engleski

ERRORS CAUSED BY UNCRITICAL USE OF MATHEMATICAL MODELS OF SEWERAGE SYSTEMS

Although in recent years the overall planning and design of sewerage systems, including wastewater treatment plants (WWTP) is mainly done by using hydraulic mathematical models, in practice, very often an uncritical acceptance of certain solutions and the results obtained are present. The aim of this paper is to point out some very frequent errors that are usually made during modeling of sewerage systems and defining the hydraulic load of WWTP. Three hypothetical case studies are created and described. First one shows the importance of using dynamic models and time regulation of pump operations in the definition of relevant hydraulic load of WWTP when there is an inflow from multiple directions (multiple pressure pipes). Any other practice often leads to unjustified oversizing of WWTP resulting in both operational and economic disadvantages. The importance of detailing of certain critical sections of pipelines and their influence on the model results when analyzing the backflow is described within the second example. In practice, due to the averaging of the results for the water depth along the long gravitational pipes, unrealistic results are frequently obtained which may lead to undersized systems. Understanding the definition of critical flow at specific locations in the modeled sewerage system (weirs, retention basins etc.) during the coincidence of wastewater inflow from different directions is shown in the third example. Not understanding the character of mixed inflows downstream of joints from multiple directions can result in overflow of critical inflow and not meeting the basic environmental criteria or on the other side can lead to retention of unjustified quantities of rainfall runoff within the sewerage system.

wastewater ; hydraulic load ; mathematical model ; pipeline ; critical inflow

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