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This study explored the potential application of plasma coupling ionic liquid on disintegration of waste activated sludge and enhanced production of short-chain fatty acids (SCFAs) in anaerobic fermentation. Under optimal conditions (dosage of ionic liquid [Emim]OTf = 0.1 g/g VSS (volatile suspended solids) and discharge power of dielectric barrier discharge plasma (DBD) = 75.2 W), the [Emim]OTf/DBD pretreatment increased SCFA production by 302 % and acetic acid ratio by 53 % compared to the control. Mechanistic investigations revealed that the [Emim]OTf/DBD combination motivated the generation of various reactive species (such as H 2 O 2 , O 3 , •OH, 1 O 2 , ONOO - , and •O 2 - ) and enhanced the utilization of physical energies (such as heat). The coupling effects of [Emim]OTf/DBD synergistically improved the disintegration of sludge and biodegradability of dissolved organic matter, promoting the sludge anaerobic fermentation process. Moreover, the [Emim]OTf/DBD pretreatment enriched hydrolysis and SCFAs-forming bacteria while inhibiting SCFAs-consuming bacteria. The net effect was pronounced expression of genes encoding key enzymes (such as alpha-glucosidase, endoglucanase, beta-glucosidase, l-lactate/D-lactate dehydrogenase, and butyrate kinase) involved in the SCFA-producing pathway, enhancing the production of SCFAs from sludge anaerobic fermentation. In addition, [Emim]OTf/DBD pretreatment facilitated sludge dewatering and heavy metal removal. Therefore, [Emim]OTf/DBD pretreatment is a promising approach to advancing sludge reduction, recyclability, and valuable resource recovery., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Biological arsenite [As(III)] oxidation is an important process in the removal of toxic arsenic (As) from contaminated water. However, the diversity and metabolic potentials of As(III)-oxidizing bacteria (AOB) responsible for As(III) oxidation in wastewater treatment facilities are not well documented. In this study, two groups of bioreactors inoculated with activated sludge were operated under anoxic or oxic conditions to treat As-containing synthetic wastewater. Batch tests of inoculated sludges from the bioreactors further indicated that microorganisms could use nitrate or oxygen as electron acceptors to stimulate biological As(III) oxidation, suggesting the potentials of this process in wastewater treatment facilities. In addition, DNA-based stable isotope probing (DNA-SIP) was performed to identify the putative AOB in the activated sludge. Bacteria associated with Thiobacillus were identified as nitrate-dependent AOB, while bacteria associated with Hydrogenophaga were identified as aerobic AOB in activated sludge. Metagenomic binning reconstructed a number of high-quality metagenome-assembled genomes (MAGs) associated with the putative AOB. Functional genes encoding As resistance, As(III) oxidation, denitrification, and carbon fixation were identified in these MAGs, suggesting their potentials for chemoautotrophic As(III) oxidation. In addition, the presence of genes encoding secondary metabolite biosynthesis and extracellular polymeric substance metabolism in these MAGs may facilitate the proliferation of these AOB in activated sludge and enhance their capacity for As(III) oxidation. IMPORTANCE AOB play an important role in the removal of toxic arsenic from wastewater. Most of the AOB have been isolated from natural environments. However, knowledge regarding the structure and functional roles of As(III)-oxidizing communities in wastewater treatment facilities is not well documented. The combination of DNA-SIP and metagenomic binning provides an opportunity to elucidate the diversity of in situ AOB community inhabiting the activated sludges. In this study, the putative AOB responsible for As(III) oxidation in wastewater treatment facilities were identified, and their metabolic potentials, including As(III) oxidation, denitrification, carbon fixation, secondary metabolite biosynthesis, and extracellular polymeric substance metabolism, were investigated. This observation provides an understanding of anoxic and/or oxic AOB during the As(III) oxidation process in wastewater treatment facilities, which may contribute to the removal of As from contaminated water.

Thermal hydrolysis (TH) treatment has been verified to effectively reduce antibiotic resistance genes (ARGs) in waste activated sludge. This study focused on the effect of TH parameters on ARGs reduction, and the optimal conditions basing on tetracycline (tet) resistance genes reduction rate in sludge phase were pH 3, temperature 160 °C and reaction time 2 h. The pH was found to play a critical role in tet genes reduction behavior. Additionally, the tet genes distributions in TH supernatant are considered as well because genes will release from solid to liquid phase as sludge cell breaking. The lowest genes content in TH supernatant was also observed at pH 3. Further investigation revealed that contents of DNA and organics released from sludge phase to liquid phase under pH 3 were less than that in neutral and alkaline condition; moreover, the organics in TH supernatant was found to protect DNA. Therefore, under the acidic condition, the genes had less releasing from the sludge phase and the DNA protection effect of organics was weaker, resulting in the lowest tet genes content in TH supernatant. Moreover, bacterial community structure after TH was closely related with the ARGs content. The bacterial on phylum and genus level showed various responses to TH pH values. Although the Firmicutes phylum and Escherichia-Shigella genus exhibited the stronger resistance and had higher accumulation in TH acidic condition, more possible total tet genes hosts were destroyed in acidic condition, causing less ARGs remaining in the sludge phase under pH 3., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Tetracycline resistant bacteria (TRB) screened from activated sludge were used to study the effect of tetracycline (TC) antibiotic on the transcriptional expression of tetracycline resistance genes (TC-ARGs). The gene abundances of seven TC-ARGs including tetA , tetC , tetG , tetM , tetO , tetW , and tetX , as well as their expression levels, were quantified by quantitative PCR (qPCR) and reverse transcriptional PCR (RT-PCR). The correlations between TC concentrations and gene abundance of TC-ARGs and their expression levels were discussed. The results showed that the gene abundances of tetA , tetG, and tetW generally increased with increasing TC exposure concentrations during the entire culture cycle, whereas other TC-ARGs fluctuated greatly. The impact of TC stress on the transcriptional expression level of different TC-ARGs varied to a great extent. The gene expression of tetA was relatively stable and exhibited an upregulated trend with increasing TC concentrations. When the TC concentration was 100 mg·L -1 , the upregulation of tetA expression was as high as 5.3-fold compared with the control. Under short-term TC stress (one day), the transcriptional expression level was upregulated with increasing TC concentration. The correlation results showed that gene abundances of tetA and tetW correlated significantly with their respective expression levels, indicating that they can evaluate expression levels to a certain extent, which can further mirror functional activities and environmental risks.

The problem of bacterial resistance has become an important issue in the area of global ecological safety and human health. Waste sludge is an important reservoir and discharge source for antibiotic resistance genes (ARGs). In this study, the quantities of seven tetracycline resistance genes (TC-ARGs), including tetA, tetC, tetG, tetM, tetO, tetW , and tetX , as well as those of class 1 integron ( intI1 ) genes, during anaerobic sludge digestion process were comprehensively quantified by quantitative PCR (qPCR). The effects of different doses of zero valent iron (Fe 0 ) on the decrease and increase in the quantities of TC-ARGs and intI1 genes were investigated. The influence of plasmid conjugation on the horizontal gene transfer (HGT) of the target TC-ARGs was preliminarily analyzed. The correlations between the quantities of TC-ARGs and intI1 gene have been discussed. The results showed that the quantities of TC-ARGs and intI1 genes decreased in different degrees during anaerobic sludge digestion, and the abundance of tetX gene was reduced by 2.4 orders of magnitude. When Fe 0 was added, no significant reduction in the quantities of TC-ARGs and intI1 genes was observed. However, as the addition of Fe 0 increased, the quantities of TC-ARGs and intI1 genes increased correspondingly, as compared to those in the control group. The results obtained from the quantities of TC-ARGs carried by plasmid DNA showed that plasmid conjugation probably promoted the HGT of TC-ARGs. A positive significant correlation was found between the quantities of tetG and intI1 genes, indicating that intI1 might play an important role in the evolution of tetG during sludge anaerobic digestion process.

To investigate the effects of zero valent iron (Fe 0 ) on the decline of antibiotic resistance genes during thermophilic anaerobic digestion of sludge, the abundances of seven tetracycline resistance genes (TC-ARGs, including tetA, tetC, tetG, tetM, tetO, tetW , and tetX ) and class 1 integron gene ( intI1 ) were quantified by quantitative PCR (qPCR). Also, the concentrations of volatile fatty acids (VFAs) were determined. The correlations between the abundances of TC-ARGs and intI1 gene and the concentrations of VFAs were discussed. The results showed that appropriate dose of Fe 0 such as 0.10 g·g -1 VSS could enhance the anaerobic digestion process of sludge, and the production of total VFAs and acetic acid increased significantly. The decrease in the abundances of TC-ARGs and intI1 gene was also enhanced. However, excessive Fe 0 such as 1.17 g·g -1 VSS could not further improve the reduction in the abundances of TC-ARGs and intI1 gene, probably resulted from the occurrence of horizontal gene transfer. The abundances of TC-ARGs except tetO gene, as well as intI1 gene exhibited significant negative correlation with the concentration of acetic acid, indicating that acetic acid probably had an enhanced effect on the decline of TC-ARGs and intI1 gene during thermophilic anaerobic digestion of sludge.

Activated sludge system is an important process of domestic and industrial wastewater treatment containing highly diverse microbial communities. In this study, high-throughput sequencing was applied to examine the microbial community composition and diversity of activated sludge samples from four full-scale municipal wastewater treatment plants (WWTPs) in Shanghai. A relationship between microbial communities and environmental variables was examined. Proteobacteria was the most dominant phylogenetic group, followed by Bacteroidetes and Firmicutes. A total of 166 genera were commonly shared by all seven sludge samples, including Zoogloea, Dechloromonas, Thauera, Nitrospira, Arcobacter, etc. Besides these shared populations, certain unique bacterial populations were found abundant in individual sludge sample. Canonical correspondence analysis (CCA) indicated that influent COD and pH had the greatest influence on microbial community compositions, whereas dissolved oxygen (DO) exhibited the least influence. The operating process was likely to foster diversity of the microbial communities inhabiting the wastewater treatment facilities. Alternative operation methods including a fluctuation of anoxic, oxic, and anaerobic conditions were favorable for promoting the growth of diverse microbial populations in activated sludge systems.

The shift of microbial communities during a transition from mesophilic anaerobic digestion (MAD) to thermophilic anaerobic digestion (TAD) was characterized in two treatments. One treatment was inoculated with sludge and the other was inoculated with manure. In this study, methane was produced both in MAD and TAD, but TAD has slightly more methane produced than MAD. A broad phylogenetic spectrum of bacterial, archaeal, and fungal taxa at thermophilic conditions was detected. Coprothermobacter, Bacillus, Haloplasma, Clostridiisalibacter, Methanobacterium, Methanothermobacter, Saccharomycetales, Candida, Alternaria, Cladosporium, and Penicillium were found almost exclusively in TAD, suggesting their adaptation to thermophilic conditions and ecological roles in digesting the organic compounds. The characterization of the lesser-known fungal community revealed that fungi probably constituted an important portion of the overall community within TAD and contributed to this process by degrading complex organic compounds. The shift of the microbial communities between MAD and TAD implied that temperature drastically affected the microbial diversity in anaerobic digestion. In addition, the difference in microbial communities between sludge and manure indicated that different source of inoculum also affected the microbial diversity and community.

Occurrence and distribution of twelve pharmaceutical and personal care products (PPCPs) were investigated in a sewage treatment plant in Shanghai using solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS/MS). Quantitative PCR (qPCR) was used to determine the distribution and removal of seven erythromycin resistance genes (ERY-ARGs). The results showed that five PPCPs including sulfamethoxazole, erythromycin, tetracycline, carbamazepine and triclosan were detected in the collected wastewater samples with concentrations in the ranges of 24.5- 38.7, 47.5-49.2, 43.1-85.4, 2.5-3.9 and 423.2-8 973.3 ng x L(-1), respectively. During the wastewater treatment process, a significant reduction of triclosan was observed, but the removal efficiencies for the other detected PPCPs were relatively low. Additionally, all target ERY-ARGs were detected in the wastewater samples ranging from 9.28 x 10(3) (ermA) to 1.83 x 10(8) (ereA) copies x L(-1) in raw influent. Though significant reductions (1.19 log-3.97 log) of ERY-ARGs were obtained, their concentrations found in the final effluent were still high. Moreover, the concentration of ERY-ARGs exhibited significant positive correlation with the concentration of erythromycin and triclosan (P < 0.05), respectively, elucidating that erythromycin played an important role in the occurrence and spread of ERY-ARGs, while triclosan may confer cross-selection for ERY-ARGs.

Sludge flocs morphology and effluent qualities of nonwoven bioreactor during filamentous bulking and normal sludge status were compared. Flux variations, analysis of filtration resistances and extracellular polymer substances (EPS) contents during filamentous bulking and normal sludge status were studied. The results showed that the average particle size of bulking sludge flocs and normal sludge flocs was 448.6 microm and 234.8 microm, respectively. During the bulking sludge status, the average COD and NH4(+) -N removal rate and effluent turbidity were 90.1%, 93.1% and 1.33 NTU, respectively, compared with 91.4% , 97.0% and 0.99 NTU during the normal sludge status. Filamentous bulking had little impact on COD removal, while it inhibited NH4(+) -N removal to a certain extent and had slight impact on effluent turbidity. Average membrane flux decay rates during the bulking sludge status and the normal sludge status were 3.29 L x (m2 x h2)(-1) and 4.87 L x (m2 x h2)(-1), respectively, and the fouling during bulking sludge status was slighter. Reversible fouling was the main fouling when sludge was bulking while irreversible fouling was the main fouling when the sludge was in normal status. The prior occurrence of reversible fouling could reduce irreversible fouling therefore slow down the flux decline. Soluble microbial products (SMP) contents in normal sludge mixed liquid and bulking sludge mixed liquid were 21.369 mg x L(-1) and 10.182 mg x L(-1), respectively, protein/polysaccharide (P/C) was 0.370 and 0.497, respectively, SMP gross was related to fouling resistance and P/C was associated with reversible fouling proportion. The relation between loosely bound EPS in mixed liquid sludge and membrane fouling was similar to SMP. Sludge with more EPS could accumulate on membrane more easily, and the EPS that accumulated on membrane was mainly protein. EPS gross in mixed liquid sludge, EPS in membrane surface sludge and their P/C all had positive correlations to reversible fouling.

Occurrence and removal efficiencies of fifteen pharmaceuticals were investigated in a conventional municipal wastewater treatment plant in Michigan. Concentrations of these pharmaceuticals were determined in both wastewater and sludge phases by a high-performance liquid chromatograph coupled to a tandem mass spectrometer. Detailed mass balance analysis was conducted during the whole treatment process to evaluate the contributing processes for pharmaceutical removal. Among the pharmaceuticals studied, demeclocycline, sulfamerazine, erythromycin and tylosin were not detected in the wastewater treatment plant influent. Other target pharmaceuticals detected in wastewater were also found in the corresponding sludge phase. The removal efficiencies of chlortetracycline, tetracycline, sulfamerazine, acetaminophen and caffeine were >99%, while doxycycline, oxytetracycline, sulfadiazine and lincomycin exhibited relatively lower removal efficiencies (e.g., <50%). For sulfamethoxazole, the removal efficiency was approximately 90%. Carbamazepine manifested a net increase of mass, i.e. 41% more than the input from the influent. Based on the mass balance analysis, biotransformation is believed to be the predominant process responsible for the removal of pharmaceuticals (22% to 99%), whereas contribution of sorption to sludge was relatively insignificant (7%) for the investigated pharmaceuticals., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

[Display omitted] • Cr, Cu, Zn and Cd could be removed simultaneously by nZVI@SBC. • NO 3 – and HA promote the removal of Cr, Cu, Zn and Cd. • Cr and Cu were reduced by nZVI and then removed through co-precipitation. • The removal of Cd and Zn were driven by alkali precipitation and complexation. Cr, Cu, Zn, and Cd commonly coexisted in the electroplating wastewater with high salinity and organics, while their removal was often investigated individually. In this study, the simultaneous removal of Cr, Cu, Zn, and Cd was investigated by nano zero-valent iron modified sludge biochar (nZVI@SBC). The results showed that nZVI@SBC could significantly improve the removal efficiency of the four heavy metals (HMs) in high salinity wastewater. NO 3 – (N-NO 3 –) and humic acid (HA) could promote the removal of Cr, Cu, Zn, and Cd, and PO 4 3- (P-PO 4 3-) could enhance the removal of Cd. EPR analysis demonstrated the generation of 1O 2 in different water matrices. The 1O 2 intensity increased in the presence of NO 3 – and HA, which indicated the acceleration of the nZVI corrosion and the promoted electron transfer in the system. To further understand the reaction mechanism, the variation of nZVI@SBC structures and compositions during the treatment process were characterized by SEM-EDS, XRD, BET, and XPS. Cr and Cu were removed through adsorption and co-precipitation after reduction by nZVI, while Cd and Zn were removed by alkali precipitation and complexation. This work improves the understanding of simultaneous removal of HMs by nZVI@SBC and provides a cost-effective approach for the electroplating wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances on wastewater recovery of high value-added products are reviewed. • Optimized OLR, temperature, SRT, and COD/N enhance alginate-like polymer recovery. • P can be recovered as struvite by regulating ratios of Mg, N, and P, and pH value. • Various streams can be used for polyhydroxyalkanoate recovery via factor adjustment. • Sulfated polysaccharides as new value-added products in wastewater merit attention. Wastewater resource recovery not only allows the extraction of value-added products and offsets the operational costs of wastewater treatment, but it is also conducive to alleviating adverse environmental issues due to energy and chemical inputs and associated emissions. A number of attractive compounds such as alginate-like polymers, struvite, polyhydroxyalkanoates, and sulfated polysaccharides, were found and successfully obtained from wastewater and have a wide range of application prospects. The aim of this work is to provide a comprehensive review of recent advances in recovery of these popular products from wastewater, and their physicochemical properties, main sources, and current recovery status are summarized. Various factors influencing the recovery performance of these materials are thoroughly discussed. Moreover, the research needs and future directions towards wastewater resource recovery are highlighted. This study can provide valuable insights for future research endeavors aiming to improve wastewater resource recovery through the retrieval of high value-added products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sewage sludge-derived biochar (SBC) was effective in activating PMS in sludge. • PMS/SBC favored sludge cell lysis and enhanced sludge biodegradability. • PMS/SBC enhanced the yield and quality of short-chain fatty acids (SCFAs). • Surface-bound radicals functioned the most, with contribution of 1O 2 > •OH > •SO 4 −. • Key functional microbes and genes for SCFA accumulation were enriched by PMS/SBC. This study reports on the potential use of sewage sludge-derived biochar (SBC) as an activator for peroxymonosulfate (PMS) to improve the solubilization of waste activated sludge (WAS) and the production of short-chain fatty acids (SCFAs) during anaerobic digestion. The SBC produced by pyrolysis of WAS has active sites consisting of metals species and C = O groups, which can effectively activate PMS. SBC-activated PMS (PMS/SBC) can destroy cellular structures in WAS and release large amounts of organic matter, increasing the rate of hydrolysis and promoting subsequent SCFA production. Compared with the control, PMS/SBC treatment increased SCFA production by 801 % at a PMS dose of 0.14 g/g VSS (volatile suspended solids) and SBC dose of 0.24 g/g VSS. Moreover, PMS/SBC could degrade refractory organic pollutants in WAS (sulfamethoxazole removal efficiency >63 %), improving SCFA quality. Mechanistic investigations revealed that SBC activates PMS to produce •SO 4 −, 1O 2 , and •OH. The contributions of these species to sludge solubilization were 1O 2 > •OH > •SO 4 −, with surface-bound radicals on SBC playing major roles. In addition, PMS/SBC treatment enriched hydrolysis and SCFA-forming bacteria and increased the expression of key genes for SCFA production during sludge anaerobic fermentation, which also contributed to SCFA accumulation. This work provides new insights into the mechanism of SBC activation of PMS and its potential applications in WAS resource utilization. [ABSTRACT FROM AUTHOR]