of
50 g, dilution ratio of 8 pH of 8 and contact time of 4 days. From the validation experiments, it was
found that the experiments were reproduced at an optimum values found from the experiments
conducted for the removal of TDS and sulphate in a textile industry effluent. The first order kinetic
model is fitted well with the experimental data obtained from textile industry effluent. From the
results of removal of TDS and sulphate, Lemna minor L. might be used for removing various
parameters in any type of textile industry effluent.
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Lemna minor reduces contaminants in textile effluent

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