Flow microcalorimetry in monitoring biological activity of aerobic and anaerobic wastewater-treatment processes

A flow microcalorimetric system which is compatible with the experimental conditions of industrial processes was used to monitor the biological activity of wastewater-treatment systems. Two industrial wastewater-treatment processes were investigated: an activated-sludge (aerobic) treatment of a textile factory effluent and a methane fermentation (anaerobic) treatment of effluents from a cheese factory. In both types of system, the heat flux resulting from metabolic reactions during bacterial degradation of organic substances in the effluent could be measured adequately. Depending on the measurements selected, the calorimetric data could be used to monitor the bacterial activity in the bioprocess, or the effluent degradability or toxicity, or the overall content of degradable substrates in the effluent (loading). The non-invasive measurement of heat flux enabled continuous or semi-continuous on-line monitoring of these biological processes. The response time of the flow calorimetric unit is of the order of minutes, thus yielding process data with minimal delay. These data enable rapid intervention to optimize process parameters (e.g., to control the inlet flow rate or dilution, divert or dilute toxic contaminants, etc.).