Waste treatment
Waste treatment refers to the processing of waste materials to alter their physical, chemical, or biological composition, aiming to concentrate or neutralize potentially harmful substances. As the volume of waste generated continues to rise, particularly due to industrialization, effective waste treatment has become critical for protecting the environment and conserving landfill space. Improper waste disposal can lead to significant environmental issues, as excess waste can overwhelm natural systems that manage air, water, and land resources.
Waste can be categorized into various types, including organic, inorganic, hazardous, and more, each requiring tailored treatment approaches. The primary methods of waste treatment fall into three categories: physical, chemical, and biological. Physical methods typically focus on reducing volume and separating components, while chemical processes aim to detoxify or neutralize hazardous properties. Biological treatment utilizes microorganisms to break down organic materials.
A wide range of specific processes exists within these categories, such as sedimentation, incineration, and anaerobic digestion, each designed to address different characteristics of waste effectively. Ultimately, the choice of treatment method depends on the waste's nature, regulatory standards, and the intended disposal outcomes, highlighting the complexity and importance of waste management practices in safeguarding environmental health.
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Waste treatment
DEFINITION: Processing that alters the physical, chemical, or biological composition of waste in order to concentrate or neutralize it
Given the potential environmental hazards posed by improper disposal of wastes and the ever-increasing problem of lack of sufficient landfill space, the need for cost-efficient and effective methods of waste treatment is widely recognized.
Rapid advances in technology and industrialization have resulted in the of increased quantities of wastes into the environment. Adverse environmental effects develop if the concentrations of wastes exceed the natural capacity of air, water, and land systems to assimilate them. In the United States, where control is exercised by the federal government, virtually all of the environmental control legislation has been written and passed since the end of World War II, when dramatic increases in urban and industrialization occurred.
The principal wastes associated with industrial and municipal facilities can be categorized as and inorganic, solid (suspended and dissolved), acid and base, and hazardous. Organic wastes are oxygen-demanding and lower the amount of dissolved oxygen in the receiving waters. Suspended solids settle and cause benthic deposits. Acid and base wastes destroy natural buffers, and acid rain has the potential to have devastating impacts on aquatic life and forests. Hazardous wastes—which include explosive, flammable, volatile, radioactive, toxic, and pathological wastes—can cause serious damage to people or property. The storage, collection, transportation, treatment, and disposal of such wastes require special caution.
Waste treatment processes can generally be divided into three categories: physical, chemical, and biological. Physical treatment is used to concentrate wastes, reduce volume, and separate different components for further treatment or disposal. Chemical treatment is used to precipitate, detoxify, or destroy the hazardous properties of wastes. Biological treatment utilizes microorganisms to stabilize organic wastes.
The degree of treatment required for any stream depends on the characteristics of the waste, the maximum discharge limit, and the final disposal requirements imposed by regulatory agencies. Waste treatment facilities utilize a number of processes to achieve the desired degree of treatment. More than twenty types of physical treatment processes—also called unit operations—are commonly used for handling wastes.
Removal of wastes is achieved by physical forces. Common examples of physical treatment processes are sedimentation, centrifugation, flotation, evaporation, drying, distillation, stripping, carbon adsorption, exchange, membrane processing, freeze crystallization, and solidification. Sedimentation, centrifugation, and flotation processes are typically used to remove suspended solids. Evaporation, drying, and distillation are utilized to concentrate wastes. Stripping removes ammonia and volatile organic compounds. Carbon and resin is used for removal of organic solute from waste streams. Their applications include separation or removal of phenols, fats, colors, pesticides, carcinogens, and chlorinated hydrocarbons. Membrane processes such as reverse osmosis, ultrafiltration, and electrodialysis utilize synthetic membranes to concentrate industrial and hazardous wastes; such processes are also used in the desalination of brackish water. In freeze crystallization, the is cooled so that pure water (in the form of ice crystals or solid ice) can be separated from the contaminants, which concentrate in liquid. Solidification is the transformation of into a nonhazardous solid product through fixation or encapsulation.
Chemical processes are used for the treatment of industrial wastes, usually in conjunction with other methods to achieve desired end results. Common processes used for waste treatment include neutralization, oxidation, reduction, precipitation, hydrolysis, catalysis, chlorinolysis, electrolysis, photolysis, and incineration. Neutralization is adjustment of level through the introduction of either acids or bases. This process has wide application in the treatment of wastes from many industries. Oxidation is used mainly for detoxification of hazardous wastes. Chlorine, ozone, hydrogen peroxide, and potassium permanganate are excellent oxidizing agents often used in the presence of ultraviolet light. Reduction is achieved through the use of a reducing agent such as sulfur dioxide. As an example, hexavalent chromium, a very toxic substance, is reduced to trivalent chromium, which is much less toxic, and then precipitated. Hydrolysis, catalysis, chlorinolysis, electrolysis, and photolysis are destructive processes used to break chemical bonds. Incineration is the thermal destruction of hazardous organic wastes.
Biological waste treatment processes involve reactions that take place in or around microorganisms. Generally, organic compounds are decomposed in suspended or attached growth reactors. The most common biological waste treatment processes use biological reactors to stabilize organic matter, followed by the separation of solids and liquid. The waste solids, referred to as sludge, are combined with other solids and treated separately. Anaerobic is used for of sludge and high-strength wastes. With proper controls, biological waste treatment processes are reliable and environmentally sound; no chemicals are added to the wastes, and operational costs are relatively low.
Bibliography
Chiras, Daniel D. “Hazardous and Solid Wastes: Sustainable Solutions.” In Environmental Science. 8th ed. Sudbury, Mass.: Jones and Bartlett, 2010.
LaGrega, Michael D., Philip L. Buckingham, and Jeffrey C. Evans. Hazardous Waste Management. 2d ed. New York: McGraw-Hill, 2001.
Manahan, Stanley E. Fundamentals of Environmental Chemistry. 3d ed. Boca Raton, Fla.: CRC Press, 2009.
Sanito, Raynard Christianson. "A Review on Medical Waste Treatment in COVID-19 Pandemics: Technologies, Managements, and Future Strategies." Journal of the Air and Waste Management Association, vol. 74, no. 2, 30 Jan. 2024, pp. 72-99, doi.org/10.1080/10962247.2023.2282011. Accessed 24 July 2024.
Silva, Jorge Alejandro. "Wastewater Treatment and Reuse for Sustainable Water Resources and Management: A Systematic Literature Review." Sustainability, vol. 15, no. 14, 12 July 2023, p. 10940, doi.org/10.3390/su151410940. Accessed 24 July 2024.