Energy potential of biogas and sludge from UASB reactors in the State of Paraná, Brazil

Lucas Sampaio Lopes,Tayane Cristiele Rodrigues Mesquita,Júlia Silva Marco,Andre Pereira Rosa,Gustavo Rafael Collere Possetti

doi:10.4136/ambi-agua.2398

Abstract

Upflow Anaerobic Sludge Blanket (UASB) reactors are widely used for domestic sewage treatment in Brazil, and generate sludge and biogas as by-products. Typically, the sludge is sent to sanitary landfills, and the biogas is burned in flares. This study assessed the energy potential of these by-products in sewage treatment plants (STPs) located in the state of Paraná, Brazil. First, an overview of biogas energy recovery potential in a full-scale STP based on UASB reactors was carried out. Afterwards, a total of 239 STPs in the state of Paraná were assessed, and the energy potential of the by-products was estimated by a mathematical model. Data were spatially classified using ArcGIS®, taking into account the different effluent characteristics (worst, typical and best scenario), sludge dehydration systems (drying bed and centrifuge) and sizes (small, medium and large). Among the states in Brazil, Paraná presented the highest biogas potential, although nowadays it exploits only 0.4% of its capacity. Biogas was the main by-product generated by UASB reactors in Paraná, and if used in the entire state, it could supply the energy demands of a city with 111,000 inhabitants. Biogas corresponded to 65, 64 and 74% of the total potential (sludge and biogas) for small, medium and large STPs, respectively. The study of the energy potential of the by-products associated with GIS tools positively contributes to the decision-making process in sanitation management and to improve energy sustainability.

Highlights

Among the technological alternatives for sewage treatment in Brazil, the anaerobic systems can be highlighted (Santos et al, 2016), especially with the wide use of upflow anaerobic sludge blanket reactors (UASB)
An overview of biogas energy recovery potential in sewage treatment plants (STPs) based on UASB reactors First, an inventory of full-scale STPs that implemented the biogas energy recovery in Brazil was carried out
The States of São Paulo, Minas Gerais and Paraná include all of the STPs that exploit energy recovery of biogas, though their potential is not sufficiently explored

Summary

Introduction

Among the technological alternatives for sewage treatment in Brazil, the anaerobic systems can be highlighted (Santos et al, 2016), especially with the wide use of upflow anaerobic sludge blanket reactors (UASB). Chernicharo et al (2018) have recently accounted for more than 650 full-scale UASB based STPs with treatment capacity of 43 m3 s-1, corresponding to nearly 23 million inhabitants The interest in such systems is associated with their low costs for installation and operation, as well as the low demand for area and energy consumption (Khan et al, 2011). The expansion of STPs that use anaerobic treatment systems in Brazil has increased the generation of by-products of anaerobic digestion, such as biogas and sludge (ROSA et al, 2018) These by-products can be used for energy recovery purposes, which has raised interest in their management, due to the possibility of diversifying and expanding the Brazilian energy matrix and reducing the consumption of fossil fuels and the emission of greenhouse gases (Bernal et al, 2017). A great part of the biogas produced in STPs in developing countries is not used to produce energy, as observed in Brazil, where such use is still incipient and limited to a small number of treatment plants (Santos et al, 2016)

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Results

Conclusion