Details zur Publikation
|DOI / URL|
|Volltext||Publikationsdokument einer UFZ-Veröffentlichung|
|Titel (primär)||Microbial sulfur transformations in novel laboratory-scale constructed wetlands treating artificial wastewater|
|Journal / Serie||PhD Dissertation|
|POF III (gesamt)||T41;|
|UFZ Bestand||Leipzig, Bibliothek, Reportsammlung, 00520584, 17-0080 F/E|
|Abstract||Constructed wetlands (CWs) are near-natural wastewater treatment systems. There, pollutant transformations are either direct components of or interlinked with the redox cycles of major chemical elements, such as sulfur. CWs have been applied in treatment of sulfate-rich wastewaters such as mining, tannery, textile wastewaters. However, hydrogen sulfide produced from sulfate reduction can cause environmental problems such as toxicity to plants and aquatic organisms. Hence, treatment of sulfur-rich wastewaters without sulfide accumulation is highly desirable. To date most prior work have focused on dynamics of sulfur compounds in CWs based on physicochemical evaluations, and little is known on the
presence and the role of sulfur and sulfide oxidizing bacteria (SOB), specially in sulfide detoxification, in CWs.
The aim of the present study was to generate an enhanced view of microbial sulfur transformations and identify key microbial drivers for sulfur transformations with special focus on SOB in CWs. To this end, two newly designed laboratory-scale horizontal subsurface-flow constructed wetland models (CW1, CW2) were built. The wetlands’s design favored a plug flow with the aim of limiting the physicochemical heterogeneity rectangular to the flow direction. Each wetland model had six separate compartments filled with gravel and was fed with artificial wastewater containing 300 mg/L of sulfate. In CW1, all six compartments were planted with soft rush, Juncus effusus, whereas only two middle compartments of CW2 were planted in order to observe microbial community shifts and effects of plants on sulfur transformations. Samples for physicochemical measurements and molecular analysis were collected from the individual compartments at the middle depth along the flow path. Next-generation 454 pyrosequencing was employed to dissect complex microbial communities in the wetland models, using the 16S rRNA gene as phylogenetic marker.
The results confirm previous findings that sulfate reduction and sulfur reoxidation occurred simultaneously in CWs. Sulfate reduction was predominant near the inlet zones, followed by the dominance of sulfur reoxidation. The role of J. effusus via oxygen release from the roots in enhancing sulfur reoxidation was observed. The abundances of SOB and sulfate reducing bacteria (SRB) were correlated to sulfur oxidation and sulfate reduction, respectively. Key players in oxidation of inorganic sulfur compounds were found to be Thiobacillus, Thiomonas, and Thiothrix (at the roots). In addition, the identification of many other colorless and colored SOB in the systems reflects diverse SOB communities and their potential activities in sulfur oxidation. Dominant SRB were Desulforhabdus, Desulfobacter, Desulfocapsa, Desulfovibrio, and Desulfobacula. It appears that the roots of J. effusus were beneficial for the inhabiting and growth of SOB. In contrast, oxic environments at the roots’ surfaces could inhibit growth of SRB. The results also demonstrate that plants significantly affected microbial community compositions in CWs. Furthermore, the findings add additional evidence for the interconnections between sulfur transformation processes and nitrogen and organic carbon removal in CWs. Nitrification and denitrification were likely to be inhibited
by sulfide toxicity. Organic carbon removal was assumed to be mostly attributed to sulfate reduction. Detrimental effects of sulfide on growth of J. effusus were observed.
In conclusion, the results from this study enhance our understanding of microbial sulfur transformations in CWs by revealing key microbes involved in the sulfur cycle, underlining their role in sulfur transformations occurring in the wetlands and suggesting their interactions with plants. Such information could be of great help in optimizing design and operational conditions in CWs to achieve better performance in wastewater treatment.
|Nguyen, P.M. (2016):
Microbial sulfur transformations in novel laboratory-scale constructed wetlands treating artificial wastewater
Dissertation, TU Dresden
PhD Dissertation 6/2016
Helmholtz-Zentrum für Umweltforschung - UFZ, Leipzig, 172 pp.