Environmental impact and risks of waste management in storage tanks

Introduction

Storage tanks, located in refinery yards and tank terminals, are used to store large volumes of crude oil and flammable fuels. Large quantities of hazardous wastes are emitted during the maintenance operations of these components, which is aggravated by the occurrence of spills. The environmental management of these wastes is essential, as they can be highly polluting and harmful to the environment and human health.

Given this reality, important questions arise: What types of waste are generated by storage tanks? How is this waste managed to mitigate its environmental impact and associated risks? This article addresses these questions, examines the importance of maintaining a comprehensive industrial waste management plan and presents the most effective solutions applied to minimize the impact on this environment, thus complying with environmental and legal requirements.

Why is proper waste management in storage tanks important?

Proper management of industrial wastes, especially those generated by hydrocarbons stored in storage tanks, is essential to mitigate environmental risks and hazards. These wastes, which include toxic, flammable, and corrosive substances, require careful handling during their handling to avoid serious repercussions on the environment and human health.

The management process for these wastes begins with their generation and continues with storage, separation, and/or classification according to their composition. It is then transported to specialized waste treatment facilities, where it is safely processed before final disposal. Implementing an effective management system prevents pollution, the infiltration of toxins into soils and bodies of water, and the emission of harmful gases.

Proper management of these wastes translates into economic benefits, such as reduced costs associated with cleaning up contaminated areas and optimizing the use of resources. Currently, complying with established regulations and implementing sustainable practices during waste management improves the corporate image and strengthens competitiveness in the market.

Storage tank waste classification

In the management of fuel storage tank waste, it is essential to identify the different types that are generated and classify them properly according to their composition and associated risks, these include:

• Sludge and sediments: This is the largest amount of waste generated by a tank, these can be solid or semi-solid, accumulate at the bottom, and contain a mixture of hydrocarbons and other toxic components as seen in figure 1. Proper management requires specialized treatment processes in certified facilities, to prevent soil and groundwater contamination.

• Cleaning waste: Materials such as textiles, sponges, and other absorbents used in tank cleaning are saturated with hazardous substances and require careful disposal. Segregation and proper classification of these wastes as hazardous are steps to ensure that they are handled safely and in compliance with environmental regulations, avoiding secondary contamination.
• Wastewater: Tank washing and chemical cleaning activities, as shown in figure 2; generate wastewater contaminated with hydrocarbons and various chemicals. The management of this water involves treating it by means of oil and water separation techniques, thus ensuring that it is adequately treated before final disposal or reuse.

• Contaminated soil: When oil spills occur, the management of contaminated soil is quite complex and requires a number of specialized strategies, usually removal for treatment or storage in specialized facilities.

Common techniques for remediation of contaminated soil include both in situ methods, such as bioremediation or phytoremediation that contribute to the ecological restoration of the site; and ex situ methods, which may include soil washing techniques, thermal treatments to volatilize and destroy contaminants, or even incineration. The choice of method depends on the environmental impact assessment, the extent, and type of contamination, and the sensitivity of the affected site.

• Contaminated equipment waste: In the event of extreme spills of heavy crude oil, the surrounding equipment and accessories, such as pipes and pumps, become contaminated requiring strategic cleaning or decontamination prior to disposal or recycling.

Proper classification and management of these industrial wastes is imperative to mitigate the associated environmental risks. Each type of waste, from sludge to contaminated equipment, requires specific handling to ensure its safe treatment and disposal.

Environmental impacts of storage tank wastes

Industrial waste generated in fuel storage tanks must be properly managed to avoid a series of environmental impacts. These include the following:

• Soil contamination: Through the leaching of hydrocarbons and other toxic compounds that can leach through the soil and contaminate groundwater, as well as reduce soil fertility and inhibit plant growth.
• Water pollution: This can occur through spills or leaks of contaminated liquids that affect surface water bodies, deteriorating aquatic life and the quality of drinking water, as well as persistent organic compounds that contaminate aquifer sources.
• Air pollution: Emissions of volatile organic compounds (VOCs) during waste handling and disposal contribute to the formation of tropospheric ozone, while the combustion of certain wastes can release greenhouse gases, exacerbating climate change.
• Impacts on biodiversity: Soil and water contamination destroys natural habitats due to direct toxicity to wildlife, which can result in disease and death.
• Fire hazards: Hydrocarbon residues are highly flammable. Improper handling would increase the risk of fires and explosions, with serious consequences for the environment.

These impacts highlight the importance of maintaining control over the management of polluting and hazardous waste, identifying and mitigating the aspects that can generate risks, including effective measures for containment, treatment, and proper disposal.

Traditional and new methods of storage tank waste management

Waste management methods for fuel storage tanks can be classified as either traditional or new, based on their prevalence and adoption in the industry over time:

Traditional methods

• Solidification/stabilization: A technique used to encapsulate contaminants present in solid waste contaminated with hydrocarbons; it is a technique used to reduce the mobility and toxicity of the contaminants, therefore, leaching of the waste.
• Wastewater treatment: Contaminated water generated in tank cleaning and spill processes is treated by physical, chemical, and biological processes to remove contaminants prior to discharge into sewage systems or reuse. These processes include sedimentation, filtration, biological treatment, and reverse osmosis.
• Incineration: Subjecting hazardous and non-hazardous waste to incineration allows total destruction of organic compounds and reduction of waste volume, although it must be handled carefully to avoid the emission of dioxins and other pollutants.
• Storage or disposal: refers to the intermediate phase where waste that cannot be treated or disposed of immediately is safely stored until it is properly processed.
• Final disposal in authorized facilities: This is the final step in industrial waste management, where treated waste is sent to specifically designed and regulated facilities for safe disposal, such as specialized landfills or hazardous waste treatment plants.

New methods

• Advanced mobile systems²: Recently, mobile systems have been developed to recover residues during storage tank cleaning, simplifying and automating the process. These systems reduce pollutant emissions, water and solvent use, and minimize the need for direct human access to the tanks. The recovered sludge is efficiently separated into solids, water, and oil; the oil is reintegrated into production, the water is reused, and the solids are sent to landfills, reducing waste sent to landfills and reducing environmental pollution.

The following video shows the most technologically advanced process in the field of automatic tank cleaning services, achieving crude oil recovery by separating the sludge by 70%. Source: Dominion.

Automatic tank cleaning services with crude oil recovery.

• Bioremediation: This method uses microorganisms to degrade contaminants present in solid waste, helping to reduce the amount of contaminants prior to the final disposal of the waste.
• Reuse and recycling: Solid wastes contaminated with hydrocarbons are processed to extract useful materials or convert them into energy, thus minimizing the need for final disposal. This method is sustainable because it takes advantage of waste residues and spills, recycling or reusing them for other purposes, marking a modern practice in waste management¹.

All processes used are intended to minimize present and future environmental damage. These pollutants must be treated to ensure safety, preserve natural resources, and maintain the health of ecosystems.

Integrated approach to waste management in storage tanks

This type of waste management must consider a complete cycle from generation to final disposal. This includes implementing preventive measures that minimize generation, optimize tank cleaning processes, select the most appropriate treatment, and promote reuse and recycling¹.

The active participation of all personnel, from operators to regulators, is a strategic point. In addition, continuous training in safety and environmental management ensures that all those involved in management act responsibly, promoting a safe and sustainable work environment.

Conclusions

Optimal waste management in storage tanks is a differentiating factor in the industry, allowing compliance with environmental regulations that prevent contamination of ecosystems, protect human health, and reduce risks and operating costs. Accurate classification and proper treatment of waste, such as sludge and contaminated water, is the first step in selecting the most appropriate treatment. Precise actions combining prevention, treatment, and final disposal in authorized facilities ensure sustainable management of these industrial wastes.

References

1. MISSOURI. DEPARTAMENT OF NATURAL RESOURCES. Management of Petroleum Storage Tank Wastes. Retrieved August 8, 2024 from https://dnr.mo.gov/document-search/management-petroleum-storage-tank-wastes-pub2040/pub2040
2. DAMINION. Limpieza Automática de Tanques. Accessed on August 12, 2024 from https://www.dominion-global.com/es/areas-de-actividad/industria/servicios-ambientales/limpieza-automatica-de-tanques