ABSTRACT

This study assessed the capacity of two fungi AspergillusflavusandTrichodermasp.individually

and synergistically to remove hydrocarbon, cadmium (Cd), lead (Pb), and nickel (Ni), from broth

cultures charged with raw refinery effluents. Raw effluent from refinery were collected in 200 ml

sample        bottle       and       transported       to       the       laboratory        for       isolation        of

AspergillusflavusandTrichodermasp. using Potato Dextrose Agar (PDA). The physicochemical

qualities of the raw refinery effluent were investigated using standard methods. The effluent

contained very high concentrations of oil and grease (26.42 mg/l), COD (171.2 mg/l), Dissolved

solids (592.20 mg/l), Conductivity (866 µs/cm) and phosphate (8.1 mg/l), but low in

sulphate(39), nitrate(0.01) and pH(7.52) which were within the permissible limit. Biochemical

oxygen demand (BOD) was determined at intervals of five days for twenty days to assess the

capacity of Aspergillusflavusand Trichoderma sp. to remove hydrocarbon from raw refinery

effluent using the modified Winkler method. It was observed that the amount of hydrocarbon

removed increased from day 0 to day 20. The concentrations of the three metals in the raw

refinery effluents and tissues of the test fungi were determined both before and after the

mycoremediation studies using Microwave Plasma Atomic Emission Spectrophotometer (MP-

AES AGILENT 4200). Both the percentage removal as well as the potential of the test isolates to

bioaccumulate the metals in their tissues were calculated following standard procedures. It was

observed that the two isolates tested could remove from 18 to 29% of Cd, 87 to 95% of Ni and

49 to 79% of Pb. Trichoderma sp. proved to be the most efficient in the removal of the three

metals from raw refinery effluent while Aspergillusflavus was consistently the least efficient. It

was also observed that co-culture ofAspergillusflavusand Trichoderma sp. proved to be more

efficient when compared to Aspergillusflavus alone but less efficient when compared to

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1.0                                                          INTRODUCTION

With the rapid increase in human population worldwide, there is an increased demand for

petroleum products such as diesel, petrol, kerosene and other industrial chemicals (Chakrabarty

et al., 1998). However, refinery and petrochemical plants generates solid waste and sludge which

act globally as environmental pollutant (Smita et al., 2012). Petroleum refinery effluents are

wastes originating from industries primarily engaged in refining crude oil and manufacturing

fuels, lubricants and petrochemical intermediates (Harry, 1995). The effluents are composed of

oil and grease along with many other toxic organic and inorganic compounds. These effluents

are a major source of aquatic environmental pollution (Wake, 2005).

Reports from several investigations have shown that hydrocarbons and heavy metals constitute

an important group of pollutants often found in effluents released from refineries and other

petrochemical plants, common example of such compounds include paraffin‘s (methane,

propane, isobutene), nephthenes (cyclohexane, dimethyl cyclopentane) and aromatics (benzene,

toluene, xylenes) (Atlas and Philip, 2005; Benson et al., 2007; Hargrave et al., 2000 and Lee et

al., 2000). These hydrocarbons and heavy metals are biopersistent, bioaccumulative and can

cause deleterious effects to aquatic fauna and flora as well as to humans (Benson et al., 2007).

Heavy metals have been shown to pose significant problems to human health. They are said to

contaminate food sources in the environment (i.e. through soil, water and air). Excess loading of

hazardous wastes has also led to scarcity of potable water and pollution of soil, thus limiting crop

production (Hargrave et al., 2000; Lee et al., 2000 ). Metals may be accumulated, concentrated

and magnified within food chains, causing organisms at higher trophic levels to become

contaminated with high concentrations of chemical pollutants and metal contaminants than their

preys (Hargrave et al., 2000; Lee et al., 2000). Effluents from refinery operations do contain

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toxic and hazardous materials that settle in rivers as part of the bottom sediment. They pose

health hazards to the urban population that depends on the water as source of supply for domestic

uses (Rahman et al., 2005). Metal toxicity appears in metabolic processes like nitrogen fixation,

nitrogen reduction, irregularities on enzyme synthesis (Nwuche and Ugoji, 2008). The treatment

of effluent generated by industrial activity is a major concern for plant operators and in particular

those of refineries and petrochemical units (Arpita et al., 2014). Industrial effluents are

conventionally treated using a variety of hazardous chemicals for pH correction, sludge removal,

colour and odour removal. Extensive use of chemicals for effluent treatment results in huge

amount of sludge which forms the so called hazardous solid waste generated by the industry and

finally disposed of by depositing them in landfills, the conventional methods are inefficient but

effluents are readily degradable by microbes, hence hydrocarbons can be removed (Gupta and