Post on 26-Dec-2015
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I. Water Supply Networks and Facilities
Topic I.3. Sources for Water Supply - Surface Waters and Groundwater : Quality and Peculiarities
Water Quality
General classification of water quality parameters: Physical - temperature, transparency, turbidity, colour, smell, taste,
conductivity, suspended solids
Chemical - dry residuals (total, soluble), hardness, alkalinity, pH, oxidability, gas saturation
bacteriological and biological - pathogens, coli-index, coli-test, etc. and hydrobionts, algae, fitoplancton, zooplancton, etc.
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Water Quality
A. Physical Water Quality Parameters
Temperature
Rivers - 0o - 26o C
Lakes - relatively constant (equal to the mean air temperature)
Bulgarian State Standards (BSS) - 6o - 12o C (degree santigrade)
Transparency/Turbidity
Snelen’s type (symbol) - for transparency (30 cm according to the BSS)
Suspended solids concentration, SS (SS < 2 mg/l according to the BSS)
Colour
Platinum-cobalt scale (solution of K2PtCl6 and CoCl2 in H2SO4)
Roubliov’s scale (solution of K2CrO2 and CoSO4), [degree];For natural waters - 10 - 20; For drinking water < 30 degree according to the BSS
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Water Quality
Taste
Salty, sweet, bitter, sour (no any taste is permissible in drinking water)
Smell
Aromatic (pleasant), hydrosulfuric (H2S), phenolic, marsh, chloric (Cl2);
5-grade scale (based on probe dilution) is applicable for smell detection; smell < 2 degree is permissible for drinking water according to the BSS
B. Chemical Water Quality Parameters
Dry residuals (DR)
DR < 1000 mg/l is the standard limit for drinking water accord. to the BSS
Non-organic residuals (NOR)
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Water Quality
Hardness
It is due to presence of Ca2+ and Mg+ salts of carbonic acid (temporal hardness) and/or Ca2+ and Mg+ salts of strong acids (permanent hardness)
Measures - mg-equiv./l, degree (German, French and English); 1o Germ. = 10 mg/l CaO
According to the BSS, hardness > 25o Germ. is not permissible for drinking water
Alkalinity
It is due to presence of HCO3-, CO3
2-, K2SO4, Na2SO4,KCl, NaCl
pH (active reaction)
H2O H+ + OH-
[H+] = 10-7 mol/l - neutral
pH = -log[H+] = -log(10-7) = 7 - neutral active reaction
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Water Quality
Oxidability
Measure - the mass of KMnO4, necessary for oxidation of the organic substances in a unit water volume, [mg/l]
Standard limit - 2,6 [mg/l]
Content of Fe2+ and Mn+
In groundwater Fe2+ and Mn+ are usually in the form of Fe(HCO3)2 and Fe(HCO3)2 , respectively
On the surface: 4Fe(HCO3)2 +O2 + 2H2O = 4Fe(OH)3 + 8CO2
4MnHCO3 + O2 + 2H2O = 4MnOH + 4HCO32-
The Fe(OH)3 and MnOH create a bitter taste and a black colour of water
Standard limits:0,2 mg/l for Fe(OH)3 and 0,1 mg/l for MnOH, respectively
Carbonic acid balance
4HCO32- CO3
2- + CO2 + H2O
The above balance depends strongly on pH value
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Water Quality
Dissolved gases
CO2 presents in natural water at pH < 8,3
O2 concentration depends on water temperature and atmospheric
pressure
H2S (and/or its ions HS- and S2- in ratio, depending on pH and
temperature) present in some groundwater
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Water Quality
C. Bacteriological and biological water quality parameters
Bacterial content
Bacteria general division: pathogens (creating illness); saprophytes (non-
harmful)
Esherihia Coli - a saprophyte, accommodating at the human stomach and
faeces is an indicator for faecal pollution of water
Measures: coli index - number of the coli-bacteria in 1 l water volume;
Standard limit: coli index < 10
Biological content
General division: Fauna - zooplancton (suspended), bentos (sediment),
hydrobionts (attached); Flora - phytoplancton (suspended), algae
(suspended, rooted)
Saprobility (symbioses): polysaprobe, mezosaprobe ( and ) and
oligosaprobe
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Water Supply Sources Peculiarities
A. Surface Waters: Rivers
Source of feeding - atmospheric water and groundwater
Runoff regime - great variety of flowrates and water levels
Water intake Water level security, %
category min max
I 1 97
II 3 95
III 5 90
Water quality - depends on geological, climatic and anthropogenic factors
Erosion and silt regime
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Water Supply Sources Peculiarities
B. Surface Waters: Lakes and Reservoirs
Stratification in depth
I zone (0 - 4 m) - higher temperature and pollution, low O2 concentration, plankton development
II zone (under 4 m) - lower temperature (1o C decrease in every 1 m depth), highest O2 concentration
III zone (above the bottom) - lowest temperature and O2 concentration, high H2S, Fe2+ and Mn+ concentrations
Water quality
It depends on: geological features of the catchment and the lake bottom; anthropogenic impact; evaporation (increasing water salinity), euthrophication (phytoplankton “blooming”).
Silting
(The “dead” volume filling)
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Water Supply Sources Peculiarities
C. Groundwater
General classification:
I. According to the salinity (mineral salts content) Fresh (sweet) water - up to 1 g/l dry residuals Slightly mineral water - 1 - 3 g/l dry residuals Average mineral water - 3 - 10 g/l dry residuals Mineral water - 10 - 50 g/l dry residuals Strong mineral water - above 50 g/l dry residuals
II. According to the temperature Very cold water - about 4o C Cold water - 4o - 20o C Hot water - 20o -37o C Warm water - 37o - 42o C Very warm water - 42o - 100o C
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Water Supply Sources Peculiarities
III. According to the hydrogeological conditions Shallow aquifer (water-bearing stratum) -less than 10 m Deep (10 - 30 m) non-pressurised aquifer - over impervious
layer (clay) Deep (10 - 30 m) pressurised aquifer - between two
impervious layers
IV. According to water location At the river terrace (send, gravel) At the rock cracks Springs - water coming out of pressurised or non-
pressurised aquifers Artesian water - coming out of pressurised aquifer and
with
piesometric head above the ground level