Search

The characteristics of excess aerobic granular sludge, related to its structure and chemical composition, limit the efficiency of anaerobic digestion. For this reason, pre-treatment methods and compositions with other organic substrates are used. In earlier work, no attempt was made to intensify the methane fermentation of the excess aerobic granular sludge by adding fatty waste materials. The aim of the research was to determine the effects of co-digestion of pre-hydrodynamically cavitated aerobic granular sludge with waste fats on the efficiency of methane fermentation under mesophilic and thermophilic conditions. The addition of waste fats improved the C/N ratio and increased its value to 19. Under mesophilic conditions, the highest effects were observed when the proportion of volatile solids from waste fats was 25%. The amount of biogas produced increased by 17.85% and CH4 by 19.85% compared to the control. The greatest effects were observed in thermophilic anaerobic digestion at 55 °C, where a 15% waste fat content in volatile solids was ensured. This resulted in the production of 1278.2 ± 40.2 mL/gVS biogas and 889.4 ± 29.7 mL/gVS CH4. The CH4 content of the biogas was 69.6 ± 1.3%. The increase in biogas and CH4 yield compared to pure aerobic granular sludge anaerobic digestion was 34.4% and 40.1%, respectively. An increase in the proportion of waste fats in the substrate had no significant effect on the efficiency of methane fermentation. Strong positive correlations (R2 > 0.9) were observed between biogas and CH4 production and the C/N ratio and VS concentration. [ABSTRACT FROM AUTHOR]

It has been proven that the biocenosis of microalgae and bacteria improves the chemical properties of biomass for its use in anaerobic digestion. However, this anaerobic digestion can be limited by the strong, compact, and complex structure of granulated biomass. Therefore, there is a need to search for an effective method for microalgal–bacterial granular sludge pretreatment, which has not been undertaken in previous scientific works. In this study, ultrasonic pretreatment was used to determine the effects of sonication on anaerobic digestion efficiency. Anaerobic digestion was performed in batch respirometric reactors. It was found that the ultrasonic pretreatment enhanced the biomass solubility; thus, the organic matter concentration increased more than six times compared to the variant without pretreatment. The study showed a positive effect of sonication on the kinetics of the anaerobic process and methane production. The highest methane yield was found in the variants in which the ultrasonication lasted from 150 s to 200 s, and this yield was from 534 ± 16 mL CH4/g VS to 561 ± 17 mL CH4/g VS. The data analysis confirmed strong correlations between the pretreatment time, the amount of biogas and methane production, and the gross energy gain. The highest net energy output and net energy gain were obtained for 150 s of sonication, and, respectively, were 4.21 ± 0.17 Wh/g VS and 1.19 ± 0.18 Wh/g VS. [ABSTRACT FROM AUTHOR]

Regulations in force urge for thermal pre-treatment of post-slaughter waste prior to its anaerobic digestion. Increased interest in biomethane as a fuel in gas networks or vehicles of road transport forces the need to look for heating methods that are alternative to heat recovery from cogeneration. The goal of this study was to determine the synergistic effect of simultaneous ultrasound heating and disintegration on the technological efficiency and energetic balance of the anaerobic digestion of high-load slaughter poultry wastewater. The highest efficiency of anaerobic digestion was obtained for the ultrasound thermal pre-treatment (60 min, 90 °C, OLR = 2.0 gCOD/dm3). In this experimental variant, the biogas production rate reached 9.0 ± 0.2 cm3/gCOD·h, biogas yield was 492 ± 10 cm3/gCOD, and the biogas produced contained 69.8 ± 1.4% CH4. Given the incurred energy outputs, the highest net energetic efficiencies, i.e., 5.92 ± 0.43 Wh and 5.80 ± 0.42 Wh, were obtained in the variants with the conventional thermal pre-treatment (60 min, 70 °C, OLR = 6.0 gCOD/dm3) and ultrasound thermal pre-treatment (60 min, 70 °C, OLR = 6.0 gCOD/dm3), respectively. [ABSTRACT FROM AUTHOR]

Production and consumption of confectionery products have increased worldwide, thus, effective management of wastewater produced is now an important issue. The confectionery high-load sewage was explored for biogas production in an innovative-design anaerobic reactor with labyrinth flow. The experimental studies were focused on determining the best technological parameters of anaerobic digestion for the effective removal of pollutants and obtaining high CH4 production efficiency. It was found that organic loading rate (OLR) of 5.0–6.0 g COD/L·d contributed to the highest CH4 generation of 94.7 ± 6.1 to 97.1 ± 5.1 L CH4/d, which corresponded to a high COD removal of 75.4 ± 1.5 to 75.0 ± 0.6%. Under such conditions the FOS/TAC ratio was below 0.4, indicating reactor stability, and pH was on the level of 7.15 ± 0.04 at OLR 5.0 g COD/L·d and 7.04 ± 0.07 at OLR 6.0 g COD/L·d. [ABSTRACT FROM AUTHOR]