Planning for achieving low carbon and integrated resources recovery from sewage treatment plants in Minas Gerais, Brazil

Abstract

There is an enormous deficit in sanitation infrastructure in most Brazilian cities. To tackle this challenge, it is crucial to conceive the new sanitation infrastructure based on sustainability principles, including an integrated approach for the management of the liquid, solid and gaseous phases. This study aimed at developing sustainable sewage treatment flowsheets for different scales and regional scenarios in the state of Minas Gerais. Two watersheds were chosen as study areas, due to their remarkable regional importance and socioeconomic and environmental diversity, i.e. Rio das Velhas and Jequitaí-Pacuí. Currently available processes for sewage treatment and resources recovery were assessed based on: literature review and benchmarking of operational practices, experiences reported by sanitation companies, techno-economic feasibility of resource recovery and carbon footprint assessment of anaerobic-based technologies. Social acceptance was also considered. A total of 15 sustainable flowsheets were proposed, comprising passive/natural systems (stabilization ponds, constructed wetlands and controlled land application), anaerobic process combined with natural systems (UASB reactors followed by controlled land application, constructed wetlands or polishing ponds) and compact anaerobic/aerobic systems (UASB reactors followed by activated sludge or trickling filters). Processes selected for small-scale sewage treatment plants (STPs) (people-equivalent - PE < 10,000 inhab.) intended to be integrated into local communities and economic activities. Large-scale STPs (especially those with PE > 100,000 inhab.) were conceived as industries, where a wide range of resources (e.g. sand for non-structural concrete, biogas for electricity, sludge for thermal energy) could be recovered from the influent sewage. Results obtained from the current study could serve as support for decision-making on the planning and implementation of new sustainable sanitation solutions in the state of Minas Gerais and possibly in other regions of Brazil and other developing countries.