The objective of the study is to show that the correlation and spectral analysis of the stochastic input and output signals obtained from technological systems can be used for mathematical description of the process on the basis of the information theory. The statistical analysis and the new quantum informational criterion is proposed. These analyses may be successfully applied to the description of the chemical engineering systems [V. Zhukov, V. Mizonov, P. Filitchev, S. Bernotat, The modeling of grinding processes by means of the principle of maximum entropy, Powder Technol. 95 (1998) 248; S. Masiuk, R. Rakoczy, The entropy criterion for the homogenisation process in a multi-ribbon blender, Chem. Eng. Process., 45 (6) (2006) 500]. In this paper, the informational approach is used for evaluation of the informational power characteristic of the phosphorus reduction in the raw sewage in the functioning sewage treatment plant. These considerations permit to formulate the quantum information criterion for the new predicting system (NS) and the subsystems (functioning sewage treatment system, OS) and (additional system, AS). (c) 2007 Elsevier B.V. All rights reserved.