Lack of Organic Carbon as the Condition that Limits Denitrification in the Living Machine Marsh

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Lack of Organic Carbon as the Condition that
Limits Denitrification in the Living Machine Marsh
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Introduction

• We knew the LM marsh wasnt denitrifying as much
  as possible.
• We were asking why?
• Two hypotheses
• Too much dissolved oxygen
• Not enough organic carbon
• We found that lack of organic carbon is the main
  condition that prohibits denitrification

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Why is this important?

• Excessive nitrate can produce eutrophication and
  microbial growth in the ALJC plumbing would be
  problematic.
• Ideally, Living Machines should produce water
  that could be put directly back into the
  ecosystem.
• Producing info that could be used in future
  research about these types of systems that would
  improve their performance.

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Background

• Wastewater is part of all of our lives and we
  need to process it somehow
• Living Machines are an attractive alternative to
  traditional wastewater treatment plants because
  they use natural processes. They are also
  sufficiently pleasant facilities to locate in a
  residential area, which allows for the reuse of
  water.
• The more compact, reliable and efficient these
  systems are, the more people will be interested
  in constructing and using them.

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Methods

• Sampling
• Took samples from sampling ports in the LM marsh
  and measured DO and nitrate levels
• Took samples from the marsh influent and effluent
  sumps
• Manipulations
• Added sodium acetate to marsh influent water at
  different concentrations and incubated them in
  BOD bottles for one to three days.
• Measured nitrate levels after incubations to
  determine denitrification rates.

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Results and DiscussionThe marsh already has
some denitrification
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Carbon works!
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Denitrification over Time
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But too much carbon interferes
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It doesnt take much
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Conclusion and Future Research

• Carbon matters and the LM marsh doesnt have
  enough.
• We have an idea of how much carbon is needed
• We can use that information to add appropriate
  quantities of carbon directly to the system
• If future research determines how much carbon
  plants exude that would tell us how many plants
  the marsh needs.