Anaerobic digestion of Azolla pinnata biomass grown in integrated industrial effluent for enhanced biogas production and COD reduction: Optimization and kinetics studies

In this study, anaerobic digestion of Azolla pinnata biomass grown in SIIDCUL effluent for enhanced biogas production was investigated. The nutrient-enriched A. pinnata biomass harvested after phytoremediation of SIIDCUL industrial effluent was subjected to anaerobic digestion for a period of 28 days. Response surface methodology based central composite design having 13 triplicated experimental trials was used to perform anaerobic digestion experiments. Three experimental levels of A. pinnata biomass loading (low: 0%, medium: 40%, and high: 80% inoculated with cow dung) as substrate and temperature (low: 30, medium: 35 and high: 40 degrees C) were used to maximize the net biogas yield (mL), methane production (%), and COD reduction (%). The maximum reduction of substrate parameters such as total solids (69.41%), organic carbon (69.21%), volatile solids (68.69%), COD (50.18%), and total Kjeldahl's nitrogen (45.23%) was encountered in medium biomass loading rate (40%) except of pH (21.22) which was maximally reduced in high biomass load (80%) at 35 degrees C temperature. The highest kinetic rate of COD removal was 0.3383 mg/Lw(-1). Overall the modeling results showed maximum predicted biogas yield (3571.14 mL), methane production (55.62%), and COD reduction (52.03%) at 35.36 degrees C temperature and 49.70% of A. pinnata biomass load, respectively. The findings of this study are helpful for maximized anaerobic digestion of A. pinnata biomass and sequential bioenergy production to meet sustainable fuel demands. (C) 2020 Elsevier B.V. All rights reserved.