Energetic Valorization of Eichhornia crassipes and Pistia stratiotes by Methane Production in an Anaerobic Co-digestion Process

Eichhornia crassipes and Pistia stratiotes are often used in phytoremediation of wastewater. Nevertheless, these macrophytes must be renewed after use to avoid recontamination of treated wastewater by dead plants. This study aims to produce of energy from a mixture of these two macrophyte es by anaerobic co-digestion in the presence of the activated sludge which acts as an inoculum. The study was carried out using a 4 L digesters batch under mesophilic conditions (35°C). The scenarios 3/1; 2/1 ratios between substrate and inoculum as well as control were used to evaluate the quantity biogas produced over a 25-day period. The pH, NH4+, BOD5 and COD were monitored to verify the stability of the process. The results of this study show that the pH varies from 6.39 to 7.31 while the NH4+, COD and BOD5 concentrations vary from 39.6 to 86.4 mg L−1, 1965.8 to 2940.4 mgO2 L-1 and 1200 to 1500 mgO2/L-1 respectively. The varying ranges of these parameters have no effect on methanogenesis. When the two macrophytes were mixed in a 3/1 ratio, a volume of 13797 mL of biogas was produced with a methane content of 70.53%, a value within the range of a good quality of biogas.