Avaliação do tratamento anaeróbio na biodegradação de efluente contaminado por biodiesel

Abstract

The generation of effluent contaminated by biodiesel has been increasing due to the search for renewable fuels. Anaerobic biological treatment has been widely used for effluents and has been adopted in this study. Initially experiments were performed with optional mixed culture (C1) from pond contaminated by diesel oil and gasoline. This culture was initially adapted in synthetic effluent contaminated with biodiesel under an intermittent aeration condition in the concentrations of biodiesel of 2.5, 5.0, 10.0, 20.0 and 50.0 g / L. The process under anaerobic conditions was developed in 100 ml hermetically sealed penicillin flasks with a gas capture system, with biodiesel concentration of 5.0 g / L. In this condition, the effect of inoculum preparation was evaluated on the biodegradation process. The results showed that, regardless of the inoculum preparation condition (under intermittent or anaerobic aeration condition), the maximum biodiesel removal obtained in 14 days of the process was higher than 85%. Sludge anaerobic (C2) was used in the studies, this was obtained from a UASB reactor of an anaerobic treatment unit of effluent from a tobacco industry (Souza Cruz). The C2 sludge was able to adapt the concentrations of biodiesel from 2.5, 5.0 and 7.5 g / L, in conical reactors of 500 mL capacity, hermetically sealed and adapted with a gas collection system for 16 days of process at table oscillatory at 150 rpm. During adaptation of this sludge followed a mid-exchange protocol in predefined time intervals, an experiment was performed without exchange of medium in two concentrations of sodium bicarbonate, employed as a coagulant agent of the medium. After that, the tests were carried out to verify the effect of: supplementation of the culture medium, A/M ratio (food / microorganism-COD/SSV) and NaHCO3 concentration (gHCO3-/gDQO) on biodiesel biodegradation, using 5.0 g / L of biodiesel in a conical bench reactor for 16 days. According to the results, the experiment with nutrient supplementation, with A/M ratio of 0.4 and 0.3 gHCO3-/gDQO was the condition that presented the highest biodiesel removal with approximately 87% and higher biogas production (CH4 with 0.889 mmol and CO2 of 1.308 mmol), respectively. In this best process condition, an experiment was carried out in a UASB reactor with a capacity of 8.2 L, under the condition of mesophilic temperature in the concentration of 5.0 g / L of biodiesel. The maximum biodiesel removal in this condition was 74% and with a mean biogas production of 6.14 ± 1.5 mL / h and a ratio of 0.57 mmol of CH4 to 0.250 mmol of CO2.