-The aim of the present study was to evaluate the efficacy of treating vinasse using anaerobic digestion (AD) followed by ozonation. The AD process was performed using a laboratory-scale upflow anaerobic filter reactor (UAFR) under continuous operation at 29 ± 1 °C. Stable conditions were reached at 10 kgCOD m -3 d -1 and a hydraulic retention time (HRT) of 5 days. Under these conditions, the efficiency of reduction of the chemical oxygen demand (COD) and the methane yield were 75.1% and 0.315 m 3 CH 4 kgCODr -1 , respectively. The anaerobically digested effluent was further treated using ozone in a bubbling column. An experimental 2 3 array [C(0 3 ) g = 70; 100 mgO 3 L -1 ; pH= 7.5; 10; tc = 1 and 3 h] was used. The best conditions for effluent ozonation were 100 mgO 3 L -1 , pH 7.5 and 3 hours of contact with ozone. The average efficiencies for COD, color and turbidity reduction were 82.4, 93.8 and 99.3%, respectively.

The effect of natural mineral on the mono-digestion of maize straw was evaluated in continuously stirred tank reactors (CSTRs) at 38 °C. Different strategies of mineral addition were studied. The organic loading rate (OLR) was varied from 0.5 to 2.5 g volatile solid (VS) L(-1) d(-1). A daily addition of 1 g mineral L(-1) in reactor 2 (R2) diminished the methane production by about 11 % with respect to the initial phase. However, after a gradual addition of mineral, an average methane yield of 257 NmL CH4 g VS(-1) was reached and the methane production was enhanced by 30 % with regard to R1. An increase in the frequency of mineral addition did not enhance the methane production. The archaeal community was more sensitive to the mineral than the bacterial population whose similarity stayed high between R1 and R2. Significant difference in methane yield was found for both reactors throughout the operation.

The influence of the bonding form distribution of Fe, Ni, Co and Mn and their potential bioavailability during the anaerobic degradation of maize straw was investigated. Two reactors were operated over 117 days at 37°C and different dosage strategies of mineral were studied in reactor (R2). Control reactor (R1) was metal‐limited over time. mineral supplementation (1 g L−1) once a week reported the highest methane yield (257 mL g−1 VS) with 30% of increment. Ni and Co predominated in their oxidizable bonding forms and Fe mainly existed as residual and oxidizable fractions. The potential bioavailability (Mn ˃˃ Co ≈ Ni ˃ Fe) of R2 was higher comparing to R1. Metal deprivation in R1 led to depletion of both sequential extraction fractions and total metal concentrations until the end of the process. This study confirmed that the dosage strategy of mineral has a stimulatory effect on methane production from crop maize waste.

The anaerobic treatment of raw vinasse in a combined system consisting in two methanogenic reactors, up-flow anaerobic sludge blanket (UASB) + anaerobic packed bed reactors (APBR), was evaluated. The organic loading rate (OLR) was varied, and the best condition for the combined system was 12.5 kg COD mday with averages of 0.289 m CH kg COD rfor the UASB reactor and 4.4 kg COD mday with 0.207 m CH kg COD r for APBR. The OLR played a major role in the emission of HS conducting to relatively stable quality of biogas emitted from the APBR, with HS concentrations <10 mg L. The importance of the sulphate to COD ratio was demonstrated as a result of the low biogas quality recorded at the lowest ratio. It was possible to develop a proper anaerobic digestion of raw vinasse through the combined system with COD removal efficiency of 86.7% and higher CH and a lower HS content in biogas.

En la etapa de despulpe del beneficio húmedo de café se generan residuales sólidos constituidos fundamentalmente por cáscara y pulpa. Debido a que el contenido de materia orgánica que presentan en su composición se encuentra en el intervalo del 90.5 ± 1.69 % en base seca, estos aportan una elevada carga contaminante al medio en que son vertidos. Esta característica también otorga a dichos residuales potencialidades como fuente de carbono para el proceso de digestión anaerobia. En el presente trabajo se determinó el potencial de biometano y el efecto del incremento de la carga orgánica volumétrica al tratar pulpa de café fresca (Pc I) tras un periodo de almacenamiento congelada (Pc II) y cáscara de café secada naturalmente (Cs). Los ensayos se desarrollaron a temperatura mesofílica (37 ± 1 ºC), en régimen discontinuo y semicontinuo. La pulpa de café fresca presentó un rendimiento de metano de 259.80 ± 15 NmL CH4/g SV. Los ensayos semicontinuos se evaluaron en términos de rendimiento y productividad de metano. Al implementar diferentes estrategias de alimentación, variando las cargas orgánicas volumétricas iniciales en los sistemas, se constató que los mejores resultados se reflejan con la menor carga aplicada (0.2 g SV/L d). No se recomienda la operación de sistemas anaerobios para el tratamiento de residuos sólidos cafetaleros a cargas superiores a 0.5 g SV/L d.