Leachability and Microstructural Analysis of Clay and Lime Stabilized/Solidified Polluted Sediment – Long-Term Performance

The objective of this study is to enable a better understanding of the effectiveness of solidification/stabilization (S/S) technique in treating polluted sediment, and provide the much needed validation of the longevity of the technology. In this research kaolinite and montmorillonite, with a certain proportion of lime, were used for S/S treatment of sediment polluted with metals. Leachability of metals was examined using the toxicity characteristic leaching procedure (TCLP) and the German standard leaching test (DIN 3841-4 S4) prescribed in national legislative. Results indicated successful S/S treatment using both clays and lime, from the aspect of all leached metals even with pH variations over time and slight changes in structural integrity of specimens. X-ray diffraction (XRD), scanning electron microscope (SEM) analyses and porosity measurement were also performed on the prepared monolithic matrices. XRD qualitative and semi-quantitative analysis proved hydration and pozzolanic product formation with increase in their content and finer crystallites formation over time. SEM analysis confirmed the presence of morphologically dense and stable structures while pore size distribution indicated on mesoporous matrices with ongoing compaction over time. Generally, structural microanalysis indicated the formation of hardened matrices over time and hydration process has been fully completed and further carbonation took place. Unconfined compressive strength measurement gave the satisfying results and matured monolite with 30 % of montmorillonite and 10 % of lime can be considered potentially applicable as non-load-bearing material. In summary, all results indicated that this kind of S/S treatment can achieve satisfactory durability and represent reliable and economically feasible technique for long-term remediation of metal polluted sediment

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

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

The use of cardboard factory sludge in the remediation of zinc contaminated sediment

Paper and cardboard factory sludges are generated by various processes during pulp, cardboard and paper production, and the increasing quantities produced make the disposal of this sludge a problem. This study investigates the use of cardboard factory sludge as a stabilizing agent in the solidification/stabilization (S/S) treatment of zinc polluted sediment. Semidynamic and toxicity leaching tests were conducted to assess the effectiveness of the solidification/stabilization treatment and long-term zinc leaching behaviour. A diffusion-based model was used to elucidate the controlling leaching mechanisms. The applied S/S treatment was effective in immobilizing zinc, and the controlling leaching mechanism appeared to be diffusion, which indicates that a slow leaching of zinc could be expected when cardboard mill sludge is applied as a S/S agent

BIOLOŠKO UKLANJANJE AMONIJUM JONA IZ VODE ZA PIĆE

Biološki procesi uklanjanja amonijum jona iz vode za piće, poput biofiltracije, zauzimaju sve više paţnje, s obzirom dase primjenom ovih procesa mogu izbjeći toksiĉni nusproizvodi dezinfekcije, ali i problemi koji se pojavljuju udistribucionom sistemu. Istraţivanja su sprovedena na poluindustrijskom postrojenju („Pilot―) u a.d. „Vodovod― BanjaLuka projektovanom za ispitivanje i optimizaciju procesa pripreme vode za piće iz površinske vode (rijeka Vrbas).Ciklus istraţivanja biološkog uklanjanja amonijum jona na filterima proveden je u ljetnom, jesenjem i zimskom periodupri hidrauliĉkom opterećenju sirove vode od 1,2–2 m3/h. Biološka filtracije na poluindustrijskom postrojenju, praćenaje na jedno- i dvo-medijumskim filterima uz promjenu brzine filtracije i temperature ulazne vode. Pri brzini filtracije od3,3 m/h nije postignuta potpuna nitrifikacija. Nepotpunost nitrifikacije ogleda se u nepotpunosti njene druge faze –nitratifikacije, dok je proces nitritifikacije konstantan na oba filtera (pijesak; pijesak+antracit), za sve primijenjeneinicijalne koncentracije amonijum jona (γ = 0,6-1,3 mg NH4+- N/L). Pri brzini filtracije od 0,8 m/h postiţe se potpunanitrifikacija ĉak i pri sniţavanju temperature sa 11,1° na 8,8°C

Removal of copper ions present in waste offset printing developer by electrocoagulation-electroflotation process

The offset printing processes produce large amounts of waste liquids (printing developers, fountain solution, cleaning solvents and inks) which can be damaging for the environment if not monitored in the appropriate manner. The application of electrocoagulation-electroflotation process helps monitor the concentration levels of copper ions in waste offset printing developer. Purpose of this study was to investigate the effects of current density on removal of copper ions from a waste offset printing developer in the batch electrocoagulation–electroflotation process. The electrochemical process was investigated at current densities of 2, 4 and 8 mA/cm2 (corresponding to 0.08, 0.16 and 0.32 A, respectively) for the contact time of 1, 5, 10, 20, 40, and 60 minutes, respectively. The results show that, for a given time, the removal efficiency of copper ions increases significantly with the increase of current density. The current density of 2 mA/cm2 produces the slowest treatment with 90.18% of copper ions reduction which occurs after only 20 minutes. The removal efficiency of copper ions at a current density of 4 mA/cm2 was 92.44% after 10 minutes. The kinetics of electrocoagulation–electroflotation process at a current density of 8 mA/cm2 is very fast (5 minutes), and the removal rate reached 92.02%. The electrocoagulation–electroflotation process was successfully applied to the purification treatment of waste offset printing developer where an effective reduction of copper ions concentration under prescribed limits was obtained. The conclusion has been drawn that the electrocoagulation–electroflotation process has a future as a printing effluents treatment technology

Solidification/stabilization of metal polluted sediment of Krivaja river

The Krivaja River is the longest natural water body (109 km) that flows completely within the borders of Serbian province of Vojvodina. In the absence of national legislation, the sediment quality was assessed in accordance with the Dutch classification methodology. It was found that the river sediment is highly contaminated with copper and zinc (192 mg kg-1 and 1218 mg kg-1 respectively), and as such is an extreme risk to the environment and human health. The solidification/stabilization (S/S) treatment with local clay, that has high capacity of cation exchange 70.2 meq/100 g and specific surface area of 630 m2 g-1, was employed for remediation of the contaminated sediment. The sequential extraction procedure showed that the copper and zinc have medium risk for the environment, with the percentage in the carbonate fraction of 18 and 22% respectively. The results of sequential extraction are not in full agreement with the results of pseudo-total metal concentration in the sediment, which only confirms that the total metal concentration is not sufficient to define the real danger to the environment. Based on the pseudo-total metals concentration, the sediment is of Class 4 (Dutch standards). However, judging from the results of sequential extraction, the metals show medium risk. Obviously, these results have to be taken into account in the assessment of the sediment quality, remediation procedures and sediment disposal in general. After the treatment, the proportion of these two metals in the first fraction is significantly reduced (Cu less than 2%, Zn 10%) in most of samples. In order to determine the long-term behavior of S/S mixtures, leaching tests were conducted in accordance with semi-dynamic ANS diffusion test for 90 days. The results indicated that clay can effectively immobilize Cu and Zn: the cumulative leached fraction of copper in mixtures with clay was in the range from 0.001% (mixture with 80% clay) to 0.15% (mixture with 10% clay), and the cumulative leached fraction of zinc in the range of 0.06% (mixture with 80% clay) to 0.10% (mixture with 10% clay). The diffusion coefficients, ranging from 1.5×10-12 cm2s-1 to 3.7×10-14 cm2s-1, showed an effective immobilization of both metals which suggests that these metals are practically immobilized in S/S mixtures even if the level of clay is low. From the point of LX values, all S/S mixtures can be used for the controlled utilization, because the leaching indices ranged from 11.8 to 13.4 for both metals. In all clay and sediment mixtures the dominant leaching mechanism is diffusion (slope values of 0.35 to 0.60), which once again confirms the effectiveness of the applied treatment and can be expected that only a very small amount of contaminants would leach into the environment over time. Future research is heading in the direction of troubleshooting the accumulation of used natural adsorbent after treatment, the possibility of permanent disposal, its regeneration or the possibility of its application as construction material

Impact assessment wastewater discharge on water quality DTD canal Bečej-Bogojevo

Pressure and impact analysis requires information on the main drivers and changes in conditions. In order to analyze such pressures and impacts, each river basin requires: an analysis of its characteristics, a review of the impact of human activity on the status of the surface water and an economic analysis of water use. Pressure and impact analysis plays a central role in the planning of river basin management. The quality of the stream at any point depends on several major factors: lithology of the basin, weather conditions, climate, and human impacts. Most of the polluters are located in the big cities next to canal DTD Bečej-Bogojevo canal (Odzaci,Vrbas, Srbobran, Becej). Per year, 2900000 m3 of wastewater was discharged into the Bečej-Bogojevo section of the DTD canal: 1,4 tCOD, 0,8 0tBOD, 260 kg of nitrogen, 19 kg of phosphorus and 282 kg of suspended solids. Of the total volume of wastewater, 20% comes from industry and 80% from municipal wastewater. Most of the wastewaters from the studied polluters is discharged untreated or insufficiently treated (only primary treatment). This poor quality wastewater threatens the receipients into which its is discharged. Comparison of the wastewater quality results to the Decree on emission limits and deadlines for their achievement, shows that many polluters exceed the limits for all parameters (COD, BOD, nitrogen, phosphorus, suspended solids). On the basis of the physico-chemical analysis of the water from the DTD Bečej-Bogojevo canal it can be concluded that the water quality is unsatisfactory. According to the national legislation, the water quality exceeds the values for good potential streams for most parameters at all sampling locatio dissolved oxygen, organic matter and nutrients). Thus, we can conclude that the water in the studied section of the DTD Bečej-Bogojevo canal does not meet the criteria for "good ecological potential". The most vulnerable locations are downstream of the Vrbas and downstream of the Bečej, while the best quality canal water is at the furthest upstream location (CS Bogojevo). Risk assessment based on monitoring results indicates that the water of the studied section of the DTD Bečej-Bogojevo canal is probably at risk of failing to meet the objectives of the Water Framework Directive, as 33% of the analyzed parameters to calculate specific risk ratios were greater than 1, and thus fall into the category of pollutants medium risk. In order to achieve the quality (to achieve good status and good potential), there must be a response from industrial producers, which consists primarily of comprehensively understanding the problems and implementing measures to minimize the impact of these problems. [Projekat Ministarstva nauke Republike Srbije, br. TR37004

Carbon paste electrodes bulk-modified with carbon nanotubes and chemically oxidized carbon nanotubes for the determination of hydrogen peroxide

Carbon paste electrodes (graphite/paraffin oil) bulk-modified with multiwalled carbon nanotubes (MWCNT) and chemically oxidized MWCNT (O-MWCNT) were used as sensors for the hydrodynamic chronoamperometric determination of hydrogen peroxide (H2O2). Experimental parameters, such as the type and pH of the supporting electrolyte or the working potential(s) applied were investigated in the batch arrangement