Abstract
Novel systems that are combinations of ecosystems and machines (technoecosystems) are the product of a new form of design called ecological engineering. One class of these ecotechnologies has as a goal some form of autonomous behavior independent of direct human control. This research presents the design and operational dynamics of a technoecosystem that consists of a wetland soil microcosm in which redox potential is the feedback control variable. This feedback loop allows novel system behavior in that it affords the ecosystem control over its own energy sources. The feedback control system was constructed using a standard Pentium computer running Labview. Redox potential in the sealed wetland soil microcosms was monitored over time by the computer using platinum-tipped electrodes. A redox value higher than a userdefined upper threshold triggered addition of a carbon solution, whereas a redox value lower than a lower threshold triggered addition of a nitrate solution. Experimental trials exhibited an oscillatory trend in redox potential over time, compared to steady decline in redox potential in the control trials. The feedback transformed the soil-based ecosystem from a reduced state into an alternative state of oxidation. The difference in behaviors between the control and experimental microcosms can be seen as the result of the artificial feedback in the technological interface. Practical applications for the automatic optimization of the denitrification rate in wastewater treatment wetlands can be envisioned. Also, a taxonomy for the emerging variety of possible technoecosystems, based upon the types of interactions between living and nonliving system components, is proposed.
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