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1) bacteriological examination
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1) bacteriological examination
a) Coli-index: The number of non pathogenic intestinal bacteria in one liter of water, e. g. centralized water not more than 3, local water not more than 10.
b) Coli-titer: the minimum quantity of water in which there is one intestinal bacteria. In rural area not less than 100 ml. In centralized water not less than 300 ml.
c) Total count of bacteria in I ml (e. g. centralized water not more than 100, local water 300-400).
2) chemical examination:
There should not a high level of chemical constituent in quantities which cause a health hazard (sanitary standard of safety limits of the elements).
a) fluoride: Trace element which is involved in the process of ossification a high level (normal 0, 7 - 1, 5 mg/liter) predisposes to dental and skeletal fluorosis, (Fluorosis, Disease resulting from the excessive intake of fluoride causing hypercalcification accompanied by various bone disorders and paralysis), a low content is associated with dental caries.
b) Methemaeglobinemia: is caused by high concentration of NO3 (nitrates) in water when consumed by infants under six months of age those who are on artificial feeding (this reaction does not occur in older children or adults).
c) The absence of dissolved iodides in water is usually accompanied by relatively high endemic index of goiter in the locality
3) physical:
Transparency. (Ground waters are normally clear due to the filtering action of the soil it passes through). b) Colour - Colour is Caused by foreign material in solution or colloidal state.
c) Temperature (water having a temperature between 10°C and 15°C is most palatable).
d) High concentration of calcium and magnesium carbonate and bicarbonate cause hardness.
d) Test and odour - they can be caused by foreign mittens as organic compound, inorganic salts or dissolved gasses.
Exercise
Write your conclusion about the quality of sample of pi water after bacteriological, chemical and physical examinations. Compare it with sanitary standards tables.
1. Transparency 30cm
2. Colour 2 units
3. Solids 237 mg/l
4. Hardness 4, 3 mg eq/1
5. Coli-titer 200ml
6. Chloride 333mgA
7. Flourid I mg/l
8. Nitrate 7mg/l
LOCAL WATER IN RURAL AREA
A. self purification of streams
1. physical factors: a) dilution of matter in the water; b) currents of the waste; c) sedimentation of solid parts; d) sunlight as a disinfectant.
2. Chemical factors: oxygenation of organic matter
3. Biological factors: bacterial treatment
В. hardness of water
Causes: calcium and magnesium bicarbonate or calcium and magnesium sulphate.
Disadvantages: a) unpalatable tests; b) increase of soap consumption; c) unsuitable for boiler use; d) causing gastrointestinal troubles; e) they are corrosive to tubes and boilers; f) spoil the colour of cooked food.
Method of softening: water softening by using lime, boiling or using washing soda.
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Wells: these are artificial holes or pits dug in the ground to reach the underground water course.
Types of wells
1. Shallow wells
a) dug wells: 30m deep and Ш more than I m diameter;
b) driven wells:
5-8 cent, diameter.
2. Deep wells: artesian well mote than 30 m deep.
Protection of wells:
- platform must be built at least One foot above the and I m around the well (sloping) surface
- well-tube made of cement and brick top of well should be covered up
- washing and bathing should not be done near the well
- disinfection of the well must take place after construction. with 5% of chlorine solution,
- 50 m away from the source of contamination
Protection zones of water supply's
a) The zone of strict regime around the well or station (a control the sanitary situation in this area, periodical medical examination of the stuff in the station).
b) The zone of restriction about 10 km up to the station and about 200m after the station to prohibit any water pollution, and about 100m around the well in rural area.
Exercise
• types of wells?
• the construction and protection of shallow well?
• write your conclusion about the quality of water from well.
Transparency - 25cm
Solids - 700 mg/1
Hardness - 10, 2 mg/1
Coli-index - 20
Fluoride0, 2 mg/1
Nitrate - 0, 3 mg/1
Chloride - 500 mgA
Iron - 0, 5 mg/1
Sulphate - 500 mg/l
PURIFICATION OF WATER
Water has to be treated before use and it must be; confirm the sanitary standard.
Purification is done to make the water safe an to remove any trace, of contamination that may give rise to disease.
Methods of purification
The main methods Special methods
1. Plain sedimentation(storage), . 1, Softening juods
2. Coagulation 2. Defluoridation
3. Radioactive material remove
3. Filtration
4. Disinfecting:
a) physical method:
1) Boiling
2) Ultraviolet rays (short waves)
3) Ultra sonic waves
b) chemical methods
1) Chlorinazation;
2) Ozonization
1. Plain sedimentation: it is a process of gravity settling and deposition of comparatively heavy suspended material in water. Period ranging from few hours to few days.
2. Coagulation: it is the process of forming flocculent in raw water by the addition of a chemical coagulant as aluminum sulfates. The process of coagulation takes place in three successive tanks:
• flash Mixing tank where coagulant is added
• flocculation tank:
•the settling tank, period: 1-3 hours.
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3. Filtration: is the process of removing suspended matter from water the degree of removal depends on the characters and size of the filter media, the thickness of the bed, and the size and quantity of the suspended solids (the Filter beds are made of fine sand and gravel).
4. Types of filters:
• slow sand filters; the speed of water: 0, 3-0, 5 m/h, efficiency: 99%, these filters usualy used in rural area (in villages), it remove the bacteria better than anothers filters because of zoogleal layer.
The size of sand particles in filter is 1-2 mm.
• rapid sand filters: 5-7 m/h, efficiency 85 %. It is less efficient than slow sand filter
• double filters: 15m/h - 75%, usualy used in the cities
Disinfection:
The most important water treatment process is disinfecting, to destroy all pathogenic bacteria or other harmful organisms present in the drinking water. Chlorinization is the most common method which is easy to control, and low cost in addition to its effectiveness.
Chlorine Dose: is the amount of chlorine added to cover all purposes of water disinfecting.
Normal chlorine dosage: 1-5 mg/1
Hyperchlorination: more than 10 mg/1
Chlorine demand: is the amount of chlorine needed to react with, and oxidize the organic matter in water.
Residual chlorine: is the amount of free chlorine remained from the chlorine dose after covering the chlorine demand (0, 3-0, 5 mg/1) for one hour. The disinfecting action of chlorine due to hypochlorous acid.
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