DRINKING WATER QUALITY PARAMETER
Parameters of water quality
There are three types of water quality parameters physical, chemical, and biological.
Physical parameters of water quality ;
Turbidity
Turbidity is the cloudiness of water . It is a measure of the ability of light to pass through water. It is caused by suspended material such as clay, silt, organic material, plankton, and other particulate materials in water .
Turbidity in drinking water is esthetically unacceptable, which makes the water look unappetizing.
Temperature :
Palatability, viscosity, solubility, odors, and chemical reactions are influenced by temperature . Thereby, the sedimentation and chlorination processes and biological oxygen demand (BOD) are temperature dependent . It also affects the biosorption process of the dissolved heavy metals in water . Most people find water at temperatures of 10–15°C most palatable.
Color :
Materials decayed from organic matter, namely, vegetation and inorganic matter such as soil, stones, and rocks impart color to water, which is objectionable for esthetic reasons, not for health reasons
Taste and odor :
Taste and odor in water can be caused by foreign matter such as organic materials, inorganic compounds, or dissolved gasses . These materials may come from natural, domestic, or agricultural sources.
Solids :
Solids occur in water either in solution or in suspension . These two types of solids can be identified by using a glass fiber filter that the water sample passes through. By definition, the suspended solids are retained on the top of the filter and the dissolved solids pass through the filter with the water
Electrical conductivity (EC) :
The electrical conductivity (EC) of water is a measure of the ability of a solution to carry or conduct an electrical current. Since the electrical current is carried by ions in solution, the conductivity increases as the concentration of ions increases. Therefore, it is one of the main parameters used to determine the suitability of water for irrigation and firefighting
Chemical parameters of water quality ;
pH :
pH is one of the most important parameters of water quality. It is defined as the negative logarithm of the hydrogen ion concentration . It is a dimensionless number indicating the strength of an acidic or a basic solution . Actually, pH of water is a measure of how acidic/basic water is .Acidic water contains extra hydrogen ions (H+) and basic water contains extra hydroxyl (OH−) ions [2
Acidity :
Acidity is the measure of acids in a solution. The acidity of water is its quantitative capacity to neutralize a strong base to a selected pH level. Acidity in water is usually due to carbon dioxide, mineral acids, and hydrolyzed salts such as ferric and aluminum sulfates . Acids can influence many processes such as corrosion, chemical reactions and biological activities .
Alkalinity :
The alkalinity of water is its acid-neutralizing capacity comprised of the total of all titratable bases. The measurement of alkalinity of water is necessary to determine the amount of lime and soda needed for water softening (e.g., for corrosion control in conditioning the boiler feed water). Alkalinity of water is mainly caused by the presence of hydroxide ions (OH−), bicarbonate ions (HCO3−), and carbonate ions (CO32−), or a mixture of two of these ions in water.
Chloride :
Chloride occurs naturally in groundwater, streams, and lakes, but the presence of relatively high chloride concentration in freshwater (about 250 mg/L or more) may indicate wastewater pollution. Chlorides may enter surface water from several sources including chloride-containing rock, agricultural runoff, and wastewater
Chlorine residual :
Chlorine (Cl2) does not occur naturally in water but is added to water and wastewater for disinfection. While chlorine itself is a toxic gas, in dilute aqueous solution, it is not harmful to human health. In drinking water, a residual of about 0.2 mg/L is optimal. The residual concentration which is maintained in the water distribution system ensures good sanitary quality of water .
Sulfate :
Sulfate ions (SO42−) occur in natural water and in wastewater. The high concentration of sulfate in natural water is usually caused by leaching of natural deposits of sodium sulfate (Glauber’s salt) or magnesium sulfate (Epson salt) . If high concentrations are consumed in drinking water, there may be objectionable tastes or unwanted laxative effects [26], but there is no significant danger to public health.
Nitrogen:
There are four forms of nitrogen in water and wastewater: organic nitrogen, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen . If water is contaminated with sewage, most of the nitrogen is in the forms of organic and ammonia, which are transformed by microbes to form nitrites and nitrates Nitrogen in the nitrate form is a basic nutrient to the growth of plants and can be a growth-limiting nutrient factor .
Fluoride :
A moderate amount of fluoride ions (F−) in drinking water contributes to good dental health. About 1.0 mg/L is effective in preventing tooth decay, particularly in children
Copper and zinc :
Copper (Cu) and zinc (Zn) are nontoxic if found in small concentrations . Actually, they are both essential and beneficial for human health and growth of plants and animals . They can cause undesirable tastes in drinking water. At high concentrations, zinc imparts a milky appearance to the water .They are measured by the same methods used for iron and manganese measurements.
Hardness :
Hardness is a term used to express the properties of highly mineralized waters . The dissolved minerals in water cause problems such as scale deposits in hot water pipes and difficulty in producing lather with soap. a
Calcium (Ca2+) and magnesium (Mg2+) ions cause the greatest portion of hardness in naturally occurring waters [9]. They enter water mainly from contact with soil and rock, particularly limestone deposits.
Biochemical oxygen demand (BOD) ;
Bacteria and other microorganisms use organic substances for food. As they metabolize organic material, they consume oxygen . The organics are broken down into simpler compounds, such as CO2 and H2O, and the microbes use the energy released for growth and reproduction .
Bacteria :
Bacteria are considered to be single-celled plants because of their cell structure and the way they ingest food. Bacteria occur in three basic cell shapes: rod-shaped or bacillus, sphere-shaped or coccus, and spiral-shaped or spirellus [19]. In less than 30 min, a single bacterial cell can mature and divide into two new cells .
Algae :
Algae are microscopic plants, which contain photosynthetic pigments, such as chlorophyll . They are autotrophic organisms and support themselves by converting inorganic materials into organic matter by using energy from the sun, during this process they take in carbon dioxide and give off oxygen .
Viruses
Viruses are the smallest biological structures known to contain all genetic information necessary for their own reproduction .They can only be seen by a powerful electronic microscope . Viruses are parasites that need a host to live.
They can pass through filters that do not permit the passage of bacteria.
Protozoa :
Protozoa are single-celled microscopic animal , consume solid organic particles, bacteria, and algae for food, and they are in turn ingested as food by higher level multicellular animals . Aquatic protozoa are floating freely in water and sometimes called zooplankton . They form cysts that are difficult to inactivate by disinfection.
Indicator organisms :
A very important biological indicator of water and pollution is the group of bacteria called coliforms . Pathogenic coliforms always exist in the intestinal system of humans, and millions are excreted with body wastes . Consequently, water that has been recently contaminated with sewage will always contain coliforms.
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