This work designed and assessed the performance of a structured-bed hybrid baffled reactor (SBHBR) with anaerobic/anoxic chambers, treating different dairy wastewater. The anoxic chambers in SBHBR were exposed to intermittent aeration for the simultaneous removal of organic matter and total nitrogen (TN) under a low COD/TN ratio. The hydraulic retention time (HRT) in SBHBR was 48h, with 16.3h in the anoxic zone, where intermittent aeration was implemented, consisting of 60 minutes of aeration and 30 minutes without aeration. The COD/TN ratios tasted were 2.1 ± 0.6, 0.84 ± 0.5, and 0.35 ± 0.1 in the inlet of the anoxic chambers. The SBHBR provided COD removal efficiencies above 90% in all experimental stages. The relevant results achieved in this research regarding carbon and nitrogen removal efficiencies were obtained in stage III. The SBHBR achieved a TN removal efficiency of 82.3 ± 11.4% during this stage. The nitrification and denitrification efficiencies were 85.9 ± 17% and 85.2 ± 9%, respectively, resulting in the anoxic zone TN removal efficiency of 74.6 ± 14.7% with a C/N ratio of 0.35 ± 0.1. Stoichiometric calculations based on nitrogen removal and the C/N ratio required by the denitrification process were used to corroborate the activity of bacteria that perform the anammox pathways as their main mechanism.
This project aimed the structuring of an energy balance of the process that includes the production of bio-oil by hydrothermal liquefaction of the spent coffee grounds and biogas recovery from the study of anaerobic biodegradability of the effluent resulting from this emerging physicochemical process. The system proposed the waste recovery by using it in the biofuels production to meet growing energy demand and dissociate the focus from the use of fossil fuels. The hydrothermal liquefaction process was conducted by means of an association between the high moisture solid fraction, spent coffee grounds, residue of the soluble coffee production process, and water in a 1:20 ratio, at a temperature of 275 °C and time of 10 minutes. After the hydrothermal liquefaction reaction, a characterization stage of the effluent was conducted. After the characterization, anaerobic biodegradability of the effluent and adaptation of anaerobic sludge was carried out. After characterization, the study proceeded to the anaerobic effluent assays. The sludge previously exposed to the effluent was applied in variant initial COD assays aimed at the determination of biogas production, in order to obtain kinetic parameters of the anaerobic digestion of the effluent as substrate. The assays were carried out in 1000 ml flasks operated in batch and subjected to N 2 atmosphere at 37 o C.Calculating the kinetic constants, the intermediate digestion compounds were determined.Once determined the volatile acids, a mathematical modeling was performed according to the Anaerobic Digestion Model No 01 (ADM1). The model proposed by Wu et al. (1988) presented the highest correlation coefficient (R 2 ) when adjusted to experimental data of effluent degradation kinetics. For this adjustment, the n index was 4.61 ± 0.93, which indicates intense inhibition by substrate excess at concentrations above 5304 ± 235 mg L -1 .The modified ADM1 modeling of the data indicated inhibition of hydrogenotrophic and acetoclastic methanogenesis due to the toxicity of the effluent.
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