Adsorption behaviour od selected organic xenobiotics relevant for water treatment

Fokus ove doktorske disertacije je bilo izučavanje sorpcionog ponašanja tri herbicida koji se nalaze na listi prioritetnih supstanci prema Okvirnoj Direktivi o vodama EU (2000/60/EC) sa generalnim ciljem dobijanja podataka korisnih za prioritizaciju na osnovu novog fundamentalnog znanja o efikasnosti (ad)sorpcije za uklanjanje ovih supstanci iz  vode u lokalno specifičnim uslovima. Odabrani su ksenobiotici različite rastvorljivosti, hidrofobnosti i donorsko-akceptorskih osobina, koji  pripadaju  različitim klasama  herbicida (dinitroanilinski-trifluralin, hloroacetamidni-alahlor i triazinski-  atrazin). Prva faza je obuhvatala karakterizaciju sorbenata i vodenih matriksa .U sintetičkom matriksu, trifluralin pokazuje veći afinitet na ispitivanim sedimentima u odnosu na alahlor i atrazin. I u slučaju organoglina, sorpcija je najizraženija za trifluralin. Alahlor i atrazin pokazuju slične sorpcione kapacitete na TMA-K, dok je na TMA-B, sorpcija izraženija za alahlor u odnosu na atrazin. U  zavisnosti od prirodnog matriksa, na oba sedimenta, najveće  Kd vrednosti su dobijene za trifluralin, dok su Kd vrednosti za atrazin i alahlor  bile veoma slične ili pak veće za atrazin. U slučaju organoglina, vrednosti  Kd su rasle sa porastom log  KOW vrednosti herbicida na TMA-K u oba prirodna matriksa. Kada je u pitanju TMA-B, rast Kd vrednosti sa rastom log  KOW vrednosti uočava se u površinskom matriksu pri Ce  = 0,05 mg/l i 0,5 mg/l, i podzemnom matriksu pri najvećoj ravnotežnoj koncentraciji Ce  = 0,5 mg/l. Kao najefikasniji sorbenti su se pokazali  TMA-B (Kd  = 10,5 -  483 l/kg) i model sediment (Kd = 16,4 -  761 l/kg). Odsustvo jasne linearne korelacije izmeĎu  Kd i  % TOC upućuje na važnost interakcija mineralne faze i herbicida. U slučaju sedimenata nisu utvrđene korelacije Kd sa log  KOW vrednostima, dok kod organoglina one postoje. K d  /KOW odnosi su najveći kod atrazina na svim sorbenti ma pa se pretpostavlja da on najviše učestvuje u  uspostavljanju specifičnih interakcija zbog svojih donorsko-akceptorskih osobina. Što se tiče uticaja DOC,  zaključuje se da poreĎenje efikasnosti sorbenata treba sprovoditi u prirodnim matriksima jer sorpcioni koeficijenti variraju u zavisnosti od koncentracije polutanata, tipa i sadržaja DOC. Kolonskim eksperimentima je pokazano da atrazin i alahlor prolaze kroz kolonu sedimenta, dok je trifluralin skoro u potpunosti adsorbovan i u vrlo maloj koncentraciji detektovan u efluentu što je u saglasnosti sa rezultatima šaržnih eksperimenata na ovom sorbentu. Procenjeni faktor retardacije pomoću modela TransMod za atrazin je veći u prirodnim matriksima (R  d  = 54 i Rd = 55 u podzemnoj i površinskoj vodi, redom) nego u sintetičkoj vodi (R d = 40). Kod alahlora nisu uočene značajne promene faktora retardacije meĎu matriksima (R d = 30-35). Ovi rezultati su suprotni očekivanjima na osnovu hidrofilnosti ksenobiotika i mogu biti  rezultat upravo interakcija sa organskim materijama koje su bile izražene u kolonskim testovima, verovatno i više nego u šaržnim testovima gde se nije pojavilo povećanje Rd vrednosti u prirodnim matriksima u odnosu na sintetički matriks.  Bez obzira što je  alahlor hidrofobniji od atrazina, u uslovima datog matriksa i sorbenta ispoljava slične (šaržni testovi) ili slabije sorpcione karakteristike  (kolonski testovi)  koje upućuju na mobilnost kroz prvi zaštitini sloj.  Treća faza je obuhvatala ispitivanje adsorpcije herbicida na aktivnim ugljevima u prahu. Ispitana je kinetika adsorpcionog procesa određivanjem koeficijenta za unutarčestični prenos mase herbicida u sirovim i ozoniranim prirodnim matriksima. Određena je efikasnost uklanjanja herbicida na razlilčitim ugljevima u prahu. Efikasnost uklanjanja se kretala u različitim opsezima u zavisnosti od odabranog uglja, vodenog matriksa i doze uglja. Na komercijalnim ugljevima najveća postignuta efikasnost (doza uglja od 15 mg/l) za  alahlor iznosi u površinskoj vodi 95%, a u podzemnoj 76%. Za atrazin to je u površinskoj vodi 58% i u podzemoj vodi 56%, a za trifluralin u površinskoj vodi 87%, a u podzemnom matriksu 92%. Na uglju sitnih čestica koji se koristi u kombinaciji sa membranskom filtracijom ove vrednosti su  i veće. Stepen uklanjanja DOC na komercijalnim ugljevima (pri dozi od 15 mg/l) iznosi do 57% za površinski matriks i do  51% za podzemni matriks. Slična efikasnost u uklanjanju DOC je postignuta i na uglju sitnih čestica u oba matriksa. Ozonizacija je ispoljila očekivan negativan uticaj, više ili manje izražen. U slučaju ksenobiotika, uticaji ozonizacije su bili različiti, u zavisnosti od primenjenog uglja, matriksa i supstance. Najizraženiji uticaj je kod alahlora,  i to u negativnom smislu, zbog pada efikasnosti uklanjanja, verovatno zbog kompeticije sa organskom materijom ili efekta solubilizacije. U nekim slučajevima, ali mnogo manje, taj efekat je primećen i kod trifluralina. Na oba komercijalna uglja primećen je pozitivan uticaj ozonizacije na uklanjanje atrazina, ali u različitim matriksima,  pa se može spekulisati pretpostavljanjem da dolazi do favorizovane raspodele u novim oblogama  POM na uglju formiranim nakon ozonizacije koje su i dovoljno adsorbabilne, ali i sa dovoljno reaktivnim osobinama za asociranje sa polarnim supstancama, što je delimično i potvrđeno rezultatima adsorpcione analize.  The focus of  this doctoral thesis was the study of the sorption behavior of three herbicides which are on the list of priority substances according to Water Framework Directive (2000/60/EC). The aim  was  to obtain the  data useful for prioritization on the basis of the  new fundamental knowledge about (ad) sorption efficiency  for the removal of these substances from the  locally specific water matrices. Selected xenobiotics  were  differing  in  solubility, hydrophobicity, and donor-acceptor properties, which belong to different classes of compounds(trifluralin as herbicide, alachlor as chloracetamide herbicide and atrazine as triazine herbicide).  In the first phase  of the thesis  characterization  of sorbents and water matrices  was performed. The aim of the second phase was the testing  of  the sorption and desorption of organic xenobiotics in the sediments and organoclays. The equilibrium  sorption parameters and removal efficiencies of herbicides were determined in different water matrices.  In the synthetic matrix, trifluralin showed a higher sorption affinity onto tested sediments in comparison to the alachlor and atrazine. In the case of organoclays, sorption was mostly  pronounced for trifluralin. Alachlor and atrazine have similar sorption capacities onto the TMA-K. For the TMA-B, the sorption was more pronounced for alachlor than atrazine. Depending on the natural water matrices,  the highest  Kd values were obtained for trifluralin onto both sediments. The  Kd values for atrazine and alachlor were very similar or even greater for atrazine. In the case of organoclays, Kd values increased with increasing log  KOW values of herbicides onto TMA-K in both natural matrices. When it comes to TMA-B,  Kd  valuesincreased with increasing log  KOW values in  the surface matrix for Ce = 0,05 mg/l and 0,5 mg/l, and in groundwater at the highest equilibrium  concentration  C e   = 0,5 mg/l. TMA-B (Kd = 10,5  -  483 l/kg) and model  sediment  (kd= 16,4 to 761 l/kg) were the most efficient s orbents. The absence of  the  clear linear correlation between  Kd and % TOC  indicates the importance of the interaction of mineral phases and herbicides. Correlation between K d  and KOW values did not existed in the case of sediments,  contrary to the organoclays.  Since K d  /KoW ratios were the h  ighest for atrazine onto all sorbents, it  was  assumed that atrazine mostly participate in specific interactions due to its donor-acceptor properties. Regarding the  influence of DOC on sorption, it was concluded that a comparison of sorbents efficiencies should be carried in  native matrices as sorption coefficients vary depending on the concentration of pollutants, the type and content of DOC. Column  experiments showed that atrazine and alachlor passed through the column of the sediment, while the trifluralin almost completely was adsorbed and in very low concentrations detected in the effluent which is in accordance with the results of the  batch experiments.  Estimated retardation factors of atrazine were higher in natural matrices (R d  = 54 and Rd = 55 in groundwater and surface water, respectively) than in  the synthetic water (Rd = 40). In the case of alachlor, retardation factors were similar among water matrices (Rd = 30-35). These results are in the opposition  based on the xenobiotic hydrophilicity, and they could be the consequence of interaction with the organic matter  present  in the column tests, probably more than in the batch tests. Estimations of  Rd based on batch tests  did not show an increase of Rd values in natural matrices, in comparison to the synthetic matrix. More hydrophobic alachlor, in the circumstances of the sorbent matrix exerts similar  (batch  tests) or lower sorption (column tests) characteristics that indicate mobility through the first protective layer.  The third phase  included herbicide adsorption tests onto powdered activated carbons. The adsorption kinetics was examined by determining the intraparticle mass transfer coefficients for herbicides in raw and ozonated natural water matrices. The removal efficiencies of herbicides for different powdered activated carbons were determined. Removal efficiencies were in different ranges depending on the selected carbon, water matrix and carbon dose. The highest removal efficiencies  for commercial carbons (for carbon dose of 15  mg/l)  for  alachlor were 95% and 76% in surface and groundwater, respectively. The highest  removal of atrazine was  58% in surface water and 56% in groundwater. In thecase of trifluralin, removal efficiencies were  87% in surface water and 92% in groundwater. The removal efficiencies for the carbon with fine particles  (usually  used in combination with a membrane filtration)  were greater. The removal of DOC    by  commercial carbons (at the dose of 15 mg/l) was less than 57% in the surface water and 47% in groundwater. A similar efficiency in DOC removal was achieved for the carbon with fine particles in both water matrices. Ozonation showed the expected   negative influence on  DOC  removal efficiencies, more or less pronounced. In the case of xenobiotics, ozonation influence was different, depending on the applied carbon and xenobiotic. The most important negative influence was  in the case of alachlor probably due to competition with organic matter or solubilization effect. The  same, but less pronounced effect was observed for trifluralin. The positive influence of ozonation was observed in removal of atrazine  by  both commercial carbons but in   different water matrices.  One can speculate that it comes to the favorable distribution in new NOM coatings on carbons formed upon ozonation, which are sufficiently adsorbable, but with enough reactive qualities for association with polar substances, which is partly confirmed by the results of adsorption analysis

Assessing the possibility of solidification and stabilization of pyrite cinder by using quicklime and fly ash

The aim of this study was to determine the possibility of using two low-cost binders,quicklime and fly ash for the solidification/stabilization (S/S) of pyrite cinder.Pyrite cinder, used in this study, represents a remnant from sulfuric acid productionin fertilizer factory IHP “Prahovo” A.D. (Serbia), and has a very high toxicmetal content. High contents and leachability of copper, lead and zinc make thiswaste material hazardous, representing an extraordinary risk to the environment.In order to determine the leaching behavior of the S/S mixtures, four single-stepleaching tests were performed, each one having a different sort of leaching fluid(deionized water, inorganic and organic acidic solutions). X-ray diffraction (XRD),scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDS)were implemented to elucidate the mechanisms responsible for immobilization ofCu, Pb and Zn. Overall, the test results indicated that S/S treatment using bothquicklime and fly ash was effective in immobilizing these metals, especially whenthere is a higher share of binder present. Treated waste can be safe for disposal andeven considered for “controlled utilization”. Furthermore, the use of fly ash for S/Streatment of pyrite cinder solves the disposal problems of two waste types, as it alsorepresents a secondary industrial product

Assessing the possibility of solidification and stabilization of pyrite cinder by using quicklime and fly ash

The aim of this study was to determine the possibility of using two low-cost binders, quicklime and fly ash for the solidification/stabilization (S/S) of pyrite cinder. Pyrite cinder, used in this study, represents a remnant from sulfuric acid production in fertilizer factory IHP “Prahovo” A.D. (Serbia), and has a very high toxic metal content. High contents and leachability of copper, lead and zinc make this waste material hazardous, representing an extraordinary risk to the environment. In order to determine the leaching behavior of the S/S mixtures, four single-step leaching tests were performed, each one having a different sort of leaching fluid (deionized water, inorganic and organic acidic solutions). X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDS) were implemented to elucidate the mechanisms responsible for immobilization of Cu, Pb and Zn. Overall, the test results indicated that S/S treatment using both quicklime and fly ash was effective in immobilizing these metals, especially when there is a higher share of binder present. Treated waste can be safe for disposal and even considered for “controlled utilization”. Furthermore, the use of fly ash for S/S treatment of pyrite cinder solves the disposal problems of two waste types, as it also represents a secondary industrial product

Optimization of homogenous fenton process using definitive screening design applied for flexographic printing wastewater

The treatment of flexographic cyan dye synthetic solution and real printing effluent has been studied by using homogeneous Fenton process with the addition of FeSO4*7H2O as a catalyst. The study demonstrate that applied treatment could significantly reduce dye concentration in the examined aqueous solutions. Operating parameters, such as initial dye concentration, iron dosage, hydrogen peroxide concentration and pH were varied to investigate their influence on decolorization efficiency, as well as their mutual interactions. The optimal conditions, found with definitive screening design (DSD) statistical method, were: dye concentration = 123 mgL-1 , Fe concentration = 60 mgL-1 , H2O2 concentration = 5.44 mM and a pH value = 2. Under these conditions decolorization efficiency resulted with 87% and 37% for cyan synthetic solution and real printing effluent, respectively

Characterization and kinetic study of magenta printing effluent after homogeneous fenton treatment

The objectives of this study were to determine the physico-chemical characterization of Magenta printing effluent treated with homogeneous Fenton process, as well as kinetic model that best describes degradation process of organic pollutant. Physico-chemical characterization of printing effluent before and after homogeneous Fenton treatment included measurements of pH, electrical conductivity, temperature, turbidity, chemical oxygen demand, biochemical oxygen demand, total organic carbon and toxicity test. Three kinetic models (first-order, second-order, and Behnajady-Modirshahla-Ghanbary) were evaluated in order to best describe Magenta degradation process. Results indicated that dye degradation process is followed with the increase of conductivity and biological oxygen demand due to the formation of various by-products and release of inorganic ions. The obtained results are in accordance with the established dye mineralization degree on the basis of chemical oxygen demand and total organic carbon content. However, treated printing effluent is characterized as nontoxic due to the Vibrio fischeri inhibition of 18.16%

Removal of Diclofenac and Metformin from Water in Laboratory Photo Reactor

Diclofenac (DCF) and metformin (MET) are pharmaceuticals often detected in influents and effluents of municipal sewage treatment plants and surface waters which may cause adverse effects to human health and the environment. In recent years, advanced oxidation processes (AOPs) have been demonstrated to be effective technology for the removal of many organic pollutants. The objective of this study was to evaluate the removal and toxicity of investigated pharmaceuticals by UV and UV/H2O2 processes. UV irradiation was provided by a Pen Ray lamp emission at 254 nm which was covered with a quartz tube and placed in the middle of the reactor. Experimental conditions of the process were: [DIC, MET] = 10 mg/L, [H2O2] = 2.5 mM, reaction time 3 h. Results obtained by only UV exposition of solution showed that diclofenac and metformin were degradated 30% and 50% during 3 h test. Addition of 2.5 mM H2O2 to photo reactor contributed to 90% and 100% removal of DCF and MET, respectively. Inhibition toxicity test of MET increased in the following range: 13% (C0) < 38% (UV) < 77% (UV/ H2O2), while toxicity measured for DCF solutions followed the range: 33% (UV) < 75% (C0) < 78% (UV/H2O2). The results confirmed that addition of hydrogen-peroxide accelerated the removal of investigated pharmaceuticals, but at the same time, lead to formation of the more toxic intermediates. The possible reason for better removal efficiency of metformin can be related to its simpler aliphatic structure in comparison to more aromatic diclofenac

Adsorption behaviour od selected organic xenobiotics relevant for water treatment

Fokus ove doktorske disertacije je bilo izučavanje sorpcionog ponašanja tri herbicida koji se nalaze na listi prioritetnih supstanci prema Okvirnoj Direktivi o vodama EU (2000/60/EC) sa generalnim ciljem dobijanja podataka korisnih za prioritizaciju na osnovu novog fundamentalnog znanja o efikasnosti (ad)sorpcije za uklanjanje ovih supstanci iz  vode u lokalno specifičnim uslovima. Odabrani su ksenobiotici različite rastvorljivosti, hidrofobnosti i donorsko-akceptorskih osobina, koji  pripadaju  različitim klasama  herbicida (dinitroanilinski-trifluralin, hloroacetamidni-alahlor i triazinski-  atrazin). Prva faza je obuhvatala karakterizaciju sorbenata i vodenih matriksa .U sintetičkom matriksu, trifluralin pokazuje veći afinitet na ispitivanim sedimentima u odnosu na alahlor i atrazin. I u slučaju organoglina, sorpcija je najizraženija za trifluralin. Alahlor i atrazin pokazuju slične sorpcione kapacitete na TMA-K, dok je na TMA-B, sorpcija izraženija za alahlor u odnosu na atrazin. U  zavisnosti od prirodnog matriksa, na oba sedimenta, najveće  Kd vrednosti su dobijene za trifluralin, dok su Kd vrednosti za atrazin i alahlor  bile veoma slične ili pak veće za atrazin. U slučaju organoglina, vrednosti  Kd su rasle sa porastom log  KOW vrednosti herbicida na TMA-K u oba prirodna matriksa. Kada je u pitanju TMA-B, rast Kd vrednosti sa rastom log  KOW vrednosti uočava se u površinskom matriksu pri Ce  = 0,05 mg/l i 0,5 mg/l, i podzemnom matriksu pri najvećoj ravnotežnoj koncentraciji Ce  = 0,5 mg/l. Kao najefikasniji sorbenti su se pokazali  TMA-B (Kd  = 10,5 -  483 l/kg) i model sediment (Kd = 16,4 -  761 l/kg). Odsustvo jasne linearne korelacije izmeĎu  Kd i  % TOC upućuje na važnost interakcija mineralne faze i herbicida. U slučaju sedimenata nisu utvrđene korelacije Kd sa log  KOW vrednostima, dok kod organoglina one postoje. K d  /KOW odnosi su najveći kod atrazina na svim sorbenti ma pa se pretpostavlja da on najviše učestvuje u  uspostavljanju specifičnih interakcija zbog svojih donorsko-akceptorskih osobina. Što se tiče uticaja DOC,  zaključuje se da poreĎenje efikasnosti sorbenata treba sprovoditi u prirodnim matriksima jer sorpcioni koeficijenti variraju u zavisnosti od koncentracije polutanata, tipa i sadržaja DOC. Kolonskim eksperimentima je pokazano da atrazin i alahlor prolaze kroz kolonu sedimenta, dok je trifluralin skoro u potpunosti adsorbovan i u vrlo maloj koncentraciji detektovan u efluentu što je u saglasnosti sa rezultatima šaržnih eksperimenata na ovom sorbentu. Procenjeni faktor retardacije pomoću modela TransMod za atrazin je veći u prirodnim matriksima (R  d  = 54 i Rd = 55 u podzemnoj i površinskoj vodi, redom) nego u sintetičkoj vodi (R d = 40). Kod alahlora nisu uočene značajne promene faktora retardacije meĎu matriksima (R d = 30-35). Ovi rezultati su suprotni očekivanjima na osnovu hidrofilnosti ksenobiotika i mogu biti  rezultat upravo interakcija sa organskim materijama koje su bile izražene u kolonskim testovima, verovatno i više nego u šaržnim testovima gde se nije pojavilo povećanje Rd vrednosti u prirodnim matriksima u odnosu na sintetički matriks.  Bez obzira što je  alahlor hidrofobniji od atrazina, u uslovima datog matriksa i sorbenta ispoljava slične (šaržni testovi) ili slabije sorpcione karakteristike  (kolonski testovi)  koje upućuju na mobilnost kroz prvi zaštitini sloj.  Treća faza je obuhvatala ispitivanje adsorpcije herbicida na aktivnim ugljevima u prahu. Ispitana je kinetika adsorpcionog procesa određivanjem koeficijenta za unutarčestični prenos mase herbicida u sirovim i ozoniranim prirodnim matriksima. Određena je efikasnost uklanjanja herbicida na razlilčitim ugljevima u prahu. Efikasnost uklanjanja se kretala u različitim opsezima u zavisnosti od odabranog uglja, vodenog matriksa i doze uglja. Na komercijalnim ugljevima najveća postignuta efikasnost (doza uglja od 15 mg/l) za  alahlor iznosi u površinskoj vodi 95%, a u podzemnoj 76%. Za atrazin to je u površinskoj vodi 58% i u podzemoj vodi 56%, a za trifluralin u površinskoj vodi 87%, a u podzemnom matriksu 92%. Na uglju sitnih čestica koji se koristi u kombinaciji sa membranskom filtracijom ove vrednosti su  i veće. Stepen uklanjanja DOC na komercijalnim ugljevima (pri dozi od 15 mg/l) iznosi do 57% za površinski matriks i do  51% za podzemni matriks. Slična efikasnost u uklanjanju DOC je postignuta i na uglju sitnih čestica u oba matriksa. Ozonizacija je ispoljila očekivan negativan uticaj, više ili manje izražen. U slučaju ksenobiotika, uticaji ozonizacije su bili različiti, u zavisnosti od primenjenog uglja, matriksa i supstance. Najizraženiji uticaj je kod alahlora,  i to u negativnom smislu, zbog pada efikasnosti uklanjanja, verovatno zbog kompeticije sa organskom materijom ili efekta solubilizacije. U nekim slučajevima, ali mnogo manje, taj efekat je primećen i kod trifluralina. Na oba komercijalna uglja primećen je pozitivan uticaj ozonizacije na uklanjanje atrazina, ali u različitim matriksima,  pa se može spekulisati pretpostavljanjem da dolazi do favorizovane raspodele u novim oblogama  POM na uglju formiranim nakon ozonizacije koje su i dovoljno adsorbabilne, ali i sa dovoljno reaktivnim osobinama za asociranje sa polarnim supstancama, što je delimično i potvrđeno rezultatima adsorpcione analize.  The focus of  this doctoral thesis was the study of the sorption behavior of three herbicides which are on the list of priority substances according to Water Framework Directive (2000/60/EC). The aim  was  to obtain the  data useful for prioritization on the basis of the  new fundamental knowledge about (ad) sorption efficiency  for the removal of these substances from the  locally specific water matrices. Selected xenobiotics  were  differing  in  solubility, hydrophobicity, and donor-acceptor properties, which belong to different classes of compounds(trifluralin as herbicide, alachlor as chloracetamide herbicide and atrazine as triazine herbicide).  In the first phase  of the thesis  characterization  of sorbents and water matrices  was performed. The aim of the second phase was the testing  of  the sorption and desorption of organic xenobiotics in the sediments and organoclays. The equilibrium  sorption parameters and removal efficiencies of herbicides were determined in different water matrices.  In the synthetic matrix, trifluralin showed a higher sorption affinity onto tested sediments in comparison to the alachlor and atrazine. In the case of organoclays, sorption was mostly  pronounced for trifluralin. Alachlor and atrazine have similar sorption capacities onto the TMA-K. For the TMA-B, the sorption was more pronounced for alachlor than atrazine. Depending on the natural water matrices,  the highest  Kd values were obtained for trifluralin onto both sediments. The  Kd values for atrazine and alachlor were very similar or even greater for atrazine. In the case of organoclays, Kd values increased with increasing log  KOW values of herbicides onto TMA-K in both natural matrices. When it comes to TMA-B,  Kd  valuesincreased with increasing log  KOW values in  the surface matrix for Ce = 0,05 mg/l and 0,5 mg/l, and in groundwater at the highest equilibrium  concentration  C e   = 0,5 mg/l. TMA-B (Kd = 10,5  -  483 l/kg) and model  sediment  (kd= 16,4 to 761 l/kg) were the most efficient s orbents. The absence of  the  clear linear correlation between  Kd and % TOC  indicates the importance of the interaction of mineral phases and herbicides. Correlation between K d  and KOW values did not existed in the case of sediments,  contrary to the organoclays.  Since K d  /KoW ratios were the h  ighest for atrazine onto all sorbents, it  was  assumed that atrazine mostly participate in specific interactions due to its donor-acceptor properties. Regarding the  influence of DOC on sorption, it was concluded that a comparison of sorbents efficiencies should be carried in  native matrices as sorption coefficients vary depending on the concentration of pollutants, the type and content of DOC. Column  experiments showed that atrazine and alachlor passed through the column of the sediment, while the trifluralin almost completely was adsorbed and in very low concentrations detected in the effluent which is in accordance with the results of the  batch experiments.  Estimated retardation factors of atrazine were higher in natural matrices (R d  = 54 and Rd = 55 in groundwater and surface water, respectively) than in  the synthetic water (Rd = 40). In the case of alachlor, retardation factors were similar among water matrices (Rd = 30-35). These results are in the opposition  based on the xenobiotic hydrophilicity, and they could be the consequence of interaction with the organic matter  present  in the column tests, probably more than in the batch tests. Estimations of  Rd based on batch tests  did not show an increase of Rd values in natural matrices, in comparison to the synthetic matrix. More hydrophobic alachlor, in the circumstances of the sorbent matrix exerts similar  (batch  tests) or lower sorption (column tests) characteristics that indicate mobility through the first protective layer.  The third phase  included herbicide adsorption tests onto powdered activated carbons. The adsorption kinetics was examined by determining the intraparticle mass transfer coefficients for herbicides in raw and ozonated natural water matrices. The removal efficiencies of herbicides for different powdered activated carbons were determined. Removal efficiencies were in different ranges depending on the selected carbon, water matrix and carbon dose. The highest removal efficiencies  for commercial carbons (for carbon dose of 15  mg/l)  for  alachlor were 95% and 76% in surface and groundwater, respectively. The highest  removal of atrazine was  58% in surface water and 56% in groundwater. In thecase of trifluralin, removal efficiencies were  87% in surface water and 92% in groundwater. The removal efficiencies for the carbon with fine particles  (usually  used in combination with a membrane filtration)  were greater. The removal of DOC    by  commercial carbons (at the dose of 15 mg/l) was less than 57% in the surface water and 47% in groundwater. A similar efficiency in DOC removal was achieved for the carbon with fine particles in both water matrices. Ozonation showed the expected   negative influence on  DOC  removal efficiencies, more or less pronounced. In the case of xenobiotics, ozonation influence was different, depending on the applied carbon and xenobiotic. The most important negative influence was  in the case of alachlor probably due to competition with organic matter or solubilization effect. The  same, but less pronounced effect was observed for trifluralin. The positive influence of ozonation was observed in removal of atrazine  by  both commercial carbons but in   different water matrices.  One can speculate that it comes to the favorable distribution in new NOM coatings on carbons formed upon ozonation, which are sufficiently adsorbable, but with enough reactive qualities for association with polar substances, which is partly confirmed by the results of adsorption analysis

Assessment of the retardation of selected herbicides onto Danube sediment based on small column tests

Purpose: This study utilizes column tests to investigate the retardation of certain herbicides with different hydrophobicities (atrazine, alachlor and trifluralin) during transport through surface Danube sediment. The influence of water matrix on the retardation factor Rd and Freundlich constant Kf is investigated. The results are compared with batch tests to establish whether different methodologies result in similar or different conclusions. Materials and methods: A stainless steel column was filled with natural Danube sediment. Three water matrices were investigated: synthetic, Danube surface, and deep groundwater rich in natural organic matter (NOM). The goal was to examine whether different water matrices would result in changes in the Rd and corresponding Kf values. After a tracer experiment, single herbicide solutions were tested in the three water matrices. Herbicides were analyzed by gas chromatography coupled with electron capture detector (GC/ECD). Retardation factors obtained in the column experiments were calculated using Transmod software (version 2.2). The Kf values calculated were compared with the values obtained in previous batch experiments. Results and discussion: A breakthrough curve (BTC) for trifluralin could not be obtained during the experiment. Atrazine Rd values were almost the same in the natural matrices (54 and 55 for the ground and surface waters, respectively), and lower in the synthetic water (40). Alachlor Rd values in the three water matrices were very similar (30–35). The corresponding Kf values for alachlor (8.47–17.4) were lower than those of atrazine (13.5–27.9). These results differ from those obtained by earlier batch tests, which showed similar Kf values for both atrazine (4.4–9.2) and alachlor (4.43–10.35) in all three matrices. In contrast to the results observed during the batch tests, the column tests exhibited higher Kf values in the natural water matrices than the synthetic water, possibly due to the influence of dissolved organic carbon on herbicide sorption. Conclusions: Of the three herbicides investigated, the smallest retardation was observed for alachlor. This was unexpected given the relative hydrophobicities of alachlor and atrazine. The potential risk of transport through the sediment may therefore be greater for alachlor than the other two herbicides. This was indicated neither by the batch tests nor from the Koc–Kow estimations. Both herbicides exhibited similar Kd and Kf values in the batch tests, and lower values in the natural water matrices. In comparison, the column tests showed higher Kf values, with higher values in the natural matrices than in the synthetic water matrix

The Impact of Public Policy Measures during the COVID-19 Pandemic on the Characteristics of Urban Wastewater in the Republic of Serbia

The change in the way of life caused by the introduction of social restriction measures (closures, the restriction of working hours, and restriction of movement) by governments and thus, the resulting changes in people’s behavior, have affected all aspects of life, i.e., social activities, business, the environment and the performance of the infrastructure of the water supply system. Social distancing policies around the world in response to the pandemic have led to spatio-temporal variations in water consumption and therefore, to changes in the flow of wastewater, creating potential problems in the infrastructure, operation and quality of services. The goal of this work was to examine how these changes and how the pandemic itself affected the characteristics of municipal wastewater. Data on the quantity and quality of municipal wastewater in four settlements of different sizes in the Republic of Serbia in the period from 2015 to 2022 were collected. The data indicated an increase in the amount of wastewater generated in 2020, which may be a consequence of excessive water use. An increase in the mean concentrations of most parameters in 2020 compared to the previous five-year average was also observed. The most significant changes were observed concerning the concentrations of organic matter (2–124%), nitrogen (6–80%), phosphorus (14–91%), suspended matter (8–308%), fats and oils (97–218%) and surfactants (12–110%). Changes in terms of increasing concentrations were also noticed after the peak of the pandemic, i.e., in the period from 2021 to 2022. In addition, an increase in the COD/BOD ratio from around 2 to around 4 in the year 2020 was also observed (COD—Chemical Oxygen Demand; BOD—Biological Oxygen Demand). This is very important and should be taken into account in wastewater treatment procedures in order to achieve high efficiency in the operation of the plant itself

Optimization of Cyan flexo dye removal by nano zero-valent iron using response surface methodology

Application of nano zero-valent iron (nZVI) as a catalyst in a decolorization process is a simple and sensitive method for Cyan flexo dye removal from the aqueous solution. In this paper, a central composite design (CCD), under the response surface methodology (RSM), was applied in order to optimize experimental conditions of the Cyan removal from aqueous solution. The influence of four independent variables was studied: nZVI dosage (5–45 mg L-1), initial dye concentration (2–14 g L-1), pH (2–10) and removal time (20–100 min), in order to build second order quadratic model and to predict the responses. The highest removal percent of 96.35% was attained, and the optimum parameters are achieved after 1h/24h precipitation: nZVI dosage (5/45 mg L-1), initial dye concentration (2/14 g L-1), removal time (20/100 min) and pH (2/10). The Cyan removal efficiency of 38% and 62% were estimated under optimized experimental conditions