Calorimetric assessment of activity in WWTP biomass.

A heat flux bench-scale calorimeter (Bio-RC1) has been used to assess the metabolic activity of microbial populations involved in wastewater treatment biological processes under aerobic, anoxic and anaerobic conditions. Under strictly aerobic conditions, a linear correlation was observed between oxygen uptake rate and heat flux for heterotrophic and nitrifying bacterial populations. Using the same calorimetric approach and the same apparatus, toxicity and biodegradability of a pesticides factory wastewater were investigated. The activity of heterotrophic and nitrifying aerobic communities was monitored considering both oxygen consumption and heat dissipation, whereas, under anoxic conditions, calorimetric data were compared to the traditional NUR (nitrate uptake rate) test. Heterotrophic activity was found to be 52% inhibited after toxic wastewater exposure under both aerobic and anoxic conditions and 30% inhibition was observed on autotrophic ammonia oxidation. Additionally, calorimetric measurements have been successfully applied to investigate anaerobic digestion. The thermal response of a mesophilic granular sludge to repetitive glucose pulses has been evaluated and a toxicity test has been performed by exposing the biomass to increasing concentrations of formaldehyde.