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The slow breakdown of sludge is the primary obstacle hindering the conversion of waste-activated sludge to short-chain fatty acids (SCFAs) by anaerobic fermentation. This study proposed a novel method incorporating sodium pyrophosphate and thermal hydrolysis (SP-TH) for sludge pretreatment and evaluated its effectiveness regarding SCFA production. The combined pretreatment of SP at 0.4 g/g of total suspended solids and TH at 140 °C enhanced SCFA production from 2,169 ± 208 to 4,388 ± 184 mg chemical oxygen demand/L. SP strips extracellular polymeric substances, and the subsequent TH decomposes cells in the sludge, thus promoting sludge hydrolysis. SP-TH pretreatment promoted SCFA accumulation by enhancing enzyme activity and enriching acidifying bacteria. This study demonstrated that SP-TH pretreatment can effectively promote acid production from sludge, providing a new avenue for organic matter recovery through sludge anaerobic fermentation pretreatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Ofloxacin (OFL) is a commonly used antibiotic that can enter wastewater treatment plants and be adsorbed by the sludge, resulting in a high OFL concentration in sludge and affecting the subsequent sludge anaerobic digestion process. However, the micro mechanisms involved in this process have not been thoroughly studied. Therefore, this study focuses on the effect of OFL on the sludge anaerobic digestion of sludge to provide such support. The experimental results showed that the maximal methane yield decreased from 277.7 to 164.7 mL/g VSS with the OFL concentration increased from 0 to 300 mg/L. Additionally, OFL hindered the intermediate biochemical processes of hydrolysis, acidogenesis, acetogenesis, and acetoclastic methanogenesis. However, it promoted hydrogenotrophic methanogenesis process, using H 2 as substrate, with the concentration of 300 mg/L OFL was 5.54 fold methane production of that in the control. Further investigation revealed that the negative effect of OFL was likely due to the induction of reactive oxygen species, which led to a decrease in cell activity and interference with the activity of key enzymes. Microbiological analysis revealed that OFL reduced the relative abundance of hydrolysis and acidogenesis bacteria, and Methanosaeta archaea, while increasing the relative abundance of hydrogenotrophic methanogenesis microorganism from 36.54% to 51.48% as the OFL concentration increase from 0 to 300 mg/L., Competing Interests: Declaration of competing interest This is a new research article named “The resistance of hydrogenotrophic methanogenic microorganisms to ofloxacin in sludge anaerobic digestion process” and all the authors have reviewed the final version of the manuscript and approved to submit it to your journal. We guarantee that this manuscript will not be submitted elsewhere for publication while being considered by the Journal of Environmental Management, that it is not under consideration for publication elsewhere, that its publication is approved by all authors and tacitly or explicitly by the responsible authorities where the work was carried out, and that, if accepted, it will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder. There are no conflicts of any interest, including employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding. I am very appreciated by your kindness, looking forward to hearing from you., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Thermal hydrolysis (TH) is promising for sludge pretreatment, but the refractory substances generated at high temperatures inhibit anaerobic digestion. In this study, a novel combined TH and photocatalytic pretreatment method was proposed to improve the anaerobic digestion performance of waste activated sludge. The results showed that the combined pretreatment (170 °C, 0.5 g/L TiO 2 ) increased methane yield by 66 % from 111 ± 5 m L/g VS to 185 ± 5 m L/g VS. After TH pretreatment, photocatalysis further promoted sludge solubilization by destroying extracellular polymeric substances, resulting in an increase in released soluble organic matter from 292 ± 16 mg/L to 4,091 ± 85 mg/L. In addition, photocatalysis improved the biodegradability of sludge by reducing the melanoidin and humic acid contents by 26 % and 20 %, respectively. The proposed novel pretreatment method effectively overcomes the bottleneck of TH technology and provides an alternative pretreatment technology for improving sludge 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 Elsevier Ltd. All rights reserved.)

Chitosan (CTS) serves as an excellent natural flocculant in wastewater purification and sludge conditioning, but its potential impact on anaerobic fermentation of waste-activated sludge is unclear. The current study investigated the role of CTS in short-chain fatty acids (SCFAs) generation via sludge alkaline anaerobic fermentation. The results showed a drastic reduction in SCFA production with CTS, showing a maximum inhibition of 33 % at 6 mg/g of total suspended solids. CTS hindered sludge solubilization through flocculation, and acted as a humus precursor, promoting humus formation, and consequently reduced the amount of available substrates. Further, CTS promoted free ammonia production, posing a challenge to enzymes and cell viability. Additionally, CTS increased the population of Rikenellaceae sp. and weakened the dominance of hydrolyzing and acidifying bacteria. This study deepens the understanding of the potential impact of CTS on anaerobic fermentation and provides a theoretical basis for reducing the risk of polymeric flocculants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Microplastics are known to negatively affect anaerobic digestion (AD) of waste activated sludge. However, whether thermal hydrolysis (TH) pretreatment alters the impact of microplastics on sludge AD remains unknown. Herein, the effect of TH on the impact of polyethylene (PE) microplastics in sludge AD was investigated. The results showed that the inhibition of methane production by PE at 100 particles/g total solids (TS) was reduced by 31.4% from 12.1% to 8.3% after TH at 170 °C for 30 min. Mechanism analysis indicated TH reduced the potential for reactive oxygen species production induced by PE, resulting in a 29.1 ± 5.5% reduction in cell viability loss. In addition, additive leaching increased as a result of rapid aging of PE microplastics by TH. Acetyl tri-n-butyl citrate (ATBC) release from PE with 10 and 100 particles/g TS increased 11.5-fold and 8.6-fold after TH to 68.2 ± 5.5 μg/L and 124.0 ± 5.1 μg/L, respectively. ATBC at 124.0 μg/L increased methane production by 21.4%. The released ATBC enriched SBR1031 and Euryarchaeota, which facilitate the degradation of proteins and promote methane production. This study reveals the overestimated impact of PE microplastics in sludge AD and provides new insights into the PE microplastics-induced impact in practical sludge treatment and anaerobic biological processes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Total solids (TS) content may provide a regulatory strategy for optimizing anaerobic digestion enhanced by high-temperature thermal hydrolysis, but the role of TS content is not yet clear. In this study, the effect of TS content on the high-temperature thermal hydrolysis and anaerobic digestion of sludge and its mechanism were investigated. The results showed that increasing the TS content from 2% to 8% increased the sludge solubility and methane production potential, reaching peak values of 26.6% and 336 ± 6 mL/g volatile solids (VS), respectively. With a further increase in TS content to 12%, the strong Maillard reaction increased the aromaticity and structural stability of extracellular polymer substances, decreasing sludge solubility to 18.6%. Furthermore, the decrease in sludge biodegradability and the formation of inhibitory by-products resulted in a reduction in methane production to 272 ± 4 mL/g VS. This article provides a new perspective to understand the role of TS content in the thermal hydrolysis of sludge and a novel approach to regulate the Maillard reaction., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Polydimethyldiallylammonium chloride (PDDA) is an excellent flocculant for wastewater purification and sludge dewatering, but whether it poses a threat to hydrogen production from waste activated sludge is not known. In this study, the effect and underlying mechanism of PDDA on the dark fermentation of sludge was investigated. The results showed that PDDA reduced cumulative hydrogen production from 3.8±0.1 to 2.4±0.1 mL/g volatile suspended solids at 40 g/kg total suspended solids. PDDA impeded the dark fermentation process by inhibiting the activity of key enzymes, presenting a stronger inhibitory effect on the hydrogen production process than the hydrogen consumption process. Additionally, PDDA inhibited Firmicutes by enriching other microorganisms, thereby impeding hydrogen production via the acetate pathway. This study deepens the understanding of the potential effects of PDDA on sludge treatment and provides a theoretical basis for alleviating the negative effects of quaternary ammonium-based cationic flocculants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Chitosan is widely used as a dewatering flocculant, but whether it affects hydrogen production from sludge anaerobic fermentation is unclear. This study aimed to elucidate the role of chitosan in the dark fermentation of waste activated sludge for hydrogen production. The results showed that chitosan had a negative effect on hydrogen production from sludge. Chitosan at 30 g/kg total suspended solids reduced hydrogen accumulation by 56.70 ± 1.22 % from 3.94 ± 0.12 to 1.71 ± 0.10 mL/g volatile suspended solids. Chitosan hindered the solubilization of sludge by flocculation, which reduced the available substrate for anaerobic fermentation. In addition, chitosan interfered with the electron transport system by reducing cytochrome C and caused lipid peroxidation by inducing reactive oxygen species, thereby inhibiting the activity of enzymes involved in anaerobic fermentation. Hydrogen production was reduced because hydrogen-producing processes (i.e., hydrolysis, acidification, and acetification) were inhibited more strongly than hydrogen-consuming processes (i.e., methanogenesis, sulfate reduction, and homoacetogenesis). Furthermore, chitosan enriched the abundance of Spirochaetaceae sp. and Holophagaceae sp., which occupied the survival space of hydrogen-producing microorganisms. This study reveals the potential impact of chitosan on hydrogen production in dark fermentation of sludge and provide direct evidence that chitosan triggers oxidative stress in anaerobic fermentation., 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 © 2022 Elsevier B.V. All rights reserved.)

Polycarbonate (PC) microplastics are frequently detected in waste activated sludge. However, understanding the potential impact of PC microplastics on biological sludge treatment remains challenging. By tracking the changes in methane production under different concentrations of PC microplastics, a dose-dependent effect of PC microplastics on anaerobic digestion of sludge was observed. PC microplastics at 10-60 particles/g total solids (TS) improved methane production by up to 24.7 ± 0.1 % (at 30 particles/g TS), while 200 particles/g TS PC microplastics reduced methane production by 8.09 ± 0.1 %. Bisphenol A (BPA) leached from 30 particles/g TS PC microplastics (1.26 ± 0.18 mg/L) down-regulated intracellular reactive oxygen species (ROS) production, thereby enhancing enzyme activity, biomass viability, and abundance of methanogenic (Methanobacterium sp. and Methanosarcina sp.), ultimately boosting methane production. Conversely, BPA leached from 200 particles/g TS PC microplastics (4.02 ± 0.15 mg/L) stimulated ROS production, resulting in decreased biomass viability and even apoptosis. Modulation of oxidative stress by leaching monomeric BPA is an underappreciated transformative mechanism for improving the mastery of the potential behavior of microplastics in biological sludge treatment., 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 © 2022 Elsevier B.V. All rights reserved.)

Total solids (TS) content is critical for thermal hydrolysis and anaerobic digestion (AD) performance, but its role in thermal-alkaline pre-treatment (TAP) is unclear. Therefore, this study aimed to reveal the key role of TS content in TAP and AD of waste activated sludge. The results showed that the optimum TS content of TAP (at 90 °C for 1 h, pH = 10) was 8 %. Sludge disintegration and methane production increased from 19.7 ± 2.2 % to 34.3 ± 2.9 % and from 167.4 ± 4.2 to 246.0 ± 6.2 mL/g volatile solids, respectively, when TS content were increased from 2 % to 8 %. A high TS content will likely promote sludge disintegration since it will reduce heat loss and improve heating efficiency. Additionally, increasing TS content from 2 % to 10 % minimized the production of intracellular reactive oxygen species by 30.4 ± 0.7 % and increased cell viability by 11.5 ± 2.6 %. In contrast, excessive TS content (i.e., ≥10 %) deteriorated the fluidity of sludge, which prevents it from disintegration. Once TS reached 10 %, the accumulation of ammonia nitrogen and volatile fatty acids reached 812.7 ± 27.4 and 1932.0 ± 5.3 mg/L, respectively, which reduced the activity of acidulase and coenzyme F420 and shifted the archaeal community from acetylotrophic to hydrogenotrophic methanogens. This article provides new insights into the TS content in TAP and AD technology., 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 © 2022 Elsevier B.V. All rights reserved.)

The role of total solids content in low-temperature thermal hydrolysis and anaerobic digestion of sewage sludge was investigated. Increasing total solids from 2% to 6% improved thermal hydrolysis and anaerobic digestion performance, while increasing it further to 12% decreased methane production. Maximum sludge solubility (22.9% ± 0.6%) and methane production (320 ± 7 mL/g volatile solids) were achieved at 6% solids. The increase in solids content from 2% to 6% improved heating efficiency and volatile fraction content, which facilitated sludge solubilization and enrichment of methanogens. However, further increases in solids content resulted in a stable floc structure with excess ammonia nitrogen and volatile fatty acids, which limited the release of substrates and reduced the abundance of acidifying bacteria and methanogens, ultimately leading to reduced methane production. An in-depth understanding of the role of solids content opens up new avenues for improved low-temperature thermal hydrolysis of sludge., 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 © 2022 Elsevier Ltd. All rights reserved.)

The potential effect of polyethyleneimine as a flocculant on anaerobic digestion of sludge was investigated. Polyethyleneimine above 12 g/kg total suspended solids inhibited the entire anaerobic digestion process including solubilization, hydrolysis, acidification, and methanogenesis. The addition of 24 g/kg total suspended solids polyethyleneimine reduced methane production from 167 ± 5 L/kg volatile suspended solids in the control reactor (without polyethyleneimine) to 141 ± 5 L/kg volatile suspended solids. Polyethyleneimine bound to extracellular polymeric substances, thus enhancing sludge agglomeration and hindering the release of organics. Meanwhile, the reduction of cytochrome C impeded electron transport, consequently curbed direct interspecies electron transfer. The adsorption of carbon dioxide by amine groups also hampered methane conversion. This study elucidated the concept that polyethyleneimine reduces mass transfer in anaerobic digestion, providing new insights into the potential behavior of flocculants in sludge treatment., 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 © 2022 Elsevier Ltd. All rights reserved.)

The effects and key mechanisms of polydimethyldiallylammonium chloride on anaerobic digestion of waste activated sludge were investigated. Polydimethyldiallylammonium chloride at 38.1 g/kg total solids substantially reduced cumulative methane production from 138.2 ± 5.5 to 49.4 ± 5.0 L CH 4 /kg volatile solids added, a reduction of 64.3 ± 0.2%. The quaternary ammonium groups on polydimethyldiallylammonium chloride agglomerated sludge flocs by neutralizing negatively charged amino groups in in extracellular polymeric substances, which hindered the release of organic matter. Quaternary ammonium groups induce oxidative stress by inducing the production of reactive oxygen species, thereby inhibiting the activity of anaerobic digestive enzymes. In addition, quaternary amine groups reduced the abundance of hydrolyzing bacteria, acidifying bacteria, and acetylotrophic methanogens. Oxidative stress could be an underappreciated mechanism that quaternary ammonium groups deteriorate anaerobic digestion, which could be transformative for understanding the potential risks of quaternary ammonium cationic flocculants in biological sludge treatment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Poly aluminum chloride (PAC) and poly ferric sulfate (PFS) are widely used in wastewater treatment and sludge dewatering, resulting in their amounts being accumulated substantially in waste activated sludge (WAS). Till now, however, little information about their influence on WAS digestion is available. This work therefore aims to provide insights into how PAC and PFS affect sludge anaerobic digestion. The experimental results showed that PFS's inhibition to methane production was much severer than PAC, in control reactor (0 mg Al or Fe /g TSS), the maximum cumulative methane production was 152.99 ± 7.18 mL/g VSS, when flocculants concentration increased to 30 mg Al/g TSS or 30 mg Fe/g TSS, the yields decreased to 129.54 ± 6.18 mL/g VSS and 89.52 ± 4.82 mL/g VSS respectively. Mechanism explorations exhibited that protein in WAS could bond with flocculants, which would inhibit protein bioconversion. It was also observed that the apparent activation energy (AAE) of organic solubilisation of PAC and PFS-contained sludge were increased by 38.58% and 18.67% respectively. Meanwhile, compared to the PFS, PAC led to more serious suppression of hydrolysis and acidogenesis processes, with propionic acid used as substrate, PFS inhibit methanogenesis more severely than PAC. Illumina MiSeq sequencing analyses showed that the number of sulfate-reducing bacteria (SRB) enriched obviously in PFS reactor. The results revealed that although PFS reduced methane production more severely than PAC, the reduction was mainly enforced by the activity of SRB but not organic enmeshment. Furthermore, PAC severely suppresses acetotrophic methanogens but PFS depress hydrogenotrophic methanogenesis microorganism mainly. Additionally, malodor control and dewaterability enhancement of digested sludge can be realized with PAC existence. The finding obtained in this study would provide insights into the PFS or PAC-involved sludge anaerobic digestion system and might support the important implication for further manipulate WAS treatment in the future., Competing Interests: Declaration of competing interest There are no conflicts of any interest, include employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding., (Copyright © 2021. Published by Elsevier B.V.)

Perfluorooctanoic acid (PFOA), as a recalcitrant organic pollutant, inevitably enters wastewater treatment facilities and is enriched in settled sludge. However, the potential impact of PFOA on sludge treatment has never been documented. In this study, the effect of PFOA on anaerobic digestion of sewage sludge and its underlying mechanism were investigated through batch and long-term experiments. The presence of PFOA was found to be deleterious for methane production from sewage sludge. 170 mg/kg total solids PFOA reduced the cumulative methane production from 197.1 ± 1.92-159.9 ± 3.10 mL/g volatile solids. PFOA induces the production of reactive oxygen species, which directly leads to cell inactivation and interferes with methane production. PFOA stimulates microorganisms to secrete more extracellular polymeric substances (mainly proteins), which not only hinders the solubilization of organic matter but also down-regulate enzyme activities to inhibit acidification and methanogenesis. In addition, PFOA reduces the diversity of microorganisms, especially the abundance of acid-producing bacteria and methanogens, making the microbial community unfavorable for methane production., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study explored the effect of polyferric chloride (PFC) as a flocculant on waste activated sludge anaerobic digestion. The results verified that PFC has an inhibitory effect on methane production during anaerobic digestion. PFC with a concentration of 40 g/kg total suspended solids reduced methane production from 195 ± 2.10 to 156 ± 1.50 L/kg volatile suspended solids, a decrease of 20.0 ± 0.09%. PFC released hydroxyl polymers and Fe(III). Hydroxy polymers aggregated sludge flocs and hindered the release of dissolved organic matter. Fe(III) induced dissimilar iron reduction processes to contend with methyl-CoM for electrons, thereby further reducing methane production. In addition, PFC enriched iron-reducing bacteria and reduced the abundance of methanogens, resulting in microbial communities that are not conducive to methane production. This article puts forward innovative insights on the role of PFC in biological sludge treatment, which is expected to guide the flocculant selection during wastewater treatment., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, the roles of chitosan (CTS) in anaerobic digestion of Waste activated sludge (WAS) were investigated. The results show that the methane production potential of WAS is positively correlated with the CTS content. The presence of 30 g/kg total suspended solids CTS increased the cumulative methane production from 215 ± 1.52 to 272 ± 1.83 mL/g volatile suspended solids. The positively charged amino groups in CTS neutralize the hydroxyl and carboxyl groups of extracellular polymeric substances, which reduces the negative charge on the surface of sludge and promotes sludge agglomeration, thereby inhibiting the release of organic matter. CTS also inhibits hydrolysis and acidification by immobilizing hydrolases and acidulase enzymes. However, CTS flocculates humus to avoid its interference with electron transfer, thereby enhancing the activity of coenzyme F420 and methanogenesis. In addition, CTS increases the abundance of methanogens, which also contributes to methane production., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

One of the key challenges of wastewater treatment today is to understand the potential effect of residual pollutants on the management of waste activated sludge (WAS). This study aims to clarify the effect of chlortetracycline (CTC) as a residual antibiotic on the anaerobic fermentation of WAS to produce volatile fatty acids (VFAs). The results show that CTC with a concentration of 10 mg/kg total suspended solids enhances the VFA production by 21.1%. Mechanistically, CTC was found to prompt the secretion of extracellular polymeric substances to provide more substrates for anaerobic fermentation. Meanwhile, CTC stimulates acidification by increasing the activity of acetate kinase, and inhibits methanogenesis by reducing F 420 activity, thereby increasing the accumulation of VFAs. This article provides new insights into the behavior of CTC in WAS fermentation, which is essential for resource recovery from WAS containing CTC., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The presence of endocrine disruptor compounds (EDCs) in wastewater treatment plants has attracted widespread attention, but their potential impact on anaerobic fermentation of waste activated sludge (WAS) remains unclear. Therefore, this study aims to reveal the effect of typical EDC octylphenol (OP) on the recovery of volatile fatty acids (VFAs) in anaerobic fermentation. The results show that OP has a positive effect on the recovery of VFAs from WAS. The presence of 200 mg/kg dry sludge of OP increased the cumulative amount of VFAs from 3245 in the control (without OP) to 6828 mg COD/L. The increase in VFA production was mainly attributed to the accumulation of acetic acid, which rose from 1511 to 4425 mg COD/L, almost tripled. Further research found that OP promoted solubilization and hydrolysis by improving the biodegradability of WAS, and severely inhibited the methanogenesis process by inhibiting the activity of coenzyme F420, thereby significantly increasing the accumulation of acetic acid. These findings are of great significance to clarify the role of OP in anaerobic fermentation, and provide theoretical basis and guidance for the selection of target products in anaerobic fermentation of WAS containing OP., 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 © 2020 Elsevier B.V. All rights reserved.)

The removal of antibiotics and resistance genes in wastewater treatment plants has attracted widespread attention, but the potential role of residual antibiotics in the disposal of waste activated sludge (WAS) has not been clearly understood. In this study, the effect of roxithromycin (ROX) on volatile fatty acid (VFA) recovery from WAS anaerobic fermentation was investigated. The experimental results showed that ROX made a positive contribution to the production of VFAs. With the increase of ROX dosages from 0 to 100 mg/kg TSS, the maximum accumulation of VFAs increased from 295 to 610 mg COD/L. Mechanism studies revealed that ROX promoted the solubilization of WAS by facilitating the disruption of extracellular polymeric substances. In addition, ROX enhanced the activity of acetate kinase and inhibited the activities of α-glucosidase and coenzyme F 420 , and showed a stronger inhibitory effect on methane production than the hydrolysis process, thus resulting in an increase in VFA accumulation. These findings provide a new insight for the role of antibiotics in anaerobic fermentation of WAS., 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 © 2020 Elsevier B.V. All rights reserved.)

Alkaline condition (especially pH 10) has been demonstrated to be a promising method for short-chain fatty acid (SCFA) production from waste activated sludge anaerobic fermentation, because it can effectively inhibit the activities of methanogens. However, due to the limit of sludge solubilization rate, long fermentation time is required but SCFA yield is still limited. This paper reports a new pretreatment method for alkaline fermentation, i.e., using free nitrous acid (FNA) to pretreat sludge for 2 d, by which the fermentation time is remarkably shortened and meanwhile the SCFA production is significantly enhanced. Experimental results showed the highest SCFA production of 370.1 mg COD/g VSS (volatile suspended solids) was achieved at 1.54 mg FNA/L pretreatment integration with 2 d of pH 10 fermentation, which was 4.7- and 1.5-fold of that in the blank (uncontrolled) and sole pH 10 systems, respectively. The total time of this integration system was only 4 d, whereas the corresponding time was 15 d in the blank and 8 d in the sole pH 10 systems. The mechanism study showed that compared with pH 10, FNA pretreatment accelerated disruption of both extracellular polymeric substances and cell envelope. After FNA pretreatment, pH 10 treatment (1 d) caused 38.0% higher substrate solubilization than the sole FNA, which indicated that FNA integration with pH 10 could cause positive synergy on sludge solubilization. It was also observed that this integration method benefited hydrolysis and acidification processes. Therefore, more SCFA was produced, but less fermentation time was required in the integrated system., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

• ZIF-8/TiO 2 composite nanoparticles were in-situ grown on PDA-templated cotton fabrics for photodegradation of dyes. • ZIF-8/TiO 2 composite nanoparticles were uniformly grown on cotton fabrics and and the role of pDA was proposed. • The fabrics showed visible-light-driven photocatalytic performance in degrading MB solution with stability and reliability. • The possible photocatalytic mechanism of ZIF-8/TiO 2 /pDA/CF was proposed. Excellent photocatalytic activity was achieved on textiles via polydopamine-assisted deposition of Zeolitic Imidazolate Framework-8 (ZIF-8)/TiO 2 composite nanoparticles. Cotton fabrics as the substrate were templated with polydopamine followed by in-situ deposition of ZIF-8/TiO 2 photocatalysts. The heterogeneous nucleation growth of ZIF-8 was effectively improved by the chelation effects between polydopamine and Zn2+. SEM, FTIR, XPS, XRD, and TG analysis were employed to study the morphology, chemical constituent, micro-structure and thermal stability of ZIF-8/TiO 2 deposited fabrics. Photoluminescence (PL) spectra have indicated that the composite structure is beneficial in improving the charge transfer ability and decreasing the re-union rate of photogenerated electron pair holes. The mechanism was proposed to reveal both the in-situ deposition of nanocomposites on fiber surface and photocatalytic activity. The ZIF-8/TiO 2 deposited cotton fabrics exhibit good photocatalytic activity and recyclability leading to potential industrial wastewater treatment applications. [ABSTRACT FROM AUTHOR]

In this work, both short-term and long-term experiments were therefore conducted to assess the effects of ciprofloxacin (0.2 and 2 mg·L − 1 ) on wastewater nutrient removal. The results showed that both levels of ciprofloxacin had no acute and chronic adverse effects on the surface integrity and viability of activated sludge. Short-term exposure to all the ciprofloxacin levels induced negligible influences on wastewater nutrient removal. However, the prolonged exposure to ciprofloxacin decreased total phosphorus and nitrogen removal efficiencies from 96.8, 95.8% (control) to 91.7, 84.9% (0.2 mg·L − 1 ) and 90.5%, 80.2% (2 mg·L − 1 ), respectively. The mechanism study showed that ciprofloxacin exposure suppressed denitrification and phosphorus uptake processes. It was also found that ciprofloxacin affected the transformations of intracellular polyhydroxyalkanoates and glycogen in the oxic and anoxic stages. Moreover the activities of nitrite reductase and polyphosphate kinase were inhibited by the presence of ciprofloxacin. Further analysis with high-throughput sequencing revealed that compared with the control, the abundances of polyphosphate accumulating organisms, glycogen accumulating organisms and denitrifying bacteria in ciprofloxacin exposure reactors reduced, which were consistent with the decreased nutrient removal performance measured in these reactors. [ABSTRACT FROM AUTHOR]