Start-up and performance of UASB reactors using zeolite for improvement of nitrate removal process

A first study on the use of Chilean natural zeolite of different particle sizes (0.5, 1 and 2mm in diameter) in laboratory-scale batch denitrificant reactors was carried out with the aim of assessing the microbial communities adhered to this material. Molecular techniques such as fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) fingerprints revealed a high microbial diversity with a strong presence of Gammaproteobacteria (70% of the total microorganisms) in reactors with zeolite 0.5mm in diameter. Archaea were only detected in the reactors with zeolite 1mm in diameter. In addition, the acclimatization and start-up of two UASB reactors (one without zeolite and the other with added zeolite 1mm in diameter) were conducted following three consecutive and progressive stages using upward velocities from 0.10 to 0.44m/h in order to establish an experimental protocol suitable for the start-up of this type of reactors. Total (100%) nitrate reduction was achieved in the UASB reactors with and without zeolite on the 7th and 11th days, respectively, of the second stage of the start-up period, showing the suitability of the use of this material in this type of reactors. Finally, a third study carried out with both UASB reactors operating in continuous mode at a high organic loading rate (44kgCOD/m3d) and a very low HRT (2.5h) revealed that the reactor with zeolite achieved a nitrate removal efficiency of 92.4% at a nitrogen load of 6.42kgNO3 -/(m3d). This last study also demonstrated the robustness of the UASB reactor with zeolite under nitrate load variations. © 2014 Elsevier B.V.The authors wish to express their gratitude to Fondecyt Project No.1090414 (Chile) for its financial supportPeer Reviewe

Application of zeolites for biological treatment processes of solid wastes and wastewaters – A review

1 FiguraThis review reports the use of zeolites in biological processes such as anaerobic digestion, nitrification, denitrification and composting, review that has not been proposed yet. It was found that aerobic processes (activated sludge, nitrification, Anammox) use zeolites as ion-exchanger and biomass carriers in order to improve the seattlebility, the biomass growth on zeolite surface and the phosphorous removal. In the case of anaerobic digestion and composting, zeolites are mainly used with the aim of retaining inhibitors such as ammonia and heavy metals through ion-exchange. The inclusion of zeolite effect on mathematical models applied in biological processes is still an area that should be improved, including also the life cycle analysis of the processes that include zeolites. At the same time, the application of zeolites at industrial or full-scale is still very scarce in anaerobic digestion, being more common in nitrogen removal processes.The authors acknowledge gratefully the financial support provided by the Alexander von Humboldt Foundation, Project FONDEF ID1810053 and Project FONDECYT 1170103 of CONICYT. This work is dedicated to the memory of our well esteemed and wonderful colleague Dr. Silvio Montalvo Martinez who recently passed away

Sequential Nitrification—Autotrophic Denitrification Using Sulfur as an Electron Donor and Chilean Zeolite as Microbial Support

Sequential nitrification–autotrophic denitrification (SNaD) was carried out for ammonium removal in synthetic wastewater (SWW) using sulfur as an electron donor in denitrification. Four reactors were operated in batch mode, two with zeolite (1 mm size) used as microbial support and two without support, to assess the effect of the zeolite addition in the SNaD. Aeration, anoxic, and anaerobic cycles were established, where 96% removal of NH4+-N (oxidized to nitrite or nitrate) was achieved in nitrification, along with 93% removal of NO3−-N in denitrification for the SNaD with zeolite. It was observed that the use of zeolite assists in buffering reactor load changes. Inhibition caused by nitrite accumulation in the denitrification stage was minimized by increasing the nitrogen concentration in the SWW. The results obtained in this study are the basis for the development of ammonium removal by simultaneous nitrification–autotrophic denitrification using a single reactor