EFFECT OF CASSAVA MILL EFFLUENT ON SOIL MICROORGANISMS AND PHYSICOCHEMICAL CHARACTERISTICS WITH DEPTH

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 16^th 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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