Biodegradation of used engine oil in a wastewater sludge-amended agricultural soil

Abstract

Soil contamination by used engine oil is a common occurrence in most developing countries. This has been shown to have harmful effects on the environment and human beings at large. Used oils are considered to be hazardous waste materials. These are composed of toxic chemicals, such as heavy metals (which come from additives and wear and tear of engine parts), combustion products, light hydrocarbons, polar compounds, uninuclear and polynuclear aromatic compounds, resinous materials, and organometallic compounds. Some of these pollutants are carcinogenic in nature. The objective of this study was to evaluate the effects of used engine oil (doses of 0.5% and 5%) with hydrocarbon pollution on total petroleum hydrocarbon (TPH) removal from soil and determine the fate of TPHs at different temperatures (18 °C and 28 °C) during an incubation period of 240 days. The possible use of wastewater sludge as a biostimulating agent in used engine oil-contaminated soils was also evaluated. The results of 240 days of incubation indicated that TPH removal percentages in used engine oil-contaminated+sludge amended soils at 18 °C were 68% and 66% for doses of 0.5% and 5%, respectively. Incubation at 28 °C resulted in higher TPH removal with values of 56% (dose of 0.5%) and 74% (dose of 5%). Based on the first-order kinetics model, the high dose (5%) of used engine oil-contaminated soil amended with wastewater sludge showed the highest biodegradation rate of 0.00562/day and half-life of 123.13 days at the end of the incubation period at 28 °C. These rates were significantly higher than those of the control soil (0.00366/day and 189.01 days).

Factors Influencing the Bacterial Bioremediation of Hydrocarbon Contaminants in the Soil: Mechanisms and Impacts

“…Biostimulation is the addition of growth-limiting factors such as substrates, vitamins, oxygen, and modifying the environmental conditions (temperature, moisture, pH, redox potential, terminal electron acceptors, etc.) in the hydrocarbon-contaminated environments [49,50,52].…”

“…When hydrocarbon contaminants are greatly available, they provide high carbon and energy but nitrogen or phosphorus for bacterial growth [31]. Hence, there is the need for the addition of nutrients in hydrocarbon-contaminated sites to increase the required nutrients and stimulate the growth of indigenous bacteria [52]. However, there are certain limitations for effective biostimulation application.…”

“…As temperature increases, solubility, bioavailability, diffusion, and enzymatic activities of microorganisms also increase [98], whereas, at a higher temperature (above 40 °C), oxygen solubility decreases, and metabolic activity of aerobic bacteria diminishes; the membrane becomes more susceptible to hydrocarbon toxicity and consequently reduces the hydrocarbon biodegradation rate [56,68]. Conversely, at lower temperatures, the oil viscosity increases; the volatility of low-molecular-weight of toxic hydrocarbons pollutants decreases; solubility decreases; the toxicity of low-molecular-weight of hydrocarbons increases; rates of enzymatic activity decreases; and hence, there is a delay microbial biodegradation [52]. Indeed, the degradation efficiency of hydrocarbons at lower temperatures could be improved with biosurfactants by influencing the viscosity and solubility of hydrocarbons.…”

“…Indeed, the degradation efficiency of hydrocarbons at lower temperatures could be improved with biosurfactants by influencing the viscosity and solubility of hydrocarbons. In addition, studies have shown that the maximum rates of microbial hydrocarbon degradation occur in a warm environment [31], particularly in the range of 30-40 °C [52,97]. In general, the rate of biodegradation decreases with decreasing temperature, while it accelerates with increasing temperature.…”

Effects of cadmium and lead on the biodegradation of diesel-contaminated soil

“…Cadmium and lead are more perilous because they tend to bioaccumulate [6]. According to Dindar et al [7], a high bioremediation rate was observed when waste water sludge containing heavy metals; zinc, copper, nickel, lead and cadmium was used as a biostimulating agent in the bioremediation of engine oil contaminated soil. Therefore, the aim of the study was to investigate the effects of cadmium and lead on biodegradation of diesel in soil.…”