1 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.

2 Water Quality A. Physical Water Quality Parameters §Temperature Rivers - 0 o - 26 o C Lakes - relatively constant (equal to the mean air temperature) Bulgarian State Standards (BSS) - 6 o - 12 o 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 K 2 PtCl 6 and CoCl 2 in H 2 SO 4 ) Roubliov’s scale (solution of K 2 CrO 2 and CoSO 4 ), [degree];For natural waters ; For drinking water < 30 degree according to the BSS

3 Water Quality §Taste Salty, sweet, bitter, sour (no any taste is permissible in drinking water) §Smell Aromatic (pleasant), hydrosulfuric (H 2 S), phenolic, marsh, chloric (Cl 2 ); 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)

4 Water Quality §Hardness It is due to presence of Ca 2+ and Mg + salts of carbonic acid (temporal hardness) and/or Ca 2+ and Mg + salts of strong acids (permanent hardness) Measures - mg-equiv./l, degree (German, French and English); 1 o Germ. = 10 mg/l CaO According to the BSS, hardness > 25 o Germ. is not permissible for drinking water §Alkalinity It is due to presence of HCO 3 -, CO 3 2-, K 2 SO 4, Na 2 SO 4,KCl, NaCl §pH (active reaction) H 2 O  H + + OH - [H+] = mol/l - neutral pH = -log[H + ] = -log(10 -7 ) = 7 - neutral active reaction

5 Water Quality §Oxidability Measure - the mass of KMnO 4, necessary for oxidation of the organic substances in a unit water volume, [mg/l] Standard limit - 2,6 [mg/l] §Content of Fe 2+ and Mn + In groundwater Fe 2+ and Mn + are usually in the form of Fe(HCO 3 ) 2 and Fe(HCO 3 ) 2, respectively On the surface: 4Fe(HCO 3 ) 2 +O 2 + 2H 2 O = 4Fe(OH) 3 + 8CO 2 4MnHCO 3 + O 2 + 2H 2 O = 4MnOH  + 4HCO 3 2- 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 4HCO 3 2-  CO CO 2 + H 2 O The above balance depends strongly on pH value

6 Water Quality §Dissolved gases CO 2 presents in natural water at pH < 8,3 O 2 concentration depends on water temperature and atmospheric pressure H 2 S (and/or its ions HS - and S 2- in ratio, depending on pH and temperature) present in some groundwater

7 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

8 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 intakeWater 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

9 Water Supply Sources Peculiarities B. Surface Waters: Lakes and Reservoirs §Stratification in depth I zone (0 - 4 m) - higher temperature and pollution, low O 2 concentration, plankton development II zone (under 4 m) - lower temperature (1 o C decrease in every 1 m depth), highest O 2 concentration III zone (above the bottom) - lowest temperature and O 2 concentration, high H 2 S, Fe 2+ 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)

10 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 g/l dry residuals §Average mineral water g/l dry residuals §Mineral water g/l dry residuals §Strong mineral water - above 50 g/l dry residuals II. According to the temperature §Very cold water - about 4 o C §Cold water - 4 o - 20 o C §Hot water - 20 o -37 o C §Warm water - 37 o - 42 o C §Very warm water - 42 o o C

11 Water Supply Sources Peculiarities III. According to the hydrogeological conditions §Shallow aquifer (water-bearing stratum) -less than 10 m §Deep ( m) non-pressurised aquifer - over impervious layer (clay) §Deep ( 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