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Journal of Applied Sciences and Environmental Management
World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
ISSN: 1119-8362
Vol. 14, Num. 2, 2010, pp. 43-49
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Journal of Applied Sciences and Environmental Management, Vol. 14, No. 2, June, 2010, pp. 43-49
Ecological and socio-economic utilization of water hyacinth (Eichhornia crassipes Mart Solms)
N Jafari
Department of Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Iran E-mail: n.jafari@umz.ac.ir, Tel: +981125242161
Code Number: ja10025
ABSTRACT
Around the world, there is an increasing trend in
areas of land, surface waters and groundwater affected by contamination
from industrial, military and agricultural activities due to either
ignorance, lack of vision, or carelessness. In the last three decades a
special interest in the world is aroused by the potential of using the
biological methods in the waste water treatment. Water hyacinth (Eichhornia crassipes)
constitutes an important part of an aquatic ecosystem. Water hyacinth
as a very promising plant with tremendous application in wastewater
treatment is already proved. Water hyacinth is used to treat waste
water from dairies, tanneries, sugar factories, pulp and paper
industries, palm oil mills, distilleries, etc. All the efforts of
scientists and technocrats all over the world to eliminate these weeds
by chemical and biological means have met with little success. The
water hyacinth have been found to have potential for use as
phytoremediation, paper, organic fertilizer, biogas production, human
food, fiber, animal fodder. @ JASEM
The fast technological and industrial development, and tumultuous
demographic growth and rapid urbanization, especially in the last two
decades, are confronting the mankind with four large problems: water,
food, energy and environment. The water problem is particularly
pronounced, because it is implicitly present in other three problems,
that is in the food and energy production which depend primarily on the
water and the key environmental problems are water quality protection
and water damage control.
In the last three decades a special interest in the world is aroused by
the potential of using the biological methods in the waste water
treatment, whose application as of natural and not artificial
procedures of tertiary processing of effluents provides the effluents
of required quality in a economically acceptable way in the technically
simple structures. The capacity of water hyacinth (Eichhornia crassipes (Martius)
Solms-Laubach) as a very promising plant with tremendous application in
wastewater treatment is already proved (Jafari and Trivedy, 2005;
Trivedy, 2001).
Water hyacinth (Eichhornia crassipes) is a free floating (but sometimes rooted) freshwater plant of the family Pontederiaceae that
has proven to be a significant economic and ecological burden to many
sub-tropical and tropical regions of the world. Water hyacinth is
listed as one of the most productive plants on earth and Water hyacinth
shows logisitic growth as does another floating aquatic weeds. Water
hyacinth has invaded freshwater systems in over 50 countries on five
continents; it is especially pervasive throughout Southeast Asia, the
southeastern United States, central and western Africa, and Central
America (Bartodziej and Weymouth, 1995; Brendonck et al., 2003; Lu et al., 2007; Martinez Jimenez and Gomez Balandra, 2007).
Geographic distribution: This tropical plant spread throughout the world in late 19and early 20century (Wilson et al., 2005).
It is widely reported that water hyacinth is indigenous to Brazil
having first been described from wild plants collected from Francisco
river in 1824. In Africa it was first reported in Egypt between 1879;
in Asia around 1888 and about 1900 in Japan; in Australia it arrived in
about 1890 (Cook, 1990). Water hyacinth originated in tropical South
America, but has become naturalized in many warm areas of the world:
Central America, North America (California and southern states),
Africa, India, Asia, Australia, and New Zealand. Water hyacinth (Eichhornia crassipes)
is the most predominant, persistent and troublesome aquatic weed in
India. It was first introduced as an ornamental plant in India in 1896
from Brazil (Rao, 1988). In india, water hyacinth has stretched over
2,00,000 ha of water surface un the country (Murugesan et al.,
2005) and its exuberance has been highly notived throughout the course
of the river Thamirabarani, a prerennial river in south India
(Murugesan et al., 2002; Murugesan, 2001). Because of its
beautiful blooms and foliage, water hyacinth has been carried by
tourists, plant collectors and botanists to over 80 countries around
the world in the last 100 years.
Chemistry of Water Hyacinth: Fresh plant contains 95.5%
moisture, 0.04% N, 1.0% ash, 0.06% P2O5, 0.20% K2O, 3.5% organic
matter. On a zero-moisture basis, it is 75.8% organic matter, 1.5% N,
and 24.2% ash. The ash contains 28.7% K2O, 1.8% Na2O, 12.8% CaO, 21.0%
Cl, and 7.0% P2O5. The CP contains, per 100 g, 0.72 g methionine, 4.72
g phenylalanine, 4.32 g threonine, 5.34 g lysine, 4.32 g isoleucine,
0.27 g valine, and 7.2 g leucine (Matai and Bagchi, 1980). Water
hyacinth roots naturally absorb pollutants, including such toxic
chemicals as lead, mercury, and strontium 90 (as well as some organic
compounds believed to be carcinogenic) in concentrations 10,000 times
that in the surrounding water.
Water Hyacinth Habitats and Characteristics: Water hyacinths
grow over a wide variety of wetland types from lakes, streams, ponds,
waterways, ditches, and backwater areas. The treatment of textile
wastewater with water hyacinth has some effects on the growth of the
plant, the small size of which may be due to nutrient imbalance mainly
of nitrogen in water (Thomas, 1983). The plant height may vary from a
few inches to 3 ft (0.9 m). The leaves, growing in rosettes, are glossy
green and may be up to 8 in (20 cm) long and 6 in (15 cm) wide. The
showy, attractive flowers may be blue, violet, or white and grow in
spikes of several flowers. The leaf blades are inflated with air sacs,
which enable the plants to float in water. The seeds are very longlived.
High levels of salinity in wastewater can limit the growth of water
hyacinth and other aquatic macrophytes (Sooknah and Wilkie, 2004). The
plant has very prominent black, stringy roots, and when it occasionally
becomes stranded in mud, it may appear rooted. Its growth rate is among
the highest of any plant known, and populations can double in as little
as 12 days (Aquatic Ecosystem Restoration Foundation, 2005). Habitats
for the water hyacinth have ranged from shallow temporary ponds,
marshes and sluggish flowing waters to large lakes, rivers and
reservoirs. A broad spectrum of physico-chemical environments
characterizes these habitats. In temporary water bodies, the plants
often have to survive on moist mud for prolonged periods, or perennate
in the form of seeds Gopal (1987). The nutrient bases provided by the
various habitats differ widely. They range from clean waters that are
poor in major nutrients such as rivers and reservoirs to highly
polluted waters with large amounts of nutrients and organic matter, as
is the case in sewage lagoons. In addition such waters may receive a
variety of organic and inorganic industrial effluents containing heavy
metals. The water hyacinth plants can stand both highly acidic and
highly alkalinic conditions, but more vibrant growth is supported by
neutral water bodies (Gopal, 1987). Wilson et al., (2001)
assumed a logistic growth model in their analysis of water hyacinth
population dynamics in temperate and tropical zones. Their results
revealed that growth rates in temperate regions vary with seasons. In
tropical zones the intrinsic rate of growth for the weed was estimated
to be in the range 0.04 to 0.08 per day. In waters with high nutrient
contents, the plants have shorter roots, which are extensive laterally,
longer shoots and relatively bigger leaves. In nutrient poor waters,
the plants have longer roots, set deeper in search for food, relatively
shorter shoots and smaller leaves. High multiplicative rates may seem
to suggest that such an unhealthy competition will impose negative
externalities for the community members and retard growth.
Ecological Factors: Water hyacinth is heliophyte plant growing best in warm waters rich in macronutrients (Center et al., 2002). Optimal water pH for growth of this aquatic plant is neutral but it can tolerate pH values from 4 to 10 (Center et al., 2002). This is very important fact because it points that Eichhornia crassipes can be used for treatment of different types of wastewater. Optimal water temperature for growth is 28-30° C (Center et al., 2002). Temperatures above 33° C inhibit further growth (Center et al., 2002). Optimal air temperature is 21-30° C (U.S. EPA, 1988). If lasting for 12 hours temperature of -3° C will destroy all leaves and temperature of -5° C during the period of 48 hours will destroy whole
plant (U.S. EPA, 1988). Work of other authors also presents similar
data about water hyacinth sensibility to low temperatures. Eichhornia crassipes can survive 24 hours at temperatures between 0.5 and -5 C, but it will die at -6 to -7° C and can not be grown in open where average winter temperature drops under 1° C (Stephenson et al., 1980). 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 (Reed and Bastian, 1980).
Low air humidity from 15% to 40% can also be limiting factor for
undisturbed growth of water hyacinth (Allen, 1997). Eichhornia crassipes tolerates drought well because it can survive in moist sediments up to several months (Center et al.,
2002). Salinity is the main obstacle for growth of water hyacinth in
costal areas (Olivares and Colonnello, 2000). De Casabianca and Laugier
(1995) have studied the production of this aquatic macrophyte in
relation to different effluent salinity value. They were also tracking
plant reactions to high levels of salinity by observing symptoms of a
different intensity (De Casabianca and Laugier, 1995). They have
concluded that production of water hyacinth was reducing and necroses
on leaves and bulbous petioles were occurring earlier with increase of
salinity.
Possible Applications of Water Hyacinth: Through water
hyacinth’s engulfing presence, large amounts of sunlight are blocked,
thorough oxygen exchange is prevented and dissolved oxygen levels drop,
the food web is altered, habitat for water fowl and other organisms is
either destroyed or changed, and the biological diversity of the
invaded area is greatly reduced (Denny et al., 2001, Brendonck,
2003). Water hyacinth can be a problem economically as it negatively
affects fisheries, slows or even prevents water traffic, impedes
irrigation, reduces the water supply, obstructs water ways, and slows
hydropower generation (Denny et al., 2001, Brendonck, 2003).
The positive aspects of the weed thus seem to outweigh its negative
attributes.
Prior research on water hyacinth’s effects on water quality
has focused mainly on the consequences of the dense mats formed by the
interlocking of individual plants. The most commonly documented effects
are lower phytoplankton productivity and dissolved oxygen
concentrations beneath mats (Rommens et al., 2003;
Mangas-Ramirez and Elias-Gutierrez, 2004; Perna and Burrows, 2005).
Water hyacinth also has been found to stabilize pH levels and
temperature in experimental lagoons, thereby preventing stratification
and increasing mixing within the water column (Giraldo and Garzon,
2002). Photosynthesis is limited beneath water hyacinth mats, and the
plant itself does not release oxygen into the water as do phytoplankton
and submerged vegetation (Meerhoff et al., 2003), resulting in
decreased dissolved oxygen concentration. The extent of dissolved
oxygen reduction is dependent on the capacity of the water hyacinth mat
to prevent light infiltration into the water column.
Water hyacinth is just beginning to be used for phytoremediation.
This use came about for a few reasons, the first being that water
hyacinth is so plentiful. People have been trying to remove the plant
from many water ways, spending billions of dollars in doing so. In many
cases this removal is nigh unto impossible. It has been discovered that
water hyacinth's quest for nutrients can be turned in a more useful
direction. Water hyacinth is already being used to clean up waster
water in small scale sewage treatment plants. Phytoremediation used for
removing heavy metals and other pollutants is a newly developed
environmental protection technique. Extensive studies on freshwater
resources decontamination revealed that some freshwater plants, among
which is the water hyacinth growing prolific in wastewater, can
efficiently accumulate heavy metals (Yahya, 1990; Vesk et al., 1999; Ali and Soltan, 1999; Soltan and Rashed, 2003; Tiwari et al., 2007). Water hyacinth also absorbs organic contaminants (Zimmels et al.,
2007), and nutrients from the water column (Aoi and Hayashi, 1996). In
California, water hyacinth leaf tissue was found to have the same
mercury concentration as the sediment beneath, suggesting that plant
harvesting could help mediate mercury contamination if disposed of
properly (Greenfield et al., 2007). On a similar note, water
hyacinth’s capacity to absorb nutrients makes it a potential biological
alternative to secondary and tertiary treatment for wastewater (Ho,
1994; Cossu et al., 2001).Water hyacinth has long been used
commercially for cleaning wastewater. The luxuriant plant’s tremendous
capacity for absorbing nutrients and other pollutants from wastewater
has long been overlooked by many wastewater engineers. Water hyacinth
is also known for its ability to grow in severe polluted waters (So et al., 2003). Eichhornia crassipes is
well studied as an aquatic plant that can improve effluent quality from
oxidation ponds and as a main component of one integrated advanced
system for treatment of municipal, agricultural and industrial
wastewaters (U.S. EPA, 1988; Sim, 2003; Wilson et al., 2005; Mangabeira et al., 2004; De Casabianca and Laugier, 1995; Maine et al., 2001). To regret water hyacinth is often described in literature as serious invasive weed (Wilson et al., 2005; U.S. EPA, 1988; Maine et al., 1999; So et al.,
2003; Singhal and Rai, 2003). In last few years a great interest has
been shown for research of aquatic macrophytes as good candidates for
pollutant removal or even as bioindicators for heavy metals in aquatic
ecosystems (Aoi and Hayashi, 1996; Maine et al., 1999). Water
hyacinth just one of the great number of aquatic plant species
successfully used for wastewater treatment in decades, was of
particular importance. It is important to emphasize that Eichhornia crassipes has a huge potential for removal of the vast range of pollutants from wastewater (De Casabianca and Laugier, 1995; Maine et al., 2001; Mangabeira et al.,
2004; Sim, 2003) and that a great number of aquatic systems with water
hyacinth as basic component were construct (U.S. EPA, 1988; Aoi and
Hayashi, 1996).
Water hyacinth harvests have been put into valuable uses in several
countries. Methods of converting the plant material into valuable
products have emerged. Apart from its ornamental value, the plant has
been found useful as a source of animal feed (Gopal, 1987), as a source
of fertilizers for use in agriculture (Oyakawa et al., 1970;
Majid, 1986), a source of biomass energy, a source of raw materials for
building, handcraft making, paper and boards. In addition the plant has
been found to be useful as a filter worth of solving man created
problems of pollution in water bodies. However all the potential uses
of the water hyacinth do not promote utilization of the weed to the
level that qualifies it as a viable control option (Ogutu-Ohwayo et al.,
1996). Below I will consider a number of possible uses for the plant,
some which have been developed and others which are still in their
infancy or remain as ideas only.
Paper: Similar small-scale cottage industry papermaking projects
have been successful in a number of countries, including the
Philippines, Indonesia, and India.
Fibre Board: Another application of water hyacinth is the
production of fibreboards for general-purpose use and also a
bituminised board for use as a low cost roofing material.
Yarn and Rope: The fiber from the
stems of the water hyacinth plant can be used to make rope. The stalk
from the plant is shredded lengthways to expose the fibers and then
left to dry for several days. The rope making process is similar to
that of jute rope. The finished rope is treated with sodium
metabisulphite to prevent it from rotting. In Bangladesh, the rope is
used by a local furniture manufacturer who winds the rope around a cane
frame to produce an elegant finished product.
Basket Work: In the Philippines water
hyacinth is dried and used to make baskets and matting for domestic
use. The key to a good product is to ensure that the stalks are
properly dried before being used. In India, water hyacinth is also used
to produce similar goods for the tourist industry. Traditional basket
making and weaving skills are used.
Charcoal Briquetting: This
is an idea which has been proposed in Kenya to deal with the rapidly
expanding carpets of water hyacinth which are evident on many parts of
Lake Victoria. The proposal is to develop a suitable technology for the
briquetting of charcoal dust from the pyrolysis of water hyacinth.
Biogas Production: The possibility of converting water hyacinth
to biogas has been an area of major interest for many years. Conversion
of other organic matter, usually animal or human waste, is a well
established small and medium scale technology in a number of developing
countries, notably in China and India. The process is one of anaerobic
digestion which takes place in a reactor or digester and the usable
product is methane gas which can be used as a fuel for cooking,
lighting or for powering an engine to provide shaft power. Other
studies have been carried out, primarily in India with quantities of up
to 4000 liters of gas per tonne of semi dried water hyacinth being
produced with a methane content of up to 64% (Gopal, 1987). Most of the
experiments have used a mixture of animal waste and water hyacinth.
There is still no firm consensus on the design of an appropriate water
hyacinth biogas digester.
Animal Fodder: Studies have shown that the nutrients in water
hyacinth are available to ruminants. In Southeast Asia some non
ruminant animals are fed rations containing water hyacinth. In China
pig farmers boil chopped water hyacinth with vegetable waste, rice
bran, copra cake and salt to make a suitable feed. In Malaysia fresh
water hyacinth is cooked with rice bran and fishmeal and mixed with
copra meal as feed for pigs, ducks and pond fish. Similar practices are
much used in Indonesia, the Philippines and Thailand. The use of water
hyacinth for animal feed in developing countries could help solve some
of the nutritional problems that exist in these countries.
Fertilizers: Water hyacinth can be used on the land either as a
green manure or as compost. As a green manure it can be either ploughed
into the ground or used as mulch. The plant is ideal for composting.
After removing the plant from the water it can be left to dry for a few
days before being mixed with ash, soil and some animal manure.
Microbial decomposition breaks down the fats, lipids, proteins, sugars
and starches. The mixture can be left in piles to compost, the warmer
climate of tropical countries accelerating the process and producing
rich pathogen free compost which can be applied directly to the soil.
The compost increases soil fertility and crop yield and generally
improves the quality of the soil. In developing countries where mineral
fertilizer is expensive, it is an elegant solution to the problem of
water hyacinth proliferation and also poor soil quality. In Sri Lanka
water hyacinth is mixed with organic municipal waste, ash and soil,
composted and sold to local farmers and market gardeners.
Fish Feed: The Chinese grass carp is
a fast growing fish which eats aquatic plants. Other fish such as the
tilapia, silver carp and the silver dollar fish are all aquatic and can
be used to control aquatic weeds. The manatee or sea cow has also been
suggested as another herbivore which could be used for aquatic weed
control. Water hyacinth has also been used indirectly to feed fish.
Dehydrated water hyacinth has been added to the diet of channel catfish
fingerlings to increase their growth. It has also been noted that decay
of water hyacinth after chemical control releases nutrients which
promote the growth of phytoplankton with subsequent increases in fish
yield (Gopal, 1987). The response of the fish communities to water
hyacinth is highly dependent on the preexisting fish community,
preferred and available fish habitat, food requirements and
availability, physiochemical conditions and, likely although not
proven, water hyacinth density. The combination of these factors makes
it very difficult to predict specific effects. However, given that
dissolved oxygen concentrations decrease with increasing water hyacinth
density, and given that macroinvertebrates and zooplankton are found at
higher densities and in great diversity along the edges of water
hyacinth mats, it is logical to suggest that fish could benefit from
highly fragmented mats of water hyacinth. Such mats will have a higher
edge-tocore ratio, providing some of the benefits of water hyacinth and
minimizing the negative effects of dense nonfragmented mats.
Conclusion: In conclusion, water hyacinth can be brought to make
compost, mulching and to clean the sewage. It is a good way to change
waste products into useful things. More research is needed in order to
define the optimum water hyacinth density in the reservoirs to
determine its influence on the water quality of the effluent. Although
all efforts must be made to control these plants where they are
nuisance from natural ecosystems, research efforts must be stepped up
to tap these recourses for human welfare. At a broader scale, we
suggest research that focuses on the potential spread of water hyacinth
into northern latitudes as a response to global climate change
(Hellmann et al., 2008; Rahel and Olden, 2008). Finally, more
research is needed on alternatives for the sustainable management of
this worldwide invader; this includes economic incentives for private
removal, spread prevention, or utilization projects that create goods
from water hyacinth. In conclusion, our understanding of water hyacinth
is still relatively weak, and hinders our ability to manage systems
appropriately where this invader occurs. With the likely spread of
aquatic invaders due to climate change, it is imperative that we
continue and refine our water hyacinth research efforts to reflect
better the needs of managers. The socioeconomic effects of water
hyacinth are dependent on the extent of the invasion, the uses of the
impacted water body, control methods, and the response to control
efforts. Ecosystem-level research programmes that simultaneously
monitor the effects of water hyacinth on multiple trophic levels are
needed to further our understanding of invasive species.
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