Strategies To Reduce Hydrocarbon Pollution For A Greener Future

Hydrocarbons are highly flammable and generate carbon dioxide, water, and heat when burned. They are naturally occurring and are derived from fossil plants and animals that have been formed over thousands of years by the forces of temperature and weight. They are mainly found deep beneath porous rock formations such as sandstone, limestone, and shale.

Hydrocarbon pollution is a serious concern for the environment, and it can be caused by toxic organic substances, petroleum, and pesticides. Petroleum hydrocarbon contamination is particularly harmful to various life forms. Crude oil contamination is common due to its extensive use and its related dumping process and accidental spills.

The combustion of mobil oil renders a non-usable form that ultimately enters the environment, causing problems to environmental health. The aliphatic and aromatic hydrocarbon fraction of mobil oil has serious human and environmental health hazards. These components, upon interaction with soil, affect its fertility and microbial diversity.

There are several methods to reduce hydrocarbon pollution, including combustion, absorption, and adsorption. Combustion involves the use of flame combustion or catalytic combustion to form carbon dioxide and harmless water. Absorption uses a liquid absorbent to absorb harmful gaseous pollutants present in the air. Adsorption involves adsorbing gaseous pollutants at the surface of a process solid to clean the air as it passes through.

Bioremediation is another method used to reduce hydrocarbon pollution. It is a cost-effective method used for the treatment of soil polluted with oil and petroleum wastes. It involves the use of natural microorganisms to decontaminate the atmosphere and convert pollutants into useful or non-toxic substances.

Phytoremediation is also a process that can be used to reduce hydrocarbon pollution. It involves the use of plants for the degradation, extraction, and elimination of contaminants from the air, water, and soil.

Finally, chemical remediation can be used to treat contaminants with various chemicals. Dispersants, solidifiers, and chemical oxidants are the three categories in which chemical remediations are grouped.

Phytoremediation: Using plants to break down, extract and remove pollutants from air, water and soil

Phytoremediation is an economical, sustainable, practical, and cost-effective technology for environmental cleanup. It is a plant-based technology that uses plants to immobilize, uptake, reduce the toxicity of, stabilize, or degrade compounds that have been released into the environment from different sources. It can be used to remediate heavy metals, organic contaminants, radionuclides, antibiotics, and pesticides.

Phytoremediation can be used to clean up hydrocarbon-contaminated soils and groundwater polluted with residual concentrations of petroleum hydrocarbons. It is particularly attractive for rural areas with residual and shallow contamination. It can also be used to clean up soils and groundwater contaminated with other hazardous substances, attenuate pollutants dispersing through the environment in agricultural drainage, landfill leachates, and other forms of surface runoff or sub-surface migration, and assimilate industrial wastewater effluents.

Phytoremediation involves the use of plants for the degradation, extraction, and elimination of contaminants from the air, water, and soil. It includes various mechanisms that can lead to the degradation of contaminants, dissipation, immobilization, and accumulation. Some of the plants that can be used for phytoremediation include grasses, legumes, alfalfa, broad beans, switchgrass, and hybrid poplar trees.

The basic physiological mechanisms involved in phytoremediation in higher plants and related microorganisms include mineral nutrition, photosynthesis, transpiration, and metabolism. The root of the plant is responsible for the uptake of organic and inorganic compounds from the soil, and it can bind and stabilize substances on its external surfaces on interaction with microorganisms in the rhizosphere. Uptake or release of molecules occurs through the exchange of gases from the aerial plant's parts with the atmosphere.

There are six phytotechnologies that have been recognized for addressing different contaminants in different substrates:

• Phytotransformation is ideal for organic contaminants in all substrates.
• Rhizosphere bioremediation is used in soil containing organic contaminants.
• Phytostabilization is used in soil for organic and inorganic pollutants.
• Phytoextraction is useful in substrates containing inorganic pollutants.
• Phytovolatilization is used for volatile substances.
• Hydraulic flow can be controlled in the contaminated environment by using evapotranspiration.

Phytoremediation is a more eco-friendly and cost-saving technology compared to other remediation methods. It also offers the restoration of ecosystems, habitat to animals, biodiversity conservation, and reduces anthropogenic activities.

Bioremediation: Using natural microorganisms to decontaminate the atmosphere

Bioremediation is an eco-friendly and cost-effective method of decontaminating the atmosphere of hydrocarbon pollution. It involves the use of microorganisms such as bacteria, fungi, and yeast to break down pollutants into simpler, non-toxic substances.

The process of bioremediation can be split into two main types: bioaugmentation and biostimulation. Bioaugmentation involves the addition of microorganisms to the polluted site to aid in the breakdown of harmful hydrocarbons. On the other hand, biostimulation focuses on creating an environment that encourages the growth of indigenous hydrocarbon-degrading microbes by adding nutrients and optimising factors such as pH, temperature, and moisture.

The effectiveness of bioremediation is influenced by several factors, including the type of hydrocarbon, the concentration of the contaminant, the availability of oxygen and nutrients, and the properties of the soil, such as its pH, salinity, and porosity.

To enhance the process of bioremediation, it is possible to use genetically modified microorganisms that are specifically designed to break down certain types of hydrocarbons. Additionally, nanotechnology can be employed to create advanced materials that aid in the clean-up of hydrocarbon pollution.

Overall, bioremediation is a promising approach to combat hydrocarbon pollution, and further research and development can lead to more efficient and sustainable solutions.

Bioaugmentation: Adding microorganisms to break down harmful hydrocarbons and reduce pollutants

Hydrocarbon pollution is a pressing issue that has gained prominence since the industrial revolution and the widespread use of fossil fuels. This pollution has far-reaching consequences for aquatic, land, and atmospheric ecosystems, threatening the lives of animals and native microbial populations.

Bioaugmentation is a type of bioremediation that aims to speed up the rate of degradation of contaminants. It involves the introduction of specific consortia of microorganisms, such as bacteria, archaea, or fungi, which can break down harmful hydrocarbons without harming the native microflora. This process can be applied in situ (directly at the site of contamination) or ex situ.

The process of bioaugmentation involves studying the indigenous microbial varieties present at the contaminated site to determine if biostimulation is possible. If the native bacteria can metabolize the contaminants, more of these bacterial cultures are added to boost the degradation process. This is done because the indigenous microorganisms may already be able to break down waste but in an inefficient and slow manner.

The addition of more microbial cultures enhances the contaminant degradation process, while biostimulation, which involves adding nutritional supplements, promotes bacterial metabolism. If the indigenous microorganisms lack the necessary metabolic capabilities, exogenous varieties with more advanced pathways are introduced.

Benefits and Applications of Bioaugmentation

Bioaugmentation has been successfully applied in municipal wastewater treatment to restart activated sludge bioreactors and treat contaminated soils that have undergone bioremediation but still pose environmental risks. It is particularly useful for breaking down chemicals in contaminated soil that the original bacteria were unable to address due to environmental stresses or changes in the microbial population.

Bioaugmentation has been used to address chlorinated solvent contamination in soil and groundwater, as well as in the petroleum industry to metabolize polycyclic aromatic hydrocarbons, significantly reducing environmental damage from drilling activities.

Factors to Consider

When considering bioaugmentation, it is essential to evaluate the overall setting, including the size of the site. The success of bioaugmentation also depends on the ability of the introduced microorganisms to compete with the native microbial community and adapt to the specific site conditions.

Additionally, the wrong type of bacteria can result in clogged aquifers, and the remediation result may be incomplete. Other challenges include predation, nutritional competition, insufficient inoculations, and disturbances to the ecological balance due to large inoculations.

Examples of Successful Bioaugmentation

An example of successful bioaugmentation is the treatment of coke plant wastewater in China, which contains harmful contaminants like ammonia, thiocyanate, phenols, and other toxic organic compounds. Bioaugmentation has been effective in removing these contaminants, including 3-chlorobenzoate, 4-methyl benzoate, toluene, phenol, and chlorinated solvents.

Another example is the use of bioaugmentation in oilfield drilling pits. By introducing advanced microbes, companies can treat the problem in the pit instead of transferring the waste. This approach has successfully reduced environmental damage by metabolizing polycyclic aromatic hydrocarbons.

Bioaugmentation is a valuable tool for reducing hydrocarbon pollution by introducing specific microorganisms to break down harmful contaminants. It has been successfully applied in various settings, including wastewater treatment and contaminated soil remediation. However, careful consideration of the microbial community dynamics and potential challenges is essential for the successful implementation of this technique.

Biostimulation: Adding nutrients to help natural hydrocarbon-degrading microbes break down harmful compounds

Biostimulation is a process that involves the degradation of harmful compounds by adding the nutrients required by indigenous hydrocarbon-degrading microbes. The growth of these microbes is activated by the addition of carbon, and the tendency of the microbes to degrade the hydrocarbons is enhanced by the addition of a suitable concentration of supplemental nutrients. The maximum biostimulation is achieved by obtaining the ideal nutrient concentration required for the maximum growth of the microbes and maintaining that concentration for as long as possible.

Biostimulation is often used in combination with bioaugmentation, which involves the degradation of harmful hydrocarbons by the addition of microorganisms. Bioaugmentation is not often used for the remediation of oil spills because microorganisms that are responsible for hydrocarbon degradation naturally exist in the environment.

Biostimulation can be used to remediate soil that has been contaminated by waste motor oil (WMO). This process involves the application of a crude fungal extract (CFE) and Cicer arietinum as a green manure (GM). The CFE contains the extracellular enzymes of mitosporic ligninolytic fungi (LMF), from Aspergillus sp., Fusarium solani, and Penicillum chrysogenum, which generate manganese peroxidase (MnP), lignin peroxidase (LiP) and laccase. The GM balances the C:N ratio of the soil to facilitate the mineralization of the WMO in adverse soil environmental conditions.

The process of biostimulation can be followed by phytoremediation, which involves the use of plants for the degradation, extraction, and elimination of contaminants from the air, water, and soil. One such plant is Sorghum vulgare, which can be inoculated with Rhizophagus irregularis and/or Rhizobium etli to reduce the concentration of WMO in the soil.

Chemical remediation: Using chemicals to treat contaminants

Chemical Remediation of Hydrocarbon Pollution

Chemical remediation is a process that uses chemicals to alter the physical and chemical properties of contaminants. This method is often used in conjunction with biological and ecological techniques to reduce hydrocarbon pollution. Here are some specific chemical remediation approaches:

• Dispersants: Surfactants in dispersants break down oil slicks into smaller droplets, which can then be diluted and degraded more easily by bacteria. This method is particularly effective for treating oil spills in marine environments, as it reduces the harmful effects on marine life.
• Solidifiers: This method involves using dry granular materials to solidify liquid oil, making it easier to remove. However, solidifiers can be challenging to recover and are less efficient overall.
• Chemical oxidation: This technique uses chemical agents to oxidise organic pollutants, and it is rapid and suitable for a wide range of oils. However, it does not recover the oil, and it may not be effective on highly viscous or waxy oils.
• In situ soil vapour extraction (SVE): SVE is an in-situ remediation method that uses a vacuum to remove volatile organic compounds (VOCs) and semi-VOCs from unsaturated soils. It is effective for contaminants like VOCs but not for heavy oils, metals, or PCBs.
• In situ steam injection vapour extraction: This technique uses steam and hot air to volatilise and displace contaminants from the soil. It can be applied using mobile or stationary systems and is particularly useful for small areas.
• Air sparging: Air sparging involves injecting air into a contaminated aquifer to remove volatile contaminants through volatilisation. It is effective for lighter petroleum compounds and chlorinated solvents.
• Excavation: Excavation is a fundamental remediation method where contaminated soil is removed and treated on-site or off-site. It is often used for localised contamination and point sources but has limitations due to the high cost of transportation and final disposal.

Frequently asked questions