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03 August 2011

Water Quality - Physical, Biological, Chemical & Radiological Characteristics




PAUL HAY Capital Projects



Topic:            Water Quality
Author:          Paul Hay
e-mail:            paul.hay@phcjam.com
profile:           www.linkedin.com/in/phcjam


1.0       INTRODUCTION           


1.1            Precipitation typically has few impurities, almost no bacterial content, and minimal amounts of minerals and gases;

1.2       Pollutants affect the physical, biological, chemical and radiological characteristics of water:
            1.2.1   Precipitation may be contaminated with physical pollutants from the catching surfaces;
            1.2.2   Ground water is susceptible to chemical alteration in percolation;

1.3       The designer’s task is to specify water quality appropriate to its task; but

1.4       Reliability and dependability should be primary concerns in the choice of potable water supply (i.e. cost is secondary).


2.0       PHYSICAL CHARACTERISTICS

2.1       Turbidity is visible and therefore undesirable:
            2.1.1   Turbidity is the  result of suspended particles which can be either (a) inorganic, as clay, silt, etc., or (b) organic, as plankton;
            2.2.2   Health may not be adversely affected.

2.2       Colour is similarly undesirable because of its visibility:
            2.2.1   Colour results from micro-organisms or dissolved materials that can be (a) inorganic, as iron, or (b) organic, as decayed vegetation;
            2.2.2   Health may not be adversely affected.

2.3       Taste and Odor results from (a) inorganic salts, (b) dissolved gases and (c) organic compounds.

2.4       Water is generally preferred at temperature ranges between 10 deg. C and 16 deg. C.

2.5       Foamability usually indicates concentration of detergents:
            2.5.1   Drinking water should be promptly investigated;
            2.5.2   Foaming may indicate dangerous pollutants associated with domestic waste;
            2.5.3   Modern detergents are not bio-degradable under anaerobic conditions as exists in some septic-tank drainage fields.


3.0       BIOLOGICAL CHARACTERISTICS

3.1       Biological contamination results from disease-producing organisms as (a) bacteria, (b) protozoa, and (c) viruses.

3.2       Organisms and by-products are readily destroyed at treatment plants:
            3.2.1   Biological water tests are complex and time consuming;
            3.2.2   The coliform group of bacteria (a) outnumbers other disease-producing organisms in water; and (b) is always present in fecal wastes of humans, many animals and birds.

3.3       Human settlement should be kept away from water-sheds.

3.4       Water should be stored in the dark at low temperatures.


4.0       CHEMICAL CHARACTERISTICS

4.1       pH value is the measure of (a) hydrogen ion concentration in water, as well as (b) acidity and (c) alkalinity:
            4.1.1   pH value is initially tested to determine the need for (a) corrosion control, (b) disinfection, and (c) chemical doses;
            4.1.2   In nature, the pH values of water can range between 0 and 14:
                        4.1.2.1 A pH value of 7 is neutral;
                        4.1.2.2 pH values lower than 7 indicates (a) acidity and (b) corrosiveness;
                        4.1.2.3 pH higher than 7 indicates alkalinity.

4.2       Alkalinity indicates the levels of bicarbonate, carbonate or hydroxide components.

4.3       Hardness indicates the level of calcium and magnesium salts:
            4.3.1   “Hard” water (a) inhibits cleaning action of detergents and (b) deposits scale on hot-water pipes and cooking utensils, as kettles;
            4.3.2   Temporary hardness is removed when water is heated; but not permanent hardness.

4.4       Toxic chemicals include: arsenic, barium, cadmium, chromium, cyanides, fluoride, lead, selenium, and silver.

4.5       Other chemicals of concern are: chlorides, copper, iron, manganese, nitrates, pesticides, sodium sulfates, and zinc.


5.0       RADIOLOGICAL CHARACTERISTICS: Radiological contamination results from the mining and the use of radio-active materials.




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FURTHER READING

Mechanical and Electrical Equipment for Buildings, Benjamin Stein & John S. Reynolds, John Wiley & Sons Inc., U.S.A.
Construction Materials & Processes, Don G. Watson, McGraw-Hill Book Co., USA.

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