ABSTRACT
The effect of cassava mill effluent on soil microorganisms and the physicochemical parameters of the soil at various depths were studied. The results revealed the bacterial isolates as Proteus spp, Bacillus spp, Staphylococcus spp, Streptococcus spp, Clostridium spp, Pseudomonas spp and Klebsiella spp, while the fungi isolates were Aspergillus spp, Penicillium spp, Mucor spp, Rhizopus spp, Fusarium spp and Yeast cells like Sacchromycetes spp. At various depths, there are significant differences in the total aerobic bacterial counts at surface (7.25x108±2.92cfu/g), subsurface (8.6x108±2.79 cfu/g) and deeper sample counts (6.4x108±2.67cfu/g). Total fungal counts also showed significant differences at P<0.05 between the surface (2.7X103±1.2cfu/g) and subsurface (4.9x103±3.1cfu/g) sample counts as well as between surface and deeper sample counts (3.3x103±1.3 cfu/g), while there was no significant difference observed between surface and deeper sample counts at P>0.05. The pH and the Cyanogenic glucosides, increased with depth while %N, %OM, Mg, Ca, Moisture Content ratios, all decreased with depth. Cassava Mill Effluent (CME) negatively affected the microbial populations and physicochemical parameters of the soil around it at various depths. Hence, waste generated in the environment should be properly treated before discharging them into the environment.
TABLE OF CONTENTS
Title Page i
Certification ii
Dedication iii
Acknowledgements iv
Table of Contents v
Abstract viii
List of Figures ix
List of Tables x
CHAPTER
ONE: INTRODUCTION AND LITERATURE REVIEW
1.1 Introduction 1
1.2 Aims and Scope of the Study 3
1.3 Literature
Review 3
1.3.1 Cassava Mill Effluent 3
1.3.2 Types of Wastes generated from Cassava Mill
Effluent 5
1.3.3 Chemistry and Processing of Cassava 6
1.3.4 Biological Properties of Soil 10
1.3.5 Cyanide
Utilization and Degradation by Microorganisms. 11
1.3.6 Physical Properties of Soil 12
1.3.7 Chemical
Properties of Soil 14
1.3.8 Effects
of Cassava Mill Effluent wastes on soil
16
CHAPTER TWO: MATERIALS AND METHODS
2.1 Materials 17
2.2 Study
area 17
2.3 Methods 18
2.3.1 Preparation
of Chemicals, Reagents, Media and Sterilization. 18
2.3.2 Soil
Sample Collection and Preparation 18
2.3.3 Sample
Preparations 18
2.3.4
Media Preparation 19
2.3.5
Determination of Bacterial Load 19
2.3.6
Techniques for Identifying Bacterial
Isolates 21
2.3.7
Determination of Microbial Flora 25
2.3.8
Methods for Physicochemical Analysis 26
CHAPTER THREE
3.0 Results
31
CHAPTER FOUR: DISCUSSION, CONCLUSION AND
RECOMMENDATIONS
4.1 Discussion 41
4.2 Conclusion 43
4.3 Recommendations 43
References
Appendices
List of Figures
Figure Title Page
1 Flow Chart Showing Operational
Units involved in Garri
Processing. 9
LIST OF
TABLES
Table Title Page
1 Morphology and Biochemical Characteristics
of Bacterial Isolates. 32
2 Cultural Characteristics of Fungi Isolates. 33
3 Total Bacterial Count at the Various Soil
Depths. 34
4 Total Fungal Count at the Various Soil
Depths. 35
5 Physico-chemical Constituents of Cassava Mill Effluent. 36
6 Summary of Mean Bacterial Counts. 37
7 Summary of Mean Fungal Counts. 38
8 Summary of Cassava Mill Effluent 39
CHAPTER ONE
INTRODUCTION AND LITERATURE REVIEW
1.1 INTRODUCTION
Cassava
(Manihot esculanta Crantz) is
believed to have originated from South America. In Africa, cassava was
introduced about the 16th century in the Congo River Basins (Cock
1985). Manihot esculanta Crantz,
synonymous with Manihot utilissima Rhol,
belongs to the family Euphorbiaceae is a root crop that is widely cultivated in
the tropical regions of the world, whose tubers are harvested between 7-13
months based on the cultivars planted, mainly for food (Iyayi and Losel 2001,
Oboh and Akindahunsi, 2003a).
As
a shrubby perennial crop that grows to a height of 6-8 feet, it is usually
propagated by planting short section of the stem (O’Hair 1995, Oboh 2005).The
tubers are quite rich in carbohydrates (85 – 90 %) with very small amount of
protein (1.3%) in addition to cyanogenic glucosides (Linamarin and
Lotaustrallin), (Nwabueze and Odunsi
2007, Oyewole and Afolami 2001). This high carbohydrate content makes
cassava a major food item especially for the low income earners in most
tropical countries especially Africa and Asia (Desse and Taye 2001, Aderiye and
Laleye 2003). Suffix to say that different cultivators of cassava which are
around wide mature at different rates. However, certain varieties contains
large amount of cyanogenic glucosides (Linamarin and Lotaustrallin) which can
be hydrolysed to hydrocyanic acid (HCN) by their endogenic enzymes (Linamarase)
when the plant tissue is damaged during harvesting, processing or other
mechanical processes. (Oboh and Akindahunsi, 2003b).the protein content of
cassava products can be increased by adding protein to the deficient food in a
way that will not utter the organoleptic qualities of the original food (Oboh
2005). Also, through controlled fermentation, micro-flora could be made into
large numbers in the mesh (Rainbault 1998, Oboh et al., 2002; Oboh and Akindahunsi 2003a), thus increasing the
protein content of the cassava products.
The
ability of cassava to grow and produce high yield under condition of poor
fertility and low rainfall, also its capability to produce relatively well in
marginal environmental under low management levels makes it an attractive crop
for poor resource (Bencini 1991).This food crop fits well into the farming
systems of the small holder farmers in Nigeria because it is available year
round, thus providing household food security. Its tuber can be kept in the
ground prior to harvesting for up to two years, but once harvested, they begin
to deteriorate. To forestall early deterioration, and also due to its bulky
nature, cassava is usually traded in some traded form. The bulky roots contains
much moisture (60-65%) making their transportation from rural areas difficult
and expensive. Processing the tubers into a dry form reduces the moisture
content and converts it into a more durable and stable product with less
volume, which makes it more transportable (IITA 1979; Ugwu 1996).
Over
the years, cassava has been transformed into a number of products both for
domestic (depending on the preferences and local customs) and industrial uses.
In sub-Saharan Africa, cassava is a major stable food that is consumed in processed
forms in many areas. In West Africa and Nigeria in particular, the crop is most
commonly consumed as garri, a dry granular meal made from fermented cassava
(IITA 1985). In South-eastern Nigeria, many cassava processing industries have been
established, even residential homes. Many people are involved in garri
processing, particularly among the rural farmers. Raw materials are mainly
fresh cassava which is very abundant and cheap. The edible tubers are processed
into various forms which include chips, pellets, cakes and flour. The flours
could be fried to produce garri or steeped into water to ferment to produce
fufu when cooked (Oyewole and Odunfa 1992).The production and consequent
consumption of cassava have increased extensively in recent times. The
increased utilization of processed cassava products has equally increased the
environmental pollution associated with the disposal of the effluents. The
highly offensive odour emanating from the fermenting effluents calls for
regulation in discharge of the waste generated (Akani et al., 2006, Adewoye et al.,
2005). In most areas, cassava mills are mainly on small scale basis, owned and
managed by individuals who have no basic knowledge of environmental protection.
Though on small scale basis, there are many of them, which when put together,
creates enormous impact on the environment.
1.2 AIMS
AND SCOPE OF THE STUDY
This
work is intended to ascertain the extent of Cassava Mill Effluents (CME) impact
on the soil microbial populations and the soil physico-chemical parameters, pH,
organic matter/carbon, soil texture, total aerobic bacteria and fungi contents.
It is on this note that the effects of this effluent can be checked on soil
physical and chemical properties and growth of microorganisms in the soil,
hence, forestalling good soil productivity.
This
is also aimed at isolating and identifying microorganisms associated with soils
contaminated with Cassava Mill Effluent (CME) with the objective of evaluating
potentials for applications in remediation of cyanide – contaminated CME dump
sites and proffering a lasting solution to its indiscriminate disposal and
possible benefits on soil microorganisms.
1.3
LITERATURE REVIEW
1.3.1 Cassava
Mill Effluent (CME)
Cassava
mill effluent (CME) is the water produced after separating starch and fibre
during the process of fermentation. According to Stauber and Rampton (2003),
mill effluent (sludge) is an end product of waste treatment plants.Nigeria,
very unfortunately, has consistently generated so much waste from cassava mills
which are usually discharged on land or water indiscriminately and this in
turn, affects the biota especially in the southern part of the country where
most of the mills are located (FAO 2004 and Oloronfemi et al., 2008).
Traditionally,
garri production is associated with the discharge of large amount of water,
hydrocyanic acid and organic matters in the form of peels and sieves from the
pulp as waste product. Due to increase in cassava production, CME production
has also increased dramatically. Around the cassava mills, this liquid waste is
indiscriminately dumped and allowed to accumulate, even near residential homes,
producing offensive odours and unsightly scenarios (FAO 2004 and Okafor 2008).
The
high cyanide content of the effluent would equally poss a significant threat to
humans and the environment (Adewoye et
al., 2005 and Akani et al.,
2006). Oboh (2005) identified two important biological wastes that are
generated during the processing of cassava tubers to include cassava peels and
liquid squeezed out of the fermented parenchyma mash. These solid and liquid
residues generated from cassava processing are hazardous in the environment
(Cumbana et al., 2007, Jyothi et al., 2005). These wastes such as
peelings, fibrous by-products and waste water effluents are indiscriminately
disposed into the environment without prior treatment to reduce the volume,
toxicity or mobility of the hazardous substances (Burrell 2003). On the
average, 2.62m3 ton-1 of residues from washing and 3.68m3
ton-1from water residues of flour production are generated during
each processing (Horsfall et al.,
2006 and Isabirye et al., 2007).
Therefore, it is very important to reduce and minimize its environmental
impacts because if not properly managed, can lead to environmental hazard.
(Akpan et al., 2011).
1.3.2 Types of Wastes Generated From Cassava Mill Effluent
Basically,
two forms of wastes are generated during processing of cassava which are as
follow:
The Solid Wastes
The
solid waste is one of the important biological wastes derived from cassava
processing which constitute great environmental hazards such that the cassava
peels derived from its processing are normally discharged as wastes and allowed
to rot (decay) in the open with a small portion used as animal feeds thus
resulting in health and environmental hazards. The pollutant potential of an
effluent is measured by the amount of oxygen needed to oxidize the organic
matter, the Chemical Oxygen Demand (COD) and the amount of oxygen necessary to
stabilize the organic matter by microorganisms and enzymes that is, the
Biochemical Oxygen Demand (BOD). Compounds that bare generally toxic to living
organisms will also, at toxic concentrations, prevent germination as well as
inhibit growth. The highest proportion of cyanide is found in the peels and
cortex layer immediately beneath the peels. It is for this reason, that the
cassava root is always peeled before being processed or consumed. Peeling
removes the cortex and the outer periderm layer adhering to it. As these peels
are thrown on the ground, HCN accumulates in the soil. Peels can represent 10
to 20% of the fresh root weight, of which the periderm amounts for 0.5 to 20%
(ATSDR 2006).
The Liquid Waste
The
liquid waste is another important biological waste generated from cassava
processing which forms residues that are hazardous in the environment. The
(waste water) contains heavy loads of microorganisms lactic acid, lysine (from
L.coryneforms), and amylase (from L. delbruckii) capable of hydrolysing the
glucosides (Rainbault 1998; Akindahunsi et
al., 1999). Cassava mills effluents is reported to contain large amounts of
cyanogenic glucosides, tanic acid, Lotaustrallin, and high contents of
carbohydrates and fats (Oboh and Akindahunsi 2003a). These substances could
deteriorate materials e.g metals if immersed in cassava effluent.
Research
had shown that the waste water contains organisms which can be important in the
industries. The industrial applications of amylase as additives in detergents
for the removal of starch from dextides, liquefaction, of starch and proper
formation of dextrin in baking have been reported (Shaw et al., 1995). Also used in high fructose corn syrup preparation,
saccharification of starch for alcohol production and in brewing (Uzochukwu et al., 2011; Aiyer 2004). Cellulase are
utilized in the textile industries for colour brightness (Csizar et al., 2001) and for stone wash look in
jeans (Haki and Rakshik 2003), paper processing, production of ethanol for fuel
from the non-edible portion of corn and wheat (Logen Corporation 2003).
Therefore, the industrial application of these enzymes cannot be underscored.
1.3.3
Chemistry and Processing
Of Cassava
Chemistry of cassava
Manihot esculenta Crantz
is one of the most important food crops in the tropical countries and is
probably the most widely distributed human food crop with high content of cyanogenic
glucosides (Akinrele 1985). Known cyanogenic glucosides in plants include
amygdalin, linamarin, prunasin, dhudrin, lotaustralin and taxiphyllin with
their structural formulars given below; transports of cyanide in the soil are
mostly influenced by volatization and distribution (FAO 2004). According to the
FAO (2004) report, a high production of cassava in 1993 with Africa (74.8
million tons, Latin America, 28.5 million tons). Asia (50.2 million tons,
oceania 0.2 million tons). High cyanide intake from the consumption of
insufficient processed cassava has been advanced as a possible actiologic
factor in some diseases such as iodine deficient disorder and tropical ataxic
neuropathy (Kamlin 1995).
The
leave and root of the plant contains cyanogenic glucoside (Linamarin). The
linamarin is readily hydrolysed to glucose and acetone cyanohydrine in the
presence of the enzyme linemarose, which decomposes rapidly to cyanide ion.
During processing of cassava, the cyanogenic glucoside that are easily
hydrolysed into the toxic compound of hydrogen cyanide (Oti 2002, Abiona et al.,2005).
Cyanide
is toxic to several forms of life because it binds the key enzymes of
importance in aerobic respiration such as cytochrome oxidase, leading to
inhabitation of respiration (Cipollone et
al., 2007).
Cassava
in the fresh form contains large amount of cyanide, which is extremely toxic to
human and animal. There is therefore a need to process it to reduce the cyanide
content to safe levels (Eggelston et al.,
1992).
Processing of cassava
The
poor post-harvest storage life of fresh cassava tubers is a major economic
constraint in its utilization (Kehinde 2006). The highly perishable nature of
harvested cassava roots and the presence of cyanogenic glucosides in bitter
cultivars calls for immediate processing of the storage roots into more stable
and safer products. The hydrocyanic acid content of cassava tubers can be
removed by either washing, exposure to air, heating or pressing. A lot of
processing equipment and technology has been developed by various governmental
and private organizations in Nigeria to facilitate the processing of cassava
roots to reduce losses (IITA 2005). In Nigeria, cassava can be converted to
diverse traditional delicacies which includes; garri, fufu, lafun flour etc,
some of which are fermented products (Oti 2002). Among all the products
processed from cassava, garri is the most common in Nigeria, garri production
is done in varying scales; small, medium and large (Uzoije et al., 2011). Cassava processing into garri involves several units
operations vis-vis, harvesting, peeling, washing, grating, pressing and
fermenting, sieving, frying or roasting, drying and packaging (Okafor 2008).
The flow chat shown below illustrates the processes involved in cassava processing
into garri.
Fig.
(1) Flow chart showing
operational units involved in garri processing (Okwu
et al., 1999).
In
this part of the country, cassava tuber is processed and made ready for
consumption mainly either as garri, starch, or as dried or wet cassava flour.
In each of these, the major processing stage is the milling stage and this
leads to the location of cassava milling machines all over the environment. The
residues obtained during this process are the solid and liquid wastes. In
Nigeria and in most tropical countries also, processed cassava tuber is
gradually transforming from a famine reserve commodity and rural staple food to
cash crop for urban consumption and to an export commodity for international
market (IFAD 2005; Ohochukwu 2005).
The
sum of the amount (HCN equivalent) of Linamarina cetocyanohydrin, hydrogen
cyanide and cyanide ion equals the cyanogenic potential of the cassava sample.
Hydrogen cyanide (H-C
N) equivalents should be processed to
reduce the cyanogenic potential before use for human consumption. Some
traditional methods of processing in South America and west Africa remove
nearly all the cyanogens from cassava products, but other method such as those
used for cassava flour production in east Africa and Indonesia reduces, but do
not eliminate the cyanogens present.
1.3.4 Biological Properties of Soil
Soil
as an important natural habitat for microorganisms, plants, animals and human
is probably the most complex and diverse on the planet. It is a biomembrane and
can be a source or sink for most gases. A further source of complexity in the
soil biological activity is the existence of exo-cellular enzymes, presumably
derived from past population of organisms but stabilized by sorption on mineral
surfaces and retaining at least part of their activity (Burns 1978).
Soil
is also used for waste disposal, so detoxification and filtering functions are
important. A vast range of organic wastes are applied to soil including sewage
sludge, composted manicipal waste and effluents from biologically- based
industries such as the processing of cassava and oil palm (Powlson et al., 2001).
Hydrogen
cyanides are ubiquitous in nature. Principal natural sources of cyanides are
from over 2,000 plants species, including fruits and vegetables that contain cyanogenic
gluosides which can release cyanide on hydrolysis when ingested. The variation
in concentrations of cyanogenic glucosides is as a result of genetic and
environmental factors, location season and soil type (JECFA 1993).Transport of
cyanide in the soils are mostly influenced by volatilization and distribution.
Cyanides enters the soil from both natural processes and industrial activities
and it is fairly mobile in soil, though can be removed via several processes,
one of which is via volatilization from soil surface. Some can form hydrogen
and evaporate, whereas some compounds of cyanide will be transformed into other
chemical forms by microorganisms in soil. But at high concentration, it becomes
toxic to soil microorganisms and can no longer change cyanide to other chemical
forms, cyanide is capable of passing through soil into underground water
(Callahan et al., 1979).
Soil
with pH less than 9.2, hydrogen cyanide is expected to be highly mobile and in
cases where cyanide levels are toxic to microorganisms (i.e Landfill) HCN may
leach into groundwater (ATSDR 2006). Hydrogen cyanide is not strongly
partitioned into sediments or suspended absorbents, primarily due to its high
stability in water (Callahan et al.,
1979). Exposure of high levels of cyanide, such as hydrogen cyanide gas for a
short time harms the brain and heart and can cause coma and death over time
(ATSDR 2006).
1.3.5 Cyanide Utilization and Degradation
by Microorganisms.
Various
microorganisms can produce (cyanogensis) or degrade cyanide. They degrade
cyanide either to detoxify it, or to use it as a source of nitrogen for growth.
Significantly, cyanides are formed as a secondary metabolite by a wide range of
fungi and bacteria by decarboxylation of glycine when cyanide has been formed
by the snow mould fungus it is degraded by conversion to carbon dioxide and
ammonia via an unknown pathway. In contrast, cyanogenic bacteria either, do not
further catabolize cyanide or they convert it into beta-cyanoalanine by
addition to cysterine or Q-acetylserine. Several non-cyanogenic fungi that are
pathogens of cyanogenic plants are known to degrade cyanide by hydration to
form amide by the enzyme cyanide hydratase such fungi can be immobilized and
used in packed-cell columns to continuously detoxify cyanide (Dashet al.,2009). ICI-Biological products
business market a preparation of spray-dried fungi mycelia ‘‘CYCLEAR’’ to
detoxify industrial wastes. NOVO industry had also introduced a cyanide
preparation to convert cyanide directly into formate and ammonia. Bacteria have
been isolated that uses cyanide, as KCN or NACN, is toxic for growth, the
bacteria (Pseudomonas fluorenscens)
have to be grown in fed-batch culture with cyanide as the limiting nutrient.
Cyanide is converted to carbon dioxide and ammonia (which is then assimilated
by an NADH-linked cyanide oxygenase system (Gupta 2010).
1.3.6 Physical Properties of Soil
The
rate at which water moves through the soil (permeability) and water holding
capacity (WHC): (the ability of the soil microspores to hold water for plant
use) are all affected by the amount, size and arrangement of pores; microspores
control a soil’s permeability and aeration, and microspores which are
responsible for a soil texture, structure, compaction and organic matter (Gray
2005).
Soil Texture
Soil
texture is the relative proportion of sand silt and clay and is important in
determining the water holding capacity of soil. Fine textured soils hold more
water than coarse textured soil but may not be ideal, while medium textured
soil (loam family) are most suitable for plant growth. Particles of 2 - 0.05mm =
sand, while those of 0.05 – 0.002mm = silt and those particles < 0.002mm =
clay. The texture of soils are usually expressed in terms of percentage (%) of
sand, silt and clay. The loam textural class contains soils whose properties
are controlled equally by clay, silt and sand. Separated soil horizons are
sometimes separated on the basis of differences in texture (Paul and Clarke
1989).
Soil Structure
The
nature of the arrangement of primary particles into naturally formed secondary
particles, called aggregates, is soil structure. A sandy soil may be structure
less because each sand grain behaves independently of all others. A compacted
clay soil may be structured less because the particle are clamped together in
huge massive chunks. Structural horizons can be differentiated on the basis of
structural, class or grade. Structural class is based on aggregate size, while
structural grade is based on aggregate strength. Organic materials especially
microbial cells and waste products, act to cement aggregates and has to
increase their strength. The structure, particularly in fine-textured soils,
increases total porosity because large pores occur between aggregates, allowing
penetrations of roots and movements of water and air (Zengler et al., 1999).
Soil Consistency
This
describes the consistency of a soils physical condition at various moisture
contents as evidence by the behaviour of the soil to mechanical stress or
manipulation. Descriptive adjectives such as hard, loose, firm, plastic and
sticky are used for consistency. The consistency of a soil is determined to a
large extent by the texture of the soil, but is related also to other
properties such as content of organic matter and type of clay minerals (Vogel
1962).
Soil Colour
The
colour of objects including soils can be determine by minor components.
Generally, moist soils are darker than dry soils and the organic component also
makes soils darker. Thus, surface soils tend to be darker than sub-soils. Red
and fellow lines are indicate of good drainage and aeration, critical for
activity of aerobic organisms in soils. Mottled zones, splotches of one or more
colours in matrix of different colour, often are indicative of a transition
between well drained, aerated zones and poorly drained, poorly aerated ones.
Gray lines indicate poor aeration, soil colour chart have been developed for
the quantitative evaluation of colours (Gray 2005).
1.3.7 Chemical Properties Of Soil
Soil pH
The
pH indicates the acidity or alkalinity(base) of soil. Different plants have
different optimum soil pH requirements. The soil pH is important in determining
the availability of soil minerals. The application of different fertilizers can
affect the pH of the soil. Soil pH can have an effect on microbial ability in
the soil (Skyllberg 1993).
Soil Organic Matter
Soil
organic matter is chiefly composed of carbon, hydrogen, oxygen, nitrogen and
smaller quantities of sulphur and other elements. The organic fraction serves
as a reservoir for the plant essential nutrients, nitrogen, phosphorus, and
sulphur, increases soil water holding and cation exchange capacities and
enhances soil aggregation, and structure (Batjes 1996).
Plant Nutrients
Plants
require a number of essential nutrients for their growth and development. Both
the soil and the atmosphere can provide these nutrients. Some of these minerals
are needed in large amounts (major elements or macronutrients) and others are
needed in small amounts (trace elements or micronutrients). Alternatively, the
elements are classified into three groups: (Batjes 1996).
- Major
elements – Nitrogen, Phosphorus, Potassium (NPK)
- Secondary
elements – Calcium, Magnesium, Sulphur (Ca; Mg, S)
- Trace
or Minor Elements – Iron, Manganese, Copper, Zinc (Fe, Mn, Cu, Zn).
Exchangeable Cation
Cation
exchange is the ability of soil clays and organic matter to absorb and exchange
cations with those in soil solution (water in soil pore space). Positive
charged cations are attracted to those negatively charged particles, just as
opposite poles of magnets attract one another. A dynamic equilibrium exists
between absorbed cations and those in soils solution. Cations absorption is
reversible if other cations in soils solution are sufficiently concentrated to
displace those attracted to the negative charge clay and organic matter
surfaces. Cation exchange capacity of soils is dependent upon both organic
matter content and type of silicate clays (Walkey 1947).Cation exchange
capacity is important phenomena for two reasons;
- Cations
absorbed to exchange sites are more resistant to leaching; on downward
movement in soils with water.
- Exchangeable
cation like Ca, Mg and K are readily available for plant uptake. The
cations of Ca, Mg, K, Na, produce an alkaline reaction in water and are
termed bases or basic cations. Aluminium and hydrogen ions produce acidity
in water and are called acidic cations. The percentage of the cation
exchange capacity occupied by basic cation is called present base
saturation. The greater the per cent base saturation, the higher the soil pH
(Amadi and Odu1993).
1.3.8 Effects of Cassava Mill Effluent
Wastes On Soil
In
the present study, an attempt has been made to investigate the effect of CME on
the microbial populations in the soil (Obuh and Akindahunsi 2003a). Increasing
levels of heavy metals in the environment from various anthropogenic sources
has become a source of concern for environmentalists (Opeolu et al., 2008). Evidence of the potential
and observed human hazard due to environmentally acquired heavy metals and
harsh substances contributes to the ecological impact of the environment have
been studied (Ademoroti 1996; Shegerian 2006; Killburn and Washaw 1993; Willis
and Saviry 1995; Davis and Weiss 1990). According to Akani et al., (2006), the deleterious effects of cassava mill effluents
on soil organisms can be traced to high levels of cyanogenic glucocides,
biochemical oxygen demand (BOD) and soluble carbohydrates and proteins in the
effluents are highly lethal, it is fairly mobile in the soil and destroy
microbes (Akani et al., 2006).
Dumping of CME on land results in sand reduction and the textural composition
of the soil and becomes more of clay, and the
cyanide concentration increases with depth (Okwu and Nwosu 1999; Okafor 2008
and Uzoije et al., 2011). As a result
of large volume of waste produced from cassava processing which are also indiscriminately discharged onto the
surrounding soil, where they accumulate and sink, hence, posing serious health
challenges and environment hazards as it continuously spread into the soil, air and water.
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