waste productbiology
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excretory systems
( in excretion: Types of waste: metabolic and nonmetabolic )
Waste products may be categorized as metabolic or nonmetabolic. The difference lies in whether the substances in question are produced by the chemical processes of a living cell or are merely passed through the digestive tract of an organism without actually entering into its life processes.
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business logistics logistics
A firm’s waste materials must be positively managed. The firm attempts to both sell them at a profit and follow environmentally sound practices. The key to many recycling efforts is to have scrap and waste materials properly sorted, so that they can be sold to various processors who specialize in recycling glass, plastics, and metals. The public is becoming increasingly concerned about each...
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excretory systems excretion
Waste products may be categorized as metabolic or nonmetabolic. The difference lies in whether the substances in question are produced by the chemical processes of a living cell or are merely passed through the digestive tract of an organism without actually entering into its life processes.
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extraction of salts mining
Increasing attention has been devoted to the extraction of salts from brines discharged as effluent after the distillation of fresh water from seawater. By using these brines for the extraction of minerals, several important advantages are gained. First, the cost of pumping is carried by the conversion plant; second, the brine temperature is relatively high, which aids in evaporation; and,...
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water desalination environmental works
Desalination produces fresh water but also a significant volume of waste effluent, called brine. Since the primary pollutant in the brine is salt, disposal in the ocean is generally not a problem for facilities located near a coastline. At inland desalination facilities, care must be taken to prevent pollution of groundwater or surface waters. Methods of brine disposal include dilution,...
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- Waste News
- Web component of publication from Akron, Ohio, U.S., covering the waste recycling and disposal industry. Offers business news, links to resources, directories of products and services, and information on career opportunities. Texts available through subscription.
the process by which animals rid themselves of waste products and of the nitrogenous by-products of metabolism. Through excretion organisms control osmotic pressure—the balance between inorganic ions and water—and maintain acid-base balance. The process thus promotes homeostasis, the constancy of the organism’s internal environment.
Every organism, from the smallest protist to the largest mammal, must rid itself of the potentially harmful by-products of its own vital activities. This process in living things is called elimination, which may be considered to encompass all of the various mechanisms and processes by which life forms dispose of or throw off waste products, toxic substances, and dead portions of the organism. The nature of the process and of the specialized structures developed for waste disposal vary greatly with the size and complexity of the organism.
Four terms are commonly associated with waste-disposal processes and are often used interchangeably, though not always correctly: excretion, secretion, egestion, and elimination.
Excretion is a general term referring to the separation and throwing off of waste materials or toxic substances from the cells and tissues of a plant or animal.
The separation, elaboration, and elimination of certain products arising from cellular functions in multicellular organisms is called secretion. Though these substances may be a waste product of the cell producing them, they are frequently useful to other cells of the organism. Examples of secretions are the digestive enzymes produced by intestinal and pancreatic tissue cells of vertebrate animals, the hormones synthesized by specialized glandular cells of plants and animals, and sweat secreted by glandular cells in the skins of some mammals. Secretion implies that the chemical compounds being secreted were synthesized by specialized cells and that they are of...
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