Removal of natural organic matter from groundwater by coagulation and flocculation process

Podzemne vode istočne Hrvatske sadrže prirodne organske tvari u koncentracijama koje uzrokuju nepoželjna senzorska svojstva, a dodatna problematika nastaje kod prerade takvih voda. Naime, prilikom provođenja neizostavnog postupka dezinfekcije vode za piće klorom ili sredstvima na bazi klora, nastaju kancerogeni dezinfekcijski nusprodukti, tzv. trihalogenmetani (THM). Danas je u praksi niz tehnoloških rješenja kojima je moguće smanjiti koncentraciju organskih tvari u vodi pri čemu učinkovitost procesa ovisi o svojstvima i količini prirodnih organskih tvari u vodi te optimiranju procesnih parametara obrade vode. Najčešće se prirodne organske tvari iz vode uklanjaju metodom koagulacije i flokulacije koja se temelji na reakciji neutralizacije negativno nabijene čestice organskih tvari doziranjem koagulanata (otopina soli željeza ili aluminija). Kako učinkovitost navedene metode ovisi o vrsti koagulanta i fizikalno-kemijskim karakteristikama sirove vode, u ovom radu je ispitan učinak uklanjanja prirodnih organskih tvari doziranjem tri željezova koagulanta (FeCl3, Fe(NO3)3 i FeSO4) u podzemne vode s tri izvorišta na području istočne Hrvatske (Antin, Osijek i Valpovo) te njihov utjecaj na smanjenje potencijala nastanka trihalogenmetana. Ispitivanja su provedena dodavanjem koagulanata s ukupnom koncentracijom željeza u sirovoj vodi od 2-8 mg/L. Rezultati su pokazali da je najbolji učinak uklanjanja postignut koagulantom FeCl3, dok je potencijal nastanka THM najviše smanjen doziranjem Fe(NO3)3.Groundwater in the area of eastern Croatia contains natural organic matter in concentrations that impair sensory water quaulity and causing additional problems during drinking water disinfection. During the disinfection process, natural organic matter reacts with chlorine or chlorine-based products and carciogenic disinfection byproducts, such as trihalomethanes (THM), can be formed. Nowdays there are various technological solutions which can effectively reduce natural organic matter concentration in water, as well as process parameters. Natural organic matter are removed by coagulation/floculation a process wich is based on neutralization of negative charged organic substances by iron or alim coagulants. Efficiency of coagulation (flocculation method primarily depends on coagulant type, coagulant dosage and physical-chemical characteristics of raw water. In this paper, efficiency formation potential (TFP) were examined using three coagulants (FeCl3, Fe(NO3) and FeSO4 ) on groundwater obtained from three different water wels. Coagulants were added to achieve the rang of removal were added to achieve the range of initial iron concentrations from 2-8 mg/L. The highest natural organic matter removal were obtained when coagulant FeCl3 was used, while the TFP was highly reduced in sets with Fe(NO3)3 was applied