Evaluation of HRT on Treatment of Coffee Processing Wastewater in EGSB Bioreactor

What is it about?

The coffee processing agro-industry generates large quantities of wastewater requiring systematic treatment prior to disposal. For this reason, the aim of this study was to evaluate the hydraulic retention times (HRT) in treatment of coffee processing wastewater (CPWW) using a laboratory scale Expanded Granular Sludge Bed (EGSB) bioreactor at different HRT (3 to 9 days). The EGSB was evaluated in mesophilic condition (26 ± 2 ◦C) with an average pH of 7.5 ± 0.2 to determine the chemical oxygen demand (COD) removal efficiency. According to the results, the COD removal efficiency increases from 94 to 98% when the HRT increase from 3 to 9 days; the α factor remained stable (0.98) throughout the evolution of the bioreactor. The HRT ́s between 7–9 days generated effluents capable to be dischargeable into water bodies with a permitted COD concentration according to World Health Organization (WHO) and Official Mexican Environmental Regulations permissible limits. Results evidenced that the HRT of 9 days was the one that greater COD removal generated, so the EGSB bioreactor can be a sustainable alternative to solve the environmental problems, compared to other conventional methods to CPWW treatment.

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Why is it important?

Our findings show that the EGSB bioreactor exhibited high efficiency in treating coffee processing wastewater of with a COD removal of 98% was achieved at HRT greater than 7 days and OLR less than 2.5 kg COD m−3day−1. These effluents meet the maximum permissible limit established by the WHO and Official Mexican Environmental Regulations. The EGSB bioreactor was stable in terms of pH, VFAs and α index during all the operation time, so the EGSB bioreactor can be an efficient and sustainable alternative for treatment of coffee processing wastewater compared to other conventional methods.

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