Reliability Evaluation of Wastewater Treatment Plant Impact on the Receiving Waters

The paper presents the results of the study on reliability of the "Wastewater Treatment Plant (WWTP) – Receiver" system, using different models for predicting probability that the river will stay in the required purity class after receiving the discharge from a WWTP. A probabilistic model based on the total probability theorem and Monte Carlo (MC) simulations of the water quality below the wastewater discharge were used. The results show that probabilistic model generates lower values of "WWTP-Receiver" system’s reliability than the MC simulations. The results from the MC model may give more realistic values, being able to reflect the stochastic nature of the process, also showing that for the overall reliability of the "WWTP-Receiver" system – the quality of the receiver is a more sensitive factor than the WWTP’s reliability.