Capacity Expansion Study of the Santos Ocean Outfall, Brazil

Home to approximately four hundred thousand inhabitants and an important touristic center, the City of Santos is the largest seaport in South America. This coastal city is located in the State of São Paulo, Brazil. Since 1979, an ocean outfall has been in use for combined sewage disposal from the City of Santos and neighboring City of São Vicente. The existing pipeline is 4.4 km long and 1.7 m in diameter. It is laid out within a relatively shallow depth of 10 m and its discharge capacity is 5.3 m³/s. Enhance primary treatment and increase the length of the outfall are alternatives in the study in order to improve the outfall system and deal with population increase and new environmental requirements. The fate and transport of sewage effluent, in light of proposed improvements of primary treatment and the augmentation of outfall’s length are evaluated in this paper. Delft3D is used to simulate plume dispersion and other key variables. This is done while considering the non-steady nature of coastal hydrodynamics, tidal effects, wind, current speed, climate conditions, and other drivers. The modified dispersion processes for each alternative are presented and the results from a physical model of the Santos Bay and estuary are coupled to better represent the plume simulations. This research helps find that the proposed alternatives of enhanced primary treatment and a longer outfall give the answer to an improved disposal system that meets environmental requirements.