Ref # S2SMALL-12891
N.Sleiman*1,2, V. Deluchat1, V. Kazpard2, M. Wazne3, M. Baudu1
1University of Limoges, 123 Avenue Albert Thomas, 87000 Limoges, France
2 Lebanese University, Hadath campus, Lebanon
3 Lebanese American University, Byblos Campus, Lebanon
* Corresponding Author: nathalie.s.sleiman@gmail.com
Keywords: Phosphorus removal, zero valent iron, column experiment, preconditioning effect
INTRODUCTION
Phosphorus (P) is an essential nutrient for plant and living organisms. However an excessive concentration of P in water bodies can lead to an ecological unbalance manifested by eutrophication. This may further deteriorate the water quality. Eutrophication is recognized as one of the major threats for small lakes and reservoirs. It has become a serious problem as a result of increased urbanization and industrialization. Several techniques were developed for the removal of phosphate. Zero valent iron has gained considerable attention for the removal of different organic and inorganic compounds. Some research work focused specifically on phosphate removal using ZVI. The removal of P using ZVI has been previously investigated in batch and column experiments (Sleiman et al. 2016, 2017).
MATERIAL AND METHODS
In this study, the effectiveness of ZVI for the removal of phosphate in an upflow ZVI /sand 1% WFe/WSand packed columns was assessed along with the determination of the maximum ZVI phosphate trapping capacity (Figure 1).
Figure 1. Schematic representation of the column dimensions.
ZVI and its oxidation products may change over time along with their reactivity. In order to assess the evolution of ZVI oxidation products reactivity, phosphate removal was investigated in column reactors with different preconditioning durations. Phosphate removal was also investigated along the various depths of the columns. To attain this goal, phosphate concentration was measured at different sampling ports along the column and the results were assessed in relation to the corresponding phosphate amounts trapped inside the column.
Phosphate retention capacities were confirmed through analyzing total phosphorus and iron in the ZVI/sand support collected at the end of the experiment. After column dismantling, a
sequential extraction was done on the solid samples collected at different levels from the column in order to identify the phosphorus and iron forms. Solid samples were also characterized using SEM, XRD and XPS in order to understand the mechanism of phosphate removal.
MAIN RESULTS AND CONCLUSIONS
In order to see the capacity of the support in different layers to remove phosphate, the ratio P/Fe was calculated. P/Fe ratios were determined as a function of time at P1, P2 and P3. P profile evolved to a homogeneous one at saturation. This evolution of the behavior of phosphate trapping inside the column as a function of time can be explained by the DO con- centration migration along the column. When the first layers get saturated and/or the ZVI surface is protected (no oxidation is taking place) DO cannot be consumed and it may migrates to the next layers which become active and efficient to remove phosphate. The concentration of dissolved oxygen was found to be a key parameter in the removal of phosphate using ZVI/sand columns.
The preconditioning or aging phenomenon was defined as the period in which the columns were pumped with a solution of NaCl 0.01M in closed circuit at 100 rpm. After a defined aging time, the columns were then pumped with phosphate solution having a concentration of 20 mgP/L. After column dismantling, the solids collected were studied for their phosphate and iron concentration. Results showed that the mean value of P trapped inside the columns were 94 and 38 respectively for the fresh and 10d aged column. As a function of time, the surface of ZVI may be covered by iron oxides which evolves under aging from amorphous to crystalline phases which may explain the lower efficiency for the 10d aged column compared to the fresh one. These results pointed out the effect of preconditioning on the behavior of the columns for phosphate removal.
In order to verify the hypothesis, a sequential extraction was done on the fresh and 10d aged columns at different sampling points. Results are presented in Figure 2 for Fe and P in the different extractable phases. Figure 2a showed that for the fresh and 10d aged columns, the amorphous phase showed the highest percentage about 90% of P were extracted in the amorphous phase. When comparing the fraction percentages for iron for the fresh and 10d aged columns, we found that the percentage of the crystalline phases were higher for the 10d aged column than the fresh one. XRD results showed that the only iron oxidation products identified at the different layers inside the columns were lepidocrocite and maghemite/magnetite (Wan et al., 2014). XPS results confirmed the sorption of phosphate at the surface of ZVI and its oxidation products and highlighted the formation of an iron phosphate complex.
LIST OF REFERENCES
Sleiman, N., Deluchat, V., Wazne, M., Courtin, A., Saad, Z., Kazpard, V., Baudu, M., 2016.
Role of iron oxidation byproducts in the removal of phosphate from aqueous solution. RSC Adv. 6, 1627e1636. http://dx.doi.org/10.1039/ C5RA22444F.
Sleiman, N., Deluchat, V., Wazne, M., Courtin, A., Saad, Z., Kazpard, V., Baudu, M., 2017.
Phosphate removal from aqueous solutions using zero valent iron (ZVI): Influence of solution composition and ZVI aging, Colloids and Surfaces A: Physicochem. Eng. Aspects 514,1–10.
http://dx.doi.org/10.1016/j.colsurfa.2016.11.014
Wan, J., Pressigout, J., Simon, S., Deluchat, V., 2014. Distribution of As trapping along a ZVI/sand bed reactor. Chem. Eng. J. 246, 322e327. http://dx.doi.org/10.1016/
j.cej.2014.02.073.
Parallel session 4 - Anaerobic Digestion 1 14:00-15:20 Session chair: Paula Paulo
516 - Two- vs. single-stage anaerobic wastewater treatment: Evaluation of effluent quality and energy pro-duction potential
MOTA Vera Tainá - University of São Paulo
301 - Evaluation of spatial alkalinities distribution in an up-flow fixed bed anaerobic digestion reactor HMISSI Maha - Laboratory of Hydraulic Modelisation and environnement, Tunisia
552 - Post-treatment of UASB effluent by phototrophic reactors for sulphide and organic matter removal BRESSANI Thiago - Federal University of Minas Gerais, Department of Sanitary and Environmental Engineering (UFMG/
DESA)
466 - Acclimation of mesophilic granular sludge for the anaerobic digestion of agroindustrial effluents un-der thermophilic conditions
CARRILLO-REYES Julian - University of Mexico
Parallel session 5 - Anaerobic Digestion 2 15:40-17:00
Session chair: Philippe Ker Rault
451 - Anaerobic municipal wastewater treatment in centralized and decentralized treatment systems: bio-logical methane potential and microbial community at 20 and 35°C
GAO Mengjiao - University of Alberta
470 - Hybrid Anaerobic Upflow Sludge Blanket Baffled Reactor for Source-separated Blackwater Treatment MOGES Melesse Eshetu - PhD Candidate
510 - Anaerobic digestion of sieved, statically and mechanically thickened blackwater at different organic loading rates
MORANDI Carlo G. - Kaiserslautern University of Technology
604 - Carbon footprint assessment and management of sludge and gaseous emissions in decentralized an-aerobic-based sewage treatment plants
BRESSANI Thiago - Federal University of Minas Gerais
Parallel session 6 - Anaerobic / Aerobic systems 17:20-18:20
Session chair: Yves Andres
467 - Coupling wastewater treatment based on microalgae-bacteria with the continuous methane recovery:
effect of digester temperature
CARRILLO-REYES Julian - University of Mexico
488 - Sequential “electrochemical-peroxidation – electro-Fenton” process for the treatment of anaerobic sludge from a poultry farm
OLIVIER Lefebvre - National University of Singapore
490 - Identifying optimal conditions for the start-up of an AnMBR treating concentrated domestic wastewater FERRARI Federico - Catalan Institute for Water Research