Biodegradation and toxicity of vegetable oils in contaminated aquatic environments: Effect of antioxidants and oil composition

Enhancing biodegradation of vegetable oil-contaminated soil with soybean texturized waste, spent mushroom substrate, and stabilized poultry litter in microcosm systems

Industrial activities contribute to environmental pollution, particularly through unregulated effluent discharges, causing adverse effects on ecosystems. Vegetable oils, as insoluble substances, exacerbate this pollution, forming impermeable films and affecting the oxygen transfer, leading to serious habitat disruption. Organic wastes, such as soybean texturized waste, spent mushroom substrate, and stabilized poultry litter, were assessed for their efficacy in enhancing the degradation of vegetable oil in contaminated soil. For this purpose, contaminated soil was amended with each of the wastes (10% w/w) using microcosm systems, which were monitored physico-chemically, microbiologically and toxicologically. Results indicate that the wastes promoted significant oil degradation, achieving 83.1, 90.7, and 86.2% removal for soybean texturized waste, spent mushroom substrate, and stabilized poultry litter, respectively, within a 90-day period. Additionally, they positively influenced soil microbial activity, as evidenced by increased levels of culturable microorganisms and hydrolytic microbial activity. While bioassays indicated no phytotoxicity in most cases, soybean texturized waste exhibited inhibitory effects on seed germination and root elongation of Lactuca sativa. This study significantly enhances our comprehension of remediation techniques for sites tainted with vegetable oils, highlighting the critical role of organic waste as eco-friendly agents in soil restoration. Emphasizing the practical implications of these findings is imperative to underscore the relevance and urgency of addressing vegetable oil contamination in soil. Moving forward, tailored strategies considering both contaminant characteristics and soil ecosystem traits are vital for ensuring effective and sustainable soil remediation.

The degradation and toxicity of commercially traded vegetable oils following spills in aquatic environment

The production of commodity and specialty vegetable oils is increasing every year to fulfill the ever-increasing demand where the trading of oils occurs primarily via sea shipping. Spills of vegetable oil into the aquatic environment may result in detrimental effects on aquatic ecosystems. Environmental degradation of vegetable oil spills occurs mainly via microbial activity, chemical oxidation, wave and wind actions. However, the polymerization of oils can hinder their ability to naturally degrade. Thus, human intervention in the form of both short- and long-term remediation, is desirable to reduce the effects of vegetable oil spills on aquatic ecosystems. Studies have been conducted to determine how the type and concentration of the vegetable oil contamination influence its toxicity on various organisms. Some studies show that the effect of vegetable oil spills is found to be relatively short-lived and to a certain extent increase the survivability of certain organisms. However, the integrated effect of vegetable oil spills on aquatic organisms and their environment is still being researched. This review summarizes the existing knowledge on the reported occurrences of vegetable oil spills, their degradation, and their toxicity towards the surrounding aquatic environment which would be helpful in the knowledge transfer of remediation of vegetable oils.

Insights on the criteria of selection of vegetable and mineral dielectric fluids used in power transformers on the basis of their biodegradability and toxicity assessments

Leakage of transformer dielectric fluids is a concern because it may pose a risk of environmental contamination. In this study, the deleterious effects of vegetable and mineral dielectric fluids in water bodies were investigated using biodegradability and acute toxicity tests with Danio rerio and Artemia salina. Regarding biodegradability, all four tested vegetable oils (soy, canola, sunflower and crambe) were considered as easily biodegradable, presenting degradation rates significantly higher than the Lubrax-type mineral fluid. Acute toxicity tests were performed in two separate experiments without solution renewal. In the first experiment, the organisms were exposed in direct contact to different concentrations of vegetable (soy) and mineral (Lubrax) oils. Total soy-type vegetable oil has a higher toxic effect than Lubrax-type mineral oil. In the second experiment, the organisms were exposed to increasing percentages of the water-soluble fraction (WSF) of both types of tested oils. The LC₅₀ values for the water-soluble fraction of the Lubrax-type mineral oil were about 5 and 8% for the Danio rerio and Artemia salina bioindicators, respectively, whereas the vegetable oil did not present toxic effect, regardless of its WSF. These results have shown that a strict selection of dielectric fluids and monitoring the leakage from power transformers is a serious duty of environmental protection agencies.

Assessment of three plant-based biodiesels using a Daphnia magna bioassay

Biodiesel is an alternative fuel that is gradually replacing petroleum-based diesel use. Although biodiesel is considered friendlier to the environment, the potential toxic effects of biodiesel to aquatic organisms are still uncertain due to the wide range of feedstocks used to generate the fuel. The aquatic cladoceran Daphnia magna (D. magna) has been commonly used as a lethal and/or sub-lethal toxicological model organism in ecological risk assessments for contaminated water environments. In this work, we evaluated whether significant differences exist in the sensitivity of freshwater aquatic life to different biodiesels. The acute toxicity of three plant-based biodiesels was investigated using D. magna over a 96-h period. In addition, diesel fuel was tested as a reference. Increased immobility was observed as time progressed following exposure. Testing revealed of the four fuel products, diesel proved most toxic to D. magna, with half maximal effective concentration (EC₅₀) values of 4.7 μg/mL (24 h) and 3.4 μg/mL (72 h). Among the biodiesels, safflower methyl biodiesel was most toxic, with EC₅₀ values of 1026 μg/mL (24 h) and 71 μg/mL (48 h). Our data indicate that although not all biodiesels were toxic, the short-term exposure of D. magna to sub-lethal concentrations of biodiesels affects their mobility and thus decreases their reproductive potential. Overall, this research provides insights into the sub-lethal effects of biodiesels on an aquatic organism.

Emerging usage of electrocoagulation technology for oil removal from wastewater: A review

Electrocoagulation is a simple and efficient treatment method involving the electrodissolution of sacrificial anodes and formation of hydroxo-metal products as coagulants, while the simultaneous production of hydrogen at the cathode facilitates the pollutant removal by flotation. Oil is one of the most important hydrocarbon products in the modern world. It can cause environmental pollution during various stages of production, transportation, refining and use. Electrocoagulation treatment is particularly effective for destabilization of oil-in-water emulsions by neutralizing charges and bonding oil pollutants to generated flocs and hydrogen bubbles. The development of electrocoagulation technologies provided a promising alternative for oil removal from wastewater. This paper presents a review of emerging electrochemical technologies used for treating oil-containing wastewater. It includes a brief description of the oily wastewater origin and characteristics. The treatment processes developed so far for oily wastewater and the electrocoagulation mechanisms are also introduced. This paper summarizes the current applications of electrocoagulation for oil removal from wastewater. The factors that influence the electrocoagulation treatment efficiencies as well as the process optimization and modeling studies are discussed. The state-of-the-art and development trends of electrocoagulation process for oil removal are further introduced.