Anaerobic Digestion of Macrophytes (Lemna Minor, Spirodela intermedia, Spirodela Polyrhiza and Wolffia Columbiana) And Anaerobic Sludge From Uasb Reactor: Effect of I/S Ratio (Inoculum/substrate) and Temperature

Abstract

The present study aimed to explore floating macrophytes biogas and methane production potential (Lemna minor, Wolffia columbiana, Spirodela polyrhiza, and Spirodela intermedia) through the digestion process using anaerobic sludge from a UASB reactor as inoculum. Substrate (macrophytes) and inoculum (anaerobic sludge) came from domestic wastewater treatment. Two exploratory trials were conducted at different operating conditions to determine their influence on biogas and methane production. The assays were carried out using biodigesters with a volume of 50 liters and operated in batches, using macrophyte in nature. The experiments were carried out in triplicates for blank (anaerobic sludge) and different I/S ratios (inoculum/substrate). In Test 1, who evaluated four I/S ratios (0.5, 1.0, 1.5, and 2.0), biodigesters operation occurred under winter temperature conditions (mean 18±2.4°C) for 66 days. Test 2 evaluated the effect of temperature on biogas and methane production in the biodigesters. This experiment maintained the same I/S ratios of Test 1, but at summer temperature (26.6±1.1°C), and the duration of the batches was 37 days. The results obtained in the operational conditions tested in this work indicated that the biomass of macrophytes contributed positively to the increase in biogas and methane production. The highest yields (YCH4) achieved in winter and summer conditions were for I/S=2.0 with 184 NmL CH4/gVS and for I/S=1.0 with 323.3 NmL CH4/gVS, respectively. It evidenced that biogas and methane production varied in function of the operational parameter I/S that determines the amount of substrate fed in the biodigesters and the test application temperature.