Anaerobic treatment of agro-industrial wastewater in expanded granular sludge bed bioreactor

What is it about?

Untreated agro-industrial wastewaters are undesirable in the aquatic environment due to the presence of high organic matter contents. However, they may constitute a large potential for biogas production. The present investigation is focused on three laboratory-scale anaerobic expanded granular sludge bed (EGSB) bioreactors, continuously operated for 60 d under mesophilic condition with the aim of exploring the feasibility of treating three most significant agro-industrial wastewaters in Chiapas, Mexico (i.e., cheese whey, vinasse, and coffee-processing wastewater). The EGSB bioreactors were operated with a hydraulic retention time (HRT) of 6 d under stable conditions (i.e., buffer index (BI) of 0.31, 0.34, and 0.03), generating a maximum chemical oxygen demand (COD) removal efficiency of 91, 74, and 96% with an average methane production of 340, 245, and 300 mL/g COD∙d for cheese whey, vinasse, and coffee-processing wastewater, respectively. According to the obtained results, the EGSB bioreactors could be a sustainable alternative to simultaneously solve the environmental problems and to produce bioenergy.

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Why is it important?

Our findings show that the EGSB bioreactors can be a sustainable alternative to solve the environmental problems generated by agro-industrial wastewater. In the present study, COD removal efficiency 91% for R1 (Cheese whey), 74% for R2 (Vinasse), and 96% for R3 (Coffee-processing wastewater) were achieved. Moreover, this bioreactor type was also proved to be a sustainable alternative for bioenergy production; 340, 245, and 300 mL CH4/gCOD∙d with a calorific value of 22.80, 25.46, and 28.84 MJ/m3 from R1, R2, and R3 waste streams, respectively.

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