Determination of the effect of aluminium sulphate on natural microbial coenoses in experiment.

The methods of determining the effect of chemical compounds on the processes of microbial self-cleaning of waters are mainly based on the calculation of the number of indicator microorganisms grown after being incubated on complex nutrient media following exposure of the waters with the substances under study. These methods examine the reaction of specific microorganisms under conditions rather different from those really existing in the water reservoir. The author proposes to use the method of heterotrophic assimilation of CO2 for the determination of the activity of natural bacterial associations in the study of the effect on them of both multicomponent sewage waters of industrial plants and specific chemical compounds. The determination of the values of bacterial productivity according to heterotrophic assimilation of CO2 by natural microbial coenosis was used as the criterion of the effect of the toxicant. Toxicity of the substance under study is evaluated according to its inhibitory effect on the production of natural bacteriocoenosis (test object). Field of application: water toxicology, supervision of toxicity of aqueous media, evaluation of the quality of water. Standard experiment examining the effect of aluminium sulphate on natural bacterial coenosis is considered an example. It has been demonstrated that the effect of aluminium sulphate begins to be felt in concentrations starting from 1 mg X l-1. Statistical analysis of results was carried out by calculating the mean value and confidence intervals. The investigations have shown that application of the method of heterotrophic assimilation of CO2 for these purposes is feasible and of considerable interest with a view to its high sensitivity and precision.