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Water purification is the process of removing undesirable chemical and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water) but water purification may also be designed for a variety of other purposes, including to meet the requirements of medical, pharmacology, chemical and industrial applications. In general the methods used include physical process such as filtration and sedimentation, biological processes such as slow sand filters or activated sludge, chemical process such as flocculation and chlorination and the use of electromagnetic radiation such as ultraviolet light.

The purification process of water may reduce the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, fungi; and a range of dissolved and particulate material derived from the minerals that water may have made contacted after falling as rain.

The standards for drinking water quality are typically set by Governments or by international standards. These standards will typically set minimum and maximum concentrations of contaminants for the use that is to be made of the water.

It is not possible to tell whether water is of an appropriate quality by visual examination. Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all the possible contaminants that may be present in water from an unknown source. Even natural spring water - considered safe for all practical purposes in the 1800s - must now be tested before determining what kind of treatment, if any, is needed. Chemical analysis, while expensive, is the only way to obtain the information necessary for deciding on the appropriate method of purification.

According to a 2007 World Health Organization report, 1.1 billion people lack access to an improved drinking water supply, 88 % of the 4 billion annual cases of diarrheal disease are attributed to unsafe water and inadequate sanitation and hygiene, and 1.8 million people die from diarrheal diseases each year. The WHO estimates that 94 % of these diarrheal cases are preventable through modifications to the environment, including access to safe water. Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, and storing it in safe containers could save a huge number of lives each year.

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Environmental Engineering Science (EES) is a multidisciplinary field of engineering that combines the biological, chemical and physical sciences with the field of engineering. This major traditionally requires the student to take many basic engineering classes in fields such as thermodynamics, advanced math, computer modeling and simulation as well as technical classes in subjects such as statics, mechanics, hydrology, and fluid dynamics. As the student progresses, the upper division elective classes define a specific field of study for the student with a choice in a wide range of science, technology and engineering related classes:

In chemical engineering and related fields, a unit operation is a basic step in a process. For example in milk processing, homogenization, pasteurization, chilling, and packaging are each unit operations which are connected to create the overall process. A process may have many unit operations to obtain the desired product.

Historically, the different chemical industries were regarded as different industrial processes and with different principles. Chemical engineering unit operations consist of five classes:

Fluid flow processes, including fluids transportation, filtration, solids fluidization;

Heat transfer processes, including evaporation, condensation

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Rubber

The Part Played by Rubber in Modern Life. – Rubber is indispensable to modern civilization. Its importance in every form of transport for tyres and tubes is self-evident. In its other applications it plays equally important roles. About 80 per cent of all rubber is used in the motor industry, a large proportion of the remainder going into such articles as belting, packings, hose, and innumerable other types of products. Most of these articles are absolutely vital to the operation of the industry in general. A large quantity of rubber is made into rubber footwear and rubberised fabrics. Rubber has been in use for well over a century. But its really important and large-scale application runs parallel with the development of the motor-car.

Historical. – Rubber trees are native to many parts of Africa and the Far East, but there is no record of rubber or the trees that produce it prior to the discovery of America.

By the end of the eighteenth century the general properties of rubber were known to scientists throughout Europe. In the 19th century Charles Macintosh discovered that naphtha, one of the by-products from gas manufacture, was an excellent solvent for rubber.

In 1823 Macintosh patented his discovery. The original process was for the manufacture of what came later to be known as double-texture fabric. A “sandwich” was made with cotton or other fabric on the outside and a ‘‘filling” of rubber which had been deposited from solution. This method, still in use, has the advantage that the cloth protects the rubber.