MOD 3: Water Treatment Methods Flashcards
This process can be employed to remove some suspended matter from water by allowing time and
inactivity of water to do the work of sorting out heavier suspended particles. Heavy suspended materials settle at the bottom of vessels thereby rendering water clear or non-turbid.
Sedimentation
In this process a chemical namely alum (hydrated aluminum sulfate) is added to turbulent water. This process removes suspended matter, along with some coloration.
Coagulation
surface of the water is exposed to
air as much as possible. This process can improve the taste and color of water, remove iron and manganese, and decrease its corrosiveness. The
possibilities for this method are varied in its aesthetic
applications such as spraying water into air, water
cascading into a spillway, flowforms or sculptural waterfalls designed to carry water in a rhythmic, pulsating pattern
Aeration (oxidation)
a powerful oxidizing and disinfecting method used to destroy bacteria, viruses and other pathogenic organisms. This is done by passing dry air (or pure oxygen) through a system of high voltage electrodes to produce ozone where 80% of the energy is converted into heat. Bacteria, viruses or any other pathogenic organisms that are directly exposed to ozone is eradicated. This has a very wide range of treatment options.
Ozonation
This common means of water treatment can remove some suspended particles, some bacteria,
and some color.
Filtration
generally used in rainwater application. This is a low maintenance
method and can easily be constructed. Devices used in this method should be cleaned as often as
possible depending on the degree of turbidity of water. It can be cleaned by the removal of filters,
which are either washed for reuse or may be discarded. (Filtration method)
Slow sand filtration
uses pressure to force water out of a containment vessel such as tank. Sand is used as a filtering agent. Periodic cleaning is required as dirt
accumulates over time and with the constant passage of turbid water. It may require the removal of sand filter or backwashing as a
method of cleaning filters. This system of water filtration is commonly used in swimming pool application.
Pressure sand filtration
uses a filter obtained from diatomite, a naturally occurring siliceous sedimentary rock that easily crumbles into fine powder that is used as a filter agent. This agent filters out particles of bigger
size than the filter itself thus retaining suspended particles in a tank or containment vessel. The
resulting product is a clean and dirt-free water.
Diatomaceous earth filtration
This kind of filter consists of a permeable porcelain unglazed tube called bisque that contains a ring of enameled porcelain through which water flows and filtered in the process. This is usually produced in small sizes for ready attachment to water faucets.
Porous Stone, Ceramic or Unglazed
Porcelain Filters (Pasteur Filters)
This method of filtration is a combined process used in removing iron and/or manganese from water. In this process chlorine chemically oxidizes iron or manganese which creates precipitates. It kills iron bacteria which can form a slimy mass.
Fine filtration by chlorination
granulated carbon which attracts large quantities of dissolved gases,
soluble organics, and fine solids. This works through a process known as
adsorption whereby contaminant molecules are trapped inside the pore structure of the carbon substrate. This is particularly effective in removing undesirable taste and odor in water, commonly used in domestic water purification
Activated carbon filters
A widely used method in removing many types of dissolved or suspended chemical as well as biological contaminants. This method is also used in desalting seawater by reducing the mineral content in water. This uses an inert semipermeable membrane where higher water pressure supply on one side forces water out on the other side through a filtering membrane,
most of the chemicals (dissolved solids) are removed. However, dissolved chemicals remain
Reverse Osmosis (RO)
This is the most important health-related water treatment. Chlorination is considered as the standard approach to removing harmful organisms from water. Other alternatives includes: UV (ultraviolet) light, bromine, iodine, and heat treatment among others. Although chlorine affects the taste and odor of water, it is also effective in removing less desirable tastes and odors
Disinfection
the most widely-used disinfectant in
municipal water systems across most of the world. This has been under scrutiny because of its propensity to form possible carcinogens
(trihalomethanes) upon reaction with naturallyoccurring organic material such as humic acid or
human-made organic effluent.
Chlorine
These compounds result from the reaction of ammonia with chlorine in water solution. They are commonly used in municipal water systems due to the superior stability of this chemical disinfectant compounds over chlorine, however, it
are not as strong as chlorine and thus have less bacteria-killing ability in comparison.
Chloramines
exhibits stronger disinfecting
characteristics than chloramines, but there is little evidence of extensive use of the disinfectant.
Chlorine Dioxide
This common relative of chlorine has been used for years for disinfecting drinking water of unknown quality. Unfortunately, certain kinds of gram-negative bacteria can develop resistance to this chemical.
Iodine
condensation. As the water turns to vapor, virtually all pollutants are left behind. When this purified vapor makes contact with cooler surfaces, it condenses, leaving behind pure water. The resulting water may be flat in terms of taste. This method relies on evaporation to purify water. It effectively removes inorganic compounds such as metals (lead), iron and nitrates. IT also kills microorganisms such as bacteria and some viruses.
Distillation
A major advantage of water from this method is that children who drink this water have lower rates of tooth decay. However, this benefit only
applies to children, not adults, and in amounts
higher than those used in water treatment;
fluoride is toxic and can cause mottle teeth. As
such, while fluoridation units can be installed into small water systems, fluoride levels in the water supply must be carefully monitored.
Fluoridation
Corrosion is defined as the slow degradation of a metal by the flow of an electric current from the metal to its surroundings. It is important to control corrosion in order to keep water systems operating freely and to prevent corrosive water from increasing the concentration of hazardous materials (such as those from copper pipes).
Corrosion control
Some organisms may not be injurious to health but can multiply so rapidly that piping or filters become clogged, or affect the quality of the water’s taste, odor, and appearance. One of the most prevalent nuisances, algae growths, can be usually controlled by the addition of copper sulfate (blue stone or blue vitriol) to the body of water. Cooling towers are an especially difficult problem for water treatment. In order to successfully their water supply successfully, a method for microbial control is used, which removes organics and precipitating organics.
Nuisance control
A mechanism of contaminant removal making use of the adsorption phenomenon, the act of physical adhesion of molecules or colloids to the surface of the medium without chemical reaction. Some
porous materials have the ability
to attract contaminants to their surfaces, thereby removing them from solution.
Adsorption
One means of treating relatively small-scale water supplies is using this method. In this process, the water is exposed to UV radiation after it has been filtered. Only momentary exposure is required to kill bacteria, but these conditions may not be fulfilled if the bacteria are shielded by particles of sediment in the water.
Ultraviolet Irradiation
This procedure is done by heating seawater, then pumping water into a low pressure tank, where the water partially vaporizes. The water vapor is condensed and removed as pure water. This process is then repeated many times. The remaining liquid, called brine, contains a large amount of salt, and is removed and often processed for minerals.
Water desalination
