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Anaerobic digestion (AD) is a promising technique for waste management, which can achieve sludge stabilization and energy recovery. This study successfully prepared Fe 3 O 4 @ceramsite from WAS and applied it as an additive in sludge digestion, aiming to improve the conversion of organics to biomethane efficiency. Results showed that after adding the Fe 3 O 4 @ceramsite, the methane production was enhanced by 34.7% compared with the control group (88.0 ± 0.1 mL/g VS). Further mechanisms investigation revealed that Fe 3 O 4 @ceramsite enhanced digesta stability by strong buffering capacity, improved sludge conductivity, and promoted Fe (III) reduction. Moreover, Fe 3 O 4 @ceramsite has a larger surface area and better porous structure, which also facilitated AD performance. Microbial community analysis showed that some functional anaerobes related to AD such as Spirochaeta and Smithella were enriched with Fe 3 O 4 @ceramsite treatment. Potential syntrophic metabolisms between syntrophic bacteria (Syntrophomonas, associated with DIET) and methanogens were also detected in the Fe 3 O 4 @ceramsite treatment AD system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Wastes recycling and reutilization technique could simultaneously fulfill waste control and energy recovery sustainably, which has attracted increasing attention. This work proposed a novel waste reuse technology utilizing ceramsite and amended Fe 2 O 3 -ceramsite made from waste activated sludge (WAS) as additives to promote the yield of methane from WAS anaerobic digestion (AD). Experimental results demonstrated that compared to the control (85.05 ± 0.2 mL CH 4 /g-VS), the cumulative methane yield was effectively enhanced by 14% and 40% when ceramsite and Fe 2 O 3 -ceramsite were added. Further investigation revealed that ceramsite, especially the Fe 2 O 3 -ceramsite, enriched the populations of key anaerobes involved in hydrolysis, acidification, and methanogenesis. Meanwhile, potential syntrophic metabolisms between syntrophic bacteria and methanogens were confirmed in the Fe 2 O 3 -ceramsite AD system. Mechanisms studies exhibited that ceramsite and Fe 2 O 3 -ceramsite reinforced intermediate processes for methane production. The favorable pore structure, enhanced Fe (III) reduction capacity and conductivity also contributed a lot to the AD process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Energy conversion of waste activated sludge alkaline fermentation liquor (WASAFL) to medium-chain fatty acids (MCFAs) is promising for sludge treatment and carbon recovery. However, the single electron donor (ED) fermentation for MCFAs production has irreparable defects. To resolve the respective shortcomings of single electron donor (ED) and improve the MCFAs production efficiency from WASAFL, a novel biotechnical process utilizing ethanol and lactate as co-EDs within different combination ratios were investigated. The results verified that MCFAs production was highest with ethanol to lactate ratio of 1:3 (6988.54 ± 208.18 mg COD/L), being 1.46 and 1.87 times of that with ethanol and lactate as single ED. The kinetic analysis results confirmed that ethanol to lactate ratio of 1:3 resulted in the highest MCFAs yield and formation rate. The microbial taxa results uncovered that the relative abundance of Sphaerochaeta and Haloimpatiens showed positive correlation with MCFAs production. The metabolic pathway analysis indicated that the ethanol oxidization, lactate oxidization, acrylate pathway, reverse β oxidization and fatty acid biosynthesis pathway might take place in the WASAFL fermentation system, contributing to the WASAFL-to-MCFAs conversion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this study, a batch of acid-tolerant inoculation sludge was domesticated as inoculum, and different concentrations of nano-magnetite were added to the propionic acid (PA) anaerobic digestion system to explore its effect on the PA degradation. It was found the PA degradation rates of nano-magnetite groups were 10.96-74.62% higher than the control group without magnetite in the 6th day, especially with the dosage of 100 mg/L. Microbial community analysis showed some potential DIET participants of Chloroflexi, Proteobacteria and Bacteroidetes had the highest abundance, while metabolite analysis showed that nano-magnetite promoted the transformation of malic acid to oxaloacetic acid and the PA disproportionation to butyric acid. It indicated that nano-magnetite could effectively promote the early degradation of PA in the sludge acclimation system by accelerating DIET or PA disproportionation, so as to prevent the PA accumulation, which could provide reference for the acid accumulation regulation of anaerobic digestion system., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Conversion of sewage sludge (SS) into value-added material has garnered increasing attention due to its potential applications. In this study, we propose a new application of the sewage sludge-derived carbon (SSC) as an electrode without binder in microbial fuel cells (MFCs). SS was firstly converted into SSC monoliths by methane chemical vapor method at different temperature (600, 800, 1000 or 1200°C). Scanning electron microscopy images showed that carbon micro-wires were present on the surfaces of the samples prepared at 1000 and 1200°C. The results showed that it was beneficial for converting sludge into a highly conductive electrode and increasing carbon content of the electrode at higher temperatures, thereby improving the current generation. The conductivity results show that a higher temperature favors the conversion of sludge into a highly conductive electrode. The MFC using an SSC anode processed at 1200°C generated the maximum power density of 2228mWm -2 and the maximum current density of 14.2Am -2 . This value was 5 times greater than that generated by an MFC equipped with a graphite anode. These results present a promising means of converting SS into electrode materials., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Microbial fuel cells (MFCs) are promising for converting biomass energy into electricity, and have attracted much research interest. However, few inexpensive high-performance anode materials for MFCs exist. In this study, MFC anodes composed of sewage sludge and different contents of fly ash (0%, 20%, 40%, 60%, and 80%) are fabricated via a one-step carbonization method. The maximum current density of 25.5 A m -2 is achieved using the electrode with 20% fly ash, which is 37.5% higher than that of the electrode without fly ash. The improved anode performance is attributed to its good hydrophilicity, which is indicated by its water contact angle of less than 60°, facile adsorption of exoelectrogens, low electron transfer resistance, and good biocompatibility. In addition, the mechanical strength of the electrode with 20% fly ash is approximately 18 times that of the electrode without fly ash. This study reveals a promising method to fabricate high-performance MFC anodes and sheds light on the future development of MFCs using abundant municipal solid waste products., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Two addition modes were used to explore the maximum addition of municipal sewage sludge as a raw material in cement clinker production. The clinker and cement product quality were determined by chemical analysis, cement quality testing, characterization of the clinker crystalline phases, and leaching tests. Municipal sewage sludge addition in the raw mix could be up to 30% based on the cement clinker moduli, and the cement quality met the P.O 42.5 cement standard (GB 175-2007). The amount of municipal sewage sludge added based on the direct addition mode should be less than 15% because of an insufficient early-term cement strength (third day). The leaching concentrations of heavy metals in all cements were below the threshold (GB 30760-2014) using the latest leaching procedure (GB 30810-2014). The municipal sewage sludge could be used with a high addition (30%) in the raw mix as a raw material in cement clinker production.

This study investigated the effect of organic shock loads on the stability of anaerobic granular sludge (AnGS). At double and triple shock intensity (8 and 12 kg COD/m 3 d organic loading rate (OLR), respectively), the accumulation of volatile fatty acids resulted in the decreasing pH of the reactors. The unstable performances of AnGS also appeared in the macroscopic properties, including the decreasing contents of relative hydrophobicity (RH), granular strength and diameter, and the fluctuation of EPS production. Noteworthily, the contents of loosely bound and tightly bound polysaccharide increased obviously and were higher than that in the control under double and triple OLR shock load. However, the growing trend of protein content was only found in the double OLR shock reactor. In addition, the N-hexanoyl-homoserine lactone (C6-HSL) content increased following the shock and then decreased during the recovery. The autoinducer-2 (AI-2) content gradually decreased under OLR shock conditions, and then rapidly increased during the recovery phase. The behaviour of the diffusible signal factor (DSF) was opposite that of AI-2. The combination of C6-HSL, AI-2 and DSF had a degraded effect on the properties of AnGS. The results provide a new reference for further research into the inter-effects among multiple signal molecules in anaerobic sludge., Abbreviations: 3-oxo-C6-HSL: N-3-oxo-hexanoyl-homoserine lactone; AHLs: acyl-homoserine lactone; AI-2: auto-inducers-2; AnGS: anaerobic granular sludge; C4-HSL: N-hydroxybutanoyl-homoserine lactone; C6-HSL: N-hexanoyl-homoserine lactone; COD: chemical oxygen demand; DSF: diffusible signal factor; EPS: extracellular polymeric substance; HPLC: High-performance liquid chromatography; HRT: hydraulic retention time; IC: integrity coefficient; LB-: loosely bound; MLSS: mixed liquor suspended solids; MLVSS: mixed liquor volatile suspended solids; OLR: organic loading rate; PN: protein; PS: polysaccharide; QS: quorum sensing; RH: Relative hydrophobicity; SS: suspended solids; TB-: tightly bound; UPLC-MS/MS: ultra-performance liquid chromatography-tandem mass spectrometry; VFAs: volatile fatty acids.

The effect of adding position for tannery sludge in a co-processing cement rotary kiln on the chromium leachability of the cement produced was assessed in laboratory scale. Cement clinkers and pastes were produced and evaluated based on analysis of the cement quality, characterization of the clinker crystalline phases, and extraction toxicity of heavy metals in the resulting cements (using the toxicity characteristic leaching procedure (TCLP) and the Chinese GB/T 30810-2014 standard). It was found that the amount of sludge added (up to 0.7% of the feed composition) and use of different addition points for the sludge had no detrimental effect on the resulting cement quality. The retention ratios of heavy metals during sintering were related to their volatilities and the sludge addition points. The Cr concentration in leachate generated by the TCLP was far below the regulatory limit (5mg/L); however, when using the GB/T 30810-2014 procedure, the Cr concentration in the leachate exceeded the regulatory limit (200μg/L) when the sludge addition was greater than or equal to 0.5% and it was added at the kiln main burner position. Based on our laboratory study, tannery sludge might be added at the decomposing furnace addition point to reduce the Cr leachability of the resulting cement., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Quorum sensing is a concentration-sensing mechanism that plays a vital role in sludge granulation. In this study, the regularities of distribution of different signal molecules, including intra- and interspecific signal molecules (diffusible signal factor, DSF), interspecific signal molecules (autoinducter-2, AI-2) and intraspecific signal molecules (acyl-homoserine lactones, AHLs), from three types of anaerobic granular sludge were investigated. The results showed that 70-90% of DSF was distributed in sludge, while AI-2 in the Water phase accounted for over 80% of the total content. Interestingly, there was a positive correlation between DSF and AI-2, which played opposite roles in granulation. Moreover, more than 55% of short and medium acyl chain AHLs tended to spread in aqueous water, while the long acyl chain AHLs were closer to granular sludge than the short and medium acyl chain AHLs. With the exception of one type of sludge, the percentage of long acyl chain AHLs in the sludge phase was greater than 70%. The different distributions of signal molecules were primarily determined based on their physicochemical properties, including molecular weight and solubility in water or organic solutions. In addition, the basic properties of sludge, such as the granular level or the production of EPS, were closely related to the diversity, distribution and concentration of signal molecules. As a medium in granulation, extracellular polymeric substances production was regulated by different signal molecules from different parts of anaerobic granular sludge. This study provides a foundation for investigation of quorum sensing in the system of anaerobic granular sludge., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The effects of feed strength, hydraulic residence time (HRT), and operational temperatures on soluble microbial product (SMP) production were investigated, to gain insights into the production mechanism. A carrier anaerobic baffled reactor (CABR) treating dilute wastewater was operated under a wide range of operational conditions, namely, feed strengths of 300-600 mg/L, HRTs of 9-18 h, and temperatures of 10-28 degrees C. Generally, SMP production increased with increasing feed strength and decreasing temperature. At high temperature (28 degrees C), SMP production increased with decreasing HRT. As the temperature was decreased to 18 and 10 degrees C, the SMP production was at its peak for 12 h HRT. Therefore, temperature could be an important determinant of SMP production along with HRT. A higher SMP to soluble chemical oxygen demand (SCOD) ratio was found at high temperature and long HRT because of complete volatile fatty acid degradation. SMP accounted for 50%-75% of the SCOD in the last chamber of the CABR. As a secondary metabolite, some SMP could be consumed at lower feed strength.

The objective of this study was to evaluate the effects of the C/N ratio on the water state changes during the composting of kitchen waste (KW) and vegetable waste (VW) mixtures. The C/N ratios in KW and VW were 50.70 and 27.07, respectively, and the VW was added to the KW to amend the C/N ratio. Five composting treatments were used, R1 with 0% KW, R2 with 25% KW, R3 with 50% KW, R4 with 75% KW, and R5 with 100% KW, and the initial C/N ratios increased in the order R1 < R2 < R3 < R4 < R5. As the composting process progressed, the capillary water (CW) and multi-molecular-layer water (MMLW) were changed into entrapped water (EW), and a high C/N ratio could delay the changes in the water state. The percentage of EW and CW significantly positively correlated with the C/N ratio during the composting of KW. The composting process performed better in treatments R2 and R3 than in the other treatments, and it was found that treatments R2 and R3 each had a lag phase of around 4 d until the water states started to change. [ABSTRACT FROM AUTHOR]

A strain of Ralstonia sp. FD-1 capable of using 4-fluoroaniline (4-FA) as the sole carbon and nitrogen source was investigated for its ability to utilize 4-FA isomers (2-FA, 3-FA) and homologs (2,4-DFA, 3,4-DFA, and 2,3,4-TFA). Both 4-FA and 3-FA could be mineralized as the sole carbon and nitrogen source by FD-1. 2-FA, 2,4-DFA, 3,4-DFA, and 2,3,4-TFA could not be degraded by FD-1, respectively, and were selected as secondary substrates for cometabolism with 500 mg/L 4-FA as growth substrate. Bacterial growth (OD600), F− concentrations, and fluoroanilines contents were measured to determinate the degradation ability of 4-FA isomers and homologs by FD-1. FD-1 growth was inhibited by 2,4-DFA, 3,4-DFA, and 2,3,4-TFA at higher concentrations (400 mg/L), except for 2-FA. Complete fluoroanilines degradation was achieved while incomplete defluorination was characterized by the stoichiometric fluoride release indicating partial degradation but not total mineralization. When fluoroaniline was supplied to the resting cells of strain FD-1, a relatively effective removal was showed. Strain FD-1 had broadened application prospect of toxicity and low nutrition fluoroanilines wastewater. [ABSTRACT FROM AUTHOR]