Water Quality General classification of water quality parameters:

1. I. Water Supply Networks and FacilitiesTopic 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 - 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

3. 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)

4. 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); 1oGerm. = 10 mg/l CaO According to the BSS, hardness > 25oGerm. is not permissible for drinking water • Alkalinity It is due to presence of HCO3-, CO32-, K2SO4, Na2SO4,KCl, NaCl • pH (active reaction) H2O  H+ + OH- [H+] = 10-7mol/l - neutral pH = -log[H+] = -log(10-7) = 7 - neutral active reaction

5. 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-  CO32- + CO2 + H2O The above balance depends strongly on pH value

6. 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

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 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

9. 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)

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 - 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

11. 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