water hyacinth

ISSN: 1579-4377
WATER HYACINTH: AVAILABLE AND RENEWABLE RESOURCE
M.F.Abdel-sabour
Recycling and Environment consultant
freemfs73@yahoo.com
ABSTRACT
Recently, attention is being devoted to the utilization of water hyacinth since the efforts to
control plant growth by chemical; biological and mechanical means have met with little
success. The real challenge is not how to get rid of this weeds but how to benefit from it and
turn it into a crop. Thus the issue of water hyacinth should be looked from a different view. In
this article the potential uses of water hyacinth are classified and discussed.
Data indicated that the application of water hyacinth co-compost as soil amendments
especially to the sandy soils, can improve some soil hydro-physical and chemical parameters
and supplies the growing crops with several nutrients. On the other hand, if the composted
water hyacinth was collected from a clean water bodies the levels of heavy metals would be
lower than other common organic fertilizers in the market.
Water hyacinth removed various pollutants through the absorption and uptake of toxic
organic matter and heavy metals. Water hyacinth has drawn attention as a plant of rapid
growth and high biomass production, and capable of removing pollutants from domestic and
industrial waste effluents. Reduction of heavy metals in situ by plants may be a useful
detoxification mechanism for phytoremediation. Therefore, water hyacinth could be
employed for biological treatment of contaminated water. Water hyacinth rhizomes and roots
could help in the removal of heavy metals from the aquatic habitat or constructed wet-land.
Therefore, it is undesirable to involve contaminated rhizomes and roots in fodder or co-
compost organic fertilizer. From these results the contaminated water hyacinth may be dry
ashed and heavy metals could be extracted and recycled.
KEYWORDS
Water recycled, renewable resource.

Abdel-sabour, M.F. et al. EJEAFChe, 9(11), 2010 [1746-1759]
1746
BACKGROUND:
Water hyacinth (Eichlorina cassipes (Mart. sol ms), was introduced to Egypt in 1879, and was
cultivated in ponds of public gardens, then it found its way to water canals. Nowadays it is
hardly possible to find a water habitat in Egypt -particularly in delta- not menaced by this
plant. Huge floating islands of this weed mixed later with other sub-emergent and emergent
aquatic weeds are common in huge areas in Upper Egypt, Dammiata and Rossata branches of
the Nile, drainage canals as well as El-Manzalla Lake.
The productive potential of water hyacinth is reported to be tremendous Hussein,
(1992) reported that in 50 days, a single plant produces 43 offsets which produce 1894 offsets
in another 50 days and after 200 days from the start, one expects to have 3,418,800 new
offsets. He indicated that about 20 dry tons per hectare can be harvested from standing water
hyacinth plants, wherease a 5 to 8 harvests can be collected per year.
Water hyacinth causes serious harms and has an adverse effect on water resources,
fisheries, irrigation, drainage canals and public health. (Hussein, 1992, Obeid, 1984;
Batanouny and EL- Fiky, 1984 and Sculthrope, 1967)
Methods to control water hyacinth can be classified into: chemical, biological and
mechanical methods. Chemical control methods depend on several herbicides to control the
plant. However, these methods have several disadvantages such as the adverse effect on the
environment and public health. (Obeid, 1984) .the biological control methods on a trial bases
have been carried out to control water hyacinth using some pests as fungal pathogens, mites,
snails or insects and certain grass-eating fish species, however, the results were not
satisfactory. Moreover, introducing new pests to the environment may disturb the natural
balance and the biological diversity (Wright and Centor, 1984). Finally, several reports
recommended the mechanical control methods by using different machinery devices (e.g.
mechanical mooring and rolling machines, conveyers…ect.).
Recently, attention is being devoted to the utilization of water hyacinth since the
efforts to control plant growth by chemical; biological and mechanical means have met with
little success.
Utilization of water hyacinth
Utilization plans do not suggest the cultivation of the plant, since it is considered as a pest.
The real challenge is not how to get rid of this weeds but how to benefit from it and turn it
into a crop. The most important consideration in the utilization of water hyacinth is its high
growth rate and dry matter production, there for the harvesting rate should equal to or more
than the growth rate. Several studies in Egypt and worldwide have been carried out to
investigate the efficient ways to utilize this weeds. In this article the potential uses are
classified and discussed.
1) Animal feed and animal production
Trials employ water hyacinth for feeding cattle; goats, pigs and rabbits have been carried out
in several countries (Shoukry, 1982, El-Serafy et. al., 1981, Osman et. al.,1981). The results
showed that non-ruminants (pigs and rabbits) can better utilize water hyacinth than cows and
goats. The efficiency of utilization was greater for rabbits. Several studies reported that dried
water hyacinth was successfully used in feeding poultry and ducks.
Recently, Costa-pierce (1998) studied the feasibility of using a designed integrated
aqua culture-wetland ecosystem (AWE) for experimental food production and inorganic
nitrogen removal from tertiary-treated wastewater. The AWE connected poly-culture
aquaculture ponds with in-pond aquatic plant systems (water hyacinths, Eichhornia crassipes,

1747
and Chinese water spinach, Ipomea aquatica), a solar energy aeration system, and an artificial
wetland. Ponds were stocked with hybrid tilapia (Oreochromis mossambicus X urolepis
hornorum), common carp (Cyprinus carpio). Mosquitofish (Gambusia affinis), and red swamp
crayfish (Procambarus clarkii), and were flushed weekly with new wastewater at 20%. Fish
were fed a 32% protein floating ratio at 1% fish body weight per day, and wheat bran was
added at 1 mg 1-1
when water conductivities exceeded 900 mmhos cm-1
. Plants were allowed
to grow until they reached approximately 50% of the pond surface area, and then maintained
at this area by manual harvesting. The results indicate that water hyacinth could play a
significant role in wetland systems.
Jantrarotai (1991) indicated that water hyacinth has potential as a roughage source for
ruminants because its dry matter has high crude protein (18%) and low acid detergent fiber
(33%) contents. However, the high moisture content of the plant (95%) may make their use as
forage uneconomical. He reported that where grass crop (Ctenopharyngodon idella) were fed
diets containing from 0 to 100% water hyacinth meal, weight gain, and protein efficiency
ratio decreased as the amount of water hyacinth meal increased.
2- Organic fertilizer (green manure or compost) or mulching materials:
One of the important use of water hyacinth residues is as a compost and mulch
(Mukhopadyay and Hossain, 1990), because water hyacinth contains high concentrations of
plant nutrients such as N, P, Ca, Mg and K. Goel et. al., (1989) Indicated that it concentrates
these nutrients from water by factors ranging from 36 to 14000 folds. Table (1) shows the
averages of common elemental content in water hyacinth tissues and its nutritional values
(from several studies). The plant leaves were reported to contain 15.9, 13.9, 8.8 and 8.5 mg of
Ca, K, Mg, P and N per gram of dry weight, respectively. Also, the laminae had higher
concentrations of K and P than the petioles (Oke and Elmo, 1990). Water hyacinth would be
very desirable to be used as a green manure since the release of the nutrients was reported to
be easier, compared to other plants residues (Para and Hortenstine, 1974).
Table (1) Nutrational and elemental content of water hyacinth tissues (general means from several studies on
non-polluted plants.
Shoots Roots Whole plant
Crude protein %
Crude fiber %
Ash %
Phosphorus %
K %
Ca %
Mg %
Fe ppm
Mn ppm
Zn ppm
Cu ppm
Co ppm
Cr ppm
Ni ppm
Cd ppm
Pb ppm
Hg ppm
14.8
15.6
22.5
0.5
3.16
2.13
1.69
7854
693
18.4
32.5
10.8
31.8
2.5
0.7
26.9
0.2
9.3
110.0
49.6
0.48
0.83
3.27
2.77
14825
2790
93.6
53.5
32.1
66.5
7.3
2.1
74.7
0.40
11.4
63.9
36.8
0.51
1.99
2.70
2.23
10676
1669
55.80
40.00
21.40
49.00
4.90
1.60
51.21
0.39

1748
1. Moreover, the tremendous amount of mechanically removed water hyacinth from water streams
could be utilized as compost. Co-composts of water hyacinth with other organic residues (crop
residues, sewage sludge, municipal solid waste … ect.) were found to increase the yields, protein
and neutron content of several crops (Singh and Yadav, 1986,Ahmed et. al., 1992, Rabie et. al.,
1995, Abdel-sabour and Abo El-Seoud, 1996). They reported that single application of different
tested composts had resulted in a remarkable increase in dry matter yield, seed yields, protein
content, neutron content and chlorophyll in plant tissue (corn, sesame, sunflower, and common
bean. The results of Rabie, et. Al., (1995); Abdel-Sabour and El-Seoud, 1996; Abdel-Sabour et.
al., 1997, and Abdel –Sabour et. al.,1997b, showed the superiority of water hyacinth compost
compared to other tested composts (sewage sludge or municipal solid waste co-composts. Their
data indicated that the application of water hyacinth co-compost as soil amendments especially to
the sandy soils, can improve some soil hydro-physical and chemical parameters and supplies the
growing crops with several nutrients. On the other hand, if the composted water hyacinth was
collected from a clean water bodies the levels of heavy metals would be lower than other common
organic fertilizers in the market.
Another potential usage was reported by Soerjaini, (1984). A substrate from water
hyacinth petioles mixed with rice barn and lime (100:10:5) and with urea and phosphate
fertilizers (up to 1.5% of medium weight) was composted for 4-5 days, spread over shelves,
sterilized and then used as substrate for mushroom cultivations. This substrate gave after 10
days a very satisfactory harvest, which ranged from 20 to 25% of the weight of the used
substrate medium.
3- Biogas production:
In several countries water hyacinth is successfully used for biogases production in
fermentators of different capacities (Ikhtyar and Shamsuzzaman, 1984, Dhahiyat et al., 1984
and Haripada Sarker et. al., 1984). They concluded that a mixture of 25% cow doing and 75%
of dry water hyacinth yield best rates of methane production. Their results indicate the huge
potential of water hyacinth as a non-conventional energy source. They estimated that one-ton
of dry water hyacinth could yield 370,000 L of biogas.
4- phytoremediation :
Water hyacinth has drawn attention as a plant of rapid growth and high biomass production,
and capable of removing pollutants from domestic and industrial waste effluents. Water
Hyacinth (Eichhornia crassipes) has demonstrated its ability to remove nutrients and other
chemical elements from sewage and industrial effluents (Saltabas and Akcin, 1994). In their
study, 10.00 ppm chromium, 35.00 ppm copper and 14.00 ppm nickel solutions were used,
and absorption ability of water hyacinth was observed. Due to the positive experimental
results on the removal of chromium, copper and nickel, they suggested that water hyacinth
may be used for industrial effluents. Haselow et. al., (1992) indicated that managed growth
and harvesting of water hyacinth can be utilized for water quality improvement in lakes, but
only if the plants are mechanically removed from the system. Aoyama and Nishizaki (1991)
evaluated the practical use of water hyacinth grown in natural water channels or ponds for
water purification. They recommended a shorter harvesting interval to obtain more yield of
the biomass. Jebanesan (1997) indicated that water hyacinth was found to be more effective in
the treatment of dairy wastewater. The wastewater from a dairy was treated with the water
hyacinth for a retention period of 25 days, Water various physico-chemical parameters were
analyzed at 0, 5,10, 15, 20 and 25 days after treatment. After the retention period of 25 days,
water total solids, Ca, Mg and total hardness were reduced by 37, 5, 47.5, 54 and 33%,
respectively. Water chloride, Cr, nitrous nitrogen, nitric nitrogen, pH, alkalinity, COD, BOD,

1749
bicarbonates and specific conductance were also reduced considerably than the control. In
another investigation on natural shallow eutrophicated wetland receiving influx of domestic
sewage and agricultural rub-off of the watershed, heavily infested with water hyacinth,
located in Ujjain city, Madhya Pradesh, State in India was studied (Billore et al., 1998). The
aims of the study were to determine the role of dense growth of hyacinth in the removal of
particulate matter attached to root system, and nitrogen as contained in the root attached
particulate matter (RAPM) and in the plant tissue. The recorded hyacinth density was 79
plants per square meter with 1.549 kg dry plant tissue. They found that the plant in one square
meter could retain 663 g RAPM (about 42% of dry plant tissue), which potentially removed
upon the mechanical harvest of the plants on per meter square basis. In addition to the
significant amount of RAPM, the harvested hyacinth plant also brought about removal of
1.396 g of organic matter, 0.536 g of total nitrogen, 0.482 g of ammoniacal nitrogen, and
0.338 g of nitrate nitrogen per m2
waterscape basis. In other words, when the hyacinth plants
are manually/mechanically removed from the wetland, potentiality of total nitrogen removal
is 37.32 kg through the plant tissue + 5.36 kg nitrogen/hectare in the RAPM, besides 6630
kg/h of particulate matter through roots attachment (RAMP). The extensive root systems of
the hyacinth provide a huge surface area for attached particulate matter and microorganisms,
acting as ‘suspended sediment layer’ and rich in nitrogen. Thus, for a eutrophicated wetland
receiving wastewater rich in particulate matter, the hyacinth growth has substantial potential
for the removal of particulate matter and nitrogen through their attachment to roots, in
addition to the nitrogen concentrated in the plant tissue.
Another important usage for water hyacinth is its use as biological treatment for raw
sewage effluent. Ayade (1998) reported that pioneering research efforts in the handling of
municipal sewage in developing countries have involved the use of water hyacinth to purify
sewage for possible domestic purposes re-use. The ability of water hyacinth to remove
pollutant from raw sewage effluent has been found to be impaired by sewage toxicity. Trials
were therefore carried out to adapt water hyacinth to toxicity and thereby increase its ability to
remove pollutants from raw sewage. The plants were adapted using an active bio-degrader
consisting of different bacteria species such as, Pseudomonas aeruginosa, Escherichia coli,
Klebsiella ozaenae, Klebsiella edwardsiella and Baccillus subtilis. The adaptation progressed
through 20, 40, 60 and 80% sewage dilution until plants capable of growth in 100% raw
sewage were obtained. Plants were observed for morphological growth and at four weeks,
samples were collected for tissue analysis. The plants progressively absorbed nutrients from
sewage up to the fourth week, when signs of toxicity were observed (through wilting, loss of
turgidity and reduction in leaf number). However, plants that survived through a series of
adaptations under various sewage dilutions exhibited luxuriant growth on raw sewage. In
synergy with the active bio-degrader, the efficiency of the adapted water hyacinth to remove
pollutants (nutrients) from raw sewage was enhanced by 93%.
I) Removal of heavy metals:
Water hyacinth (eichhorina cassipes) has drawn attention as a plant capable of removing
pollutants, including toxic metals from surface water (Kelly et al., 1999). Reduction of heavy
metals in situ by plants may be a useful detoxification mechanism for phytoremediation
Studies were conducted to determine the phytotoxic effect and uptake capacity of heavy
metals by water hyacinth (Delgado et al., 1993, Akcine et. al., 1994, Abdel-Sabour et.
al.,1996 and lytle et. al., 1998). Shine et. al., (1998) investigated lake Chpala, mexico
(1990-1991 ) historically the lake has received poorly characterized domestic, industrial and
agriculture wastes. Heavy metals (i.e. As, Cd, Pb, Cr and Zn) displayed high levels during the
dried seasons (presumably, due to high evaporation). They reported high levels of both Cd
and Pb, which were above the chronic criteria according to EPA standards for protection of

1750
aquatic ecosystem health.
A Study case:
In a case study (unpublished data) the bioaccumulation of both Cd and Pb in water
hyacinth was investigated in greenhouse experiment. Plants were exposed to water containing
different levels of Cd ranging from 0 up to 20 ppm and its possible combination with different
levels of Pb ranging from 0 up to 100 ppm in complete randomized blocks with three
replicates. The aim of the study was to determine the accumulation, translocation, interaction
and removal capacity of Cd and Pb by water hyacinth plants.
The data showed that water hyacinth accumulated both Cd and Pb mainly in the roots. No
adverse effect or phyto-toxicity symptoms on plant were observed due to increasing levels of
both Cd and Pb in water. A positive significant effect of tested element on its accumulation in
different plant parts and simple linear or polynomial regression equations between plant tissue
content of element in question and its levels in solutions were observed as shown in Figs (1-2).
As it could seen from the Figures roots retained higher levels of Cd or Pb than leaves or
stems. Cadmium content in whole plant was enhanced by both Cd and Pb addition (synergetic
effect) however, an antagonistic effect was noticed between Pb whole plant content and Cd
application.
As shown in Table (2) the enrichment ratio (ER = metal content in treated plant / metal
content in control plant) varied widely according to plant part (leaves, stems and roots) and
tested metal interactions (Cd and Pb). The application of Cd drastically increased Cd-ER
ratios for all testd plant parts at any levels of Pb. As expected the ER values were always
higher in case of roots > stems > leaves. Cd-ER ratios for whole plant showed a
remarkable increase up to 427 times than control treatment however, in case of Pb-ER ratios it
was only 40.78 times higher than its relevant treatment. It is worth mentioning, that the
increasing levels of Cd in solution reduced the value of Pb-ER ratio for any tested plant part,
which again confirm the antagonistic effect of Cd on Pb uptake. The relative high increase in
Cd-plant tissue compared to the corresponding values for Pb-plant tissue (as determined by
ER ratio) may indicate the high plant affinity for Cd uptake. Delgado et al. (1993) indicated
that after 24 days of growth, Cd, Cr, Zn in water were depleted totally from the nutritive
solution suggesting complete absorption of these metals by the plants.
To evaluate the translocation of both Cd and Pb from roots to stems and leaves, the ratio
between total metal content in leaves divided by total metal content in roots (L/R) was
calculated and presented in Table (3). Similarly, total metal content in stems compared by its
relevant value in root (S/R) and sum of L+S compared to R are presented in Table (3). The
inspection of the Table suggested that Cd is more mobile and could be translated form roots to
leaves and stems than Pb. Generally, Water hyacinth rhizomes and roots could help in the
removal of heavy metals from the aquatic habitat or constructed wet-land. Therefore, it is
undesirable to involve contaminated rhizomes and roots in fodder or co-compost organic
fertilizer. From these results the contaminated water hyacinth may be dry ashed and heavy
metals could be extracted and recycled.

1751
Fig (1) Effect of Cd and Pb on Cd content in
different plant tissue (mg/kg)
0
2 0 0 0
4 0 0 0
6 0 0 0
8 0 0 0
1 0 0 0 0
1 2 0 0 0
0 5 1 0 1 5 2 0 2 5
C d r a te (u g /g )
Cdcontent
(
mg
/kg
)
0 -P b 1 0 -P b 2 0 -P b 4 0 -P b
- 5 0 0
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
3 0 0 0
3 5 0 0
4 0 0 0
0 5 1 0 1 5 2 0 2 5
Cdcontent
(
mg
/
kg
)
- 5 0
0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0
4 0 0
0 5 1 0 1 5 2 0 2 5
Cdcontent
(
mg
/
kg
)
0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
5 0 0 0
6 0 0 0
7 0 0 0
8 0 0 0
9 0 0 0
0 5 1 0 1 5 2 0 2 5
Cdcontent
(
mg
/
kg
)

1752
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
Pbcontent
(ug
/g
)
0
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
6 0 0
7 0 0
8 0 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0
Pbcontent
(
ug
/
g
)
0
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0
Pbcontent
(
ug
/
g
)
0
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0
P b r a t e ( u g / g )
Pbcontent
(
ug
/g
)
0 - C d 2 - C d 4 - C d 8 _ C d
Fig (2) Effect of Cd and Pb on Pb content in different plant
tissue (mg/kg)

1753
Table (2) Cadmium or lead enrichment in water hyacinth tissues as affected by Cd and Pb treatments.
Cd rate mg/L Plant part Pb rate mg/L
0 5 50 100
Cd-ratio
0 L
S
R
W
1
1
1
1
0.99
3.01
1.17
1.13
0.91
1.22
2.32
1.18
0.92
1.14
6.47
1.34
5 L
S
R
W
12.10
38.87
295.90
59.08
10.82
32.36
308.10
58.24
12.92
32.36
326.40
62.00
8.31
21.79
409.30
68.05
10 L
S
R
W
17.58
51.13
547.20
100.70
35.02
60.57
535.90
112.10
32.01
60.47
596.20
306.30
42.65
58.11
652.8
132.00
20 L
S
R
W
34.52
133.90
1332.0
243.20
40.36
127.40
1579.00
279.00
73.42
131.40
1628.00
306.3
97.03
126.40
2642.00
472.90
Pb-ratio
0 L
S
R
W
1
1
1
1
3.46
1.52
7.09
5.99
5.29
3.34
10.77
9.41
9.82
7.09
53.50
40.78
5 L
S
R
W
0.92
0.41
0.51
0.63
2.34
1.46
6.73
5.73
4.15
2.99
10.51
8.91
6.73
4.23
41.40
31.23
10 L
S
R
W
0.49
0.31
0.49
0.51
2.29
1.40
6.39
5.25
4.63
2.96
10.19
8.78
6.70
4.15
41.20
30.87
20 L
S
R
W
0.48
0.27
0.49
0.51
2.11
1.33
6.29
5.13
3.99
2.87
9.91
8.44
6.59
4.09
41.1
29.79

1754
Table (3) Cadmium or lead ratios in water hyacinth tissues as affected by Cd and Pb treatments.
Cd rate mg/L Ratio Pb rate mg/L
0 5 50 100
Cd-ratio
0 L/R
S/R
L+S/R
1.05
0.96
2.02
1.02
0.71
1.73
0.84
0.77
1.62
0.35
0.33
0.69
5 L/R
S/R
L+S/R
0.07
0.19
0.25
0.09
0.14
0.20
0.10
0.13
0.20
0.11
0.09
0.15
10 L/R
S/R
L+S/R
0.05
0.14
0.26
0.06
0.13
0.22
0.07
0.16
0.22
0.06
0.12
0.19
20 L/R
S/R
L+S/R
0.04
0.15
0.19
0.04
0.10
0.14
0.08
0.11
0.19
0.07
0.06
0.13
Pb-ratio
0 L/R
S/R
L+S/R
0.07
0.22
0.29
0.06
0.05
0.11
0.07
0.10
0.17
0.02
0.03
0.06
5 L/R
S/R
L+S/R
0.20
0.25
0.45
0.04
0.06
0.10
0.04
0.08
0.13
0.03
0.03
0.06
10 L/R
S/R
L+S/R
0.11
0.20
0.31
0.03
0.05
0.09
0.06
0.10
0.16
0.02
0.03
0.05
20 L/R
S/R
L+S/R
0.11
0.18
0.29
0.04
0.06
0.10
0.04
0.09
0.13
0.02
0.03
0.05
Water hyacinth is not only capable to absorb and accumulate heavy metals, but also it
could tolerate its toxicity by converting it from chemically-active toxic stat to inactive and
nontoxic stat. Lenzi et al., (1994) evaluated the removal of chromium (III) from aqueous
solution by water hyacinth. The results showed that there was good removal of Cr at rate of
10 mg Cr/1 solution (the recovery was 87.52%), but for higher concentrations (50 or 100
mg/1), the water hyacinth did not appear to be a good absorbent. It was also seen that, higher
rations of water hyacinth mass/solution volume lead to higher solution decontamination. The
absorption of Cr (III) by the water hyacinth was lower by decreasing the pH solution. They
indicated that Cr (III) removal by water hyacinth was not influenced by the temperature in the
range 17.5 to 26.0 degree C, or by the dissolved oxygen concentration in the solution between
4.71 to 6.77 mg/l.

1755
Kelley et al., (1999) investigated the capacity of the water hyacinth to remediate
aquatic environments that have been contaminated with the lanthanide metal, europium
Eu(III). Using scanning electron microscopy (SEM) they have been able to determine that
Eu(III) is adsorbed onto the surface of the roots and the highest concentration of Eu(III) was
found on the root hairs. In their study X-ray absorption spectroscopy (XAS) techniques were
used to speciate the Eu(III) adsorbed onto the surface of the roots. The XAS data for Eu-
contaminated water hyacinth roots provides evidence of a Eu-oxygen environment wherease
Eu(III) is coordinated to 10-11 oxygen atoms at a distance of 2.44 Angstrom. This likely
involves binding of Eu(III) to the root via carboxylate groups and hydration of Eu(III) at the
root surface.
Zhu et al., (1999) demonstrated the potential of water hyacinth for the phytoremediation of six
trace elements. These plants are being used successfully for the phytoremediation of trace
elements in natural and constructed wetlands. The ability of water hyacinth to take up and
translocation six trace elements-As (V), Cd(II), Cr(VI), Cu(II), Ni(II) and Se (VI)-was studied
under controlled conditions. They indicated that water hyacinth accumulated Cd and Cr at a
higher levels, then Se and Cu at moderate levels, however water hyacinth was a poor
accumulator for As and Ni. The highest levels of Cd found in shoots and roots were 371 and
6103 mg kg-1
) dry wt., respectively, and those of Cr were 119 and 3951 mg kg-1
dry wt.,
respectively. Cadmium, Cr, Cu, Ni, and As were more highly accumulated in roots than in
shoots. In contrast, Se was accumulated more in shoots than in roots at most external
concentrations. Water hyacinth had high trace element bioconcentration factors when supplied
with low external concentrations of all six elements, particularly Cd (highest BCF = 2150), Cr
(1823), and Cu(595). They conclude that water hyacinth is a promising candidate for
phytoremediation of wastewater polluted with Cd, Cr, Cu, and Se. Therefore, water hyacinth
could be very efficient for phytoextracting trace elements from wastewater containing low
concentrations of these elements. Lytle et al., (1998) Using X-ray spectroscopy, to show that
water hyacinth, supplied with Cr (VI) in nutrient culture, accumulated nontoxic Cr (III) in
root and shoot tissues. Their data indicated that the reduction of Cr (VI) to Cr (III) appeared to
occur in the fine lateral roots, then Cr (III) was subsequently translocated to leaf tissues.
Extended X-ray absorption fine structure of Cr in leaf and petiole differed when compared to
Cr in roots. In roots, Cr (III) was hydrated by water, but in petiole and more so in leaf, a
portion of the Cr (III) may be bound to oxalate ligands. This suggests that E. crassipes
detoxified Cr (VI) upon root uptake and transported a portion of the detoxified Cr to leaf
tissues. Cr-rich crystalline structures were observed on the leaf surface. The chemical species
of Cr in other plants, collected from wetlands that contained. Cr (VI)-contaminated
wastewater was also found to be Cr (III). They proposed that this plant-based reduction of Cr
(VI) by E. crassipes has the potential to be used for the in situ detoxification of Cr
(VI)-contaminated wastestreams. Eichhornia crassipes has been grown in the presence of a
number of complexes of the platinum group metals (Farago and Parsons, 1994). Those
compounds that are taken up by the plants in larger quantities are the more toxic one and they
reported the relative order of toxicities determined from visual appraisal and in terms of
oxidation states, to be Pt(II), Pd(II) > Ru(III) similar to Ru(II) similar to Ir(III)> Pt(IV) similar
to Os(IV)>> Rh(III). In most cases the metals are accumulated in the roots, and where the
toxic symptoms were observed when the metal is translocated to the tops. Root elongation
and biomass studies confirm that Eichhornia is more tolerant to Rh(III) and Pt(IV) than to
Pt(II). Treatment with a Rh and three Pt complexes produced little differences in the
concentrations of Ca, Cu, Fe, Mn and Zn in treated plants compared with controls. Sequential
extractions of tissue from plants treated with [Pt(NH3)2Cl2] showed that in the leaves and
floats almost half the platinum is insoluble and associated with alph-cellulose and lignin.
They reported 16% of the metal was removed by the enzyme pronase and can be considered
to be associated with proteins or amino acids. In the roots, about a third of the Pt is insoluble

1756
and 9.5% is removed by pronase. More Pt in the roots appeared in the fraction containing
water-soluble low molecular weight materials.
B- removal of organic contaminant:
Water hyacinth was employed for wastewater treatment in many parts of the world.
By planting water hyacinth in wastewater pond, part of the gaseous oxygen produced by
photosynthetic activity of the green leaves is translocated to the stems and roots and to the
water body ; this oxygen is used by the aerobic and facultative bacteria in biodegrading
organic matter contained in the wastewater. Two groups of bacteria normally exists in a water
hyacinth pond (WHP), namely the suspended bacteria which are present in the liquid portion
and the biofilm bacteria which are attached on the surfaces of the roots of the water hyacinth
plants and on the side walls and bottom layers of the pond itself. Current design criteria for
WHPs do not emphasize the roles of these two groups of bacteria, but they are based on either
empirical relationships or first-order reaction rate and complete-mix flow condition.
Chongrak and Raj (1998) studied the significance of both the suspended and biofilm bacteria
and the flow hydraulics (based on dispersion number) in the reduction of organic matter in the
WHP system. Kinetic coefficient of the suspended bacteria was calculated from a first-order
reaction rate including the effect of organic loading rate. For the biofilm bacteria, the reaction
rate was also first-order and based on the substrate flux into the biofilm. The integrated
kinetic model proposed for the WHP incorporates the activities of both the suspended and
biofilm bacteria and the hydraulic dispersion number. The model was found to be satisfactory
in predicting biochemical oxygen demand (BOD) removal in a full-scale WHP treating an
anaerobic pond effluent. The model is useful to achieve improvement in BOD removal
efficiency.
Nor (1994) investigated the removal of phenols in the presence of copper and zinc by
Eichhornia crassipes was in order to assess its ability to clean up industrial wastewaters.
Results indicated that Eichhornia has tremendous capacity to absorb phenolic compounds as
well as Cu and Zn simultaneously from test solutions containing these substances. The
presence of Cu or Zn resulted in decreased phenol uptake during the first 0.5 d, while the
presence of Cu and Zn in combination resulted in higher phenol uptake. After 1 d exposure,
however, little or no differences could be discerned. Similarly, absorption of Cu and zn in the
presence of phenols did not seem to be adversely affected by different combinations of Cu/Zn
concentrations. In fact, some synergistic effect could be detected between Cu and Zn
absorption by Eichhornia crassipes. Bioassays involving filtered Eichhornia root extract
indicated that phenol was also removed by the aqueous root extracts indicating that cellular
constituents of roots were involved in the process.
Cyanide degradation by water hyacinths in solutions containing 3-300 mg/l cyanide
was investigated in batch tests (Granato, 1993). Water hyacinth was more efficient to remove
free cyanide in the first 8 hours, compared to cyanide controls (free of plant). Gold mill
synthetic effluents containing free cyanide (9 to 20 mg/l), thiocyanate (14 to 23 mg/l), and
metallocyanides (iron, copper and zinc) was fed to a continuous lab. Scale unit (61/h) to
confirm the ability of water hyacinth to degrade free cyanide and that it can remove zinc and
small amounts of iron. Copper and thiocyanate remained untouched in the solution. Water
hyacinth is only suitable to be used in conjunction with other cyanide wastewater treatments.
Water hyacinth can grow in oil-refinery wastewater after the water has undergone an
initial treatment of oil-separation, flotation and aeration (Tang and Xian-wen, 1993). They

1757
indicated that the optimum COD under which E. crassipes can be used to oxidize oil-refinery
wastewater is between 65 and 131 mg/l and the highest possible COD is 262 mg/l. They
reported that Eichhornia crassipes, grown in two 3750-m2
oil-refinery wastewater oxidation
ponds, improved the quality and transparency of the outlet water. After 2 to 4 days retention
in oxidation ponds, turbidity decreased by 32%, phenol oil decreased by 18%, COD decreased
by 8-13%, nitrogen decreased by 6-18%, phosphorus decreased by 12-24%, and several heavy
metals decreased by 3-54% more than the un-vegetated control. In addition, its oxygenated
root zone helps to bring about flotation and flocculation of oil residue, increased aerobic
degradation, and a large microbial population to stimulate decomposition.
Bio-sorption:
Low et al., (1994) Reported the potential use of Biomass of non-living dried water
hyacinth roots (Eichhornia crassipes) for sorption of copper from aqueous solutions.
Maximum sorption was 20.90 mg Cu/g as determined for Langmuir isotherm. Several factors
affecting sorption were investigated. They include effect of pH, initial concentrations,
presence of chelators and other metals. They suggested using this material in a packed-bed
system for removing copper from electroplating waste.
Biological indicators
The water hyacinth samples collected from three Egyptian water bodies and
analyzed for major elements, essential and non-essential elements using prompt gamma
ray neutron activation analysis technique (PGNAA) to evaluate water hyacinth as a
bioindicator for pollution (Abdel-Sabour et. Al., 1996 and 1997). Results showed that
plant sample analysis showed good response to the heavy metal pollutant level in water
bodies. They suggested that there is a potential use of such plant as a biological
indicator. They indicate also, the biological accumulation factor (BAF) has reflected the
levels of pollutant in the surrounding environment.
Water hyacinth stems and leaves, have been successfully used as indicators of heavy
metal pollution in tropical countries (Gonzalez et al., 1989). They reported that the
uptake of heavy metals in this plant is stronger in the roots than in the floating shoots.
To study the bioconcentration of cadmium in water hyacinth, the plants were exposed to
water containing 2 mu g Cd (2+)
/ml for extended periods of time (Xiang et al, 1994). Three
strains from several exposures during a 30-day period were sampled for the analyses of
cadmium and thiol group. The data showed that the plant concentrates cadmium mainly in the
roots and that the cadmium uptake is proportional to the increase of the thiol group content.
The latter suggests the possibility of using the thiol group content to assess the
bioconcentration of heavy metal ions in water hyacinth and as a general parameter for
monitoring the heavy metal pollution of water.
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