Effect of ozone on pollutants removal in surface water by coagulation, flocculation and adsorption processes

Abstract

<p>U radu je izvr&scaron;ena karakterizacija sirove (povr&scaron;inske) vode na lokalitetima: akumulaciono&nbsp;jezero, nizvodna deonica do izvori&scaron;ta namenjenog za vodosnabdevanje, na lokalitetu samog izvo-ri&scaron;ta i na ulazu u poluindustrijsko istraživačko postrojenje. Ustanovljene su sledeće karakteristike&nbsp;sirove vode: eutrofne karakteristike akumulacionog jezera u vremenskom periodu od kraja juna do&nbsp;sredine septembra meseca; fekalna zagađenost deonice od akumulacionog jezera do izvori&scaron;ta na-menjenog za vodosnabdevanje; veliki raspon temperature u toku godine (4-19&ordm;C); niske vrednosti&nbsp;mutnoće vode u najvećem delu godine uz povremen i kratkotrajan izrazit porast ovog parametra&nbsp;(&lt;1 NTU do &gt;90 NTU); promena sadržaja organskih materija u vodi (izraženih preko potro&scaron;nje ka-lijum-permanganata u kiseloj sredini i UV apsorbancije na 254 nm); izražen potencijal za formira-njem nusprodukata dezinfekcije (THM) u toku obilnih padavina.&nbsp;<br />Na poluindustrijskom istraživačkom postrojenju izvr&scaron;eno je ispitivanje različitih tehnolo&scaron;kih vari-janti pripreme vode za piće iz povr&scaron;inske vode namenjene vodosnabdevanju uz primenu savreme-nih tehnolo&scaron;kih re&scaron;enja i adekvatnog tretmana u slučaju ekscesa izazvanih ljudskom aktivno&scaron;ću.&nbsp;Primenjenim tretmanom vode procesima ozonizacije-koagulacije-flokulacije-sedimentacije-filtra-cije na poluindustrijskom istraživačkom postrojenju zadovoljena je primarna funkcija redukcije&nbsp;opterećenja vode pre odlaska na zavr&scaron;no bistrenje procesom filtracije. Ustanovljeni su najvažniji&nbsp;faktori uticaja na mutnoću vode nakon primenjenih procesa: vrsta koagulanta (najbolji efekti po-stignuti primenom Al₂(SO₄)_3&nbsp;i FeCl₃) i primenjena doza ozona (pozitivan, mikroflokulacioni efekat ozona postignut pri primenjenim dozama ozona od 0,5-1,0 mgO₃/l). Izračunato je da su pri primeni Al₂(SO₄)_3&nbsp;kao koagulacionog sredstva dvomedijumski filteri namenjeni zavr&scaron;nom bistrenju vode imali najduži filtracioni ciklus. Srednje vrednosti količine uklonjene mutnoće su 2,5- 3,5 puta veće u odnosu na ove vrednosti dobijene pri primeni ostalih koagulanata u fazi koagulacije vode. Značaj primenjenog procesa ozonizacije (doze ozona) uočen je i sa aspekta smanjenja sadržaja prekursora formiranja THM.</p><p>Ispitivanjem efekta predtretmana vode procesom ozonizacije, primenom vodonik-peroksida i ko-mercijalnog preparata koji u svom sastavu sadrži 25% H₂O_2&nbsp;+ 0,05% Ag u ozoniranu vodu u cilju&nbsp;redukcije broja mikroorganizama uočeni su pozitivni efekti na log_10&nbsp;inaktivacije pri dozama ozona&nbsp;&gt;0,5 mgO₃/l (u slučaju sporogenih sulfitoredukujućih klostridija) i vi&scaron;ih vrednosti odnosa H₂O₂/O_3&nbsp;i H₂O₂+Ag/O_3&nbsp;(u slučaju ukupnog broja aerobnih organotrofnih bakterija). Prednost primene preparata koji u svom sastavu sadrži 25% H₂O_2&nbsp;+ 0,05% Ag u ozoniranu vodu ogleda se u većem kapa-citetu eliminacije mikroorganizama i pri kraćem hidrauličkom vremenu zadržavanja vode.&nbsp;</p><p>Analizom frekvencije pojavljivanja jedinjenja koje prouzrokuje nepoželjan miris vode (geosmin)&nbsp;nakon primenjenih procesa ozonizacije-koagulacije-flokulacije-sedimentacije-filtracije ustanovljena je najmanja frekvencija pojavljivanja ovog jedinjenja (10% od ukupnog broja analiziranih uzo-raka) u vodi nakon procesa ozonizacije i njegova potpuna redukcija primenom koagulanta FeCl_3&nbsp;u&nbsp;fazi koagulacije vode.<br />Pri simulaciji ekscesnih situacija na poluindustrijskom istraživačkom postrojenju (doziranjem sintetičkih organskih jedinjenja pesticida i nafte) utvrđeno je da se primenom procesa ozonizacije-koagulacije-flokulacije-sedimentacije-filtracije uz dodatak AUP u fazi koagulacije vode postiže reduk-cija lindana u vodi za 97%, atrazina 99%, ukupnih ugljovodonika 91% i mineralnih ulja 89%.<br />Svi rezultati dobijeni u toku istraživanja na poluindustrijskom istraživačkom postrojenju posmatra-ni sa aspekta optimizacije tehnolo&scaron;kih uslova pripreme vode za piće i varijabilnog kvaliteta povr&scaron;in-ske vode ukazuju na prvom mestu na neophodnost primene procesa ozonizacije vode i pozitivan&nbsp;efekat unapređenih procesa oksidacije u fazi pripreme vode za dalju obradu, kao i na značaj primenjene vrste koagulanta i aktivnog uglja u prahu u fazi koagulacije i flokulacije vode.</p>

<p>The paper presents the characterisation of raw (surface) water at the following sites: accu-mulation lake, downstream section from the water supply well field at the very site of the well field&nbsp;and at the entrance into pilot plant. The following raw water characteristics have been determined:&nbsp;eutrophic properties of accumulation lake within the time frame from the end of June to the middle&nbsp;of September; faeces pollution of the section from the accumulation lake to the water supply well&nbsp;field; a wide range of temperature during the year (4-19&ordm;C); low values of water turbidity during the&nbsp;largest part of the year, with occasional and short-term emphasised growth &nbsp;of this parameter (&lt;1NTU to &gt;90 NTU); change in the content of natural organic matters in water (expressed through&nbsp;potassium permanganate consumption in acid environment and UV absorption at 254 nm); ex-pressed potential for disinfection by-products (THM) creation during high rainfall levels.</p><p>Study of different technological options for drinking water preparation from surface water desig-nated to water supply with application of the latest technological solutions and adequate treatment in cases of accidents caused by human activities has been carried out at the pilot plant.</p><p>The water treatment composed of ozonation-coagulation-flocculation-sedimentation-filtration applied at the pilot plant satisfied the primary function of reduction of water load prior to departure&nbsp;to the final clarification in filtration process. The most significant factors affecting water turbidity&nbsp;after the applied processes have been determined: type of coagulant (the best effects have been ob-tained by application of Al₂(SO₄)_3&nbsp;and FeCl₃) and the applied ozone dose (positive, micro-floccula-tion effect of ozone has been obtained with the applied ozone doses of 0,5-1,0 mgO₃/l). It has been&nbsp;calculated that two-media filters designated to final water clarification had the longest filtration cy-cle when Al₂(SО₄)_3&nbsp;was used&nbsp;as coagulation means. Medium values of quantity of the eliminated tur-bidity are 2,5-3,5 times higher in comparison to &nbsp;these values obtained when others coagulants were&nbsp;used in the water coagulation phase. The significance of the applied ozonization process (ozone&nbsp;dose) has also been found from the aspect of reduction of THM generation precursor contents.&nbsp;<br />Investigation of effects of water pre-treatment with ozonation process and application of hydrogen-peroxide and commercial preparation containing 25% H₂O_2&nbsp;+ 0,05% Ag in ozonized water aiming at&nbsp;reduction of micro-organisms count showed positive effects on log_10&nbsp;inactivation when &gt;0,5 mgO₃/l&nbsp;doses of ozone were used (in case of sulphito-reducing clostridia) and higher values of H₂O₂/O_3&nbsp;and&nbsp;H₂O₂+Ag/O_3&nbsp;ratio (in case of total aerobic organotrophic bacteria count). The advantage of appli-cation of the preparation containing 25% H₂O_2&nbsp;+ 0,05% Ag in ozonized water is reflected in higher&nbsp;microorganisms elimination capacity and shorter hydraulic retention time.&nbsp;<br />The analysis of occurrence frequency of compounds causing unpleasant water odour &nbsp;(geosmin) af-ter the applied ozonation-coagulation-flocculation-sedimentation-filtration processes showed that&nbsp;the lowest occurrence frequency for this compound (10% of the total number of the analysed sam-ples) in water after ozonisation process &nbsp;and its total reduction after the application of FeCl_3&nbsp;coagu-lant in water coagulation phase.<br />In simulation of accidents at pilot plant (dosing of synthetic organic compounds of pesticides and&nbsp;oil) it was found that reduction of lindane in water for 97%, atrazine for 99%, total hydrocarbons for&nbsp;91% and mineral oils for 89% is accomplished with application of the ozonation-coagulation-floccu-lation-sedimentation-filtration processes with addition of AUP in the phase of water coagulation.&nbsp;All the results that have been obtained during the researches at pilot plant have been considered&nbsp;from the aspect of optimisation of technological conditions of drinking water preparation and vari-able surface water quality point primarily to the necessity of application of water ozonization proc-ess and positive effect of the improved oxidation processes in the phase of water preparation for&nbsp;further processing as well as to the significance of the applied type of coagulant and active powder&nbsp;charcoal in water coagulation and flocculation phase.</p>