Abstract: In a method of monitoring and/or controlling a biologically catalyzed reaction, a trace gas which either is, or equilibrates with a metabolic intermediate is identified, and the concentration of the trace gas evolving from the reaction is measured. The measured concentration of trace gas is employed to evaluate the metabolic status of the reaction by a deterministic relationshhip, e.g. an empirical relationship or thermodynamic model. The deterministic relationship may involve other gaseous parameters of the reaction. Preferably, the measured concentration of the trace gas is converted via the deterministic relationship into an estimate of the concentration of a different chemical component of interest for a particular application of the reaction. Carbon monoxide has been found to be a suitable trace gas for purposes of monitoring the metabolic state of the anaerobic digestion process.

Abstract: An improved heat exchanger mat and a method of dislodging and retrieving the mat from the bottom of a solar pond without disturbing an established thermal gradient. The mat is separated from the pond bottom by the injection of a dislodging medium between the mat and the bottom of the pond. When the pond contains a liner, the dislodging medium is injected between the mat and the pond liner. The mat (10) utilizes a dual conduit network of one integral conduit (12) for the flow of heat exchanger fluid and a second integral conduit (26) for the flow of dislodging medium. The dislodging medium enters the dislodging conduit via an inlet (28) and exits through a plurality of outlets (30) located on the underside of the mat. The medium, as it exits, forces the mat upward and frees it from the bottom of the pond. Once the dislodging medium has separated the mat from the pond bottom, attached retrieval cords (20) are used to remove the mat by drawing it up the side of the pond.