The effect of water quality on steel corrosion

У докторској дисертацији „Утицај квалитета воде на корозију челика” повезан је квалитет воде (преко корозионих агенаса који се налазе у природним и индустријским водама) са брзином корозије челика који је најраширенији и најјефтинији конструкциони материјал. Доминантни агенси корозије у природним и индустријским водама који су анализирани су неоргански анјони (хлорид-, сулфат- и бикарбонат- јон). Концентрације наведених агенаса корозије у природним и индустријским водама веома су ниске, од 1г до неколико грама, и за њихово одређивање коришћене су различите аналитичке и електрохемијске технике. У дисертацији су коришћене методе за одређивање брзине корзије, израчунати су и одређени губици масе, струја корозије и густина струје корозије. У циљу сагледавања ефеката корозије челичне плочице мерена је pH-вредност у растворима испитиваних јона пре и после излагања плочице корозионом дејству јона. Резултати добијени спектроскопијом електрохемијске импедансе потврђују да је због ниске концентрације јона у испитиваном раствору брзина корозије малих вредности. На основу добијених резултата предложен је модел који описује кинетику корозије челика при ниским концентрацијама агенаса корозије. Поред анализе утицаја јона на корозију челика, анализиране су челичне цеви које су део система за дистрибуцију воде за пиће у Београду. У анализи су разматрани параметри који указују на међусобни утицај квалитета воде и корозије цеви као и последице ових интеракција. Изабрани су следећи параметри: pH-вредност воде, концентрација раствореног кисеоника, концентрација јона гвожђа у води и температура воде. Боља контрола цеви и заштита од корозије може се сагледати и предложити кроз ова испитивања. За материјале који се користе у водоснабдевању значајан процес обраде јесте заваривање. Део дисертације обухвата и анализу појаве корозије у близини завареног споја феритног и аустенитног нерђајућег челика. Утврђено је да је корозија завареног споја резултат деловања напонске, међукристалне (услед излуживања карбида) и микрогалванске корозије (услед присуства бакра и анодне поларизације феритног материјала у споју са аустенитним материјалом).The object of the analysis of this thesis, entitled „The effect of water quality on steel corrosion“ was to determine the interaction of water quality (through the content of compounds present in natural and industrial water) with corrosion rate of steel as the mostly used and exploited constructive material. Dominant corrosion agents that were analzyed in natural and industrial water are inorganic ions (chloride-, sulfate- and hydrogencarbonate- ions). The steel corrosion was focused on these agents. The concentration of these agents in natural and industrial water is very low, from 1g to few grams, and for their detection and analysis different analytical and electroanalytical techniques and methods were applied. Different methods have also been applied for corrosion rate detection, as well. Besides the analysis of the influence of different ions on corrosion behavior of steel, corroded steel pipes from Belgrade water distribution network were also analysed. The goal of these analysis was to find the relation between water quality and corroded deposits on the surface of pipes. Key-influencing water quality parameters that were chosen and analysed were: pH value, dissolved oxygen and temperature. On the basis of these analysis better control of pipe protection and corrosion prevention could be proposed. For materials that are used for water supply and water distribution one of the very important processes is welding. A part of this thesis was focused on the analysis of weld of ferrite and austenite stainlees steel and on the corrosion of analyzed weld. It was concluded that the corrosion of weld is the result of mutual activity of stress, intergranular and microgalvanic corrosion

Demulzifikacija naizmeničnim hlađenjem i zagrevanjem

An important step in waste water treatment is the removal of oil from an O/W emulsion and the separation of oil and water into two phases, a process usually called demulsification. Modern methods of oil removal from waste water were described in the present study. Typical demulsification techniques include thermal, electrical, chemical, acoustic, or mechanical methods of emulsion treatment. The freeze/thaw process was found to be very effective for demulsification. In the freeze/thaw process, water removal from the W/O emulsion depends on the initial oil content, freezing temperature, freezing time, thawing rate and temperature. The described method is a non-destructive and physical method of emulsion treatment and because there is no addition of chemical agents there is no problem of further waste water treatment, which usually exists when chemicals are applied for demulsification. Different methods for oil content determination in the O/W emulsion were also applied and compared in this study (gravimetric, volumetric, measurement of oxygen consumption and emulsion pH, IR analysis of the emulsion, electro analytical measurement).Ideja o razdvajanju ulja i vode u emulzijama i uklanjanju ulja iz vode postupkom hlađenja (mržnjenja) i zagrevanja intenzivno se izučava u poslednjih pet godina. U ovom radu primenjena je metoda destabilizacije emulzija: naizmeničnim zamrzavanjem i otapanjem emulzije, (-Q/+Q). U radu su ispitani i utvrđeni uslovi pri kojima se postupci mržnjenja i ponovnog zagrevanja, te otapanja zamrznute emulzije može uspešno primeniti za demulzifikaciju emulzije koja sadrži od 1 do 30% ulja. Ispitivanja su pokazala da se primenom ove metode može izdvojiti i do 90% ulja iz emulzije. U radu su prikazane i analizirane različite metode određivanja sadržaja ulja u emulziji (gravimetrijska, volumetrijska, optička, IR analiza, elektroanalitička)

The Significance of Monitoring of Water Quality in Hydropower Lakes

Pri planiranju akumulacionih hidroelektrana, važan segment je i adekvatan monitoring kvaliteta vode. Uz odgovarajući monitoring program omogućava se višenamensko korišćenje veštačkih jezera. Eutrofikacija vode u jezeru je fenomen koji je prisutan kod svih jezera. Posledica eutrofikacije jeste ugroženost akvatičnog ekosistema. Eutrofikacija je fenomen koji nastaje kao odgovor akvatičnog ekosistema na povećanu koncentraciju nutrijenata, fosfora (P) i azota (N), usled prirodnih i antropogenih aktivnosti. Pored osnovnih, klasičnih pokazatelja kvaliteta vode koji su u korelaciji sa eutrofikacijom najnovija istraživanja pokazuju da su jezera sve više izložena eutrofikaciji usled klimatskih promena i opšte prisutnog zagađenja životne sredine. U ovom radu prikazani su rezultati analize kvaliteta vode reke Komarnice, u Crnoj Gori na kojoj se planira izgradnja akumulacione pribranske HE Komarnica. Ključni zaključci istraživanja su: uvesti monitoring (permanentnu kontrolu) kvaliteta vode u jezerima kako bi se što uspešnije kontrolisala i sprečila eutrofikacija. Izuzetno je važno razumeti da ne postoji jedinstvena jednačina ili formula koja bi mogla da važi za monitoring svih jezera. Svako jezero ima svoje jedinstvene karakteristike. Zavisnost hlorofila, koncentracije fosfora i zapremine jezera menja se u zavisnosti od meseca, sezone i godine. Predlog za monitoring kvaliteta vode na jezeru koje će biti izgrađeno na Komarnici, koje predstavlja deo sistema buduće hidroelektrane je mesečno praćenje koncentracije hlorofila, nutrijenata i zapremine jezera. Sezonsko praćenje zavisi od padavina, hidroloških i limnoloških karakteristika i trendova sušnih i kišnih epizoda. Analize i dosadašnja istraživanja su pokazala da uvođenje obaveznih parametara za praćenje kvaliteta vode ne poskupljuje proizvodnju električne energije i očuvanje energije, a značajno poboljšava i unapređuje kvalitet životne sredine.When planning the construction of a hydroelectric power plant, an important segment is adequate monitoring of water quality. With an appropriate monitoring program, the multifunctional use of artificial lakes is enabled. Eutrophication (nutrient over-enrichment) of water in a lake is a phenomenon that has been noticed in all lakes. The consequence of eutrophication is the endangerment of the aquatic ecosystem. Eutrophication is a phenomenon that occurs as a response of the aquatic ecosystem to the increased concentration of nutrients, phosphorus (P) and nitrogen (N), due to natural and anthropogenic activities. Recent research indicates a correlation between local climate change and water circulation and the impact of climate change on all phenomena in the hydrological cycle. Temperature fluctuations, huge amounts of rain when precipitation is analysed, constant heating and increase in humidity all affect more intense eutrophication. The key conclusions of the research dealing with the construction of the hydroelectric power plant in Komarnica are: to introduce monitoring (permanent control) of water quality in lakes in order to minimize or control, even prevent eutrophication. Each artificial lake has its own unique characteristics. The dependence of chlorophyll, phosphorus and lake volume varies depending on the month, season and year. The proposal for the lake that will be built on Komarnica, which is part of the future hydroelectric power plant, is a monthly monitoring of the concentration of chlorophyll, nutrients and the volume of the lake. Seasonal monitoring depends on precipitation, hydrological and limnological characteristics and trends of dry and rainy episodes. Analyzes and previous research have shown that the introduction of mandatory parameters for monitoring water quality does not increase the cost of electricity production and energy conservation, but significantly improves and enhances the quality of the environment

Korozija zavarenog spoja austenitnog i feritnog nerđajućeg čelika

Dissimilar metal connections are prone to frequent failures. These failures are attributed to the difference in the mechanical properties across the weld, the coefficients of thermal expansion of the two types of steels and the resulting creep at the interface. For the weld analyzed in this research, it was shown that corrosion measurements can be used for a proper evaluation of the quality of weld material and for the prediction of whether or not the material, after the applied welding process, can be in service without failures. It was found that the corrosion of the weld analyzed in this research resulted from the simultaneous activity of different types of corrosion. In this study, electrochemical techniques including polarization and metallographic analysis were used to analyze the corrosion of a weld material of ferrite and austenitic stainless steels. Based on surface, chemical and electrochemical analyses, it was concluded that corrosion occurrence was the result of the simultaneous activity of contact corrosion (ferrite and austenitic material conjuction), stress corrosion (originating from deformed ferrite structure) and inter-granular corrosion (due to chromium carbide precipitation). The value of corrosion potential of -0.53 V shows that this weld, after the thermal treatment, is not able to repassivate a protective oxide film.Spojevi različitih metala dobijenih zavarivanjem skloni su propadanju uglavnom usled pojave različitih vidova korozije. Fizičko-hemijska, mehanička svojstva, kao i koeficijenti toplotnog širenja različitih čelika najčešći su uzrok pucanja materijala na zavarenim spojevima. Istraživanja u ovom radu su pokazala da se ispitivanje korozije materijala može koristiti za procenu kvaliteta spojeva zavarenih materijala. Različite analitičke, metalografske i elektrohemijske tehnike i metode analize su primenjene za ispitivanje korozije zavarenog spoja nerđajućih čelika feritne i austenitne strukture. Ustanovljeno je da do pojave korozije na zavarenom spoju ispitivanih materijala prevashodno dolazi usled: kontaktne korozije, naponske korozije (koja potiče od deformisane strukture ferita) i međukristalne korozije (posledica izluživanja hrom-karbida) u feritnom delu zavarenog spoja

Assessment of the Influence of Dam and Hydropower Plant on the Change of Water Quality

U ovom radu prikazana je analiza kvaliteta vode reke Komarnice pre izgradnje brane i hidroelektrane. Konkretne karakteristike okoline, dimenzije objekta definišu uticaje na životnu sredinu, kao i uticaje životne sredine na akumulacije. Pozitivni uticaji su: vodosnabdevanje, navodnjavanje, rekreativne i turističke ponude. Najvažniji negativni uticaji su: promena kvaliteta vode, uticaj na priobalje i zemljište. U radu je prikazan kvalitet vode pre izgradnje brane Komarnica, kao polazna osnova za poređenje i analizu promena koje se očekuju nakon izgradnje te brane. Pravilnim izborom mera moguće je izbeći ili u velikoj meri ublažiti proces eutrofikacije.This paper presents an analysis of the water quality of the Komarnica River before the construction of the dam and hydropower plant. Impacts that are positive, and due to which dams are built, refer to water supply, irrigation, recreational and tourist offers. The most important negative impacts are the changes in water quality, the impact on the coast and land. The paper presents the water quality before the construction of the Komarnica dam, and the changes expected after the construction of the dam. By choosing the right measures, it is possible to avoid or greatly mitigate the eutrophication process

Fizičke metode za prečišćavanje otpadnih voda - primena metode naizmeničnog mržnjenja i hlađenja i mikrotalasnog zagrevanja za obradu zauljenih voda

The main sources of oily waste water are oil- refineries, metal industry and food industry. Any technological process that uses emulsions has to take into consideration also the treatment of the used emulsions. The ultimate goal of emulsion treatment is to separate oil from water, and to attain maximum levels of cleanliness of both water and oil. The paper analyzes the possibility of emulsion separation with the use of the freeze/thaw (F/T) method, and the microwave radiation (MWR) assistance method. The F/T method and MWR are relatively new physical methods for de-emulsification, and they have the advantage of belonging to the group of green methods that are reagent-less and ecologically friendly.U radu je dat pregled metoda za prečišćavanje otpadnih voda. Predmet istraživanja rada je analiza i primena savremenih metoda za demulzifikaciju, odnosno uklanjanje ulja iz vode. Glavni izvori zauljenih otpadnih voda su rafinerije nafte, proizvodnja / obrada metala i proizvodnja hrane. U skladu sa ekološkim zahtevima svaki tehnološki proces u kome se koriste emulzije ulja u vodi mora da bude praćen odgovarajućom obradom otpadne ili iskorišćene emulzije. Cilj obrade je uklanjanje zagađivača (ulja) i dobijanje vode odgovarajuće čistoće. U ovom radu je istražena mogućnost prečišćavanja emulzija metodom naizmeničnog hlađenja / zagrevanja i metodom hlađenja praćenog mikrotalasnim zagrevanjem. Metode ispitane u ovom radu su nedestruktivne, pripadaju fizičkim metodama analize i primenjuju se bez dodavanja hemijskih reagenasa čime je ostvaren koncept ekološki prihvatljivih ("zelenih") metoda za obradu zauljenih otpadnih voda

Procena korozivnih karakteristika vode prema indeksima agresivnosti - primer bunarskog polja u Vojvodini

For the assessment of aggressiveness and corrosiveness of water many indices have been developed and some of them are presented in this paper. Although number of indices has been developed indexes none of them has been able to accurately quantify and predict corrosiveness of water or aggression. Indexes can be used as indicators of possible corrosiveness of water. Samples of raw water from four wells in Vojvodina, which are supposed to make a one-well field, have been analyzed in this paper. The assumption is that the water will be treated with filtration and disinfection before being introduced in to the system. The analysis was conducted using Langelier Index of Saturation, Ryznar Index, Puckorius Scaling Index, the Aggressiveness Index, Larson-Skold's Index and Modified Larson-Skold's Index. Most often, the development of corrosion can be seen through: deterioration of the pipes (measured by the loss in mass of pipes and oxygen consumption), the formation of deposits (measured by hydraulic loss or the buildup of deposits) and change in water quality in the system (measured by the concentration of iron, change of color and turbidity). The key water quality parameters that affect the corrosion processes are: pH, alkalinity and buffering capacity. Among the best known indices, which the aggression and corrosion properties of water express by CaCO3, are: Langelier Index of Saturation (LSI), Ryznar Index (RSI), Puckorius Scaling Index (PSI), and the Aggressiveness Index (AI). In addition to these indices, which observe the possibility of corrosion by CaCO3, other indices have been developed that take into account other parameters of water quality and their effect on corrosion of the pipe distribution network. Most common among the Larson-Skold's index (LR) and modified Larson-Skold's index (LRM). A sample from the well K3 has about the same values of LSI, RSI and PSI index as the samples from wells E1 and L2, but much worse values of LR and LRM index, which indicates that water from wells K3 has a greater potential to cause corrosion problems and the problems of water. It is recommended that water from wells K3 is not used for water supply. Assuming that the wells have the same capacity, an analysis of the indices of water that would have been a mixture of all four wells (mixture M1) and the water is a mixture of wells P2, E1 and L2 (mixture M2), has been conducted. Based on the analysis of a mixture of water M1, which includes water from all 4 wells, and mixtures M2, which uses water from wells P2, E1 and L2, negative impact water from wells K3 has been shown. According to all parameters, a mixture M1 showed a greater tendency to develop corrosion than mixture M2.Za procenu agresivnosti i korozivnosti vode razvijeni su indeksi pokazatelja korozivnosti vode, od kojih su neki predstavljeni u ovom radu. Indeksi mogu da posluže kao indikatori korozivnosti vode. U ovom radu analizirani su uzorci sirove vode iz četiri bunara u Vojvodini za koje se pretpostavlja da čine jedno bunarsko polje. Pretpostavka je da će voda biti obrađena fitracijom i dezinfekcijom pre puštanja u mrežu. Analiza je rađena pomoću Langelierov indeksa zasićenja, Ryznarovog indeksa, Pukoriusovog indeksa za korozione slojeve, indeksa agresivnosti, Larson- Skold-ov indeksa i modifikovanog Larson-Skold-ov indeksa. Najčešće se razvoj korozije može sagledati kroz: propadanje cevi (meri se gubitak mase cevi i potrošnja kiseonika), formiranje naslaga (mere se hidraulički gubici ili stvaranje naslaga) i promenu kvaliteta vode u sistemu (meri se koncentracija gvožđa, određuje boja i mutnoća). Ključni parametri kvaliteta vode koji utiču na korozione procese su: pH vrednost, alkalitet i puferski kapacitet. Među najpoznatijim indeksima, koji agresivnost i korozione karakteristike vode izražavaju putem CaCO3, su: Langelierov indeks saturacije (LSI), Ryznarov indeks (RSI), Puckoriusov indeks skaliranja (PSI), indeks agresivnost (AI). Pored pomenutih indeksa, koji mogućnost korozije sagledavaju preko CaCO3, razvijeni su i drugi indeksi koji uzimaju u obzir i druge parametre kvaliteta vode i njihov uticaj na koroziju cevi distributivne mreže. Među najpozantijim su Larson-Skoldov indeks (LR) i modifikovani Larson-Skoldov indeks (LRM). Uzorak iz bunara K3 ima približno iste vrednosti LSI, RSI i PSI indeksa kao i uzorci iz bunara E1 i L2, dosta lošije vrednosti LR i LRM indeksa, ukazuju na to da voda iz bunara K3 ima veći potencijal da izaziva koroziju i probleme sa bojom vodom . Preporuka je da se voda iz bunara K3 ne koristi za vodosnabdevanje Pod pretpostavkom da bunari imaju jednaku izdašnost, urađena je analiza indeksa korozivnosti za vodu koja bi bila mešavina iz sva četiri bunara (mešavina M1) i voda koja je mešavina bunara P2, E1 i L2 (mešavina M2). Na osnovu analize mešavina vode M1, koja uključuje vodu iz sva 4 bunara, i mešavine M2, koja koristi vodu iz bunara P2, E1 i L2, pokazan je negativan uticaj vode iz bunara K3. Prema svim parametirma, mešavina M1 je pokazala veću tendenciju za razvoj korozije od mešavine M2

Uklanjanje nitrata iz vode za piće primenom biološke denitrifikacije

Ground water pollution by nitrate from routine agricultural practices is a common and growing problem in the major agricultural areas of the world. The concentration of nitrates in these areas may exceed the maximal limited value (MLV for nitrates 50 mg/L). Nitrate removal has been successfully achieved with the use of several processes: ion exchange processes, reverse osmosis combined with membrane technology and extraction combined with electrodialysis. All the mentioned processes have been effectively applied and implemented on the treatment plants. The common disadvantage of all the applied processes is the final production of concentrated waste, contaminated with nitrates. The waste as by-product requires additional treatment and removal. Biodenitrification is a promising alternative technique for the removal of nitrate from drinking waters. The major advantages of biological denitrification is its simplicity, low-cost and complete removal of nitrate without waste production, since the final product of the process is nitrogen. The majority of biodenitrification relies on heterotrophic bacteria that require an organic carbon source and anoxic conditions for the first stage of process. Since the drinking water has a low carbon content an additional carbon source is required. Carbon source can be an external reservoir of methanol, ethanol, organic acid or hydrogen. The process of biological denitrification is typical for waste water treatment but some analysis and studies show that it is possible to apply this process for nitrate removal from drinking water. In this paper a possibility for the use of biological denitrification for removal of nitrate from drinking water has been discussed and a concrete water treatment plant for denitrification of groundwater in Česnikovo, Poland has been presented.U područjima kod kojih je poljoprivredna aktivnost značajna sadržaj nitrata u podzemnim izvorima vode može biti i iznad dozvoljenih vrednosti prema propisima za vodu za piće (MDK 50 mg/L). Uklanjanje nitrata iz vode do sada uspešno je primenjeno postupcima: jonske izmene, reversne osmoze uz membransku tehnologiju i ekstrakcije uz elektrodijalizu. Navedeni postupci primenjeni su i na postrojenjima, ali uočen je zajednički nedostatak, nastanak koncentrovanog otpadnog materijala koji zahteva dodatni tretman ili uklanjanje. Alternativa navednim tehnologijama jeste biološka denitrifikacija. Biološka denitrifikacija je relativno jednostavan, jeftin proces za potpuno uklanjanje nitrata, uz oslobađanje azota, bez nastanka otpada. Srž procesa biodenitrifikacije čine heterotrofne bakterije kojima su neophodni anoksični uslovi. Voda za piće ne sadrži dovoljno organskog ugljenika, koji obezbeđuje anoksične uslove. Spoljni izvor organskog ugljenika može biti metanol, etanol, sirćetna kiselina, ili vodonik. Proces biološke denitrifikacije tipičan je za pripremu i tretman otpadne vode, međutim ispitivanja sa vodom za piće pokazuju da se uz pravilno primenu ovaj postupak može koristiti i za pripremu vode za piće. U radu je prikazan pregled metoda za uklanjanje nitrata, prednosti i nedostaci određenih postupaka, kao i primer postrojenja za denitrifikaciju podzemne vode za naselje Česnokovo, u Poljskoj

Procena korozivnih karakteristika vode prema indeksima agresivnosti - primer bunarskog polja u Vojvodini

For the assessment of aggressiveness and corrosiveness of water many indices have been developed and some of them are presented in this paper. Although number of indices has been developed indexes none of them has been able to accurately quantify and predict corrosiveness of water or aggression. Indexes can be used as indicators of possible corrosiveness of water. Samples of raw water from four wells in Vojvodina, which are supposed to make a one-well field, have been analyzed in this paper. The assumption is that the water will be treated with filtration and disinfection before being introduced in to the system. The analysis was conducted using Langelier Index of Saturation, Ryznar Index, Puckorius Scaling Index, the Aggressiveness Index, Larson-Skold's Index and Modified Larson-Skold's Index. Most often, the development of corrosion can be seen through: deterioration of the pipes (measured by the loss in mass of pipes and oxygen consumption), the formation of deposits (measured by hydraulic loss or the buildup of deposits) and change in water quality in the system (measured by the concentration of iron, change of color and turbidity). The key water quality parameters that affect the corrosion processes are: pH, alkalinity and buffering capacity. Among the best known indices, which the aggression and corrosion properties of water express by CaCO3, are: Langelier Index of Saturation (LSI), Ryznar Index (RSI), Puckorius Scaling Index (PSI), and the Aggressiveness Index (AI). In addition to these indices, which observe the possibility of corrosion by CaCO3, other indices have been developed that take into account other parameters of water quality and their effect on corrosion of the pipe distribution network. Most common among the Larson-Skold's index (LR) and modified Larson-Skold's index (LRM). A sample from the well K3 has about the same values of LSI, RSI and PSI index as the samples from wells E1 and L2, but much worse values of LR and LRM index, which indicates that water from wells K3 has a greater potential to cause corrosion problems and the problems of water. It is recommended that water from wells K3 is not used for water supply. Assuming that the wells have the same capacity, an analysis of the indices of water that would have been a mixture of all four wells (mixture M1) and the water is a mixture of wells P2, E1 and L2 (mixture M2), has been conducted. Based on the analysis of a mixture of water M1, which includes water from all 4 wells, and mixtures M2, which uses water from wells P2, E1 and L2, negative impact water from wells K3 has been shown. According to all parameters, a mixture M1 showed a greater tendency to develop corrosion than mixture M2.Za procenu agresivnosti i korozivnosti vode razvijeni su indeksi pokazatelja korozivnosti vode, od kojih su neki predstavljeni u ovom radu. Indeksi mogu da posluže kao indikatori korozivnosti vode. U ovom radu analizirani su uzorci sirove vode iz četiri bunara u Vojvodini za koje se pretpostavlja da čine jedno bunarsko polje. Pretpostavka je da će voda biti obrađena fitracijom i dezinfekcijom pre puštanja u mrežu. Analiza je rađena pomoću Langelierov indeksa zasićenja, Ryznarovog indeksa, Pukoriusovog indeksa za korozione slojeve, indeksa agresivnosti, Larson- Skold-ov indeksa i modifikovanog Larson-Skold-ov indeksa. Najčešće se razvoj korozije može sagledati kroz: propadanje cevi (meri se gubitak mase cevi i potrošnja kiseonika), formiranje naslaga (mere se hidraulički gubici ili stvaranje naslaga) i promenu kvaliteta vode u sistemu (meri se koncentracija gvožđa, određuje boja i mutnoća). Ključni parametri kvaliteta vode koji utiču na korozione procese su: pH vrednost, alkalitet i puferski kapacitet. Među najpoznatijim indeksima, koji agresivnost i korozione karakteristike vode izražavaju putem CaCO3, su: Langelierov indeks saturacije (LSI), Ryznarov indeks (RSI), Puckoriusov indeks skaliranja (PSI), indeks agresivnost (AI). Pored pomenutih indeksa, koji mogućnost korozije sagledavaju preko CaCO3, razvijeni su i drugi indeksi koji uzimaju u obzir i druge parametre kvaliteta vode i njihov uticaj na koroziju cevi distributivne mreže. Među najpozantijim su Larson-Skoldov indeks (LR) i modifikovani Larson-Skoldov indeks (LRM). Uzorak iz bunara K3 ima približno iste vrednosti LSI, RSI i PSI indeksa kao i uzorci iz bunara E1 i L2, dosta lošije vrednosti LR i LRM indeksa, ukazuju na to da voda iz bunara K3 ima veći potencijal da izaziva koroziju i probleme sa bojom vodom . Preporuka je da se voda iz bunara K3 ne koristi za vodosnabdevanje Pod pretpostavkom da bunari imaju jednaku izdašnost, urađena je analiza indeksa korozivnosti za vodu koja bi bila mešavina iz sva četiri bunara (mešavina M1) i voda koja je mešavina bunara P2, E1 i L2 (mešavina M2). Na osnovu analize mešavina vode M1, koja uključuje vodu iz sva 4 bunara, i mešavine M2, koja koristi vodu iz bunara P2, E1 i L2, pokazan je negativan uticaj vode iz bunara K3. Prema svim parametirma, mešavina M1 je pokazala veću tendenciju za razvoj korozije od mešavine M2

Analytical methods for arsenic speciation analysis

Arsenic exists in the form of various chemical species differing in their physicochemical behaviour, toxicity, bioavailability and biotransformation. The determination of arsenic species is an important issue for environmental, clinical and food chemistry. However, differentiation of these species is a quite complex analytical task. Numerous speciation procedures have been studied that include electrochemical, chromatographic, spectrometric and hyphenated techniques. This review presents the relevant research in the field of arsenic speciation analysis with novel applications and significant advances. Stability of arsenic species and each of the analytical steps (sample collection, storage, preservation, extraction) of the arsenic speciation methods is particularly evaluated. Analytical validation and performance of these Methods are also reviewed