Application of Respirometry in the Assessment of Chromium Contaminated Waste Waters Treatment

Restrictions concerning the disposal of waste waters are getting more severe, requiring a greater reliability for the waste water treatment plants as well as a better understanding and application of biological processes which depend of the hosting media. The use of respirometry, the principle of which is based on measuring the consumed amount of oxygen by a sample of activated sludge for the metabolism of a given amount of substrate, seems to be able to contribute to the improvement of the plant management. In fact, it enables the estimation of certain characteristic variables for a good process or the detection of the influence of the physico-chemical conditions such as pH, salinity, metal toxicity, etc. Obviously these conditions have an impact on the enzymatic reaction rates and hence on the metabolism and cell multiplication. In the present study, inhibition by chromium which is a major contaminant present in tanning, metallic surface treatment and other industries waste waters, is likely to neutralise the biomass, was studied by means of the respirometry technique to detect the immediate influence of this type of stress on the activity of microorganisms (autotrophic and heterotrophic), as well as on its purifying power and its aggregation morphology.