Removal of heavy metals from waste water using water hyacinth

Abstract

Water pollution has become one of the most serious
problems of today’s civilization. In the last few years
considerable amount of research has been done on the
potential of aquatic macrophytes for pollutant removal or even
as bio-indicators for heavy metals in aquatic ecosystems. Water
hyacinth is one of the aquatic plant species successfully used
for wastewater treatment. It is very efficient in removing
pollutants like suspended solids, BOD, organic matter, heavy
metals and pathogens. This paper mainly focuses on the
treatment of waste water using the plant ‘water hyacinth’ and
has given emphasis to the removal of heavy metals by the
plant. Water hyacinth’ could grow in sewage; they absorb and
digest the pollutants in wastewater, thus converting sewage
effluents to relatively clean water. Thus, the plants hold
promise as a natural water purification system, which could
be established at a fraction of the cost of a conventional sewage
treatment facility. The study conducted in this regard revealed
how efficiently wastewater could be treated using the plant
‘Water hyacinth’.

Full text

ACEEE Int. J. on Transportation and Urban Development, Vol. 01, No. 01, Apr 2011
© 2011 ACEEE
DOI: 01.IJTUD.01.01.39 48
Removal of Heavy Metals from Waste Water Using
Water Hyacinth
A. Mary Lissy P N¹, B. Dr. G. Madhu²
¹Lecturer, Department of Civil Engineering,
Toc H Institute of Science and Technology,Arakkunnam, Kochi, India.
marylissypn@rediffmail.com
² Professor and Head (Safety & Chemical Engg ) School of Engineering,
Cochin University of Science and Technology, Kochi, India.
profmadhu@rediffmail.com.
Abstract— Water pollution has become one of the most serious
problems of today’s civilization. In the last few years
con siderable amount of research has been done on the
potential of aquatic macrophytes for pollutant removal or even
as bio-indicators for heavy metals in aquatic ecosystems. Water
hyacinth is one of the aquatic plant species successfully used
for wastewater treatment. It is very efficient in removing
pollutants like suspended solids, BOD, organic matter, heavy
metals and pathogens. This paper mainly focuses on the
treatment of waste water using the plant ‘water hyacinth’ and
has given emphasis to the removal of heavy metals by the
plant. Water hyacinth’ could grow in sewage; they absorb and
digest the pollutants in wastewater, thus converting sewage
effluents to relatively clean water. Thus, the plants hold
promise as a natural water purification system, which could
be established at a fraction of the cost of a conventional sewage
treatment facility. The study conducted in this regard revealed
how efficiently wastewater could be treated using the plant
‘Water hyacinth’.
Index Terms— macrophytes, absorption , adsorption,
heliophytes, phytoextraction, bioaccumulators.
I. INTRODUCTION
Water scarcity has been increasing all over the world
and in many countries may become absolute by the year
2025 “Ref. [17]”. This problem becomes more apprehensive
when recognizing that the severity of surface water pollution
is a worldwide problem “Ref. [18]”. To tackle the problem,
several measures for sustainable water resource utilization
have been developed, of which wastewater reclamation and
reuse is currently one of the top priorities “Ref. [14]”. It was
reported that domestic and Industrial discharges are
probably the two most important anthropogenic sources for
metals in the water environment “Ref. [4]”.
The presence of heavy metals in water are toxic even at
very low concentrations “Ref. [7]”. Pollution of the biosphere
with toxic metals has accelerated dramatically since the
beginning of the industrial revolution. Water hyacinth
(Eichhornia crassipes) an aquatic plant which could
successfully used for removing various pollutants from water
thus has great importance in wastewater treatment. It has a
huge potential for removal of the vast range of pollutants
from wastewater “Ref. [3]”.
II. RESEARCH SIGNIFICANCE
In this paper the main focus was on studying the efficiency
of water hyacinth in removing dissolved solids, B.O.D, heavy
metals mainly chromium and copper from the waste water,
and the effect of the growth of water hyacinth on the pH of
the waste water. To achieve this objective, water hyacinth
was grown in synthetic wastewater prepared by adding
varying concentrate ions of Cr and Cu. The concentrations
of heavy metals, pH, B.O.D and total dissolved solids were
noted in the waste water before and after cultivating water
hyacinth and compared the results with the standard values.
III. LITERATURE REVIEW
Wastewater could be any water that has been adversely
affected in quality by anthropogenic influence. It comprises
liquid waste discharged by domestic residences, commercial
properties, industry, and agriculture and can encompass a
wide range of potential contaminants and concentrations
“Ref. [9]”. Treated wastewater can be reused as drinking water,
in industry and in the rehabilitation of natural ecosystems
“Ref. [15]”. Although the nature has a fantastic capacity to
deal with waste water and even pollution, with billions of
gallons of polluted and dirty water, it cannot do the work
alone. There are many technologies for wastewater treatment
that can help in re-establishing and preserving physical,
chemical and biological integrity of water. But the efficient
and ecofriendly methods lacked in this regard
A. Water Hyacinth
Water hyacinth (E.crassipes.) is a fast growing perennial
aquatic macrophyte and its name Eichhornia was derived
from well known 19th century Prussian politician J.A.F.
Eichhorn “Ref. [8]”. It is well known for its reproduction
potential and the plant can double its population in only
twelve days. Water hyacinth is also known for its ability to
grow in severe polluted waters. E.crassipes is well studied as
an aquatic plant that can improve the effluent quality from
oxidation ponds and as a main component of one integrated
advanced system for the treatment of municipal, agricultural
and industrial waste waters “Ref. [6]”.

ACEEE Int. J. on Transportation and Urban Development, Vol. 01, No. 01, Apr 2011
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DOI: 01.IJTUD.01.01.39
49
Taxonomy
Division: Magnoliophyta
Class: Liliopsida
Subclass: Commeinidae
Super order: Commelinanae
Order: Pontederiales
Family: Pontederiaceae
Genus: Eichhornia
Morphology
Water hyacinth is an aquatic vascular plant with rounded,
upright and shiny green leaves and lavender flowers similar
to orchids. Individual rosette is erect and free floating with
numerous stolons. Each one carries six to eight spirally
arranged succulent leaves that are produced sequentially on
a short vertical stem. Petioles are bulbous and spongy with
many air spaces which allow plants to float on a water surface
“Ref. [6]”.
Top petal has gold yellow spot bordered with blue line.
Root system of water hyacinth is dark blue in colour with
numerous stolons. New plants are formed at the end of these
stolons. Measured from flower top to root top E. crassipes
usually reach the height of 1.5m and more. When grown in
wastewaters water hyacinth is smaller and it often reaches
heights no more than 0.5 to 1.2m. Growth of water hyacinth is
primarily dependant on the ability of the plant to use solar
energy, nutrient composition of water, culture methods and
environmental factors. Plant growth is described in two ways,
firstly, by reporting the percentage of water surface covered
of a period of time and second and more useful method is by
reporting the plant density in units of wet plant mass per unit
of surface area.
This aquatic plant reproduced in both generative and
vegetative ways. That means new plants could be produced
from seeds or they represent clones derived from stolon
elongation due to division of auxiliary meristems of mother
plant.
Figure.1 Morphology of Water Hyacinth
At first these new rosettes are attached to mother plant but
stolons are very fragile so they could easily broken enabling
young individuals to float away and colonies new areas. Only
ten plants in just eight months could produce a population
of 655,330 individuals.
Water hyacinth is mainly reproduced by generative means
in its natural habitat and it produces large number of seeds.
The flowering period lasts for about fifteen days. When
flowering cycle ends flower stalk bends and the spike go
under the water surface and seeds are released directly into
the water. Each inflorescence contains normally 1 to 20 seed
capsules and capsule caries 3 to 250 seeds. In spite of the
production of this large number of seeds there are only 3 to
3.4 seeds per plant each year that could eventually able to
germinate.
B. Ecological Factors
The environmentally-sound attribute of ecological
technology is its capability of resource recovery and reuse.
For instance, nutrients in nitrogenous and phosphorous
wastewater compounds are recycled into usable biomass by
means of the ecological food chains functioning in aquatic
ecosystems “Ref. [19]”.
Water hyacinth could grow best in warm waters rich in
macronutrients. Optimal water pH for the growth of this
aquatic plant is neutral but it could tolerate pH values from 4
to 10. This important characteristic enables E.crassipes to
treat different types of wastewater .Optimal water temperature
for growth is 28-30oC. Temperatures above 33oC inhibit further
growth. Optimal air temperature is 21-30oC. So if aquatic
systems with water hyacinth are constructed in colder
climates it would be necessary to build greenhouses for
maintaining optimal temperature for plant growth and
development. Low air humidity from 15% to 40% could also
be a limiting factor for undisturbed growth of water hyacinth.
E.crassipes tolerates drought well because it could survive
in moist sediments up to several months.
C. Effects Of Heavy Metals
Some heavy metals have bio-importance as trace elements
but, the biotoxic effects of many of them in human
biochemistry are of great concern . The term “heavy metals”
refers to any metallic element that has a relatively high density
and is toxic or poisonous even at low concentration. To a
small extent, they enter the body system through food, air,
and water and bio-accumulate over a period of time “Ref.
[10]”.
Heavy metals include lead (Pb), cadmium (Cd), zinc
(Zn),mercury (Hg), arsenic (As), silver (Ag) chromium
(Cr),copper (Cu) iron (Fe), and the platinum group elements
“Ref. [11]”. If the concentration of heavy metals exceeds their
limits in the drinking water, it can affect the human health.
Earlier experiments showed that at higher doses they can
cause anemia, liver and kidney damage and can even damage
circulatory and nervous systems “Ref. [7]”. The removal of
heavy metals from aqueous solutions has therefore received
considerable attention in recent years “Ref. [12]”.
D. Mechanisms of Waste Water Treatment Using Water
Hyacinth
Aquatic macrophytes like water hyacinth uptake
contaminants and stores in its biomass. These plants are
called bioaccumulators as they accumulate the contaminants
in their tissues “Ref. [5]”. They have high tolerance against
contaminants like heavy metals and are able to absorb large
quantities. This method of extracting heavy metal from

ACEEE Int. J. on Transportation and Urban Development, Vol. 01, No. 01, Apr 2011
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polluted water bodies is called phytoextraction . The uptake
of contaminants is by three methods
 Root absorption- The roots absorb water together
with the contaminants in water. The presence of carboxyl ·
groups at the roots system induces a significant cation
exchange through cell membrane and this might be the
mechanism of moving heavy metal in the roots system where
active absorption takes place. In sewage systems, the root
structures of water hyacinth (and other aquatic plants) provide
a suitable environment for aerobic bacteria to function.
Aerobic bacteria feed on nutrients and produce inorganic
compounds which in turn provide food for the plants. The
plants grow quickly and can be harvested to provide rich and
valuable compost. Water hyacinth has also been used for the
removal or reduction of nutrients, heavy metals, organic
compounds and pathogens from water.
 Foliar absorption- In addition to root absorption,
plants could also derive low amounts of some contaminants
through foliar absorption. They are passively absorbed
through stoma cells and cracks in cuticle.
 Adsorption- The fibrous and feathery roots not only
trap suspended solids and bacteria, but provide attachment
sites for bacterial and fungal growth. The contaminants get
adsorbed to the root surface by the bacteria present there. It
is also due to ionic imbalance across the cell membrane.
IV. EXPERRIMENTAL SET UP
Water hyacinth was collected from three different local
ponds. The experiments were conducted in tank as well as in
jars. This was done in order to find out the efficiency of the
plant in removing the pollutants when they were used as a
single plant in jars and also when they are used collectively
in tanks.
A. Water Hyacinth grown in Tank
A natural wetland was simulated in an RCC tank in
which the water hyacinth was grown. A tank of size 3m x 2.5m
x 1m having a capacity of 7.5m3 was constructed. The tank
was filled with 6000 litres of water. Then the water hyacinths
collected were grown in the tank.
B. Water Hyacinth grown in Jars
Eight quart size jars were filled with 1litre of water containing
chromium (1ppm) and copper (5ppm).The jars with chromium
and copper were then sorted separately into four treatments
with two jars in each treatment. The samples collected were
placed in three of the four treatments and two jars were
without plant as control as shown in “Fig. 3” & “Fig.4”.
The standard procedure was carried out with known
concentrations of chromium and copper. The change in pH,
TDS, B.O.D, Cr and Cu concentrations were found out at
regular intervals using APHA methods “Ref. [1]”.
V. RESULTS AND DISCUSSIONS
The experimental results of various tests conducted
are shown below:
The results given in Table: 1 showed that the quality
of the water sample collected is within the W.H.O standards
“Ref. [2]”. So the study was carried out by adding known
concentrations of heavy metal ie; 1ppm of Cr and 5 ppm of
Cu.
A. Results of the experiments carried out with Chromium
in the tank
Figure.5: Variation of chromium concentration in the tank

ACEEE Int. J. on Transportation and Urban Development, Vol. 01, No. 01, Apr 2011
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B. Results of Copper in tank
C .Results of experiments carried out in Jars with
Chromium
Figure.11 Results of TDS
D. Results of experiments carried out in Jars with
Copper
Figure.12: Results of Copper in Jars

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E .Discussions
The results of the experiments carried out in the tank
showed that the plant has the ability to absorb heavy metals
Chromium and copper from the waste water .The TDS values
increased on placing the plants in the tank .This increase
was due to the presence of clay or other fine particles present
in the plant roots. On subsequent days it showed that the
TDS value considerably decreased by the accumulation
process of water hyacinth. There was reduction in BOD also.
The jars with plant showed a considerable decrease in Cr
and Cu concentrations. For jars without plant, the decrease
of chromium and copper concentration was found to be very
less .Thus we could conclude that loss due to evaporation
and settlement were very less. There was no much change
for pH. The pH value was found to be between 6 and 8. The
value of TDS was found increasing. This might be attributed
to the decay of the single plant growing in the jar with high
Cr concentrations contributing to TDS content. The results
obtained indicated that water hyacinth could be used as an
effective means for the removal of heavy metals from waste
water if the same is used collectively as done in the RCC
tank.
CONCLUSIONS
The efficiency of waste water treatment was expressed
in terms of the variation in pH, biochemical Oxygen Demand
(BOD), total Dissolved Solids (TDS) and heavy metals before
and after treatment. When the plants were collectively grown,
the removal of pollutants from the water was very high. The
experimental results have shown that about 65% removal of
heavy metals could be achieved by water hyacinth. The plants
have also got the capacity to convert the accumulated
biomass into biogas. This system of treatment was cost
effective since cost of installation and maintenance was very
low. This system could be provided alone or together with
other systems used for treating waste water. In conclusion,
the present investigation demonstrated the feasibility of
adopting a “sustainable” and eco-friendly approach to sewage
waste water treatment using aquatic plant Eichhornia. Since
it was only a laboratory scale base - line study, further
investigations should be carried out in future on a large scale
particularly focusing on phytoremediation and resource
utilization.
ACKNOWLEDGEMENT
Authors are grateful to department of civil engineering,
TIST, Arakkunnam for the co-operation and support given
for the completion of this work. This work was supported by
Research centre of Toc H Institute of Science & Technology ,
Arakkunnam.
REFERENCES
[1] APHA (2002). Standard Methods for the Examination of Water
and Wastewater, American Public Health Association, AWWA,
and WPCF, Washington DC.
[2] G. S. Birdie (1992).Water supply and sanitary engineering,
Dhanpat Rai Publishing Company, New Delhi.
[3] Ayaz and Acka (2001). Treatment of wastewater by natural
systems, Environment International, 26,189-195.
[4] S. Muramoto and Y. Oki (1983),Removal of Some Heavy
Metals from Polluted Water by Water Hyacinth (Eichhornia
crassipes) ,Bulletin of Environmental Contaminants and
toxicology, 30, 170-177.
[5] Boyd, C. E. (1970). Vascular aquatic plants for mineral nutrient
removal from polluted waters. Economic Botany, 24, 95–103.
[6] Sangeeta Dhote & Savita Dixit(2009),Water quality improvement
through macrophytes—a review, Environmental Monitoring
and Assessment,152:149–153
[7] Tiwari, S., Dixit, S., & Verma, N. (2007). An effective means of
bio-filtration of heavy metal contaminated water bodies using
aquatic weed Eichhornia crassipes, Environmental Monitoring
and Assessment, 129, 253–256.
[8] Shree N. Singh, Rudra D.Tripathi (2007), Environmental
bioremediation technologies, Springer.
[9] Goel, P.K. (1997). Water pollution, causes, effects and control.
New Age International (P) Ltd., publishers, New Delhi: 269.
[10] Athalye, R.P., Mishra, V., Goldin Quadros, Vidya Ullal and
Gokhale, K.S. (2001). Heavy metals in the abiotic and biotic
components of Thane Creek, India. Pollut. Res., 18(3): 329-
333.
[11] Upadhyay, Alka R.; B. D. Tripathi (2007). “Principle and
Process of Biofiltration of Cd, Cr, Co, Ni & Pb from Tropical
Opencast Coalmine Effluent”. Water, Air, & Soil Pollution
(Springer) 180 (1 - 4):213–223..
[12] Abou-Shanab, R. A. I. et al.; Angle, JS; Van Berkum, P
(2007). “Chromate-Tolerant Bacteria for Enhanced Metal
Uptake by Eichhornia Crassipes (MART.)”. International
Journal of Phytoremediation 9 (2): 91–105.
[13] Sathyanarayanan, U. (2007): Textbook of Biotechnology Books
and Ailled (P) Ltd., Kolkata. pp. 667-707.
[14] Anderson, J., Adin, A., Crook, J., Davis, C., ultquist, R.,
Jimenez-Cisneros, B., Kenedy, W.,Sheik, N. , and Van der
Merwe, B., (2001).Climbing the ladder: a step by step
approach to international guidelines for waterrecycling. Water
Science Technology, 43, 1-8.
[15] Ch u, J., Chen, J., Wang, C., Fu, P. (2004). Wastewater reuse
potential analysis: implications for China’s water resource
management. Water Research, 38, 2746-2756.
[16] Nhapi I., Gijzen H.J. 2005. A 3-step strategic approach to
sustainable wastewater management. Water SA, Vol 31, No 1,
pp. 133-140
[17] Seckler, D., Barker R. and Amarasinghe U. (1999). Water
scarcity in the twenty-first century. International Journal of
Water Resources Development 15, 29-42.
[18] Yan, J., Wang, R., Wang, M. (1998). The fundamentalprinciples
and ecotechniques of wastewater aquaculture.Ecological
Engineering10,191-208.
[19] Joel de la Noue, Niels de Pauw(1988). The potential of
micro algal technology Biotechnology Advances, Volume 6,
Issue 4, 1988, Pages725-770