File Name: water and water treatment .zip
Wastewater treatment is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with acceptable impact on the environment, or reused for various purposes called water reclamation.
Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. Worldwide, a combination of coagulation, sedimentation and filtration is the most widely applied water treatment technology, and has been used since the early 20th century. For more information about the disinfection portion of the treatment process, see the Chlorination fact sheet.
When we refer to water purification, it makes little sense to discuss the subject without first identifying the contaminants that we wish to remove from water. Also, the source of the water is of importance.
Our discussion at this point focuses on drinking water. Groundwater sources are of a particular concern, because there are many communities throughout the U. The following are some of the major contaminants that are of concern in water purification applications, as applied to drinking water sources, derived from groundwater.
Heavy metals represent problems in terms of groundwater pollution. The best way to identify their presence is by a lab test of the water or by contacting county health departments. There are concerns of chronic exposure to low levels of heavy metals in drinking water. Turbidity is undesirable for three reasons: aesthetic considerations, solids may contain heavy metals, pathogens or other contaminants, 9 turbidity decreases the effectiveness of water treatment techniques by shielding pathogens from chemical or thermal damage, or in the case of UV ultra violet treatment, absorbing the UV light itself.
Water can be contaminated by a number of organic compounds, such as chloroform, gasoline, pesticides, and herbicides from a variety of industrial and agricultural operations or applications.
These contaminants must be identified in a lab test. It is unlikely groundwater will suddenly become contaminated, unless a quantity of chemicals is allowed to enter a well or penetrating the aquifer. One exception is when the aquifer is located in limestone.
Not only will water flow faster through limestone, but the rock is prone to forming vertical channels or sinkholes that will rapidly allow contamination from surface water. Surface water may show great variations in chemical contamination levels due to differences in rainfall, seasonal crop cultivation, and industrial effluent levels. Also, some hydrocarbons the chlorinated hydrocarbons in particular form a type of contaminant that is especially troublesome.
These include chemicals used in dry cleaning, wood preservation, asphalt operations, machining, and in the production and repair of automobiles, aviation equipment, munitions, and electrical equipment. These substances are heavier than water and they sink quickly into the ground. As with petroleum products, the problems are caused by groundwater dissolving some of the compounds in these volatile substances. These compounds can then move with the groundwater flow.
Except in large cities, drinking water is rarely tested for these contaminants. Disposal of chemicals that have low water solubility and a density greater than water result in the formation of distinct areas of pure residual contamination in soils and groundwater.
Because of their relatively high density, they tend to move downward through soils and groundwater, leaving small amounts along the migratory pathway, until they reach an impermeable layer where they collect in discrete pools. Once the DNAPLs have reached an aquitard they tend to move laterally under the influence of gravity and to slowly dissolve into the groundwater, providing a long-term source for low level contamination of groundwater.
Because of their movement patterns DNAPL contamination is difficult to detect, characterize and remediate. These include protozoa, bacteria, and viruses. Protozoa cysts are the largest pathogens in drinking water, and are responsible for many of the waterborne disease cases in the U. Protozoa cysts range is size from 2 to 15 m a micron is one millionth of a meter , but can squeeze through smaller openings.
In order to insure cyst filtration, filters with a absolute pore size of 1 m or less should be used. The two most common protozoa pathogens are Giardia lamblia Giardia and Cryptosporidium Crypto. Both organisms have caused numerous deaths in recent years in the U. Many deaths were a result of more than one of these conditions.
Neither disease is likely to be fatal to a healthy adult, even if untreated. Outside of the U. This could change during a survival situation. Filtration is a fundamental unit operation that, within the context of this volume, separates suspended particle matter from water.
In a very general sense, the operation is performed for one or both of the following reasons. It can be used for the recovery of valuable products either the suspended solids or the fluid , or it may be applied to purify the liquid stream, thereby improving product quality, or both. Examples of various processes that rely on filtration include adsorption, chromatography, operations involving the flow of suspensions through packed columns, ion exchange, and various reactor engineering applications.
In petroleum engineering, filtration principles are applied to the displacement of oil with gas i. In hydrology, interest is in the movement of trace pollutants in water systems, the purification of water for drinking and irrigation, and to prevent saltwater encroachment into freshwater reservoirs. In soil physics, applications are in the movement of water, nutrients and pollutants into plants.
In biophysics, the subject of flow through a porous media touches upon life processes such as the flow of fluids in the lungs and the kidney. Although there are numerous industry-specific applications of filtration, water treatment has historically and continues to be the largest general application of this unit operation. Your email address will not be published. Table of Contents. Related Books. Leave a Reply Cancel reply Your email address will not be published.
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Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water fit for specific purposes. Most water is purified and disinfected for human consumption drinking water , but water purification may also be carried out for a variety of other purposes, including medical, pharmacological, chemical, and industrial applications. The methods used include physical processes such as filtration , sedimentation , and distillation ; biological processes such as slow sand filters or biologically active carbon ; chemical processes such as flocculation and chlorination ; and the use of electromagnetic radiation such as ultraviolet light. Water purification may reduce the concentration of particulate matter including suspended particles , parasites , bacteria , algae , viruses , and fungi as well as reduce the concentration of a range of dissolved and particulate matter.
Drinking water supplies in the United States are among the safest in the world. However, even in the U. Drinking water sources are subject to contamination and require appropriate treatment to remove disease-causing agents. Public drinking water systems use various methods of water treatment to provide safe drinking water for their communities. Today, the most common steps in water treatment used by community water systems mainly surface water treatment include:. Coagulation and flocculation are often the first steps in water treatment. Chemicals with a positive charge are added to the water.
A water treatment plant employs many individual treatment processes (sometimes called unit processes and unit operations) that are linked in a process train to.
The use of conventional water and wastewater treatment processes becomes increasingly challenged with the identification of more and more contaminants, rapid growth of population and industrial activities, and diminishing availability of water resources. Three emerging treatment technologies, including membrane filtration, advanced oxidation processes AOPs , and UV irradiation, hold great promise to provide alternatives for better protection of public health and the environment and thus are reviewed in this paper. The emphasis was placed on their basic principles, main applications, and new developments. Advantages and disadvantages of these technologies are compared to highlight their current limitations and future research needs. It can be concluded that, along with the growing knowledge and the advances in manufacturing industry, the applications of these technologies will be increased at an unprecedented scale.
Most industries are thirsty and consume a lot of water. We provide extensive coverage of energy-efficient and reliable pumping, mixing, and aeration solutions for all industrial water treatment processes. Water is used for the main industrial processes, and also for washing, cooling, heating, boiler feed, firefighting, rinsing, and for many other purposes. Prior to using this water, it has to be treated to make it cleaner, potable, or ultra-pure.
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This is followed by an overview of the different treatment processes commonly used for water treatment and the processing of residuals.Reply