In this research work, the development of a waste based Biostimulant in the remediation of Crude-oil contaminated soil was investigated. Biostimulants used was plant waste (Plantain Peel) at a constant proportion of crude oil contamination and treated with varying concentration of biostimulant (10%w/w, 15%w/w, 20%w/w, 25%w/w, 30%w/w). Microsoft Excel tool and Design Expert statistical software were used in the kinetic study and optimization of the process. The treatment period was done in 28days days. At the end of the study, in the sample treated with 100g PP the TPH was found to reduce from 28346 to 17498(mg/Kg) with %D equal to 39.2%, in 150, 200, 250 and 300(g) PP treament, TPH reduce from 28344 to 16595, 28343 to 15251, 28340 to 13883 and 28338 to 12255(mg/Kg) with corresponding %D of 42.07, 46.47, 50.74% and 55.98(%) respectively. The optimization results shows that the optimum TPH and HUB value was 14190.9mg/Kg and 2.34162cfu/g at mass A=282.312g, time B= 3.38379wks and temperature C= 21.3207oC with desirability of 1. Which showed that the predicted model actually fits the experimental data. The results so obtained shows that agro waste based technology using plantain peel is a cheap and effective means of bioremediation of crude oil contaminated sites.
1.1 Background of the Study
Environmental pollution has been a major concern to man globally. It involves contamination of various media namely soil, water and air. In order to prevent destruction of the ecosystem, these media need to undergo a thorough treatment process. The remediation procedure could be as simple as introducing certain chemicals into the system, to a highly complex procedure involving several chemical and biological processes. This is normally applicable to areas involving pesticide contamination, metal and metalloid pollution, petroleum contaminations, and many more. Amongst the three media, soil contaminations has been reported to be the most threatening due to the fact that contaminants have the capacity to affect the indigenous organism that dwell in the soil and destroy the food chain. Consequently, soil remediation has been known to be among the most expensive treatments in the world. Thus, various strategies have been opted to investigate the most cost-effective solution to deal with contaminated sites.
Remediation refers to the removal, destruction, or transformation of contaminants to less harmful substances. To treat contaminated sites, physicochemical and biological remediation can be conducted.Among the highly potential approach is bioremediation since many studies have reported of its effectiveness in removing numerous pollutants from many contaminated site. Generally, bioremediation technologies can be classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site while ex situ involves the removal of the contaminated material to be treated elsewhere. Different techniques are employed depending on the degree of saturation and aeration of an area. In situ techniques are defined as those that are applied to soil and groundwater at the site with minimal disturbance. Ex situ techniques are those that are applied to soil and groundwater at the site which has been removed from the site via excavation for soil or pumping for water. It mainly involved biostimulation where organic or inorganic components were introduced to enhance indigenous microbial growth that directly degrades the contaminants(Agamuthu , Tan, & Fauziah , 2013).
Biostimulation is the addition of substrates, vitamins, oxygen and other compounds that stimulate microorganism activity so that they can degrade the petroleum hydrocarbons faster. Stimulation of microorganisms by the addition of nutrients brought large quantities of carbon
sources which tend to result in a rapid depletion of the available pools of major inorganic nutrients such as N and P. An example of this is the addition of fertilizer to an oily wastewater. This works by supplying nutrients that are limiting the growth of the bacteria for the oil contaminated wastewater such as nitrogen and phosphorous. With this addition, the organisms can rapidly degrade the oil utilizing it as the carbon source and the fertilizer as the nitrogen and phosphorous source.
Combinations of inorganic nutrients often are more effective than single nutrients where a low level of macronutrients and a high level of micronutrients were required to stimulate the activities of indigenous microbes. The greatest stimulation was recorded with a solution consisting of 75% sulphur, 3% nitrogen and 11% phosphorus. Activated sludge has been suggested to be a useful source of nitrogen for PAH biodegradation in soils as well as a range of natural materials such as peat, compost and manure.
Soil contamination occurs due to abandoned crude oil drilling sites, tank failure, flooding, accidental spillage etc, (Atagana, 2014) Several physical and chemical process have been used to remove oil contaminant from the environment, but remediation with conventional technique has some drawbacks. This kind of method is suitable for decontaminating relatively small areas and also requires site restoration ( chekol et al 2004, escalanda-Espinosa et al, 2005) as cited in (Yenn R, 2015). In contrast to these bioremediation using biostimulants is the most preferred method because of its eco-friendly nature and complete cleanup of the soil.
1.2 Statement of the Problem
Soil pollution due to crude oil contamination has posed a major hazard to the eco-system especially in a developing country like Nigeria which has negatively imparted the economic and social cultural wellbeing of the people. Two major problem is identified in this study; firstly, is the issue of waste management and secondly, is the issue of soil pollution.
These problems were addressed in this research work through the effective utilization of plant waste (plantain peels) through the microbial activity in its decay for the remediation of crude oil contaminated soil.
1.3 Aim and Objectives
The aim of this study is to develop a waste based biostimulant for the remediation of crude oil contaminated soil; thereby providing a solution for waste management as well as mitigation of soil pollution resulting from the contamination.
In other to achieve this, the following objectives were undertaken:
- Determination of the physiochemical properties of soil and plant waste.
- Determination of the effect of nutrient on the rate of crude oil degradation
- Determination of the rate of degradation and degradation efficiency of plant waste (plantain peels) on the soil sample.
- Evaluation of the optimum values of factors that affects crude oil degradation and the possible responses using design expert simulation software.
1.4 Significance of the Study
The essence of this study is to develop a biostimulant using plant waste (plantain peels) for the remediation of crude oil contaminated soil which has the same or greater potency as the conventional fertilizer or organic manure used in soil remediation.
This study shall help in addressing problems of waste management associated with agricultural waste since the raw material for the biostimulant formulation is plant waste. Hence providing a solution to waste associated with agricultural production. Also, when contaminated soil are biostimulated using Plant Biostimulants, this will modify the physiological processes of plants in a way that provides potential benefits to growth, development and/or stress response of the plant ( Jardin, 2012)The fertility level of the soil will also increase which will have positive impact on crop production.
Furthermore, this study shall address issues of soil pollution which have become an environmental problem in Nigeria with the aim of remediating it to a reasonable fertile or less contaminated state.
1.5 Scope of the Study
This study is concerned with Ex situ bioremediation technique. Soil Sample (sandy) was collected from FUPRE campus and contaminated artificially with crude oil. Analysis of crude oil, soil samples and biostimulant (plantain peels) were carried out using standard laboratory techniques to determine their physiochemical properties.
Cultures of contaminated soil samples at constant contamination level (1000g of soil and 100ml of crude oil) was treated with plant waste (plantain peels) at different concentration level of 10,15,20,25 and 30 (%w/w) and allow bacteria degradation of the carbon content in the crude oil at standard conditions of temperature, concentration, moisture content and PH.
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