Long-term effect of free ammonia pretreatment on the semi-continuous anaerobic primary sludge digester for enhancing performance: Towards sustainable sludge treatment

Achieving expanded sludge treatment capacity with additional benefits for an anaerobic digester using free ammonia pretreatment

Semi-continuous anaerobic digestion of secondary sludge with free ammonia pretreatment: Focusing on volatile solids destruction, dewaterability, pathogen removal and its implications

Free ammonia pretreatment enhances the removal of antibiotic resistance genes in anaerobic sludge digestion

The utilization of waste activated sludge (WAS) to recover energy in the form of medium-chain fatty acids (MCFAs) is increasingly attractive due to the high energy density of products. However, the anaerobic fermentation process of WAS would be restricted by the poor degradability of WAS. Herein, we propose an effective approach to improving MCFA production from anaerobic fermentation of WAS using free ammonia (FA) pretreatment. The maximum MCFA production was achieved at 8.3 g of COD/L when the pretreated FA concentration was 255 mg/L, increased by 4.8-fold compared with the control (1.4 g COD/L). In addition, FA pretreatment shortened the lag phase of MCFAs production and promoted the WAS degradation compared to the control without FA pretreatment. Mechanism analysis showed that FA improved the solubilization process, which should be attributed to FA pretreatment altering the WAS properties, that is, smaller particle size and lower hydrophobicity. Moreover, FA-pretreated sludge as feedstock also promoted hydrolysis, acidification, and chain elongation processes for MCFA production, indicating that the activity of related microorganisms has been improved, which was also strongly confirmed by the microbial analysis results. On the basis of these results, a “circle economy” hypothesis that combines FA pretreatment strategy with wastewater treatment plants (WWTPs) by using easily recovered FA from anaerobic fermentation liquor was finally proposed with potential environmental and economic benefits.

Synergistic effects of peracetic acid and free ammonia pretreatment on anaerobic fermentation of waste activated sludge to promote short-chain fatty acid production for polyhydroxyalkanoate biosynthesis: Mechanisms and optimization

Enhanced short chain fatty acids production from anaerobic fermentation of primary sludge using free ammonia pretreatment

How does free ammonia-based sludge pretreatment improve methane production from anaerobic digestion of waste activated sludge

Enhanced short-chain fatty acids production from waste activated sludge by combining calcium peroxide with free ammonia pretreatment

The effect of phenylacetic acid (PAA) pulses on anaerobic digestion (AD) performance and archaeal community structure was evaluated in anaerobic digesters treating sewage sludge from a wastewater treatment plant (WWTP). Four pilot-scale continuous stirred tank reactors were set up at a full-scale municipal WWTP in Santiago de Chile, and fed with either primary or mixed sewage sludge. AD performance was evaluated by volatile fatty acid (VFA) and biogas production monitoring. Archaeal community structure was characterized by 16S rRNA denaturing gradient gel electrophoresis and band sequencing. In the primary sludge digester, a single PAA pulse at 200 mg L(-1) was sufficient to affect AD performance and archaeal community structure, resulting in long-term VFA accumulation, reduced biogas production and community shift from dominant acetoclastic (Methanosaeta concilii) to hydrogenotrophic (Methanospirillum hungatei) methanogens. By contrast, AD performance and archaeal community structure in the mixed sludge digester were stable and resistant to repeated PAA pulses at 200 and 600 mg L(-1). This work demonstrated that the effect of PAA pulses on methanogenic activity and archaeal community structure differed according to AD substrate, and suggests that better insights of the correlations between archaeal population dynamics and functional performance could help to better face toxic shocks in AD.

Performance and microbial community analysis of anaerobic sludge digestion enhanced by in-situ microaeration

Understanding the effects of regionally available residues, wastes, and purpose‐grown energy crops on anaerobic microbes and corresponding digestion performance is important for designing and implementing suitable anaerobic digestion systems to manage them appropriately and to use them for bioenergy generation. This study analyzed and compared dynamic changes in anaerobic microbes and digestion performance using mixtures of six different materials (citrus pulp, olive pomace, cattle manure, poultry litter, whey, and corn silage) generated from Mediterranean agro‐industry. The results indicate that the feedstock mixture (FM3) with low citrus pulp (26% dry matter) and high olive pomace (18% dry matter) reached stable methane production of 210 mL methane/g volatile solids (VS) loading within 30 days after the start up. In contrast, the feedstock mixture (FM1) with high citrus pulp (44% dry matter) and low olive pomace (0% dry matter) required a longer time of at least 70 days to achieve a good methane production of 209 mL methane/g VS loading. The microbial community analysis and corresponding non‐metric dimensionless scaling (NMDS) analysis revealed dynamic relationships between microbial community, feedstock mixture, and digestion time. The feedstock mixtures with low citrus pulp content (FM2 and FM3) facilitated the accumulation of Archaea (i.e., Methanosarcinaceae), which led their digestion to reach stable methane production quicker than the digestion of FM1. This study provided useful information to valorize agricultural residues and wastes for bioenergy production in the Mediterranean region. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Anaerobic digestion is one of the most commonly accepted processes applied for the stabilization and treatment of primary sludge generated in municipal wastewater treatment plants enabling energy recovery via biogas production. Understanding and optimizing anaerobic sludge digesters play a key role in sustainability of wastewater treatment plants. Mathematical modeling of biological treatment systems provides several advantages such as better understanding of biochemical processes, interrelations of different biomass types, and impact of environmental conditions on the treatment plant performance. This research presents the modeling of a full-scale anaerobic sludge digester by implementing Anaerobic Digestion Model No. 1 with a limited number of monitored parameters. Model calibration was carried out using a long-term data set. The accuracy of the optimized parameter sets was assessed against measured data obtainedfrom the full-scale sludge digester. The model could predict the methane flow and effluent chemical oxygen demandconcentration in good agreement with the measured data. Therefore, the validated model can be used to predict full-scale sludgedigester performance under dynamic loadings, and to optimize methane production at different operation conditions.

Full-scale anaerobic digestion of sewage sludges: Fate evaluation of pharmaceuticals and main metabolites

The paper deals with the performances of the mesophilic anaerobic digestion treatment of sewage sludge from a full scale BNR process without primary settling (nominally 300,000 PE). A relation between the activated sludge observed yields, Y(obs), and the anaerobic digester performance was preliminarily found: for values of Y(obs) of 0.25 kgVSS/kgCOD the anaerobic digester specific gas production showed the best performances (0.22 m3/kgVS(fad)). This has to be confirmed with wider future studies. It was also shown the level of sludge pre-thickening to be reached for the self-sustaining warming of the digester also in wintertime. According to the energetic balance and to a comparison with an aerobic stabilisation process, it was pointed out as when a co-generation unit for heat and energy production was introduced about 3.4 kWh/PE y of energy were produced in the anaerobic digestion process. On the other hand, 4.3 kWh/PE y were spent if an aerobic stabilisation process was applied. The economic assessment, carried out on the basis of the energy balances, showed that the anaerobic digestion is always economically advantageous if compared to aerobic stabilisation processes, also for small WWTPs. According to the energetic evaluations an environmental balance was assessed, in terms of CO2 emissions. The difference between anaerobic and aerobic processes was about 5.3 kgCO2/PE y in favour of anaerobic processes application.

Effect of Fe3O4 nanoparticles on anaerobic digestion of municipal wastewater sludge