Can Floating Wetlands purify rivers contaminated by mining?

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I was fascinated by the innovation of using man-made floating wetlands to clean & purify surface water bodies that are victims of sewage pollution.

As a Mineral Resource Governance & Environmental Justice Activist I have worked with rural communities whose sources of water e.g dams, rivers have been polluted by the corporate mining activities in their area and this has led to livestock dying and humans falling sick after bathing or drinking the water.

These areas are producers of gold, diamond, coal and granite. So my question is can the Floating Wetlands also manage to purify and remove toxins deposited into the rivers and dams as a result of gold, diamond and coal mining? 

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3 Answers

  1. The short answer is YES.  The long answer is yes BUT only a well designed floating bed systems.

    For example, some contaminants eg mercury or some of the gross radioactive chemicals are not conducive to the biological treatment and need a supplementary chemical process.

    With regard mine site spillage and clean up, any and every chemical can be removed, it takes money and determination, the answer can only be yes when their is a genuine commitment by the community and the mining company if they share a responsibility to rectify the situation.

    Each project will be different.  My recommendation is to obtain competent consulting advice from a water treatment engineer with such experience in this field.  I happen to know such a person!

     

  2. Dear Ronny, the mats of floating plants are basically made for assimilating organic waste and depleting fecal bacteria. To a limited extent there should be an effect on cyanides in low concentrations (which are used for gold lixiviation) - but there is NO sanitating effect on mercury: To the contrary, this might be converted from salts to organic Hg compounds, which are much more toxic to humans and animal models than inorganic Hg compounds.

    Other compounds, like heavy metals and semi-metals like arsenic, as they frequently occur with the gold on primary deposits (in "veins"), are partially mobilized, partially precipitated and retained by plants. In higher concentrations they can damage the mats by killing the plants (for instance, if they contain copper). To assess mobilization/precipitation, there have to be studies about suitable pH / Eh ranges and their changes induced by the activity of the floating plants. Only then, mobilizing and precipitating effects can be inferred for every metal in discussion.

    The wastewater from coal mines may contain sulphates (from oxidized pyrite and other sulphides occurring in the coal beds) and possibly heavy metals. Most likely the plants have a limit for SO4 tolerance. Regarding the heavy metals, the above mentioned conditions apply.

    Finally... diamonds and granite: AFAIK no toxic compounds are used for processing despites fuels and lubricants... and, to a small extent, grease to separate diamonds from their matrix on vibrating tables. All of these do not seem to harm the plants in the concentrations that are typical for wastewater, and for the typical compounds of mineral oil (aliphatic and aromatic hydrocarbons) as well as glycerol esters, which are main component of fat, the plants might improve their natural decay (which is to be proved or falsified by other studies that possibly are offered by the manufacturer - but have to be tested on site).

    Sorry to make it more complicated: Maybe there's already an application case elsewhere in the world, which could supply experience?

    Best regards, F. Helms