Aplicação do modelo de Streeter-Phelps na sua forma fuzzy para estudar a qualidade da água em rios sujeitos a várias fontes pontuais

Abstract

This work developed a methodology to study the risk of failure relative to the dissolved oxygen in a river with multiple wastewater discharges. It uses the Mass Conservation Theory and Fick’s Law to stablish a model that representes the concentration fields along the river. Then, this model is simplified, generating Streeter-Phelps model. The equations calculated for the Biochemical Oxygen Demand fields, Oxygen Deficit and Dissolved Oxygen were Fuzzyfied and solved by a computer program written in FORTRAN. This program is capable of determinate the concentration fields in membership function forms. The Risk and Reliability are also determined in many points of the river in diferente situations. A few simulations were made, in wich values of river’s flow rate and DBO discharge concentration vary. Also simulations with one, two and three wastewater discharges along the river were made. The results show the decay of DBO, as well as the decay followed by reestablishment of the levels of oxygen and its deficit. It also shows the fields of Risk and Reliability for each simulation made. The study allowed to deduce that in the conditions simulated, the flow rate of the river exerts more influence over the model than the DBO wastecharge water concentration. The methodology showed efficient in riks analysis for rivers with multiple wastewater discharges.