A comparative solution of wastewater ocean disposal through submarine outfall with a classical sequencing batching reactor treatment system: case study – Boracéia Beach – São Paulo

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Jayme Ortiz, Lucas Pereira, Renan Papareli, Pablo Oliveira, Jacqueline Yanes

Wednesday 1 july 2015

9:15 - 9:30h at Antarctica (level 0)

Themes: (T) Special session, (ST) Marine outfall system

Parallel session: 8D: Special Session: Marine Outfall System

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In the recent years, the investments of São Paulo government and of the Japan Bank have allowed a significant improvement in the collection rates and in the treatment of wastewater in the São Paulo coast. The São Paulo´s experience in the ocean disposal systems through submarine outfalls is mainly concentrated in large cities. The work here presented shows that this alternative is also a competitive solution for the smaller communities in the northern coast of São Paulo, where are concentrated municipalities with populations of order 50,000 inhabitants or less. The case study is applied for Boracéia beach in the municipality of Bertioga, with a population, during the summer, of nearly 70,000 inhabitants projected for 2015, and it shows a comparison of sequencing batching reactor inland treatment system with ocean disposal through submarine outfall with preliminary inland treatment solutions. Submarine outfall length definition is based in a previous study considering the tide characteristic and bathymetric data in this coastal region and creating a computational grid domain for this region of interest. Representation of the effluent plume dispersion into the simulated region is done by using Visual Plumes UM3 software, which results are coupled to a 3D Delft hydrodynamic model. Numerical simulations show dilution coefficient higher than 140 in the near field for open sea 1800 m outfall length with a designed diffuser system. A comparative cost analysis for the two alternatives solutions including construction and maintenance is also presented showing a significant advantage when submarine outfall is adopted considering inland preliminary treatment. An additional environmental advantage of this alternative is that Guaratuba river could be preserved, in all its course, as Class 1, according whit the classification of CONAMA resolution 357/2005.