No 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).

No abstract

This research was conducted to determine the effect of various wastewater sludge (domestic type (B), mixture of industry and domestic type (L), aerobic food industry (P), anaerobic food industry (M)) levels on the properties of sandy soil, including pH, electrical conductivity (EC), and the levels of available N (NH4 and NO3) and P, diethylenetriamine pentaaceticacid (DTPA)-extractable microelements and heavy metals. An incubation experiment was performed in which sludges were applied at rates of 0, 40, 80, 120, and 160 tons ha(-1), and the effects on the soil properties were measured over a period of 150 days. Soil pH decreased and electrical conductivity increased with increasing levels of sludge application. The levels of NH4-N, NO3-N, available P, and DTPA-extractable heavy metals also increased with the application rate of the sludge. NO3-N content increased and NH4-N content decreased over time. The most unfavorable effects on soil properties were observed with the B sludge. Other soil characteristics changed according to the sludge properties.