Santos submarine outfall wastewater dispersion process: Computer and physical modeling evaluation

Abstract

The usage of preliminary wastewater treatment plants and subsequent ocean disposal via submarine outfalls for domestic sewage is a design choice, which has to be carefully studied for its application at the Brazilian coastal areas. To be environmental sustainable this solution demands a systematic improvement of such projects, an environmental monitoring of the disposal area starting at the diffusers, an improvement of operational rules, the maintenance and control of the treatment plants and the outfalls itself and, beyond those, previous modeling of waste plume dispersion processes for environmental impact assessments. São Paulo State coast has seven domestic submarine outfalls in operation. A physical model was constructed in the Hydraulic Laboratory of Polytechnic School at University of São Paulo -Brazil, reproducing Santos estuary - Baixada Santista and four of these submarine outfalls: Guarujá, Santos and Praia Grande (subsystems 1 and 2). The purpose of this paper is to compare the performance of plume dispersion process for different length of Santos outfall (4 and 5 km), considering two alternatives of diffuser systems. Preliminaries computer simulations followed by simulations in the physical model using a developed methodology for the plume monitoring, were done.