SPDI: General Information | (Water Treatment, Chemical Disinfectants, Water Sources)

SEDIMENTATION

This process removes some suspended matter from water simply by allowing time and the inactivity of water to do the work of settling out heavier suspended particles.

COAGULATION & FLOCCULATION

This process also removes suspended matter, along with some coloration. A chemical such as alum (hydrated aluminum sulphate), is added to turbulent water.

Coagulation

is the chemical process in which it reacts with the sediment to make it capable of combining into large particles

Flocculation

is the physical process in which the sediment particles collide with each other and stick together

AERATION (OXIDATION)

This process can improve the taste and color of water, remove iron and manganese and decrease corrosiveness. As much of the water surface as possible is exposed to air

OZONATION

This is less esthetic than aeration but more certain oxidation process. It is commonly used in cooling lower treatment and in addition, has a very wide range of treatment applications.

FILTRATION

This very common treatment can remove suspended particles, some bacteria, and some color.

Slow Sand Filters

Used for rainwater application, low maintenance, easily constructed devices that should be cleaned as often as turbidity of water demands.

Pressure Sand Filters

This is rarely used for individual water systems.

Diatomaceous Earth Filters

This can be either vacuum or the pressure type. They require periodic attention to make it effective.

Pasteur Filters

also known as Porous Stone, Ceramic, or Unglazed Porcelain Filters. These are usually made in small sizes so that they can be attached to water faucets.

Fine Filtration

A combined process that removes iron and/or manganese from water. The chlorine chemically oxidizes the iron or manganese, which form precipitates.

Activated Carbon Filters

These are particularly effective for removing tastes and odors. Water is passed through granular carbon, which attracts large quantities of dissolved gases, soluble organics, and finds solids.

Reverse Osmosis

Sometimes used to reduce the mineral content in water An inert, semi-permeable membrane has higher pressure supply water on one side as the pressure slowly forces water through this filtering membrane, most of the minerals (dissolved solids) are removed.

DISINFECTION

This is the most important health-related water treatment.

Chlorine Concentration

The higher the concentration, the faster and more complete the rate of disinfection.

Contact Time

The longer the chlorine contacts the organism in water, the more complete the disinfection.

Water Temperature

The higher the temperature during contact, the more complete the disinfection.

pH

The lower the __, the more effective the disinfection.

CHLORINE

This is the most widely used disinfectant in municipal water system in most parts of the world. Has been under scrutiny because of its propensity to form possible carcinogens (trihalomethanes) upon reaction with naturally occurring organic material such as humic acid. It is readily removed by activated carbon filters, and can be monitored with simple test kits. It is easily rinsed out of the system.

CHLORAMINES

These compounds, resulting from the reaction of ammonia with chlorine in water solution, are commonly used in municipal water supply systems because of its superior stability of compounds over chlorine. However, it is not as strong as chlorine and thus have less ability to kill bacteria.

CHLORINE DIOXIDE

Exhibits stronger disinfecting characteristics than chloramines, but there is little evidence of extensive use of the disinfectant.

IODINE

This common relative of chlorine has been used for years by campers for disinfecting drinking water of unknown quality. Unfortunately, certain gram-negative bacteria can be resistant to this.

OZONE

This powerful chemical, which consists of oxygen in a three-atom form, is used to disinfect some municipal water supply systems. It is very effective bactericide; however, it must be generated on site and has a relative short life. It can be removed by irradation or activated carbon.

DISTILLATION

In this process, water is heated to allow condensation. As the water turns to vapour, virtually all pollutants are left behind. When this vapour encounters cooler surfaces, it condenses, and pure water water although flat in tastes can be collected from this surface.

FLUORIDATION

The advantage of this is that children who drink this water have lower rates of tooth decay. Its advantages are that only children needs it, not adults, and that in amounts above these used in water treatment. It is toxic and can cause mottled teeth.

CORROSION CONTROL

In order to keep water systems operating freely and to prevent corrosive water from increasing the concentration of hazardous materials (as from copper pipes).

Corrosion

It is a slow degradation of a metal by a flow if electric current from the metal to its surroundings.

Acidity

the more acidic (low pH), the more corrosive the water

Conductivity

as dissolved mineral salts increase the water’s ___, they encourage the flow of electrical current of corrosion

Oxygen Content

dissolved ___ destroys the thin protective hydrogen film on immersed metals, thus promoting corrosion.

Carbon Dioxide Content

__ forms carbonic acid which attacks metal surfaces.

Water Temperature

increased temperature increases corrosion

Nuisance Control

algae growths, the most prevalent nuisance, can usually be controlled by applying copper sulphate (blue stone or blue vitriol) to the water body. Cooling towers are an especially difficult water treatment problem. To treat tower water successfully, a method is used for microbial control, removing organics and precipitating organics.

Adsorption

It is a mechanism of contaminant removal making use of the 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.

Ultraviolet Irradiation

It is a method of treating relatively small-scale water supplies. In this process, water is exposed to ultraviolet radiation after it has been filtered. Only momentary exposure is required to kill bacteria, but this condition may not be fulfilled if the bacteria are shielded by particles of sediment in the water

Water Desalinization

The procedure is done by heating seawater and then pumping water into allow pressure tank, where the water partially vaporized. The water vapour is then condensed and removed as pure water. The process is repeated many times. The remaining liquid, called brine, contains a large amount of salt and is removed and often processed for minerals.

GROUNDWATER

The portion of rainwater which has percolated into the earth to form underground deposits called aquifers (water-bearing soil formations).

Wells

are holes in the earth from which a fluid may be withdrawn using manual or mechanical means such as draw bucket, pumo, etc.

Dug Wells

These can be constructed with hand tools or power tools. It can be dug to a depth of about 15 m (50 ft) and can have the greatest diameter that a space may allow.

Driven Wells

These are the simplest and usually the least expensive. A steel drive-well point is fitted on one end of the pipe section and driven into the earth. The point may be driven into the ground to a depth of up to 15 m (50 ft).

Bored Wells

These are dug with earth augers, are usually less than 30 m (100 ft) deep. They are used when the earth to be bored is boulder free and will not cave in. The diameter ranges from 2 to 30 inches. The well is lined with metal, vitrified tile or concrete.

Drilled Wells

These requires more elaborate equipment of several types, depending on the geology of the site. They measure up to 300 m (984 ft)

Percussion Method

also known as cable tool method; involves raising and dropping of a heavy drill bit and stem. Having thus pulverized, the earth being drilled in mixed with water to form slurry, which is periodically removed. As drilling proceeds, a casing is also lowered (except when drilling though rock).

Rotary Drilling Methods

either hydraulic or pneumatic; utilize cutting bit to aid in the removal of particles of earth, which are then brought to the surface. After the drill pipe is withdrawn, a casing is lowered into position.

Down-the-hole Pneumatic Hammer

combines the percussion effect with the rotary drill bit

Jetted Wells

It makes use of a suction pump above, while casing acts as the pump riser

Surface Water

a mixture of surface run-off and groundwater; includes rivers, lakes, ponds, and impounding reservoirs