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Wetlands for minewaters : constructed wetland systems for biological treatment of mining wastewaters in western Tasmania

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Lichon, Michael J. (John) (2000) Wetlands for minewaters : constructed wetland systems for biological treatment of mining wastewaters in western Tasmania. PhD thesis, University of Tasmania.

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Abstract

Mining and lime-treated mineral processing wastewaters from the Hellyer Zn/Pb
Mine in western Tasmania, bearing Pb after tailings dam treatment, pass through
a series of pilot wetlands. This field-based study focuses on identifying
mechanisms behind wetland removal of residual Pb from wastewaters,
performance improvement and catchment issues. The background, aims and
significance of the industry-sponsored study are outlined. The study site for
this applied research project is described and defined. The environmental
uncertainties and practical challenges dictated the need for field-based
observations supplemented by limited scope experimentation. Problems with
sampling are identified and overcome by innovation.
Surprisingly, wastewater Pb sinks in wetlands almost exclusively in the form of
PbS in the mud. The 50% suspended fraction of Pb uptake is removed from
wastewaters by sedimentation, dependent on quiescent wetland residence time.
Several native emergent wetland plants suitable for treatment of mine
wastewaters are identified using several criteria, bulk and experimental
plantings. These include Eleocharis, Juncus, Restio and Triglochin. The wetland
plants contribute little to direct removal of Pb from wastewaters; rather, provide
structural stability and serve as in situ photosynthetic generators of organic
matter. Falling into the mud, the organic matter maintains a decomposer-rich,
low-Eh anaerobic mire, and fuels a microbial consortium including three genera of
sulphate-reducing bacteria (SR B). By dissimilatory respiration, SRB reduce
sulphate and thiosalts diffusing into the mud from the wastewaters to H2S. The
"dissolved" (filterable) 50% fraction of wastewater Pb uptake precipitates as PbS
by chemical demand of sulphide acting on various complexed and colloidal forms
of Pb present in the wastewater stream. This continues to a lesser degree
downstream into the catchment with streambed colonisation by SRB consortia.
Wetland operating parameters are measured and evaluated. Key changes to
minesite operation and wetland management, including optimising conditions for
maximum SRB activity, waste co-treatment and improving wetland hydrology, are
implemented or recommended to enhance wetland treatment performance. The
river system affected by mine operations is examined applying principles of total
catchment management. Catchment areas need a multidisciplinary approach and
cooperative, proactive management by stakeholders to minimise disturbance,
degradation and water quality problems and apply remedial strategies.

Item Type: Thesis (PhD)
Keywords: Lead mines and mining, Wetland landscape design
Copyright Holders: The Author
Copyright Information:

Copyright 2000 the Author

Additional Information:

No loan/copying until 20/11/2002. Thesis (Ph.D.)--University of Tasmania, 2000. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:40
Last Modified: 11 Mar 2016 05:54
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