Sludge Samples Research Articles

Polluticaenibacter yanchengensis gen. nov., sp. nov., A Novel Taxon Within the Family Chitinophagaceae Isolated from Activated Sludge.

A Gram-stain-negative bacterium, designated strain LY-5T, was isolated from an activated sludge sample collected from a river in Yancheng city, Jiangsu province, China. Cells of strain LY-5T, were strictly aerobic, non-motile and rod-shaped. Growth occurred at 15-37°C (optimum, 30°C), at pH 5.0-9.0 (optimum 7.0) and at 0-3% (w/v) NaCl (optimum, 0%). Phylogenetic analysis based on 16S rRNA gene and genome sequences indicated that strain LY-5T formed a distinct phyletic branch within the family Chitinophagaceae, with closest relatives being members of the genera Phnomibacter, Aurantisolimonas, and Chitinophaga, sharing 88.5-90.3% sequence similarity. Moreover, the average amino acid identity (AAI) between strain LY-5T and its closed phylogenetic neighbors was below 70%, indicating it belongs to a novel genus. The predominant cellular fatty acids of LY-5T were iso-C15:0, iso-C15:1 G and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), and the only isoprenoid quinone was menaquinone-7 (MK-7). The major polar lipids identified in strain LY-5T comprised phosphatidylethanolamine, two unidentified aminolipids and five unidentified lipids. The genome size of strain LY-5T was 4.8 Mbp with a G + C content of 38.9%. Based on the evidence presented in this study, strain LY-5T represents a novel species of a new genus in the family Chitinophagaceae, for which the name Polluticaenibacter yanchengensis gen. nov., sp. nov. (Type strain LY-5T = CCTCC AB 2023260T = KCTC 102218T) is proposed.

Analysis of the Physical and Chemical Composition of Sludge from the Water Treatment Plant

The properties and composition of the sludge generated in water treatment systems depend primarily on the type and composition of the water to be treated, the treatment methods, and the type and doses of chemical reactants. The sludge produced in the water treatment plant (WTP) under study follows the technological processes of coagulation, flocculation, sedimentation, and filtration. The analyses aimed to characterize the sludge in terms of its physico-chemical properties and classify it in terms of its potential discharge into the river and management. Four series of sediment tests were conducted over a calendar year (March, June, September and December), analysing selected parameters using various test methods, including the X-ray crystallography (XRF) method. The publication's authors showed that the sediment consists mainly of sand, clay, and silt particles with grain sizes ranging from 0.001 mm to 1 mm. Silica (53.78%), alumina (23.58%), calcium oxide (8.28%), iron (III) oxide (5.61%), and potassium oxide (2.36%) represent the main chemical constituents present in the sediment. The authors characterized the sediment in terms of the content of biogenic compounds: various forms of phosphorus and nitrogen, organic compounds – determined as total organic carbon (TOC), selected metals, and the content of individual elements (carbon, hydrogen, oxygen, nitrogen, sulfur). In addition, the sludge samples were also characterized in terms of calorific value, ash content, water content, and heat of combustion. Discharging WTP sludge into rivers, ponds, and lakes or storing dewatered sludge is an environmentally unfriendly form of disposal for this type of waste. The authors see the possibility of conducting further research on using WTP sludge in wastewater treatment, removing heavy metals from aqueous solutions, producing cement and construction materials, and recovering or recycling.

Heat and mass transfer during conductive drying of washing phosphate sludge

This study investigates the influence of drying temperature on the conductive drying behavior of washing phosphate sludge. A mathematical model, based on Fourier's Fick diffusion law and the heat transfer equation, was developed to simulate coupled heat and mass transfer during the drying process, incorporating the shrinkage effect. The sludge samples, obtained from the Khouribga phosphate plant in Morocco, were subjected to drying at temperatures of 70°C and 95°C. The experimental setup included continuous monitoring of temperature, humidity, and mass loss throughout the process. COMSOL Multiphysics software was used to solve the nonlinear equations governing heat and mass transfer. Results indicate that increasing the drying temperature significantly accelerates the drying rate. The model successfully predicts the moisture content and temperature distribution over time, aligning well with experimental data. Statistical validation, using the determination coefficient (R²) and root mean square error (RMSE), confirms that the model accurately describes the drying behavior, with R² values of 0.9957 and 0.9967 at 70°C and 95°C, respectively. The inclusion of the shrinkage effect enhances the model's precision in describing the drying kinetics under varying conditions.

Earthworm activity reduces bacterial pathogen loads in sewage sludge.

Wastewater processing plants (WWTPs) produce large amounts of sewage sludge that are mainly disposed of on the land. This represents a health hazard due to the high loads of human bacterial pathogens (HBPs) the sludge generally contains. Vermicomposting, a mesophilic process, can reduce HBPs in organic wastes. This raises the question as to how earthworms eliminate HBPs. We aimed to determine whether earthworms reduce the levels or eliminate HBPs from sewage sludge and to establish whether the reduction/elimination occur during active (earthworm casts) or maturation (vermicompost) stages of vermicomposting. To this end, we analyzed HBPs (Escherichia coli O157, Listeria monocytogenes, Salmonella spp., and total E. coli) in sewage sludge samples from three WWTPs and the fresh earthworm casts and vermicomposts by using qPCR, to assess the impact of earthworms on reducing and/or eliminating HBPs. We did not detect either Salmonella spp. nor E. coli O157 in any of the samples. Earthworms removed or significantly reduced the amounts of E. coli and L. monocytogenes (mean relative abundances of 2.4 × 10-7 and 1.5 × 10-8 respectively) in the sewage sludge. Thus, the abundance of these HBPs was lower (or not present) in casts than in sewage sludge. This was also observed in vermicomposts (95% and 43% reduction in E. coli abundance in casts and vermicompost, respectively). Finally, our findings indicate that vermicompost derived from sewage sludge meets the requirements of organic fertilizers at least regarding the microbial pathogen content. Thus, vermicomposting seems to be a promising technique for managing municipal waste.

Seasonal dynamics of bacterial composition and functions in biological treatment of coking wastewater

Seasonal dynamics of bacterial composition and functions were demonstrated for the biological fluidized-bed bioreactors combined in the anoxic/aerobic1/aerobic2 (AOO) coking wastewater (CWW) treatment sequences. The bacterial composition and functions in the CWW activated sludge samples were revealed by 16S rRNA genes amplicon sequencing. Thiobacillus, Cloacibacterium, Alkaliphilus and Pseudomonas were determined as core genera with seasonal changes. Mutable microbial community composition fluctuated in different seasons in same bioreactor. Distributions of predicted KEGG pathways along four seasons consistently demonstrated enrichment in biodegradation of carbon- and nitrogen-containing compounds. The major contaminants were removed from CWW by biochemical pathway of xenobiotics biodegradation and metabolism. This Level 2 pathway mainly owned the Level 3 pathways of benzoate degradation, drug metabolism-other enzymes, drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, and aminobenzoate degradation. The RDA results showed that dissolved oxygen with seasonal fluctuation was the main parameter shaping the microbial community. The observed dynamics within the microbial community composition, coupled with the maintained stability of CWW treatment efficiencies and a consistent profile of microbial functional pathways, underscore the presence of functional redundancy in the AOO bioreactors. The study underscored stable and effective operational performances of bioreactors in the AOO sequences, contributing the knowledge of microbiological basics to the advancement of CWW biological treatment.Key points• Seasonal fluctuations of bacterial composition described for the AOO system.• Seasonal distributions of metabolic functions focused on carbon and nitrogen removal.• Functional redundancy was revealed in the AOO microbial community.

Analysis of the potential of the electroactive biofilm growth in a microbial fuel cell type H

Microbial fuel cells (MFC) constitute an attractive alternative as an environmental remediation technology since they can generate electrical current using organic waste as a substrate. Since the performance of MFCs depends on the characteristics of the biofilm on the anode surface, it is important to assess the genetic information of the microorganisms that grow on the electrode. For this purpose, a sewage sludge sample was obtained from a wastewater treatment plant and used to inoculate a type H MFC. Electrochemical characterization, on one hand, indicates that while the biofilm has a typical electrochemical performance reflected by the generated voltage (near 0.4 V) and by the electroactivity observed in cyclic voltammetry experiments, and on the other hand, the metagenomic analysis shows that the most abundant genera are Pseudomonacea, Nitrosomonas, Hyphomonas, and Opitutus. The study also indicates that the biofilm’s electroactive microorganisms can metabolize amino acids, lipids, and carbohydrates and possess genetic tools for ionic transport and energy production. Regarding the electron acceptor/donator capabilities, several oxidases, reductases, and complexes were identified, mainly terminal cytochrome C oxidase and respiratory complex I, which could be associated with the exoelectrogenic capacity of the microorganisms. Finally, the metagenomic information indicates that the biofilm can synthesize rhamnose, sialic acid, and alginate molecules, which could possibly be associated with the formation and consolidation of the microbial biofilm.

Natural compound-induced downregulation of antimicrobial resistance and biofilm-linked genes in wastewater Aeromonas species.

Addressing the global antimicrobial resistance (AMR) crisis requires a multifaceted innovative approach to mitigate impacts on public health, healthcare and economic systems. In the complex evolution of AMR, biofilms and the acquisition of antimicrobial resistance genes (ARGs) play a pivotal role. Aeromonas is a major AMR player that often forms biofilm, harbors ARGs and is frequently detected in wastewater. Existing wastewater treatment plants (WWTPs) do not have the capacity to totally eliminate antimicrobial-resistant bacteria favoring the evolution of ARGs in wastewater. Besides facilitating the emergence of AMR, biofilms contribute significantly to biofouling process within the activated sludge of WWTP bioreactors. This paper presents the inhibition of biofilm formation, the expression of biofilm-linked genes and ARGs by phytochemicals andrographolide, docosanol, lanosterol, quercetin, rutin and thymohydroquinone. Aeromonas species were isolated and purified from activated sludge samples. The ARGs were detected in the isolated Aeromonas species through PCR. Aeromonas biofilms were quantified following the application of biocompounds through the microtiter plate assay. qPCR analyses of related genes were done for confirmation. Findings showed that the natural compounds inhibited the formation of biofilms and reduced the expression of genes linked to biofilm production as well as ARGs in wastewater Aeromonas. This indicates the efficacy of these compounds in targeting and controlling both ARGs and biofilm formation, highlighting their potential as innovative solutions for combating antimicrobial resistance and biofouling.

Sustainable enhancement of biogas production from a cold-region municipal wastewater anaerobic digestion process using optimized sludge-derived and commercial biochar additives

Anaerobic digestion (AD) of municipal wastewater sludges produces valuable solid digestate and biogas. Biogas is a source of clean energy and enhancement of its production has been of recent interest for increased electricity generation, among other products. The objective of this study was the development of a novel municipal sludge-derived biochar and its application in a municipal wastewater AD system to increase the biogas production rate. Thickened waste-activated sludge (TWAS) samples were collected from the cold-region municipal wastewater treatment plant and used to synthesize biochar applied in the simulation of AD processes using laboratory-scale reactors. The TWAS-derived biochar was synthesized using the commonly used furnace pyrolysis (sludge-based biochar, SBC), and more novel microwave pyrolysis including phosphoric acid as a microwave activator (activated sludge-based biochar, ASBC). The microwave pyrolysis conditions were optimized using a computational fluid dynamics (CFD) technique. In addition, various commercially available carbon-based additives were assessed for their impacts on the AD process including activated carbon, wood-derived biochar, and forest residue-derived biochar. Results showed that the ASBC increased the cumulative methane production by 50% (333 mL/g VS) versus the control sample (221 mL/g VS) after 30 d. The ASBC showed higher surface area, electrical conductivity, and metal contents versus the other biochars which boosted the AD microbial community growth leading to higher organic matter conversion into biogas. In the ASBC-amended digesters, the bacterial phylum Bacteroidota, which contains a major genus of the dgA-11-gut-group, exhibited a synergy between organic substrate fermentation and volatile fatty acid production, resulting in enhanced biogas production. The TWAS biochar demonstrated promising performance in enhancing the AD process fostering energy and resource self-sufficiency at municipal wastewater treatment plants. This smart sludge management aligns well with sustainable waste management practices and clean energy production strategies, especially considering that the biochar was sourced from a readily available continuous waste-product stream.

A Surveillance Study of Culturable and Antimicrobial-Resistant Bacteria in Two Urban WWTPs in Northern Spain.

Wastewater treatment plants (WWTPs) are hotspots for the spread of antimicrobial resistance into the environment. This study aimed to estimate the proportion of clinically relevant antimicrobial-resistant bacteria in two Spanish urban WWTPs, located in the region of La Rioja (Spain); Methods: Ninety-four samples (48 water/46 sludge) were collected and streaked on ten different selective media, in order to recover the culturable bacterial diversity with relevant resistance phenotypes: Extended-Spectrum β-Lactamase-producing Escherichia coli/Klebsiella pneumoniae (ESBL-Ec/Kp), Carbapenem-resistant Enterobacteriaceae (CR-E), Methicillin-resistant Staphylococcus aureus (MRSA), and Vancomycin-resistant Enterococcus faecium/faecalis (VR-E. faecium/faecalis). Isolates were identified by MALDI-TOF and were tested for antimicrobial susceptibility using the disk diffusion method. The confirmation of ESBL production was performed by the double-disk test; Results: A total of 914 isolates were recovered (31 genera and 90 species). Isolates with clinically relevant resistance phenotypes such as ESBL-Ec/Kp and CR-E were recovered in the effluent (0.4 × 100-4.8 × 101 CFU/mL) and organic amendment samples (1.0-101-6.0 × 102 CFU/mL), which are discharged to surface waters/agricultural fields. We reported the presence of VR-E. faecium in non-treated sludge and in the digested sludge samples (1.3 × 101-1 × 103 CFU/mL). MRSA was also recovered, but only in low abundance in the effluent (0.2 × 101 CFU/mL); Conclusions: This study highlights the need for improved wastewater technologies and stricter regulations on the use of amendment sludge in agriculture. In addition, regular monitoring and surveillance of WWTPs are critical for early detection and the mitigation of risks associated with the spread of antimicrobial resistance.

Study on the Influence of Sludge Biochemical Characteristics and Treatment Conditions on Rheological Properties

Abstract In response to the differences in the organic matter, oil and other components of temporary sludge stored in different storage areas of Shanghai Lao-gang, which affect the long-distance transportation of sludge, a full range sampling was conducted on the temporary sludge. Based on the results of solid content measurement, the pH value, mineral oil, total nitrogen, organic matter content, total oil and other six selected sludge samples were subjected to biochemical testing, and one sludge sample was selected for drying and concentration treatment. At the same time, sludge rheological tests were conducted on the biochemical testing sludge samples and the concentrated sludge samples, and the impact of sludge biochemical characteristics and sludge concentration on sludge rheological characteristics was compared and analyzed, which provide reference for the construction process of temporary sludge transportation.

Cofactor F420 tail length distribution in different environmental samples

Cofactor F420 is an electron carrier playing a crucial role in a variety of microorganisms during redox reactions of the primary and secondary metabolism due to its low redox potential and thus arouses increasing interest. In this study, cofactor F420 glutamyl tail length spectra in various habitats like manure, compost, soil, and digester sludge samples and their respective microbial communities were investigated using high performance liquid chromatography and an amplicon sequencing approach A previous in-silico study was used to identify F420 producing microorganisms. The highest concentration of cofactor F420 could be achieved in the horse manure, digester sludge, and mixed manure samples, which was approximately 100-fold higher than in all the other samples. The high content of the cofactor in the samples with high O2 availability pointed to the important role of the cofactor not only in redox reactions of anaerobic but also for aerobic microorganisms and indicated its ubiquitous character. The most abundant derivate was F420-3 comprising the largest part of the cofactor derivates in seven out of ten samples. The high abundance of F420-3 in samples with distinct properties (e.g. O2 and H2O availability) showed its important role in redox reactions of the primary and secondary metabolism among prokaryotes.

Dynamics of antibiotic resistance agents during sludge alkalinization treatment

This study aimed to assess the removal of antimicrobial resistance agents (antibiotics, antibiotic-resistant bacteria - ARB, and antimicrobial resistance genes - ARGs) from aerobic and anaerobic sludges treated with quicklime (chemical alkalinization). Different mixing ratios (25%, 35%, and 45%) and contact times (2 h and 72 h) were evaluated. The findings revealed that anaerobic sludge responded more effectively to alkaline treatment, achieving better removal rates of antibiotics, ARB, and ARGs compared to aerobic sludge. The 45% lime treatment yielded the highest antibiotic removal rates, with average reductions of 19% in aerobic sludge and 28% in anaerobic sludge. The 35% lime treatment was the most effective in reducing ARGs across both types of sludge (average removal of 2 logs). The 25% lime treatment proved most efficient for removing ARB, with average reductions of 4 logs (aerobic) and 5 logs (anaerobic). The contact time between the sludge and quicklime also influenced the removal of resistance agents. An increase in the proportion of antibiotics and the absolute concentration of ARB and ARGs was observed after 72 h compared to the samples analyzed after 2 h of contact. This increase was more pronounced in aerobic sludge samples treated with 35% and 45% lime. Despite the overall reduction, none of the monitored resistant genes or bacteria were completely eradicated in both sludge samples, raising concerns about their potential dissemination into the environment.

Environmental impact assessment of SONARA's oil sludge landfill in BATOKE, south-west Cameroon

The focus of this study was to assess the environmental impact of the BATOKE oil sludge dump. A field visit was conducted to evaluate the condition of the site, followed by the sampling of oil sludge, BATOKE river water, soil, and locally grown manioc and macabo tubers. Subsequent physico-chemical characterization revealed parameters such as pH, electrical conductivity, total hydrocarbons, COD, BOD5, TSS, major cations and anions, as well as heavy metals including iron, copper, zinc, nickel, chromium, lead, cadmium, mercury, arsenic, calcium, potassium, titanium, zirconium, and rubidium. The environmental impact was assessed using the Contamination Index calculation and the Correlation Matrix. Results indicated that most physical parameters met standards, except for the electrical conductivity of water and soil. However, elevated levels of iron, chromium, lead, cadmium, mercury, arsenic, and ammonium ion were found in the BATOKE River water. The soil showed heavy contamination with various metals, and cassava and macabo tubers were also found to be contaminated. The contamination index calculations confirmed severe pollution in the BATOKE environment, with a risk of further escalation without remediation efforts.

Evaluation of extraction and storage conditions for quantification and characterization of silver nanoparticles in complex samples by single particle-ICP-MS

The extraction of nanoparticles (NPs) from complex matrices and subsequent storage can potentially alter the NPs physicochemical properties and hinder cross-study comparisons. Most NP extraction methods are designed and tested at high nanoparticle concentrations, although (eco)toxicological and regulatory monitoring programs require methods capable of analyzing NPs at environmentally relevant concentrations (lower ppb range). In this study, we investigated how extraction methods affect the characteristics of PVP coated and citrate-stabilized silver NPs (AgNPs) spiked into soil, sewage sludge, and biological samples at environmentally relevant concentrations using Single Particle Inductively Coupled Plasma Mass Spectrometry spICP-MS). Further we investigated the impact of storage temperature (-80°C to 21°C) and storage duration (1-28 days) on the particle characteristics such as particle size.We found that aqueous AgNPs samples with low ionic strength media retained their original characteristics (like particle size, particle concentration and particle-based Ag mass) when preserved at 4°C for up to 28 days. AgNPs dispersed in high ionic strength media were however better preserved at -80°C. Among the extraction agents, tetrasodium pyrophosphate was more efficient in extracting AgNPs from soil and sewage sludge matrices, while Proteinase K was more suitable for biological samples from organisms (earthworms or fish).Although our study focused only on AgNPs, it provides crucial information to aid interlaboratory comparisons and data interpretation for (eco)toxicological studies.

Bacterial hosts and horizontal transfer characteristics of clinically important tet(X)-variant genes in municipal wastewater treatment plants using epicPCR-directed cultivation strategy

Mobile tet(X)-variant genes confer resistance to a wide range of tetracyclines, including the antibiotic of last-resort, tigecycline, raising significant concerns regarding their potential spread cross-environmental dissemination. However, the bacterial hosts and environmental spread of these genes remain poorly understood. Herein, a retrospective study unveiled the prevalence of tet(X)-variant genes (ranging from tet(X3) to tet(X6)) in activated sludge samples from five municipal wastewater treatment plants (WWTPs) from 2013 to 2021. Among these variants, tet(X4) exhibited the highest detection frequency (100%) and abundance [(2.48 ± 3.07) × 107 copies/g dry weight] with an increasing trend. An epicPCR-directed cultivation strategy was proposed to facilitate the targeted isolation of tet(X4)-carrying bacterial hosts in activated sludge. This strategy involves the identification of bacterial host profiles using epicPCR and subsequent selective isolating target bacteria. Enterobacteriaceae emerged as the primary bacterial host for tet(X4), alongside previously unreported genera like Providencia, Advenella, and Moheibacter. Subsequent selective isolation of the most abundant Enterobacteriaceae based on the epicPCR-informed host spectrum yielded 39 tet(X4)-carrying Escherichia coli strains from the WWTP. Whole genome sequencing of tet(X4)-positive strains revealed that plasmid-mediated horizontal gene transfer is the primary mechanism driving tet(X4) dissemination. Plasmids including IncFIA(HI1)/IncHI1A/IncHI1B(R27) and IncX1, commonly reported in various clinical and animal settings, were identified as the predominant carriers of tet(X4). E. coli strains harbouring tet(X4) in the WWTP showed substantial genetic similarity to strains from hospital and animal sources, underscoring concerns about the potential risk of across diverse sectors. This study provided the first glimpse of the presence of mobile tet(X)-variants in WWTPs, and highlighted the promise of the epicPCR-directed cultivation strategy for exploring bacterial hosts of clinically important ARGs in different habitats from a One Health perspective.

Nation-wide monitoring campaign of 49 biocides and surfactants in surface waters and wastewaters

Despite their intensive use and their impact on ecosystems, biocides and surfactants are still poorly regulated and poorly monitored at large scale. In the frame of the revision of the national regulatory surveillance plan of surface waters, France planned in 2018 a monitoring campaign at national scale focused on these two types of substances of very emerging concern. Forty-nine contaminants (32 biocides and 17 surfactants) were investigated in surface water and sediment samples from 91 sampling sites, and in effluent and sludge samples of 7 wastewater treatment plants (WWTP), in mainland France and overseas regions. Between 33 and 52 % of the target contaminants were quantified at least once in water and sediment. High frequencies of quantification were observed for the surfactants (up to 91 % in water samples and up to 57 % in sediment samples for LAS C10-C13) and for the biocides (up to 64 % for fipronil in water samples and up to 90 % for methyl nonyl ketone in sediment samples). The median concentrations of surfactants were up to 2 μg/L in mainland surface water samples and up to 528 μg/kg in sediment samples, and for biocides, the median concentrations were up to 0.18 μg/L in mainland surface water samples and up to 104 μg/kg in sediment samples. PNEC exceedances in water and sediment were determined for both types of substances. The analysis of effluent and sludge suggested significant but not total removal of these substances in the WWTP. Temporal and spatial variations of the concentrations of both types of substances in surface water samples were also observed, suggesting both punctual and diffuse contamination sources of the surface water investigated.

Low-intensity magnetization pretreatment to enhance biomethane generation and the abundance of key microorganisms for anaerobic digestion of sewage sludge

This work explores the impact of static magnetic field (SMF) intensity on biomethane production from anaerobic digestion (AD) of sewage sludge. Two different SMF intensities (20 mT and 1.5 T) were applied to magnetize the sludge destined to the AD process. The magnetic pretreatment at 20 mT was particularly effective, as it increased biomethane production by 12.7 % compared to the control test. On the contrary, exposing the sludge to 1.5 T adversely affected biomethane production, resulting in a 15.1 % decrease. The positive correlation observed between low-intensity SMF exposure and enhanced biomethane yield, in contrast to the inhibitory effect of high-intensity SMF, suggests the existence of an optimal intensity threshold within the lower range for maximizing methane production. The impact of magnetic pretreatment on the anaerobic microbial community was investigated through high-throughput sequencing analysis of magnetized sludge samples. This approach enabled the identification of specific shifts in microbial populations associated with SMF exposure, thereby elucidating the role of SMF in modulating key microbial communities for the AD process. The findings of this study provide insights into the potential mechanisms underlying these responses and underscore the potential of SMF application for improving the anaerobic valorization of sewage sludge.

Fast pyrolysis of paper sludge in a continuous stirred-tank reactor and liquid-liquid extraction of benzenoid aromatics from fast pyrolysis bio-liquid

Paper sludge is a solid waste in paper mills and is conventionally treated by, e.g., landfill, composting, and incineration. Paper sludge contains paper production fillers and lignocellulosic biomass, both of which can be recycled to recover circular minerals and produce bio-based fuels and chemicals by, e.g., thermochemical recycling technology namely fast pyrolysis, for circular bioeconomy. In this paper, three different paper sludge samples collected in The Netherlands and Spain were analyzed by thermogravimetric analysis, moisture analysis, ash analysis, CHNS elemental analysis, powder X-ray diffraction, and X-ray fluorescence spectrometry. Fast pyrolysis of paper sludge was carried out in a lab-scale continuous stirred tank reactor at 500 ± 10 °C with a paper sludge feeding rate of 1 kg h−1. The recovery of circular minerals, which are mainly calcium carbonate, is 87.1 ± 2.2 % (on mineral basis). The yields of fast pyrolysis bio-liquid and biochar are 49.2 ± 6.7 wt% (on biomass basis, equivalent to 23.7 ± 2.2 wt% on paper sludge basis) and 23.8 ± 8.3 wt% (on biomass basis). Fast pyrolysis bio-liquid is a diluted aqueous containing various oxygenates (major, including alcohols, acids, benzenoid aromatics, aldehydes, ketones, ethers, and esters) and hydrocarbons. Liquid-liquid extraction of the fast pyrolysis bio-liquid using CH3OH/H2O and SO2/H2O was further performed to obtain an improved bio-liquid with relatively high concentration of the desired bio-based chemicals (namely benzenoid aromatics with the concentration of 53.1–65.9 area%). Both SO2/H2O and CH3OH/H2O show high liquid-liquid extraction efficiency to concentrate the benzenoid aromatics for 3.4–11.0 times. This work shows the fast pyrolysis followed by liquid-liquid extraction for the valorization of paper sludge, of which the former has been recently demonstrated on a pilot-scale unit in industry. However, the latter still needs to be further developed by, e.g., focusing on the extraction solvent and continuous liquid-liquid extraction process integrated to fast pyrolysis.

Promotion of polyhydroxyalkanoates-producing granular sludge formation by lactic acid using anaerobic dynamic feeding process

To promote the formation of granular sludge with high polyhydroxyalkanoates (PHAs) synthesis ability, an anaerobic dynamic feeding process (AnDF) was proposed. This process combines the feast-famine mode with an anaerobic plug flow feeding process and involving variations in cycle length and settling time. The effects of lactic acid (LA) content (0 %, 20 %, and 40 % COD) on sludge granulation and PHAs production were investigated using three AnDF reactors (R1, R2, and R3). The results showed that the AnDF process feeding with LA not only effectively promoted sludge granulation but also improved its PHAs synthesis ability. The granules were quickly observed in R3 after 50 days of cultivation, with an average diameter of 0.69 mm. The maximum PHAs content reached 47.0 wt% in R3, representing a 30.09 % increase compared to R1. Additionally, extracellular polymeric substances (EPS)-producing bacteria observed in granular sludge may be the prime drivers of the formation of PHAs-producing granular sludge (PHAGS), which was defined as granular sludge with an average particle size larger than 0.30 mm and PHAs content above 40 % cell dry weight (CDW) of sludge samples.

Occurrence and fate of five representative neonicotinoid insecticides across different wastewater treatment plants and the impact on receiving water bodies

Neonicotinoids (NEOs), despite their widespread use as insecticides, exhibit a notable knowledge deficit in regards to their presence in wastewater treatment plants (WWTPs) and their surrounding environments. This study delves into the presence and disposition of 5 NEOs: Thiamethoxam (THM), Clothianidin (CLO), Imidacloprid (IMD), Acetamiprid (ACE), and Thiacloprid (THA) across 3 domestic WWTPs and their receiving waters. Notably, THM, CLO, and ACE were consistently detected in all water and sludge samples, with THM emerging as the most abundant compound in both influent and effluent. Among the 3 WWTPs, WWTP 2, employing a fine bubble oxidation process, achieved the highest removal efficiency, surpassing 68%, in contrast to WWTP 1 (CAST) at 37% and WWTP 3 (A/A/O) at 7%. Biodegradation played a pivotal role in NEO removal, accounting for 36.7% and 68.2% of the total removal in WWTP 1 and WWTP 2, respectively. Surprisingly, in WWTP 3, biotransformation process inadvertently increased ACE and CLO concentrations by approximately 4.1% and 4.5%, respectively. The total NEO concentration in the receiving surface waters ranged from 72.7 to 155.5 ng/L, while sediment concentrations were significantly lower, spanning between 0.10 and 1.53 ng/g. WWTPs serve as both a removal and concentration point for NEOs, thereby significantly influencing their transportation. Additionally, the concentration of most NEOs in the receiving waters progressively increased from upstream to downstream, highlighting the substantial impact of WWTP discharges on natural water environments. This research offers valuable insights into NEO pollution surrounding WWTPs in the Pearl River Delta, ultimately aiding in pollution control and environmental protection decisions.