The heat associated with biodegradation reactions in culture suspensions has been investigated by using flow microcalorimetry. Bacterial cultures obtained in batch or continuous recycling processes ...(activated sludge) were mixed with synthetic biodegradable effluents and the heat output was monitored as a function of time. With batch cultures, experiments were carried out at various growth stages and chemical oxygen demand levels. The response of both types of cultures (batch and continuous recycling) to a sudden change in the chemical oxygen demand content of the effluent (shock load) and to the addition of toxic contaminants (cyanide, cadmium, chromium, copper, and phenol) was also studied. The heat flux measured is in general accordance with the data obtained by respirometric techniques. Moreover, the fast response of the flow microcalorimeter makes it possible to follow the kinetic response of the system after composition changes. From these results, the calorimetric method shows promise for applications in the control of biological wastewater treatment.
