Recuperação de subprodutos (metano e ácidos carboxílicos) em sistemas anaeróbios tratando resíduos agroindustriais

Abstract

The objective of this work was to study different agroindustrial wastewater (ARA) from characterization, aerobic and anaerobic biodegradability and kinetic modeling, as well as analyzing anaerobic treatment routes with a view to methanization or production of carboxylic acids. The ARA studied were: wastewater (AR) from slaughterhouse (ARB), swine breeding (ARS), brewery (ARC), dairy products (ARL), fruit processing (ARBF) from the ice cream industry and biodiesel residual glycerol (GR). The tests of anaerobic biodegradability (BA) and biochemical potential of methane (PBM) were performed in borosilicate flasks, with 110 mL of total volume, 50 mL of reaction volume and 60 mL of headspace. The aerobic biodegradability test was performed using a respirometric system (Oxitop®). The carboxylic acid production potential (PPAC) assays were also carried out in batch reactors, built in borosilicate, with 300 mL of total volume, 250 mL of reaction volume and 50 mL of headspace. The ARA studied were highly biodegradable for both aerobic and anaerobic treatment. Regarding aerobic biodegradability, ARBF, ARS and ARL obtained higher DBOu / DQOT ratios (0.88, 0.79 and 0.77, respectively), indicating that ARA were more biodegradable aerobically. The most promising substrates for methane production were ARL, ARS and GR, with rates of 349, 352, and 359 mL of methane per g of COD removed, respectively. The ARB presented a highly available substrate to the acidogenic microorganisms because it presents high rates of acid formation in the first days of the experiment. The ARB showed yield of AC of 0.55 g acids per g COD available, corresponding to 0.76 g COD of acids per g COD available. The ARS showed a more gradual formation of carboxylic acids in time due to the progressive availability of soluble organic matter through the hydrolysis of the fraction of the particulate organic matter. The ARS showed yield of AC of 0.33 g acids per g COD available, corresponding to 0.40 g COD acids per gram COD available. Thus, the use of low cost substrates, such as ARA, for anaerobic routes of methanization or production of carboxylic acids, is an attractive strategy to add value to sewage treatment. Finally, it was verified, from the modeling studies, that there was great variation regarding the best model for data adjustments, which varied both between the different ARA studied, and in relation to the anaerobic route of methanization or CA production.