| Popis: |
Za pridobivanje pitne vode iz studenčnice se lahko uporablja proces reverzne osmoze. Podzemne vode, kamor po večini uvrščamo studenčne vode, so bogate z raztopljenimi minerali ter posledično vsebujejo veliko kalcijevih in magnezijevih hidrogenkarbonatov, ki povzročajo trdoto vode. V procesih s povišanim tlakom ali temperaturo kot je reverzna osmoza, se skupaj s suspendiranimi delci kot je SiO2 obarjajo ter mašijo membrane. Rešitev tega problema so različni postopki predobdelave, ki problematične snovi odstranijo oziroma dovolj zmanjšajo. V diplomski nalogi smo iskali primerno metodo, da bi čim bolj zmanjšali vsebnost kalcijevih in magnezijevih hidrogenkarbonatov ter silicijevega dioksida, ki je prav tako prisoten v uporabljeni studenčni vodi. Preizkusili smo različne postopke obdelave te vode, pri katerih smo za večjo učinkovitost med samimi postopki višali temperaturo in pH vrednost. Uporabljene metode so bile mehčanje z apnom, koagulacija ter njuna kombinacija. Pri koagulaciji smo uporabili dva koagulanta, in sicer PACl ter Al2(SO4)3. Vzorčeni vodi smo pred in po obdelavi določali: SiO2, celokupno, karbonatno, kalcijevo, magnezijevo in nekarbonatno trdoto motnost, pH, elektroprevodnost, temperaturo, skupne raztopljene snovi (TDS), železo, zeta potencial ter velikost delcev. Rezultati so pokazali, da je najučinkovitejša metoda bilo mehčanje z apnom pri temperaturi med 58 °C in 60 °C in pH 10, ki smo ga dosegli z dodatkom NaOH. Precej učinkovita je bila tudi koagulacija s PACl in apnom pri enakem temperaturnem območju. Pri tem se je sicer odstranilo veliko SiO2 vendar precej manj trdote. One of the ways of purifing well water to meet drinking water criteria is by using reverse osmosis. Well water which is usually classified as ground water is enriched with dissolved minerals and consenquently contains a great amount of calcium and magnesium bicarbonates. These ions cause hardness of the water and along with suspended particles such as SiO2 they precipitate causing membrane fouling in processes with increased pressure or temperaure such as reverse osmosis. A solution to this are different pretreatment processes that reduce or even remove problematic substances. In this thesis we were searching for a suitable method for reducing calcium and magnesium bicarbonates of the water and silica it contains to the maximum extent. We tested different pretreatment processes where we increased temperature and pH value to achieve greater efficiency. The used methods were lime softening, coagulation and the combination of both. For coagulation we used coagulants PACl and Al2(SO4)3. Before and after treatment, we measured: SiO2, total hardness, carbonate hardness, calcium hardness, magnesium hardness, non carbonate hardness, turbidity, pH value, conductivity, temperature, total dissolved solids (TDS), iron, zeta potential and particle size of the sampled water. The results showed that the most efficient was the lime softening pretreatment method with temperature between 58 °C and 60 °C and pH value of 10, which we achieved with the addition of NaOH. Also quite effective was coagulation with PACl and lime in the same temperature interval, which removed a great deal of SiO2 but a lot less hardness. |
