Abstract
In this study it was evaluated the start-up procedures of anaerobic treatment system with three horizontal anaerobic reactors (R1, R2 and R3), installed in series, with volume of 1.2 L each. R1 had sludge blanket, and R2 and R3 had half supporter of bamboo and coconut fiber, respectively. As an affluent, it was synthesized wastewater from mechanical pulping of the coffee fruit by wet method, with a mean value of total chemical oxygen demand (CODtotal) of 16,003 mg L-1. The hydraulic retention time (HRT) in each reactor was 30 h. The volumetric organic loading (VOL) applied in R1 varied from 8.9 to 25.0 g of CODtotal (L d)-1. The mean removal efficiencies of CODtotal varied from 43 to 97% in the treatment system (R1+R2+R3), stabilizing above 80% after 30 days of operation. The mean content of methane in the biogas were of 70 to 76%, the mean volumetric production was 1.7 L CH4 (L reactor d)-1 in the system, and the higher conversions were around at 0.20 L CH4 (g CODremoved)-1 in R1 and R2. The mean values of pH in the effluents ranged from 6.8 to 8.3 and the mean values of total volatile acids remained below 200 mg L-1 in the effluent of R3. The concentrations of total phenols of the affluent ranged from 45 to 278 mg L-1, and the mean removal efficiency was of 52%. The start-up of the anaerobic treatment system occurred after 30 days of operation as a result of inoculation with anaerobic sludge with active microbiota.
Highlights
The coffee production is one of the major activities in Brazil, for its participation in the socioeconomic context as well as the generation of jobs
Brazil is known as a producer of coffee beans obtained by dry method, form of production which correspond to approximately 90% of national production (LEITE & SILVA, 2000), the wet method has become more and more attractive, because, besides providing grain yield of high quality, with good prices in the market, it reduces the cost of drying of grains, and it has accentuated increase in Brazil
From the results presented by PRADO & CAMPOS (2008) and PRADO et al (2010), the maximum values of measurements of volumetric production of biogas were from 1.44 to 1.56 L (L reactor d)-1, with a methane content of 50 to 60%, which can be considered lower than the mean value of volumetric production of methane of R1, considering that the authors applied volumetric organic loading (VOL) of up to 20.3 g COD (L d)-1
Summary
The coffee production is one of the major activities in Brazil, for its participation in the socioeconomic context as well as the generation of jobs. According to CONAB (2012), the estimated national production of processed coffee beans for the harvest of 2012 will be 50.45 million bags of 60 kg. Coffee is one of the few agricultural products whose value grows considerably with improved quality. The wet method is suitable to the Coffea arábica species, and it is responsible for about one third of the world’s coffee production. Brazil is known as a producer of coffee beans obtained by dry method, form of production which correspond to approximately 90% of national production (LEITE & SILVA, 2000), the wet method has become more and more attractive, because, besides providing grain yield of high quality, with good prices in the market, it reduces the cost of drying of grains, and it has accentuated increase in Brazil
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