The Metropolitan Region of São Paulo (RMSP) encompasses 39 municipalities and has more than 20 million inhabitants. Approximately 80% of the population is covered with sewage collection and treatment services.
Most of the wastewater collected in the region is sent to five main wastewater treatment plants (WWTPs), which are operated by SABESP, the São Paulo State’s Basic Sanitation Company, that is the concessionaire responsible for providing water and sanitation services in the majority of the municipalities in the RMSP (36 localities in 2020).
The design goals for treatment capacity and organic load removal to be achieved by these treatment plants are based on very conservative technical specifications from international engineering manuals, in favor of safety. However, experiences abroad have shown that conventional treatment facilities with optimized performances can surpass the original treatment capacities and the effluent quality goals defined in design phase.
On the other hand, due to the specific urban conditions of large Brazilian cities such as São Paulo, as well as to inefficient conservation and cleaning of urban areas and infrastructures by local services, the wastewater collected generally carry also lots of coarse solids and grit, which reinforces the importance of improving the pre-treatment phase, right after the entrance to the WWTPs, to maximize solid removal.
As SABESP is expanding the collection network at an accelerated pace, there will be a significant increase in sewage flows to be sent to these WWTPs in the short term. Thus, it is vital to prepare these facilities to properly receive and treat increased wastewater flows with maximum efficiency and at minimum capital and operational costs.
In 2019, the 2030 WRG Brasil/São Paulo, in partnership with the SABESP Metropolitan Sewage Unit (MT), developed and started the implementation of a program for optimizing the performance of 4 main WWTPs in the RMSP: Barueri, Parque Novo Mundo, ABC and São Miguel plants.
The program is focused on defining priority actions and investments to eliminate bottlenecks and maximize the efficiency of the treatment process in each plant. The core idea is “making more with the same”, that is, to expand treatment capacity and improve the quality of the final effluents through priority equipment replacements, operational adjustments and maintenance procedures, hence minimizing the need for physical expansion and investments in tertiary treatment technologies, which require higher capital and operation expenditures.
When the operational performance goals are achieved and stabilized, an important environmental benefit will be perceived in the quality of the main river of São Paulo, the Tietê. The WWTPs will also be prepared to incorporate circular economy processes in a further stage, which will bring extra benefits in terms of the environmental and financial sustainability of the wastewater treatment services.
Progress to Date
Counting on support of an international expert hired by 2030 WRG, the development and implementation of the program has been carried out in a participatory manner, involving the operating teams and other SABESP technical boards in meetings, workshops and field visits since the beginning (March 2019).
The first phase of the program was concluded in April 2020 and produced preliminary analysis and strategic discussions on the performances of the Barueri and the Parque Novo Mundo WWTPs. Thanks to SABESP high-level support, the program was expanded to cover 4 WWTPs. The company also showed proactivity in immediately adopting some preliminary recommendations, which has already contributed to a significant increase in the performances of the Barueri and the Parque Novo Mundo plants.
In the second phase, initiated in May 2020 and expected to finish in November 2021, a detailed audit of each phase of the treatment process is being carried out in each plant. Instruments to measure different processes and generate on-line monitoring data are being installed. Data from the analysis of historical series and from monitoring will feed information to a modelling software that simulates the operations in a WWTP. Stress tests, oxygen transfer tests, digestion mixing studies and other field and laboratory tests are already scheduled. These will make possible to detect where are the main bottlenecks that limit the efficiency of each plant and indicate the necessary operational adjustments and priority investments so that it can reach maximum performance at a reasonable CapEx and OpEx. The general goal is to ensure removal of at least 90% of the organic load in all the WWTPs included in the program.
The methodology developed for this program can be replicated for countless WWTPs in the State of São Paulo and in the country, and should be understood as a true innovation, as it is based on a comprehensive and transforming vision of the management of basic sanitation public fixed assets, founded on the analysis of the efficiency of process engineering and focused on results.
The first step to develop a circular economy program for treatment plants is to optimize the investments already implemented.
Optimizing the existing processes generates not only better results in terms of treatment, but also in terms of investment efficiency.
Using a participative and holistic approach allows teams to incorporate improvements and best practices along the assessment process which generates immediate, concrete benefits that can be easily implemented and replicated.
Having ownership from the management team since the very beginning of the process is key to motivate a transformational dialogue and analysis while accelerate improvements along the whole process not only at the end. It enables innovative actions and shows a real commitment with circular economy solutions.
The treatment plants concepts and projects must be carefully adapted to the reality of the informal occupation and low-quality management of our cities.