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The conversion of biomass to bioenergy is one of the approaches to creating a sustainable society. In this study, the life cycle assessment and the net energy analysis of converting mixed sewage sludge and beverage waste into bioenergy via a combined hydrothermal liquefaction-anaerobic digestion (HTL-AD) system was carried out. Primary sludge (PS), winery rose lees (RL), brewery Trub (BT), the mixture of brewery trub and primary sludge (BTPS) and the mixture of winery rose lees and primary sludge (RLPS) were the feedstocks considered. Efficient energy utilization [in form of net energy ratio (NER)], and environmental emissions were evaluated. The NER of BT (2.07) and RL (1.76) increased when mixed with PS (3.18) to produce BTPS (3.20) and RLPS (2.85). Also, the HTL phase of the combined HTL-AD system produced a greater NER than the AD phase in BT, BTPS, and PS and vice-versa in RL and RLPS. Six environmental impact categories were studied namely global warming, terrestrial acidification, ionizing radiation, terrestrial ecotoxicity, human carcinogenic toxicity, and human non-carcinogenic toxicity. RL produced the greatest environmental impact while BTPS produced the least impact, thus indicating the advantage of feedstock combination. This study shows that the combination of feedstocks for bioenergy production in an HTL-AD system does not only increase the quality and quantity of products but also increases the overall NER as well as reducting the environmental impacts. The study also proved that an integrated HTL-AD system is an energy efficient system with greater resource utilization and less environmental footprint than the constituent systems. [Display omitted] • Mixed winery rose lees/brewery trub and sewage sludge generates bioproducts of higher net energy ratio. • Combined hydrothermal liquefaction and anaerobic digestion (HTL-AD) is an energy efficient and environmentally sustainable system. • In the integrated HTL-AD system, the HTL phase produced a higher net energy ratio than the AD phase. • BT (2.16) + PS (NER 3.53) = BTPS (3.35) and RL (1.38) + PS (3.53) = RLPS (2.09). • Global warming > human non-carcinogenic > terrestrial ecotoxicity > ionizing radiation > human carcinogenic > Terrestrial acidification. [ABSTRACT FROM AUTHOR]

The presence of micro/nanoplastics (MPs/NPs) in sewage sludge has sparked considerable apprehensions over their potential negative effects on anaerobic digestion (AD) performance. The occurrence of MPs/NPs can trigger oxidative stress on the anaerobic microbiome, leading to potential inhibition of the AD process. While the thermal hydrolysis process (THP) is an extensively utilized sludge pretreatment method for AD, its impact on stress induced by MPs/NPs during AD remains poorly understood. In this study, we assessed the impacts of low-temperature THP (90 °C, 90 min) on AD of sewage sludge in the presence of 150 μg/L of polystyrene nanoplastics (PsNPs) under different solid retention times (SRTs) of 20, 15, and 10 d. The presence of PsNPs resulted in a higher reactive oxygen species (ROS) production and a higher abundance of antibiotic resistance genes (ARGs). Additionally, their presence caused a significant inhibition of methane production by 28.2%, 29.3%, and 38.8% for SRTs of 20, 15, and 10 d, respectively. Introducing low-temperature THP prior to the AD could partially recover methane production by mitigating ROS-induced stress and curbing the propagation of ARGs during the AD process. These results shed light on the potential benefits of THP and further optimization opportunities in alleviating the adverse effects of MPs/NPs-induced stress during sewage sludge AD. [Display omitted] • PsNPs (150 μg/L) hindered methane production in AD under three different SRTs. • Low-temperature THP as a pre-treatment could partially recover methane production. • PsNPs caused a 41.3% increase in ROS levels under 10 d SRT. • Although PsNPs boosted ARGs propagation, THP showed an opposite pattern. • PsNPs and THP increased the abundance of hydrogenotrophic Methanobacterium. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDE) are priority contaminants historically used as flame retardants. PBDEs are known to occur in wastewater biosolids posing potential concerns with the beneficial land application of the biosolids. This study evaluated the removal of 21 congeners in nine full-scale sludge treatment systems including pelletization (P), alkaline stabilization (AS), and aerobic (AE) and anaerobic (AN) digestion. It is the first study to conduct a mass balance analysis of a broad spectrum of PBDEs during physical, chemical, and biological sludge treatment. The PBDE congener pattern in raw sludge and biosolids samples was consistent with commercial formulations. The fully brominated congener BDE-209 dominated biosolids from all sites with an average concentration of 620 ng/g dry weight (dw), followed by BDE-99 (173 ng/g dw) and BDE-47 (162 ng/g dw). Mass balance analysis on the P and AS processes showed no change in PBDE mass flows with treatment. However, aerobic and anaerobic digestion processes reported significant levels of removal and formation of individual congeners, though the results were not consistent between facilities. One aerobic digestion process (AE2) reported an overall average removal of 48%, whereas the other (AE1) reported very high levels of accumulation of tri- and tetraBDE congeners. Similarly, there were significant variations in PBDE behavior across the five anaerobic digestion plants studied. The plant with the longest solids retention time (SRT) (AN1) reported a moderate removal (50%) of overall PBDE loading and lower congeners, whereas other plants (AN2-AN5) showed significant low (−19%) to high (−166%) levels of formation of lower congeners. The results suggest that reduced SRTs result in formation of lower congeners while extended SRTs can lead to moderate removal of some PBDEs. Conventional sludge treatment result in low to moderate PBDE removal and advanced thermal conversion technologies may be needed to improve the contaminant removal during sludge treatment. [Display omitted] • Alkaline stabilization and pelletization processes did not change PBDE mass flows significantly. • Aerobic and anaerobic digestion result in PBDE removal and accumulation of lower congeners. • Operational SRT could impact PBDE removal in anaerobic digestion processes. • Conventional sludge treatment technologies result in only low to moderate PBDE removal. [ABSTRACT FROM AUTHOR]

Due to its environmental impact, the growing production of sewage sludge is a prime concern for wastewater treatment plants. In this study, advanced thermal hydrolysis, the combination of thermal hydrolysis and oxygen, was examined to enhance biogas production and overcome the disadvantages of thermal hydrolysis, including sludge colour, high energy consumption, and high level of ammonia concentration in the treated sludge. A mixture of 55 % primary sludge and 45 % waste activated sludge was pre-treated using advanced thermal hydrolysis at 100, 115, 130, and 145 °C with a processing time varied from 5 to 30 min and oxygen pressure from 10 to 30 bar before anaerobic digestion. Advanced thermal hydrolysis process at 145 °C 15 min 20 bar O₂ is the condition that provided the highest biogas yield (439.6 mL/g VS added). At this treatment condition, the concentration of ammonia nitrogen and propionic acid in the treated sludge was sufficiently low (approximately 302 mg/L and 559.7 mg/L, respectively) to minimise adverse effects on anaerobic digestion. [Display omitted] • ATHP with O₂ can make sewage sludge more biodegradable compared to THP. • Treated sludge from ATHP at 100 and 145 °C has the highest amount of acetic acid. • Treated sludge from ATHP 100 °C has a high level of propionic acid from 762.4 mg/L. • Biogas production peaks at 439.6 mL/g VS added at ATHP 145 °C 15 min 20 bar O₂. [ABSTRACT FROM AUTHOR]

Due to its environmental impact, the growing production of sewage sludge is a prime concern for wastewater treatment plants. In this study, advanced thermal hydrolysis, the combination of thermal hydrolysis and oxygen, was examined to enhance biogas production and overcome the disadvantages of thermal hydrolysis, including sludge colour, high energy consumption, and high level of ammonia concentration in the treated sludge. A mixture of 55 % primary sludge and 45 % waste activated sludge was pre-treated using advanced thermal hydrolysis at 100, 115, 130, and 145 °C with a processing time varied from 5 to 30 min and oxygen pressure from 10 to 30 bar before anaerobic digestion. Advanced thermal hydrolysis process at 145 °C 15 min 20 bar O₂ is the condition that provided the highest biogas yield (439.6 mL/g VS added). At this treatment condition, the concentration of ammonia nitrogen and propionic acid in the treated sludge was sufficiently low (approximately 302 mg/L and 559.7 mg/L, respectively) to minimise adverse effects on anaerobic digestion. [Display omitted] • ATHP with O₂ can make sewage sludge more biodegradable compared to THP. • Treated sludge from ATHP at 100 and 145 °C has the highest amount of acetic acid. • Treated sludge from ATHP 100 °C has a high level of propionic acid from 762.4 mg/L. • Biogas production peaks at 439.6 mL/g VS added at ATHP 145 °C 15 min 20 bar O₂. [ABSTRACT FROM AUTHOR]

The fate of glyphosate and its metabolite AminoMethylPhosponic acid (AMPA) was followed at the catchment of the Sûre river, mainly characterized by small population density and small and medium-sized wastewater treatment plants (WWTPs). A high concentration of AMPA was found in water samples collected in inlet from different wastewater streams, the industry being the main contributor, while glyphosate resulted mainly in domestic origin. The two molecules were also monitored in the anaerobic digestion as in the supernatant produced after centrifugation (reject water). A total of 0.0713 and 2.24 g/d of glyphosate and AMPA respectively were regularly returned to the activated sludge tank (AST) indicating a 20% impact of the sludge management line on the global wastewater mass balance. Finally, the use of Constructed Wetlands (CWs) in Vertical Flow (VF) configuration was tested as a suitable technology to retain both glyphosate and AMPA (90 and up to 50% elimination respectively) and minimize their discharge into surface water. [Display omitted] • Non-agricultural application of glyphosate is relevant for urban emission. • The origin of AMPA is mostly related to industry rather than glyphosate. • Concentrations of AMPA and glyphosate are relevant in reject water. • Vertical Flow Constructed Wetland is 90% efficient towards glyphosate. • AMPA degradation in the soil is sensitive to the wetland loading regime. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is regarded as a promising technology in energy recovery and the spread mitigation of antibiotic resistance. However, the performance of AD is dependent on various factors, and substrate type is one of the most important. In this study, the fate of antibiotic resistance genes (ARGs) response to the substrate types was investigated, and three typical environmental reservoirs of ARGs (pig manure, chicken manure and sewage sludge) were selected. The role of substrate microbial community on the fate of ARGs was clarified through the comparison between the AD of the substrates with and without a prior autoclave-disinfected step. Results showed that substrate types significantly influenced the fate of ARGs, while the influence from the substrate microbial community was limited. The concentration of antibiotics, the horizontal gene transfer reflected by intI1 and co-selection from heavy metals reflected by metal resistance genes (MRGs) were all reduced effectively. Microbial community varied from substrate types and dominated the ARGs fate concerning the standardized total effects through the mantel test and SEM analysis. The fate of tetX , ermF , tetM and ermB was mainly determined by the physicochemical parameters and the phyla of Firmicutes and Bacteroides. The phyla of Actinobacteria, pcoA and czcA contributed most to the reduction of bla TEM and mcr-1 , and the phyla of Proteobacteria, Chloroflexi, Synergistetes, Euryarchaeote, intI1 and merA correlated significantly with the fate of bla CTX-M , ereA , tetG and sulI. This study highlighted the importance of substrate types when considering the fate of ARGs during AD. Image 1 • Substrate types significantly influenced the ARGs fate during anaerobic digestion. • The influence from the substrate microbial community on the ARGs fate was limited. • The ARGs in the substrates themselves contributed little to the ARGs fate. • The dominant factors influencing the separate ARGs were determined. • Nutrient variance led to microbial community variance that dominated ARGs fate. [ABSTRACT FROM AUTHOR]

Abstract Fe 2 O 3 and Al 2 O 3 nanoparticles are widely used in products and find their way to wastewater treatment plants through the contact of water with these products. In this study, impacts of Fe 2 O 3 and Al 2 O 3 nanoparticles on methane potential of waste activated sludge (WAS) were investigated by comparing long and short term toxicity test results, modelling and FISH analysis. Methane production from the samples treated with the maximum concentration of Fe 2 O 3 nanoparticles decreased 28.9% at the end of the long term BMP test. EC 50 value for BMP test of the Fe 2 O 3 nanoparticles was calculated as 901.94 mg/gTS with high coefficient of determination. Methane production from the samples treated with Al 2 O 3 nanoparticles increased up to 14.8% (p > 0.05) at the end of the BMP test. However, short term toxicity tests for Fe 2 O 3 and Al 2 O 3 nanoparticles showed no impact on anaerobic digestion of WAS. Kinetic parameters obtained from models and captured FISH images were consistent with these results. Different impacts of nanoparticles on methane production suggested that anaerobic microorganisms can be affected from nanoparticles in various mechanisms. Hydrolysis (k H) and overall reaction rates (k R) values were determined as 0.0277 and 0.1441 d−1, respectively for each concentration of Al 2 O 3 nanoparticles and raw WAS. Similarly, methane production from WAS containing 5, 50, 150 and 250 mgFe 2 O 3 /gTS were modeled with same kinetic values. However, k H constant was calculated as 0.0149 d−1 for 500 mgFe 2 O 3 /gTS. This means that Fe 2 O 3 nanoparticles starting from this concentration inhibited the methanogenic consortium and caused decreased biogas production and spesific methane production rate. Graphical abstract Image 1 Highlights • Acute and chronic impacts were compared that reveal the importance of contact time. • Fe 2 O 3 NP inhibition depended on exposure time as well as dosage. • This study is the first contrubition of modeling of Fe 2 O 3 NP inhibition on WAS AD. • Fe 2 O 3 NP modeling results (P M , R M , λ) confirmed the inhibition impact. • Al 2 O 3 NP caused a 14.8% increase on methane production in long term evaluation. [ABSTRACT FROM AUTHOR]

Thermal hydrolysis, a sludge pre-treatment process prior to anaerobic digestion, is increasing in popularity in academia and industry due to the potential of biogas production enhancement. However, there is a limited understanding of the solubilisation mechanism, which significantly influences the biogas yield. This study evaluated the influence of flashing, reaction time, and temperature to understand the mechanism. It was found that while hydrolysis is the primary process (responsible for approximately 76–87% of sludge solubilisation), the sudden decompression via flashing at the end of the process, creating shear force to break the cell membrane, contributes a considerable percentage (approximately 24–13% depended on the treatment conditions) to the solubilisation of treated sludge. More importantly, the decompression helps significantly shorten the reaction time from 30 min to 10 min, which in turn reduces the sludge's colour, minimises energy consumption, and eliminates the formation of inhibitory compounds for anaerobic digestion. However, a considerable loss in volatile fatty acids (650 mg L⁻1 of acetic acid at 160 °C) during flash decompression should be considered. [Display omitted] • Hydrolysis is the primary mechanism in THP with flash depressurisation. • Flash depressurisation contributes to sludge solubilisation (24%). • Flash depressurisation helps shorten the reaction time from 30 min to 10 min. • Hydrothermal deconstruction can occur during THP if there is oxygen available. • A considerable amount of VFAs is lost during flash depressurisation. [ABSTRACT FROM AUTHOR]

The effects of microbial electrolysis cells (MECs) at three applied voltages (0.8, 1.3, and 1.6 V) on simultaneously enhancing methanization and reducing hydrogen sulfide (H 2 S) production in the anaerobic digestion (AD) of sewage sludge were studied. The results showed that the MECs at 1.3 V and 1.6 V simultaneously enhanced the methane production by 57.02 and 12.70% and organic matter removal by 38.77 and 11.13%, and reduced H 2 S production by 94.8 and 98.2%, respectively. MECs at 1.3 V and 1.6 V created a micro-aerobic conditions for the digesters with oxidation-reduction potential as −178∼-232 mv, which enhanced methanization and reduced H 2 S production. Sulfur reduction, H 2 S and elemental sulfur oxidation occurred simultaneously in the ADs at 1.3 V and 1.6 V. The relative abundances of sulfur-oxidizing bacteria increased from 0.11% to 0.42% and those of sulfur-reducing bacteria decreased from 1.24% to 0.33% when the applied voltage of MEC increased from 0 V to 1.6 V. Hydrogen produced by electrolysis enhanced the abundance of Methanobacterium and changed the methanogenesis pathway. [Display omitted] • The effects of high applied voltages on MEC-AD of sewage sludge were studied. • Methanization enhancement and H 2 S production reduction was simultaneously realized. • High voltages (1.3 V and 1.6 V) created micro-aerobic condition for the AD. • High voltages increased the abundances of SOB and decreased those of SRB. • High voltages enhanced the hydrogenotrophic methanogenesis. [ABSTRACT FROM AUTHOR]

In this study, we investigated the impact of intensive aeration pre-treatment on nutrient contents and phytotoxicity of anaerobically digested manure centrate. Activated sludge from conventional wastewater treatment plants was added to reinforce the aeration process. Results show that the addition of activated sludge did not negatively affect the nutrient contents, but significantly reduced the phytotoxicity of digested centrate, as indicated by an enhancement of seed germination index, during the aeration treatment. Based on the orthogonal experiment and following statistical analysis, the lowest phytotoxicity of digested centrate could be achieved under the aeration conditions: sludge concentration of 6 g/L, aeration time of 2 h, gas/water ratio of 40:1, and pH = 6.5. Of these operational parameters, the digested centrate pH dominantly determined its nutrient contents (e.g., amino acids, total phosphorus, and ammonium) and phytotoxicity. These results were further verified by hydroponic experiments, which showed that using digested centrate after sludge enhanced aeration as the nutrient solution facilitated the growth and dry biomass of maize. [ABSTRACT FROM AUTHOR]

Circular economy model, based on the "make, use, reuse, remake, recycle" approach, is an alternative to progressive depletion of non-renewable fossil fuels. Sewage sludge can be a source of renewable energy obtained through the anaerobic conversion of their organic fraction into biogas. This process is mediated by highly complex microbial communities and its efficiency depends on the availability of substrates to microorganisms. Disintegration of the feedstock in the pre-treatment step may intensify the anaerobic digestion, but re-flocculation of disintegrated sludge (reassembly of the released fractions into larger agglomerates) may result in a reduced availability of the released organic compounds for microbes. Pilot-scale studies on re-flocculation of disintegrated sludge were conducted to select parameters for scaling-up the pre-treatment and intensifying the anaerobic digestion process in two large Polish wastewater treatment plants (WWTPs). Samples of thickened excess sludge from full-scale WWTPs were subjected to hydrodynamic disintegration at three energy density levels of 10 kJ/L, 35 kJ/L and 70 kJ/L. Microscopic analyses of disintegrated sludge samples were carried out twice: i) immediately after the disintegration process at a given energy density level, ii) and after 24-h incubation at 4 °C following the disintegration. Micro-photographs of 30 randomly selected fields of view were taken for each analysed sample. A method of the image analysis was developed as a tool to measure dispersion of sludge flocs to assess the re-flocculation degree. Re-flocculation of the thickened excess sludge occurred within 24 h after hydrodynamic disintegration. This was evidenced by a very high re-flocculation degree, reaching up to 86%, depending on the origin of the sludge and the energy density levels used for the hydrodynamic disintegration. [Display omitted] • Re-flocculation reduces sludge disintegration efficiency before anaerobic digestion. • The degree of sludge re-flocculation can reach 86%. • The susceptibility to re-flocculation depends on the sludge origin. • Image analysis can be used to monitor sludge re-flocculation. [ABSTRACT FROM AUTHOR]

In this study, the effects of anaerobic digestion (AD) on molecular characteristics of dissolved organic matter (DOM) in the dewatered sludge has been described by advanced electrospray ionization combined with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) technology. With the progress of AD, molecular amounts in DOM samples increased with the lowering in the carbon atom number of average molecular formula and average double bond equivalent (DBE). CHON and CHONS groups are the two main organic substances in sludge with their relative DOM proportions of 29.64% and 32.56%, respectively. The resistants (i.e., refractory organic matter) mainly consist of the proteins regions of CHO groups as well as the proteins/lignin regions of CHON groups. The contrasting temporal trends in protein contents (e.g., decrease (CHO and CHON) vs. increase (CHONS)) may imply differences in their degradation characteristics. Likewise, the multi-N (N 3 , N 4) and S 2 organic groups in the sludge are converted to N 2 and S 1 molecules, while the relative abundance of O atoms (in Ox molecules) tends to increase. In addition, the resistants in sludge DOM contain high oxidizing C and low unsaturation. The overall results of this research are expected to provide the theoretical basis for further optimization of the sludge AD process. [Display omitted] • Dynamic molecular changes in DOM during sludge AD were first investigated by ESI FT-ICR MS. • CHON and CHONS groups are two main DOM organic substances in sludge AD process. • The resistants in DOM have high oxidizing C and low unsaturation. • Different proteins have different degradation characteristics in sludge AD process. • Relative abundance of O atoms in Ox molecules tends to increase during AD process. [ABSTRACT FROM AUTHOR]

Nowadays, there is an increasing concern over the presence of contaminants in the aquatic environment, where they can be introduced from wastewater after their incomplete removal in the treatment plants. In this work, degradation of selected emerging pollutants in the aqueous and solid phases of sewage sludge has been investigated after anaerobic digestion using two different digesters: mesophilic and thermophilic. Initially, sludge samples were screened by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS) for identification of emerging contaminants in the samples. In a second step, a target quantitative method based on LC coupled to tandem MS was applied for selected pollutants identified in the previous screening. The behaviour of the compounds under anaerobic conditions was studied estimating the degradation efficiency and distribution of compounds between both sludge phases. Irbesartan and benzoylecgonine seemed to be notably degraded in both phases of the sludge. Venlafaxine showed a significant concentration decrease in the aqueous phase in parallel to an increase in the solid phase. The majority of the compounds showed an increase of their concentrations in both phases after the digestion. Concentrations in the solid phase were commonly higher than in the aqueous for most contaminants, indicating that they were preferentially adsorbed onto the solid particles. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are plastic particles with size smaller than 5 mm: their removal in municipal wastewater treatment plants mostly results in the accumulation of the coarser fraction into the sludge. The common application of the treated sludge as soil amendment raises the issue of the uncontrolled release of MPs into the environment, which depicts the need to identify suitable counteraction strategies. This work briefly reviews the most recent studies that focus on the fate of MPs during conventional sludge treatments, and, based on the results of this analysis, proposes the thermal pretreatment (120 °C, 30 min) of waste activated sludge (WAS) containing different kinds of MPs, in order to investigate its effect on the anaerobic biodegradability as well as on the abundance and physical features of MPs. Experimental results show that high temperatures did not alter polyethylene terephthalate (PET) MPs but the biodegradable-compostable ones (BIO-MPs), complying with the UNI EN 13432 standards. The profile of methane generation from thermally pretreated samples containing PET-MPs do not indicate any inhibition of the anaerobic process, which was positively influenced by the BIO-MPs in WAS: a 100% and 25% methane increase was observed over the control samples with and without the thermal pretreatment, respectively. Further studies are needed to better understand the mechanisms underlying biodegradable MPs behavior as well as to investigate the influence of high temperature treatments on smaller size MPs during anaerobic processes. [Display omitted] • Coarser microplastics (MPs) tend to accumulate in municipal sewage sludge • Sludge anaerobic digestion may be differently affected by MP presence • MP fate during the anaerobic digestion of thermally pretreated sludge was studied • Biodegradable compostable (BIO) MPs led to a methane increase up to 60% • Sludge pretreatment at 120 °C for 30 min did not affect non-biodegradable PET-MPs [ABSTRACT FROM AUTHOR]

Compression and upgrading of biogas to vehicle fuel generates process water, which to varying degrees contains volatile organic compounds (VOCs) originating from the biogas. The compostion of this process water has not yet been studied and scientifically published and there is currently an uncertainty regarding content of VOCs and how the process water should be managed to minimise the impact on health and the environment. The aim of the study was to give an overview about general levels of VOCs in the process water. Characterisation of process water from amine and water scrubbers at plants digesting waste, sewage sludge or agricultural residues showed that both the average concentration and composition of particular VOCs varied depending on the substrate used at the biogas plant, but the divergence was high and the differences for total concentrations from the different substrate groups were only significant for samples from plants using waste compared to residues from agriculture. The characterisation also showed that the content of VOCs varied greatly between different sampling points for same main substrate and between sampling occasions at the same sampling point, indicating that site-specific conditions are important for the results which also indicates that a number of analyses at different times are required in order to make an more exact characterisation with low uncertainty. Inhibition of VOCs in the anaerobic digestion (AD) process was studied in biomethane potential tests, but no inhibition was observed during addition of synthetic process water at concentrations of 11.6 mg and 238 mg VOC/L. [ABSTRACT FROM AUTHOR]

The influence of Cephalexin (CLX), Tetracycline (TC), Erythromycin (ERY) and Sulfathiazole (ST) on methane-producing archaea (MPA) and sulfate-reducing bacteria (SRB) in anaerobic sludge was investigated using acetate or ethanol as substrate. With antimicrobial concentrations below 400 mg L −1 , the relative specific methanogenic activity (SMA) was above 50%, so that the antimicrobials exerted slight effects on archaea. However ERY and ST at 400 mg L −1 caused a 74.5% and 57.6% inhibition to specific sulfidogenic activity (SSA) when the sludge granules were disrupted and ethanol used as substrate. After disruption, microbial tolerance to antimicrobials decreased, but the rate at which MPA utilized acetate and ethanol increased from 0.95 gCOD·(gVSS⋅d) −1 to 1.45 gCOD·(gVSS⋅d) −1 and 0.90 gCOD·(gVSS⋅d) −1 to 1.15 gCOD·(gVSS⋅d) −1 respectively. The ethanol utilization rate for SRB also increased after disruption from 0.35 gCOD·(gVSS⋅d) −1 to 0.46 gCOD·(gVSS⋅d) −1 . Removal rates for CLX approaching 20.0% and 25.0% were obtained used acetate and ethanol respectively. The disintegration of granules improved the CLX removal rate to 65% and 78%, but ST was not removed during this process. [ABSTRACT FROM AUTHOR]

The sequential combination of ultrasonication and ozonation as sewage sludge treatment prior to anaerobic digestion was investigated. Synergistic volatile suspended solids (VSS) solubilization was observed when low energy ultrasonication (⩽12 kJ g −1 TS) was followed by ozonation. 0.048 g O 3 g −1 TS ozonation induced the maximum VSS solubilization of 41.3% when the sludge was pre-ultrasonicated at 9 kJ g −1 TS; while, the same ozone dosage applied without prior ultrasonication only induced 21.1% VSS solubilization. High molecular weight (MW) components (MW > 500 kDa) were found to be the main solubilization products when sludge was only ozonated. However, solubilization products by ozone were mainly in the form of low MW components (MW < 27 kDa) when sludge was pre-ultrasonicated. The high MW products generated by ultrasound were effectively degraded in the subsequent ozonation. Anaerobic biodegradability increased by 34.7% when ultrasonication (9 kJ g −1 TS) and ozonation (0.036 g O 3 g −1 TS) were combined sequentially. The maximum methane production rate increased from 3.53 to 4.32, 4.21 and 4.54 mL CH 4 d −1 after ultrasonication, ozonation and ultrasonication–ozonation pre-treatments, respectively. [ABSTRACT FROM AUTHOR]

We determined the changes in polychlorinated biphenyl (PCB) concentrations in a mixture of sewage sludge and the organic fraction of municipal waste during composting and during anaerobic digestion. The processes were carried out on a laboratory scale. The PCBs were analyzed in the waste samples using gas chromatography–mass spectrometry. We evaluated the rates at which the PCB concentrations decreased during composting and during anaerobic digestion and compared the PCB degradation kinetics during these processes. The most important conclusion of this work is that anaerobic digestion is much more effective than composting at removing PCBs from a mixture of sewage sludge and the organic fraction of municipal waste. [ABSTRACT FROM AUTHOR]

The role of bacterial interaction is vital to control bacterial functions; however, it has not been fully understood in microbial consortia (including anaerobic digestion). In this study, fluorouracil (FU), which is an anticancer agent and a quorum sensing (QS) inhibitor to some of the Gram-negative bacteria was found to inhibit methane production from sewage sludge under anaerobic conditions, as shown in a result where methane production in the presence of FU was eight times lower than the control (sewage sludge without FU). Whereas FU did not influence the hydrolysis process, in the acidogenesis/acetogenesis process, butyrate, and acetate accumulated in samples with FU. Also, in the methanogenesis process, FU remarkably inhibited methane production by acetoclastic methanogens rather than by the hydrogenotrophic ones. This result agreed with the result that growth and methane production of Methanosarcina acetivorans C2A was inhibited in the presence of FU. However, the inhibitory effect of FU was high in the condition that both bacteria and archaea were active. It indicates that FU influences methanogens and bacteria in the process of methane fermentation. The analyses of microbial communities (bacteria and archaea) showed that the abundance ratio of the Firmicutes phyla is high, and hydrogenotrophic methanogens become dominant in the presence of FU. Conversely, the abundance of Spirochaetes significantly decreased under FU. The inhibition of methane production by FU was due to the growth inhibition of methanogenic archaea and the changes in the composition of the bacterial population. [Display omitted] • Anaerobic digestion in the presence of fluorouracil showed low methane production by 8 fold. • Butyrate and acetate accumulated in the samples with fluorouracil. • Fluorouracil remarkably inhibited methane production by acetoclastic methanogens. • Growth and methane production of Methanosarcina acetivorans C2A were inhibited in the presence of fluorouracil. [ABSTRACT FROM AUTHOR]

The present work was conducted to assess whether the implementation of Supercritical Carbon dioxide Explosion (SCE) is an efficient approach for sewage sludge pre-treatment. In this context, SCE was optimized with the aim to develop a method attempting to increase the biodegradability of sewage sludge's organic matter content, and thus, to enhance the subsequent anaerobic digestion and methane production. The statistical tool of response surface methodology was applied to evaluate the effects of the main pre-treatment parameters (i.e. temperature and time) and their interactions on methane yield, which was defined as the response. Temperature was found to be the most significant variable, having the greatest effect on methane yield. Following this, an optimum set of pre-treatment conditions corresponding to a temperature of 115 °C and time of 13 min, was determined. Under these optimum conditions, the predicted response value was 300 mL CH 4 /g of volatile solids. The corresponding experimental value obtained from the validation experiment fitted well with this value, clearly demonstrating the effective use of response surface methodology in optimizing SCE. Additionally, under optimum conditions, the methane yield presented a statistically significant increment of 8.7%, compared to untreated sludge. This revealed the impact of SCE as an effective and alternative way for the efficient pre-treatment of sewage sludge. Finally, thermal pre-treatment, alkaline and acidic hydrolysis were also applied to the already pre-treated sludge. It was concluded that the combined pre-treatment techniques contributed to a further increase of methane production compared to raw (untreated) substrate. [Display omitted] • Supercritical CO 2 explosion is effective for sewage sludge pre-treatment. • RSM was successfully implemented for the optimization of supercritical CO 2 explosion. • Temperature was determined as the most significant independent variable. • An increment of 8.7% was observed in methane production under the optimum conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the benefits of co-digestion of a sludge-mix of primary sludge (PS)/thickened waste activated sludge (TWAS) with concentrated fat-oil-grease (FOG) over a wide range of FOG/sludge-mix volumetric feed ratios. The biodegradability (i.e., COD to methane conversion) of PS, TWAS, sludge-mix, and FOG was 43.0, 38.6, 41.8, and 97.7%, respectively, with a pseudo first-order rate of 0.13, 0.12, 0.13, and 0.18 d−1, respectively. Batch co-digestion of sludge-mix and FOG at COD ratios ranging from 93.2:6.8 to 27.3:72.7% resulted in methane production linearly correlated to both the total waste blend and FOG COD feed concentration. An enhanced extent of degradation of the sludge-mix COD to as much as 10.9% (increased from 42.2 to 53.1%) and an increased degradation rate by 17% (increased from 0.12 to 0.14 d−1) was observed when the feed FOG COD was 18.5% of the total waste COD feed. Overall, co-digestion of mixed municipal sludge with FOG is feasible and recommended to meet target biogas/methane levels at municipal wastewater treatment facilities taking into account the trade-off between energy production and solids destruction to fit their particular needs. [Display omitted] • FOG ultimate digestibility 2.2-fold higher than that of sewage sludge. • Co-digestion increased biogas production and sewage sludge extent of degradation. • Methane production linearly correlated to waste blend and FOG COD feed concentration. • Co-digestion of sewage sludge with FOG increased degradation rate by 17%. [ABSTRACT FROM AUTHOR]

Increasing energy demands and environmental issues have stressed the importance of sustainable methods of energy production. Anaerobic digestion (AD) of the biodegradable waste, i.e., agricultural residues, organic fraction of municipal solid waste (OFMSW), sewage sludge, etc., results in the production of biogas, which is a sustainable and cost feasible technique that reduces the dependence on fossil fuels and also overcomes the problems associated with biomass waste management. To solubilize the organic matter and enhance the susceptibility of hardly biodegradable fraction (i.e., lignocellulosic) for hydrolysis and increase methane production, several pretreatments, including physical, chemical, biological, and hybrid methods have been studied. However, these pretreatment methods under specific operating conditions result in the formation of recalcitrant compounds, such as sugars (xylose, Xylo-oligomers), organic acids (acetic, formic, levulinic acids), and lignin derivatives (poly and mono-phenolic compounds), causing significant inhibitory effects on anaerobic digestion. During the scaling up of these techniques from laboratory to industrial level, the focus on managing inhibitory compounds formed during pretreatment is envisaged to increase because of the need to use recalcitrant feedstocks in anaerobic digestion to increase biogas productivity. Therefore, it is crucial to understand the production mechanism of inhibitory compounds during pretreatment and work out the possible detoxification methods to improve anaerobic digestion. This paper critically reviews the earlier works based on the formation of recalcitrant compounds during feedstocks pretreatment under variable conditions, and their detrimental effects on process performance. The technologies to mitigate recalcitrant toxicity are also comprehensively discussed. [Display omitted] • Recalcitrant are classified into furan derivatives, phenolics compounds and weak organic acids. • Pretreatment method, type, temperature and duration affects the rate of recalcitrant formation. • High temperature pretreatment (>160 °C) alone or in conjugation with highly acidic or alkali pretreatment produced recalcitrant. • Recalcitrant toxicity resulted in reduced biogas yield with longer lag phase in AD process. • Biological detoxification, activated carbon adsorption, ion exchange, and calcium-oxide methods shows promising results [ABSTRACT FROM AUTHOR]

Waste activated sludge (biosolids) treatment is intensely a major problem around the globe. Anaerobic treatment is indeed a fundamental and most popular approach to convert organic wastes into bioenergy, which could be used as a carbon-neutral renewable and clean energy thus eradicating pathogens and eliminating odor. Due to the sheer intricate biosolid matrix (such as exopolymeric substances) and rigid cell structure, hydrolysis becomes a rate-limiting phase. Numerous different pretreatment strategies were proposed to hasten this rate-limiting hydrolysis and enhance the productivity of anaerobic digestion. This study discusses an overview of previous scientific advances in pretreatment options for enhancing biogas production. In addition, the limitations addressed along with the effects of inhibitors in biosolids towards biogas production and strategies to overcome discussed. This review elaborated the cost analysis of various pretreatment methods towards the scale-up process. This review abridges the existing research on augmenting AD efficacy by recognizing the associated knowledge gaps and suggesting future research. [Display omitted] • Biosolids (Waste activated sludge) is a significant resource for biogas generation. • Various pretreatment strategies were adopted to improve rate limiting step (hydrolysis). • Pretreatment of biosolids reduces the expenditure of digestion process. • Existence of the inhibitors in the biosolids affect the pretreatment efficiency. • Not all the pretreatment approaches are implemented in large scale. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) serves as a potential bioconversion process to treat various organic wastes/wastewaters, including sewage sludge, and generate renewable green energy. Despite its efficiency, AD has several limitations that need to be overcome to achieve maximum energy recovery from organic materials while regulating inhibitory substances. Hence, bioelectrochemical systems (BESs) have been widely investigated to treat inhibitory compounds including ammonia in AD processes and improve the AD operational efficiency, stability, and economic viability with various integrations. The BES operations as a pretreatment process, inside AD or after the AD process aids in the upgradation of biogas (CO 2 to methane) and residual volatile fatty acids (VFAs) to valuable chemicals and fuels (alcohols) and even directly to electricity generation. This review presents a comprehensive summary of BES technologies and operations for overcoming the limitations of AD in lab-scale applications and suggests upscaling and future opportunities for BES-AD systems. [Display omitted] • BES integrations can enhance process capability and economic viability of AD. • Microbe-electrode interactions for product syntheses in BES are reviewed. • Microbial and electrochemical processes are reviewed for various valuable products. • Upscaling considerations and future perspectives of BES-AD are identified. [ABSTRACT FROM AUTHOR]

Although the recovery and beneficial reuse of organic matter and nutrients from sludge represents an important move towards environmental sustainability, the accumulation of chemicals in biosolid-amended soils could pose serious environmental and human health risks. However, (eco)toxicological profiling of complex chemical mixtures in biosolids is currently limited. In particular, the effect of anaerobic digestion (AD), the most common stabilization process for sewage sludge, on the (eco)toxicity of those complex mixtures is poorly studied. In this work, we fill this research gap by applying an effect-based monitoring approach to screen sludge samples (n = 4) from a full-scale sewage treatment plant before and after conventional mesophilic (37 °C) AD using a battery of cell-based in vitro bioassays for four types of hormonal activity: estrogenic, androgenic, progestagenic and glucocorticoid activity, both in agonist and antagonist modes. We detected estrogenic, glucocorticoid and anti-progestagenic activity in all sludge samples. The glucocorticoid and anti-progestagenic activity remained mostly unchanged after AD treatment, but estrogenicity increased three-fold, likely as a result of bioactivation processes in the digestor. This study presents the first report on the concentration and fate of glucocorticoid and anti-progestagenic activity in AD. Future research should apply bioanalytical tools to a wider range of sludge samples to get a better understanding of the typical hormonal activity in sludge and develop effect-based trigger (EBT) values for biosolids to help interpret the risk posed by the hormonal activity detected in sludge. • Endocrine activity analysed in sludge from Australian sewage treatment plant. • Estrogenic, glucocorticoid and anti-progestagenic activity detected. • Anaerobic digestion had no effect on glucocorticoid and anti-progestagenic activity. • Estrogenicity in sludge increased three-fold after anaerobic digestion. [ABSTRACT FROM AUTHOR]

In this study, a double E strategy (enzymes and enhancer) characterized by high efficiency for enhancing sewage sludge anaerobic digestion (AD) is proposed. This strategy combines addition of trace elements (TEs) enhancer and enzyme pretreatment, inducing a synergistic effect on AD, and it is more effective and economical compared with TEs addition or enzyme pretreatment in isolation. When adding 400 U/g cocktail enzymes and 1.24% trance elements enhancers, the cumulative methane production and the maximum daily methane increased yield by 45.29% and 84.7%, respectively. According to microbial community analysis, the double E strategy significantly motivate the growth of acetogens and protein fermenting bacterium. The relative abundance of Fermentimonas and Lutispora increased by 6.15% and 5.4%, respectively. Archaeal community analysis and changes in the mcrA gene abundance demonstrate enrichment of hydrogenotrophic methanogens, with the methanogens exhibiting high vitalities and stress resistance. The double E strategy could be a promising way to improve industrial sewage sludge AD efficiency. [Display omitted] • Soluble protein content increased by 47.7% under low enzymes pretreatment. • Enzymes and enhancers induced a synergistic effect on anaerobic digestion. • Protein fermenting bacterium were abundant under the synergistic strategy. • Hydrogenotrophic methanogens exhibiting high vitalities and stress resistance. [ABSTRACT FROM AUTHOR]

Sewage sludge management has garnered interest in both academia and industry due to the challenges of overpopulation and its potential as a bioenergy source. Thermal hydrolysis is a promising technology for sludge pre-treatment prior to anaerobic digestion to enhance biogas production. However, the technology is facing two main problems; the dark colour of sludge can affect UV disinfection and the formation of methanogenesis inhibitors such as free ammonia and refractory compounds have a significant impact on methane production in anaerobic digestion processes. Advanced thermal hydrolysis, which is an oxidative thermal hydrolysis process, has been introduced to overcome these challenges. This study provides a comprehensive review of the mechanisms and reactions which occur during the hydrothermal hydrolysis and advanced thermal hydrolysis processes. Technical and implementation challenges of both technologies are discussed. Additionally, the prospects of the technologies are assessed through their technology readiness levels. An assessment of the relevant literature is also provided to illuminate the aspects in which research gaps exist and areas where additional studies could be performed. [Display omitted] • Heating and cooling time for the sludge before and after reaction are important. • Sludge composition should be considered to adjust the reaction condition of THP. • TRL level of 3 can be awarded to the ATHP process. • ATHP is a promising alternative technology to overcome the current problems of THP. [ABSTRACT FROM AUTHOR]

An innovative way to treat municipal wastewater and produce energy at the same time is anaerobic treatment. Anaerobic processes are traditionally used for high-strength wastewater or municipal sludge treatment and only recently have been applied for the treatment of low strength municipal wastewater To investigate the performance of anaerobic wastewater treatment through the incorporation of membrane technology, a 40 L laboratory scale Anaerobic Membrane Bioreactor (AnMBR) with a flat sheet submerged membrane along with a 40 L reservoir for trapping and measuring the biogas produced have been installed and set in operation. The scope of this study is to examine, through long term bench scale experiments, the impact that different temperatures and also different operating conditions have on the efficiency of AnMBR in order to identify the possibility of integrating this technology into Wastewater Treatment Plants (WWTPs). This paper evaluates the efficiency of AnMBR in the temperature range 14–26 °C, operating at three different hydraulic retention times (HRTs). The three different HRTs examined were 2 d, 1 d and 12 h. Each HRT is divided into two different temperature ranges. As the HRT decreased the effluent quality decreased and the membrane fouled more rapidly. AnMBR was able to produce permeate water with an average COD of 51 ± 8 mg L−1 at an HRT of 2 d during the summer period with an average temperature of 24 °C. The effluent COD increased to 67 ± 10 mg L−1 and reached 91 ± 5 mg L−1 for HRT 1 d and 12 h respectively for the same temperature range. [Display omitted] • Anaerobic MBR is an innovative approach for energy and resources recovery. • Anaerobic MBR provide for efficient COD removal even at HRT equal to12 h. • Biofouling is moderate at HRTs above 1 d while increases rapidly at an HRT of 12h. • AnMBR optimum performance for all conditions studied is achieved at an HRT of 1 d. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is the preferred method for treating sewage sludge because of its ability to reduce sludge volume and produce biogas. However, conventional anaerobic digestion has a long retention time and low degradation rate. In recent years, hydrothermal treatment has been used to improve the hydrolysis of sewage sludge and biogas production. This process tends to focus on maximizing biogas production. However, very little research has been done on anaerobic digestion residues. In this study, batch experiments were conducted to investigate the effect of hydrothermal temperature on methane production and the contents of liquid fraction after anaerobic digestion (centrate). Experimental conditions were designed using a response surface method and central composite model. A quadratic equation was used to interpret the individual and interactive effects of hydrothermal conditions on anaerobic digestion. Given the maximum biogas production and the minimum concentrate concentration, the optimal operating condition was determined by a 186 °C hydrothermal temperature and a reaction time of 106 min. Under these conditions, the following results could be obtained: methane production (200.5 ± 7.7 mL-CH 4 /gVS added), TCOD (16,572 ± 348 mg/L), sCOD (1240 ± 65 mg/L), sTN (658.9 ± 8.0 mg/L) and ammonia (525 ± 27 mg/L). • Hydrothermal method was used to treat sewage sludge for anaerobic digestion. • Effects of temperature and reaction time were examined. • Response surface methodology was used for statistical and empirical study. • Hydrothermal condition for both biogas production and effluent quality was optimized. [ABSTRACT FROM AUTHOR]

This study investigated whether 2 and 30 mg AgNPs or CuONPs/g TS present in treated sludge (biosolids) may impact the soil health by monitoring the soil characteristics and soil bacterial community for 105 days after the application of biosolids. AgNPs or CuONPs/g TS were first anaerobically digested with mixed primary and secondary sludge rather than adding pristine nanoparticles to biosolids directly. Both environmentally relevant (under the USEPA ceiling concentration limits) and high concentrations of AgNPs and CuONPs were tested. Soil tests included TOC, TN, TP, pH, cell viability and heterotrophic plate counts (HPC). Metagenomic data was generated by high-throughput sequencing of the 16S rRNA gene to explore bacterial populations and diversity. AgNPs and CuONPs at 2 and 30 mg NPs/g TS of sludge could impact soil health factors such as bacterial diversity, community structure, and the population of plant growth-promoting rhizobacteria (PGPR). The population of the highly abundant bacteria that have important physiological roles in soil decreased, while the less important bacteria for soil function were able to thrive. CuONPs exhibited a higher level of toxicity than the AgNPs at both phylum and genus taxonomic levels, and the HPC decreased with higher concentrations of AgNPs and CuONPs. Initially, most of the studied phyla abundance was affected, but the control and other reactors approached similar levels by the end of the experiments, which may be explained by the decrease in toxicity due to the transformation of nanoparticles and the defence mechanisms of bacteria, and indicates the need for long-term field studies. Image 1 • Soil health was impacted after biosolids application containing AgNPs and CuONPs. • Bacterial diversity, heterotrophic bacteria, and percentage of live cells decreased. • Population of plant growth-promoting rhizobacteria decreased. • Phyla abundance initially decreased but recovered overtime. • CuONPs exhibited a higher level of toxicity than the AgNPs. [ABSTRACT FROM AUTHOR]

This work describes the design, optimization and validation of an analytical method for the simultaneous determination of 14 pharmaceuticals and personal care products (PPCPs) in sewage sludge. A thorough optimization of the sample pre-treatment was carried out. As a result, microwave-assisted extraction (MAE) was combined with an in-situ clean-up stage and a filtration step. A combination of MilliQ® water/MeOH 95:5 (v/v) adjusted to pH 9 turned out to be the optimal solvent mixture for extraction. The instrumental part of the method presents a significant novelty based on a fully automated sample preparation for the analysis of PPCPs. It consisted of a direct immersion solid phase microextraction followed by on-fiber derivatization, online coupled to gas chromatography - mass spectrometry (DI-SPME-On-fiber derivatization - GC-MS). An isotope dilution approach was used for quantifying, which conferred high reliability to the method. This methodology was validated for 10 compounds with good analytical performance, limit of detection below 20 ng g−1 and absolute recovery in the range of 30–70% for most of the compounds. It supposes an ecological analytical alternative for many routine analysis laboratories around the world. The developed method was applied to different real samples generated in both a pilot-scale thermal hydrolysis treatment plant and an anaerobic digester operated in mesophilic conditions. Salicylic acid and naproxen were found at concentrations above 1000 ng g−1. Image 1 • A method for the determination of PPCPs in sewage sludge was optimized and validated. • Microwave-assisted extraction combined with in-situ clean-up and filtration were presented. • Online-DI-SPME-On-Fiber-Derivatization-GC-MS was used for analysis of PPCPs in sludge samples. • The analytical method was successfully applied to different real samples. • PPCPs were detected in concentration between 48 and 9355 ng g−1. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (AcoD) can increase methane production of anaerobic digesters in plants treating wastewater sludge by improving the nutrient balance needed for the microorganisms to grow in the digesters, resulting in a faster process stabilization. Substrate mixture proportions are usually optimized in terms of biogas production, while the metabolic biodegradability of the whole mixture is neglected in this optimisation. In this aim, we developed a strategy to assess AcoD using metabolomics data. This strategy was explored in two different systems. Specifically, we investigated the co-digestion of wastewater sludge with different proportions of either grass or fish waste using untargeted High Performance Liquid Chromatography coupled to Mass Spectrometry (HPLC-MS) metabolomics and chemometrics methods. The analysis of these data revealed that adding grass waste did not improve the metabolic biodegradability of wastewater sludge. Conversely, a synergistic effect in the metabolic biodegradability was observed when fish waste was used, this effect being the highest for 25% of fish waste. In conclusion, metabolomics can be regarded as a promising tool both for characterizing the biochemical processes occurring during anaerobic digestion, and for providing a better understanding of the anaerobic digestion processes. Image 1 • Microbial community-driven digestion patterns can be explored with metabolomics. • Grass anaerobic digestion is marked by the consumption of dipeptides. • Fish anaerobic digestion is marked by the consumption of biogenic amines. • Adding grass did not improve the metabolic degradability of sludge. • By adding 25% fish, the metabolic degradability of sludge was doubled. [ABSTRACT FROM AUTHOR]

Dosing of iron (Fe)-salts in sewers to control odour and corrosion problems have proven to be effective on phosphate and sulfide removal in downstream treatment units. However, the interaction of Fe with sludge may impact the sludge properties during wastewater treatment and sludge digestion. Herein, we investigated the downstream impacts of sewer-dosed Fe-salt on key digestate properties including digestate dewaterability. For this, Fe-salt was dosed to a sewer reactor and resultant iron-rich waste activated sludge (Fe-WAS) was digested in an anaerobic digester (AD) in the experimental line of integrated laboratory system running in parallel to a control system. Iron containing and non-iron containing digestates were sourced from the respective AD reactors of experimental and control lines. Results showed improved dewaterability in iron containing digestate than non-iron containing digestate, which was attributed to the variations in key digestate properties. Compared to non-iron containing digestate, iron containing digestate exhibited the decreased contents of bound water, soluble extracellular polymeric substances (S-EPS), protein, polysaccharide, and monovalent-to-divalent (M + / D ++ ) cations ratio. Likewise, we observed the increased mean particle size (D v 50) for iron containing digestate than the non-iron containing digestate, but fractal dimension (D f) values were comparable. Besides, iron containing digestate exhibited a reduced degree of thixotropy, relative sludge network strength, viscosity, yield stress, flow stress, and storage/loss/complex (G ′/ G ′′/ G∗) moduli but increased creep compliance and shear strain (%) than non-iron containing digestate. The combined synergistic effects of such favorable changes amongst the key properties of iron containing digestate, might have been responsible for improving it's dewaterability. Image 1 • Iron containing digestate exhibits improved dewaterability. • Iron containing digestate shows decreased S-EPS, bound water, PN, and PS contents. • M + / D ++ ratio, viscosity, yield/flow stress are lower in iron containing digestate. • Viscoelastic behavior is relatively weakened in iron containing digestate. • Iron containing digestate shows increased D v 50 , J(t) , and shear strain (%) values. [ABSTRACT FROM AUTHOR]

Microplastics are abundant in municipal wastewater which is mainly from personal care products and laundry. In recent years, great attention has been given to microplastics removal in wastewater treatment. In this article, the study focusing on microplastics in wastewater has been evaluated with VOSviewer. It was found that the major interest was in identification, quantification and pollution of the microplastics in the wastewater, and their transportation and final destination during wastewater treatment processes. The major microplastics and their shapes in wastewater were reviewed. Our evaluation results were consistent with other reported that fibers and fragment were the majority in terms of shape and polyethylene terephthalare (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS) are the most presented microplastics in wastewater. During wastewater treatment, the removal route of microplastics from wastewater includes settling, adsorption, entrapment, interception, etc. It confirms that microplastics are just simply transferred from wastewater to sludge. It could then bring problems to anaerobic digestion as microplastics are great vector for toxic substances such as antibiotics and persistence organic pollutants. The key to determine the microplastics effect on anaerobic digestion is the desorption behavior of the toxic substances such as antibiotics, persistent organic pollutants and heavy metals from microplastics in digestion condition. Toxic compounds which are commonly presenting in sludge have shown the tendency to release from microplastics. It indicates that microplastics in sludge have great possibility to impact on methane production. Image 103 • The work reveals the current research focus on microplastic in wastewater. • The removal pathways of microplastic in different treatment step were discussed. • The impact of microplastic in anaerobic digestion is estimated. • The research need of microplastic in wastewater treatment related field is stated. [ABSTRACT FROM AUTHOR]

Aerobic composting and anaerobic digestion with hydrolysis pretreatment are two mainstream methods used to recycle and reclaim sewage sludge. However, during these sludge treatment processes, many odors are emitted that may cause severe emotional disturbance and health risks to those exposed. This study identified odor pollution (i.e. sensory influence, odor contribution, and human risks) from samples collected during sludge aerobic composting throughout different seasons as well as during anaerobic digestion with hydrolysis pretreatment. Odor intensity, odor active values, and permissible concentration-time weighted averages for ammonia and five volatile sulfur compounds were assessed. The results revealed serious odor pollution from all sampling sites during aerobic composting, especially in winter. Excessively strong odors were identified in the composting workshop, with total odor active values between 997 and 8980 which accounted for 78.45%–96.18% of the total sludge aerobic composting plant. Levels of ammonia and dimethyl disulfide in the ambient air were high enough to harm employees' health. During anaerobic digestion, excessively strong odors were identified in dehydration workshop 2, and the total odor active values of six odors reached 32,268, with ammonia and hydrogen sulfide levels significant enough to harm human health. Image 1 • In the MSSACP, the most serious odor occurred during winter, followed by summer. • Odor intensity, odor active values, and PC-TWA assessment methods were implemented. • Key odor sites were compost workshop (CW) and dehydration workshop 2 (DW2). • Key odors were NH 3 , DMS, and DMDS in CW, and NH 3 , H 2 S, and MT in DW2. [ABSTRACT FROM AUTHOR]

Untreated sludge (total solids = 10%) and thermally hydrolysed sludge (total solids = 10%) were subjected to high-solid anaerobic digestion (HSAD) to study the effect of thermal hydrolysis pre-treatment (THP) on the conversion pathways of volatile sulphur compounds (VSCs). Typical VSCs were detected in the gas produced by THP at 160 °C for 30 min, including H 2 S, methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). After THP, the organic sulphide ratio in the treated sludge had decreased from 96% to 90%, and inorganic sulphide had increased from 4% to 10%. In the THS (THP + HSAD) group, the productivity and total volume of VSCs were significantly increased. These results suggest that THP directly promotes converting organic sulphur (OS) into VSCs. Further tests revealed that THP increased the activity of reductases (adenine phosphate sulphate reductase and sulphite reductase), OS hydrolysis was the main source of VSCs in biogas, and MM could be converted into H 2 S (78%), DMS (18%) and DMDS (4%). These findings are used to elucidate the conversion pathway of sulphides in HSAD. • Thermal hydrolysis pre-treatment (THP) enchances the sulphide conversion in sewage sludge. • Organic sulphides (Cys and Met) are directly converted to volatile sulphur compounds (VSCs) during THP. • The main source of VSCs in high-solid sludge anaerobic digestion (HSAD) is organic sulphide hydrolysis. • The conversion pathway of VSCs in high-solid sludge anaerobic digestion is identified. [ABSTRACT FROM AUTHOR]

A sludge structure perspective of the effects of humic matter (HM) on the anaerobic digestion (AD) of sewage sludge was proposed and investigated in this study. It was observed that the net cumulative methane production of sludge was significantly lower in the presence of HM. The fractal dimension values of sludge samples were increased by the addition of HM, whilst their total surface energy values were decreased, indicating that HM reinforced the stability of the sludge structure. Analyses of the physicochemical properties of different sludge samples revealed that HM enhanced the structural stability of sludge organic substances and restricted its organic solubility by interacting with the biopolymers to form a dense granular aggregate, thereby reducing the random-coil degree of extracellular organic substances and its active sites for enzymes, which suggested that HM could inhibit AD by changing the sludge structure. It was further confirmed by the biochemical methane potential (BMP) assay process. The BMP tests and corresponding kinetic analyses revealed that HM can restrict the potentials of sludge organic solubilisation, hydrolysis and acidification processes, but not necessarily the rates of these processes by enhancing the structural stability of high molecular weight readily biodegradable organic matter (RBOM) and restricting the mobility of low molecular weight RBOM (i.e., hydrolysis products). These findings can enrich understanding of the AD of sludge and may thus aid in the development of more effective methods to improve sludge treatment. Image 1 • A sludge structural view of humic matter inhibiting methane production was proposed. • Humic matter can enhance the structural stability of sludge. • Humic matter can change the spatial configurations of biopolymer in sludge. • Humic matter can limit the biodegradation of readily biodegradable organic matter. [ABSTRACT FROM AUTHOR]

Nonylphenol (NP) and nonylphenol monoethoxylate (NP1EO) have toxic and persistent characteristics, and are incompletely degraded in conventional wastewater treatment processes. These compounds are present in sewage sludge that can be reused as fertilizers or soil conditioners. Accordingly, NP and NP1EO should be properly removed before being discharged in the environment. In this study, potassium ferrate (K 2 FeO 4) containing hexavalent iron (Fe(VI)) was used as an environment-friendly oxidizing agent to mediate NP and NP1EO degradation. The aim of this study was to investigate the effects of pH and Fe(VI) dosage on the degradation of NP and NP1EO in water and anaerobically digested sewage sludge samples. In water samples, under conditions examined in this study, maximum removal efficiencies for NP and NP1EO were 98% and 92%, respectively. For digested sewage sludge samples, the maximum removal efficiencies of NP and NP1EO were 58% and 96%, respectively. The results demonstrated that Fe(VI) can potentially degrade NP and NP1EO in water and digested sewage sludge samples. However, organic matter as a matrix in the sludge sample would inhibit the degradation of NP and NP1EO by Fe(VI). The pH values before and after adding K 2 FeO 4 to the samples had an obvious influence on the removal of NP and NP1EO. • Both K 2 FeO 4 dosage and pH have an influence on removal efficiencies of NP and NP1EO. • Removal rate constants of NP and NP1EO in water are mostly enhanced by increasing Fe(VI) dosage. • K 2 FeO 4 has a good potential for NP1EO degradation in water and sludge in pH range of 3–6. • Higher K 2 FeO 4 dosage was required to remove NP and NP1EO from sludge than from water because of a matrix in sludge. • Comparison between Fe(VI) and Fe(III) showed that Fe(VI) could degrade NP and NP1EO. [ABSTRACT FROM AUTHOR]

Odours from stabilized biosolids after anaerobic digestion of wastewater sludge can cause local community impact. Apart from the well-known odorants such as sulfur compounds, contributions from other volatile organic compounds (VOCs) to nuisance odours is limited. The presence of compounds with low odour detection thresholds (ODTs) at low concentrations, can present challenges for analytical identification. Thirty-six biosolids samples were taken after anaerobic stabilisation and dewatering at a wastewater treatment plant, Sydney, Australia. Biosolid cake samples were stored outside in loosely covered trays under aerobic conditions, however without interactions with soil microorganisms as it would be in reality. All biosolids cake samples were analysed over a period of 35 days. Emissions were collected onto Tenax TA sorbent tubes using a U.S. EPA flux hood method at storage days 1, 3, 7, 10, 14, 21 and 35. Gas chromatography (GC) coupled with mass spectrometer detector (MSD) and an olfactory detection port (ODP) was used to identify a musty/moldy/earthy type odorant in the biosolids emissions as 2,4,6-trichloroanisole (TCA). Measured odour intensities, classified on a scale from 1 to 4, and odour characters were specified by three ODP assessors. TCA was identified in all biosolid cake emissions. The measured odour intensities of the TCA did not significantly alter as the biosolids were aged, however varied between biosolids cakes. Due to its odour intensity, 85% frequency of detection and its low ODT, which is orders of magnitudes lower than sulfur compounds, TCA should be considered as a potential odorant of concern in biosolids emissions. • 2,4,6-Trichloroanisole (TCA) was identified in the emission from ageing dewatered biosolids. • GC-ODP system allowed identifying TCA in the concentrations below MSD detection limit. • TCA are likely to contribute to the overall odour from biosolids emission. [ABSTRACT FROM AUTHOR]