Development of methods and procedures for the removal of arsenic from drinking water

Predmet istrazivanja ove disertacije je proučavanje fizičko-hemijskih procesa kojima se mogu ukloniti različiti oblici arsena iz voda koje se koriste za vodosnabdevanje. Za uklanjanje arsena iz vode primenjuju se razliciti postupci, u većoj ili manjoj meri efikasni. Izbor tehnologije prečišćavanja vode ne zavisi samo od efìkasnosti pojedinih postupaka već i od drugih faktora koji su podjednako važni za praktičnu implementaciju procesa u realnom sistemu za prečišćavanje vode. Zbog visoke efìkasnosti i jednostavnosti upravljanja procesom u realnim sistemima za prečišćavanje vode, eksperimentalna istraživanja u okviru ove doktorske disertacije su fokusirana na uklanjanje arsena iz vode adsorpcijom. Bez obzira na veliki broj komercijalnih sorbenata za uklanjanje arsena iz vode, iznalaženje novih, alternativnih materijala, jeftinih i dostupnih predstavlja naučni i stručni izazov u aktuelnim istraživanjima sorpcije arsena. Efikasnost uklanjanja arsena iz vode sorpcijom je ispitivana na nekonvencionalnim materijalima: prirodnim (zeolit, bentonit, sepiolit, limonit, piroluzit), otpadnim (otpadna šljaka, otpadni filtarski pesak) i modifikovanim (modifìkovana otpadna šljaka, kvarcni pesak i aktivni ugalj impregnisani gvožđe(lll)-hidroksidom). Pod istim uslovima paraleino su ispitivani komercijalni sorbenti radi poređenja rezultata. Uklanjanje arsena iz vode sorpcijom je ispitivana u tri faze: u šaržnom sistemu, protočnom sistemu i u realnom sistemu za prečišćavanje vode na konkretnom izvorištu. Dodatno, ispitivana je i mogućnost fizičkog modelovanja sorpcionih reaktora sa ispunom od sorbenata kompleksne fizičko-hemijske strukture metodologijom Rapid Small Scale Column Test (RSSCT). Najbolji rezultati u šaržnom sistemu dobijeni su sa otpadnim materijalima: 50 pg/g za otpadnu šljaku i 30 pg/g za otpadni filtarski pesak (za početne koncentracije arsena 0,5 mg/L), sto je u nivou vrednosti koje su dobijene za komercijalne sorbente. Zbog visokog sadržaja CaO, otpadna šijaka značajno povećava pH vrednost vode (pH= 11). Neutralizacijom otpadne šljake dobijen je nov materijal, modifìkovana otpadna šljaka, većeg sorpcionog kapaciteta: 55 pg/g. I u protočnom sistemu najbolji rezultati su dobijeni na otpadnoj šljaci. Za početne koncentracije arsena u vodi 0,5 mg/L, radni kapacitet šljake (do proboja MDK za arsen, 10 pg/g) je oko 10 pg/g a otpadnog filtarskog peska oko 1 pg/g. Radni kapacitet komercijalnog sorbenta na bazi granularnog gvožđe(lll)-hidroksida je oko 35 pg/g. Ispitivanja u konkretnom realnom sistemu za vodosnabdevanje, gde su ulazne koncentracije arsena nekoliko puta vece od MDK, su pokazala da sorpcija na otpadnom filtarskom pesku i komercijalnom GFH ne predstavlja održivo rešenje za uklanjanje arsena ispod MDK zbog relativno kratkog veka trajanja sorbenata. Za početne koncentracije arsena u sirovoj vodi vece od 40 pg/L, uklanjanje arsena iz vode sorpcijom bez prethodnog predtretmana nije održivo rešenje na postrojenjima malog kapaciteta. Istraživanja su pokazala da primena kućnih filtara sa ispunom od otpadnog peska i komercijalnog GFH, za prečišćavanje vode za piće i kuvanje u individualnim domaćmstvima mogu predstavljati održivo rešenje u sistemima za vodosnabdevanje gde nisu primenjive složenije tehnike prečišćavanja.The subject of this thesis is to study physical and chemical processes that can remove various forms of arsenic from drinking water. Due to the high efficiency and simplicity of process control, experimental research in this dissertation is focused on arsenic removal from water by adsorption. Efficiency of arsenic removal from water by adsorption is investigated with: natural materials (zeolite, bentonite, sepiolite, limonite, pyrolusite), waste materials (waste iron slag, waste sand filter) and modified materials (neutralized waste iron slag, iron(III)-hydroxide coated sand and activated carbon). Investigations are conducted in the batch reactor, the continuous flow reactor and in a real water supply system on the pilot model. Waste iron slag and waste filter sand exhibited equilibrium sorption capacities of 50 µg/g and 30 µg/g, respectively, which is nearly equal to values obtained for the commercial sorbents. In order to minimize its deteriorating impact on the initial water quality, the waste iron slag was neutralized. The new, modified waste iron slag exhibited the highest sorption capacity, 55 µg/g. The highest adsorption capacities in continuous flow reactor were obtained for waste iron slag as well. Operational capacity exhibited by waste iron slag and waste filter sand were 10 µg/g and 1 µg/g, respectively.Higher capacities were obtained with commercial granular ferry(III)-hydroxide, 35 µg/g. Investigations in real water supply system have shown that adsorption, with no pretreatment applied, is not sustainable treatment solution when initial arsenic concentration exceeds 40 µg/L. Adsorption is considered as a tertiary water treatment, designed for fine water quality adjustment. Arsenic removal by adsorption applied with initial arsenic concentrations several times higher than MCL, will lead to a fast exhaustion and frequent replacements of adsorption media

Development of methods and procedures for the removal of arsenic from drinking water

Predmet istrazivanja ove disertacije je proučavanje fizičko-hemijskih procesa kojima se mogu ukloniti različiti oblici arsena iz voda koje se koriste za vodosnabdevanje. Za uklanjanje arsena iz vode primenjuju se razliciti postupci, u većoj ili manjoj meri efikasni. Izbor tehnologije prečišćavanja vode ne zavisi samo od efìkasnosti pojedinih postupaka već i od drugih faktora koji su podjednako važni za praktičnu implementaciju procesa u realnom sistemu za prečišćavanje vode. Zbog visoke efìkasnosti i jednostavnosti upravljanja procesom u realnim sistemima za prečišćavanje vode, eksperimentalna istraživanja u okviru ove doktorske disertacije su fokusirana na uklanjanje arsena iz vode adsorpcijom. Bez obzira na veliki broj komercijalnih sorbenata za uklanjanje arsena iz vode, iznalaženje novih, alternativnih materijala, jeftinih i dostupnih predstavlja naučni i stručni izazov u aktuelnim istraživanjima sorpcije arsena. Efikasnost uklanjanja arsena iz vode sorpcijom je ispitivana na nekonvencionalnim materijalima: prirodnim (zeolit, bentonit, sepiolit, limonit, piroluzit), otpadnim (otpadna šljaka, otpadni filtarski pesak) i modifikovanim (modifìkovana otpadna šljaka, kvarcni pesak i aktivni ugalj impregnisani gvožđe(lll)-hidroksidom). Pod istim uslovima paraleino su ispitivani komercijalni sorbenti radi poređenja rezultata. Uklanjanje arsena iz vode sorpcijom je ispitivana u tri faze: u šaržnom sistemu, protočnom sistemu i u realnom sistemu za prečišćavanje vode na konkretnom izvorištu. Dodatno, ispitivana je i mogućnost fizičkog modelovanja sorpcionih reaktora sa ispunom od sorbenata kompleksne fizičko-hemijske strukture metodologijom Rapid Small Scale Column Test (RSSCT). Najbolji rezultati u šaržnom sistemu dobijeni su sa otpadnim materijalima: 50 pg/g za otpadnu šljaku i 30 pg/g za otpadni filtarski pesak (za početne koncentracije arsena 0,5 mg/L), sto je u nivou vrednosti koje su dobijene za komercijalne sorbente. Zbog visokog sadržaja CaO, otpadna šijaka značajno povećava pH vrednost vode (pH= 11). Neutralizacijom otpadne šljake dobijen je nov materijal, modifìkovana otpadna šljaka, većeg sorpcionog kapaciteta: 55 pg/g. I u protočnom sistemu najbolji rezultati su dobijeni na otpadnoj šljaci. Za početne koncentracije arsena u vodi 0,5 mg/L, radni kapacitet šljake (do proboja MDK za arsen, 10 pg/g) je oko 10 pg/g a otpadnog filtarskog peska oko 1 pg/g. Radni kapacitet komercijalnog sorbenta na bazi granularnog gvožđe(lll)-hidroksida je oko 35 pg/g. Ispitivanja u konkretnom realnom sistemu za vodosnabdevanje, gde su ulazne koncentracije arsena nekoliko puta vece od MDK, su pokazala da sorpcija na otpadnom filtarskom pesku i komercijalnom GFH ne predstavlja održivo rešenje za uklanjanje arsena ispod MDK zbog relativno kratkog veka trajanja sorbenata. Za početne koncentracije arsena u sirovoj vodi vece od 40 pg/L, uklanjanje arsena iz vode sorpcijom bez prethodnog predtretmana nije održivo rešenje na postrojenjima malog kapaciteta. Istraživanja su pokazala da primena kućnih filtara sa ispunom od otpadnog peska i komercijalnog GFH, za prečišćavanje vode za piće i kuvanje u individualnim domaćmstvima mogu predstavljati održivo rešenje u sistemima za vodosnabdevanje gde nisu primenjive složenije tehnike prečišćavanja.The subject of this thesis is to study physical and chemical processes that can remove various forms of arsenic from drinking water. Due to the high efficiency and simplicity of process control, experimental research in this dissertation is focused on arsenic removal from water by adsorption. Efficiency of arsenic removal from water by adsorption is investigated with: natural materials (zeolite, bentonite, sepiolite, limonite, pyrolusite), waste materials (waste iron slag, waste sand filter) and modified materials (neutralized waste iron slag, iron(III)-hydroxide coated sand and activated carbon). Investigations are conducted in the batch reactor, the continuous flow reactor and in a real water supply system on the pilot model. Waste iron slag and waste filter sand exhibited equilibrium sorption capacities of 50 µg/g and 30 µg/g, respectively, which is nearly equal to values obtained for the commercial sorbents. In order to minimize its deteriorating impact on the initial water quality, the waste iron slag was neutralized. The new, modified waste iron slag exhibited the highest sorption capacity, 55 µg/g. The highest adsorption capacities in continuous flow reactor were obtained for waste iron slag as well. Operational capacity exhibited by waste iron slag and waste filter sand were 10 µg/g and 1 µg/g, respectively.Higher capacities were obtained with commercial granular ferry(III)-hydroxide, 35 µg/g. Investigations in real water supply system have shown that adsorption, with no pretreatment applied, is not sustainable treatment solution when initial arsenic concentration exceeds 40 µg/L. Adsorption is considered as a tertiary water treatment, designed for fine water quality adjustment. Arsenic removal by adsorption applied with initial arsenic concentrations several times higher than MCL, will lead to a fast exhaustion and frequent replacements of adsorption media

Arsenic removal from water using low-cost adsorbents: A comparative study

Inorganic arsenic removal from water using low-cost adsorbents is presented in this paper. Selective removal of As(III) and As(V) from water was performed with natural materials (zeolite, bentonite, sepiolite, pyrolusite and limonite) and industrial by-products (waste filter sand as a water treatment residual and blast furnace slag from steel production); all inexpensive and locally available. Kinetic and equilibrium studies were realized using batch system techniques under conditions that are likely to occur in real water treatment systems. The natural zeolite and the industrial by-products were found to be good and inexpensive sorbents for arsenic while bentonite and sepiolite clays showed little affinity towards arsenic. The highest maximum sorption capacities were obtained for natural zeolite, 4.07 mg As(V) g-1, and waste iron slag, 4.04 mg As(V) g-1

Industrially contaminated areas in Serbia as a potential public health threat to the exposed population

Mining and mineral processing is still a vital source of income in Serbia, due to mineral abundance in copper, lead, zinc, antimony. Copper mining and metal-processing are located in the east: Bor, Veliki Krivelj, Cerovo, Majdanpek. Abandoned sites from antimony mining and processing and secondary lead smelter are at the western border: Zajača, Krupanj, Stolice. Coal mining and power plants are surrounding Belgrade: Obrenovac (2 power plants), Grabovac (plant ash landfill), Kolubara and Kostolac. Main objective is to focus on potential public health hazards from industrial contamination in Serbia. Key public health issue is presence of As and Cd in ambient air PM10 close to industrially contaminated sites due to the fact that ores have high naturally occurring contents of heavy metals and metalloids. Data originate from Serbian Environmental Protection Agency, Mining and Metallurgy Institute Bor, Belgrade Institute of Public Health, as part of continuous measurement of air quality within State network of automatic stations. Concentration of As in PM10 are extremely above the limit value in Bor and Lazarevac, with Cd values slightly increased in Bor. Serbia lacks the legal framework for continuous and institutionalized follow-up of population groups vulnerable to hazardous environmental exposure, although measured concentration indicate urgent need for such activities

New Approach: Waste Materials as Sorbents for Arsenic Removal from Water

The sorption of inorganic arsenic species (arsenite and arsenate) from aqueous solutions onto steel-mill waste and waste filter sand, under neutral conditions, was investigated in this study. Additionally, the steel-mill waste material was modified in order to minimize its deteriorating impact on the initial water quality and to meet the drinking water standards. The influence of contact time and initial arsenic concentration was investigated using batch system techniques. To evaluate the application for real groundwater treatment, the capacities of the obtained waste materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. Kinetic studies revealed that waste slag materials are the most efficient in arsenic removal, reaching equilibrium arsenic sorption capacities in the range 47.6-55.2 mu g/g, while waste filter sand exhibited capacities of 25.4-29.8 mu g/g (for an initial arsenic concentration C-o=0.5 mg/L). The higher iron content in the slag materials was considered to be responsible for the better removal efficiencies, and the specific arsenic removal efficiency was estimated to be 220 mu gAs/gFe. The specific arsenic removal efficiency of the second active substance found in waste filter sand, manganese, was estimated to be 115 mu gAs/gMn. Equilibrium studies revealed the occurrence of both chemisorption and physical sorption processes. All the waste materials exhibited higher performances for As (V). The highest maximum sorption capacity was obtained by waste iron slag: 4040 mu g/g for As (V). The waste materials reached the arsenic removal capacities of the examined commercial materials, suggesting the feasibility of their application in real groundwater treatment

New Approach: Waste Materials as Sorbents for Arsenic Removal from Water

The sorption of inorganic arsenic species (arsenite and arsenate) from aqueous solutions onto steel-mill waste and waste filter sand, under neutral conditions, was investigated in this study. Additionally, the steel-mill waste material was modified in order to minimize its deteriorating impact on the initial water quality and to meet the drinking water standards. The influence of contact time and initial arsenic concentration was investigated using batch system techniques. To evaluate the application for real groundwater treatment, the capacities of the obtained waste materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. Kinetic studies revealed that waste slag materials are the most efficient in arsenic removal, reaching equilibrium arsenic sorption capacities in the range 47.6-55.2 mu g/g, while waste filter sand exhibited capacities of 25.4-29.8 mu g/g (for an initial arsenic concentration C-o=0.5 mg/L). The higher iron content in the slag materials was considered to be responsible for the better removal efficiencies, and the specific arsenic removal efficiency was estimated to be 220 mu gAs/gFe. The specific arsenic removal efficiency of the second active substance found in waste filter sand, manganese, was estimated to be 115 mu gAs/gMn. Equilibrium studies revealed the occurrence of both chemisorption and physical sorption processes. All the waste materials exhibited higher performances for As (V). The highest maximum sorption capacity was obtained by waste iron slag: 4040 mu g/g for As (V). The waste materials reached the arsenic removal capacities of the examined commercial materials, suggesting the feasibility of their application in real groundwater treatment

Challenging analytical task: analysis and monitoring of arsenic species in water

Analysis and monitoring of arsenic is still a challenging analytical task. Due to its complex behaviour (different forms of arsenic that can be present depending on pH and oxidation states of arsenic) as well as demanding analytical procedures and instrumental tools for control of arsenic concentration in drinking water which is set to 10 mu g L-1, there are still some open questions and issues when arsenic is the scientific topic. In this paper the idea was to use a multivariate statistical approach to identify the key variables and their relation to high arsenic concentration in surface waters of Serbia. The main idea was to identify and connect the key water quality parameters with arsenic concentration and to suggest adequate treatment technologies for water purification and arsenic removal. The data set for multivariate statistical approach were water quality parameters of surface water samples from Serbia. The artificial neural network (ANN) was applied for data analysis. After applying ANN the results showed strong relation between arsenic concentration and P-tot, SO42-, COD, carbonate, N-org, DO, and SiO2 content. What could be concluded from the obtained results is that high concentration of organic matter, proportional to nutrients (nitrogen and phosphorus), silica (SiO2) and dissolved oxygen highly correlates with the dissolved arsenic which implies that the most adequate technology for the water treatment could be precipitation, which in general includes coagulation. What remains unquestioned and needs to be performed is arsenic speciation analysis

Pregled savremenih metoda za uklanjanje arsena iz vode

Inorganic arsenic removal from water using low-cost adsorbents is presented in this paper. Selective removal of As(III) and As(V) from water was performed with natural materials (zeolite, bentonite, sepiolite, pyrolusite and limonite) and industrial by-products (waste filter sand as a water treatment residual and blast furnace slag from steel production); all inexpensive and locally available. Kinetic and equilibrium studies were realized using batch system techniques under conditions that are likely to occur in real water treatment systems. The natural zeolite and the industrial by-products were found to be good and inexpensive sorbents for arsenic while bentonite and sepiolite clays showed little affinity towards arsenic. The highest maximum sorption capacities were obtained for natural zeolite, 4.07 mg As(V) g-1, and waste iron slag, 4.04 mg As(V) g-1.U ovom radu su prikazani rezultati ispitivanja efikasnosti prirodnih i otpadnih materijala za uklanjanje arsena iz vode. Efikasnost uklanjanja arsena, As(III,V) ispitana je u šaržnom sistemu. Kao sorbenti korišćeni su prirodni materijali (zeolit, bentonit, sepiolit, piroluzit i limonit) i otpadni materijali (otpadni filtarski pesak sa postrojenja za prečišćavanje voda i otpadna šljaka iz proizvodnje čelika). Ispitivanja su pokazala da otpadni materijali mogu efikasno ukloniti i As(III) i As(V) iz vode, ali da se efikasnost razlikuje i zavisi od valentnog stanja arsena, početne koncentracije i pH vrednosti vode. Eksperimenti na osnovu kojih su dobijene krive kinetike sorpcije i sorpcione izoterme su rađeni u uslovima kakvi vladaju u realnim sistemima za prečišćavanje vode. Prirodni zeolit o otpadni materijali su se pokazali kao relativno dobri materijali za uklanjanje arsena iz vode dok su bentonit, sepiolit, limonit i piroluzit pokazali slab afinitet prema arsenu. Najveći maksimalni sorpcioni kapacitet su pokazali prirodni zeolit (4,07 mgAs(V) g-1), i otpadna šljaka (4,04 mgAs(V) g-1)

Determination of inorganic arsenic species in natural waters-Benefits of separation and preconcentration on ion exchange and hybrid resins

A simple method for the separation and determination of inorganic arsenic (iAs) species in natural and drinking water was developed. Procedures for sample preparation, separation of As(III) and As(V) species and preconcentration of the total iAs on fixed bed columns were defined. Two resins, a strong base anion exchange (SBAE) resin and a hybrid (HY) resin were utilized. The inductively-coupled plasma-mass spectrometry method was applied as the analytical method for the determination of the arsenic concentration in water. The governing factors for the ion exchange/sorption of arsenic on resins in a batch and a fixed bed flow system were analyzed and compared. Acidity of the water, which plays an important role in the control of the ionic or molecular forms of arsenic species, was beneficial for the separation; by adjusting the pH values to less than 8.00, the SBAE resin separated As(V) from As(III) in water by retaining As(V) and allowing As(III) to pass through. The sorption activity of the hydrated iron oxide particles integrated into the HY resin was beneficial for bonding of all iAs species over a wide range of pH values from 5.00 to 11.00. The resin capacities were calculated according to the breakthrough points in a fixed bed flow system. At pH 7.50, the SBAE resin bound more than 370 mu g g(-1) of As(V) while the HY resin bound more than 4150 mu g g(-1) of As(III) and more than 3500 mu g g(-1) of As(V). The high capacities and selectivity of the resins were considered as advantageous for the development and application of two procedures, one for the separation and determination of As(III) (with SBAE) and the other for the preconcentration and determination of the total arsenic (with HY resin). Methods were established through basic analytical procedures (with external standards, certified reference materials and the standard addition method) and by the parallel analysis of some samples using the atomic absorption spectrometry-hydride generation technique. The analytical properties of both procedures were similar: the limit of detection was 0.24 mu g L-1, the limit of quantification was 0.80 mu g L-1 and the relative standard deviations for samples with a content of arsenic from 10.00 to 300.0 mu g L-1 ranged from 1.1 to 5.8%. The interference effects of anions commonly found in water and some organic species which can be present in water were found to be negligible. Verification with certified reference materials proved that the experimental concentrations found for model solutions and real samples were in agreement with the certified values