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This paper selects a multivariate panel data approach to understand and analyse the renewable energy augmented production function, with particular emphasis the importance of the association between capital, labour, output, the consumption of renewable energy, inflation, and trade for the eight Middle East and North Africa countries. Unlike previous studies which are not decisive on the channel by with renewable energy consumption affects trade and economic growth, we model renewable energy in the growth process as a primary element of technological development in the endogenous growth model. Utilising data between 2000 and 2016 and employing panel co-integration tests, the key findings demonstrate evidence of a longstanding association between the variables. Additionally, a bi-directional causality between real Gross Domestic Product and inflation was found. Significantly, the study found evidence of two uni-directional causalities running from inflation to renewable energy and from renewable energy to economic growth. The findings deliver an alternative macroeconomic interpretation for the influence of inflation on factor input substitution. The findings also emphasise the critical role that renewable energy plays in the production process and its comprehensive and positive economic effects. • This study applies a multivariate panel data approach to examine the renewable energy augmented production function. • We model renewable energy in the growth process as a primary element of technological development. • We demonstrate evidence of a longstanding association between the variables. • We also found significant evidence of uni-directional causalities running from inflation to renewable energy. • The findings deliver an alternative macroeconomic interpretation for the influence of inflation on factor input substitution. [ABSTRACT FROM AUTHOR]

Biochemical properties of granules are of vital importance to UASB performance. This study characterized the granules cultivated at different COD/SO 4 2− ratios to elucidate the influence of sulfidogenesis on starch wastewater (1000 mg-COD L −1 ) biodegradation kinetics and process stability. Suitable sulfate addition enriched granular microecosystems and stimulated the secretion of extracellular substances, facilitating cells cohersion and sludge aggregation. The percentage of granules larger than 2.8 mm increased from <10.0% to 58.8–69.4% with decreasing COD/SO 4 2− ratio from 10 to 2. Starch-fed granules tended to grow flagella-like filaments on the surface. The filaments overwhelmed by hydrophilic biopolymers had high affinity for biogas-bubbles and water-molecules aggravating granule floatation and washout. 16 s rRNA gene analysis revealed that decreasing COD/SO 4 2− ratio shifted Syntrophobacterales to Desulfovibrio , which co-worked with Methanosaeta while suppressing Methanobacterium thereby altering starch bioconversion routes. Decrease in Syntrophobacterales caused propionate accumulation and slight process upset. [ABSTRACT FROM AUTHOR]

Dewatering of waste activated sludge (WAS) is of major interest in its volume reduction, transportation and ultimate disposal. Persulfate-based oxidation process is a newly developed option for enhancing WAS dewaterability through the generation of powerful sulfate radicals (SO 4 − ·). However, the enhancement in WAS dewaterability by persulfate differs with the species of iron catalysts used. In this study, two types of iron catalysts (i.e. Fe 2+ vs. Fe 0 ) were employed to initiate the persulfate (S 2 O 8 2− ), and the catalyzing behaviors and the underlying principles in enhancing WAS dewaterability were investigated and compared. The Fe 2+ exhibited the high effectiveness in catalyzing the decomposition of persulfate to sulfate radicals (SO 4 − ·), inducing the greater improvement in WAS dewatering. The WAS dewaterability (indicated by dry solids content after filtration) increased with the added S 2 O 8 2− /Fe 2+ dosages, with the dry solids content reaching up to 5.1 ± 0.8 wt% at S 2 O 8 2− /Fe 2+ dosages of 1.2/1.5 mmol/g-VS after only 30 s’ filtration, roughly 1.8-fold increase than raw WAS (1.8 ± 0.1 wt%). In contrast, the influence of the persulfate oxidation when activated with Fe 0 on WAS dewaterability was statistically insignificant. The WAS dewaterability remained nearly unchanged (i.e. dry solids content of 2.0 ± 0.0 wt%), irrespective of the employed S 2 O 8 2− /Fe 0 dosages. Further analysis demonstrated that the WAS dewaterability negatively corresponded to loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS). The abundant SO 4 − · from S 2 O 8 2− /Fe 2+ system could effectively disrupt the gel-like EPS matrix, break apart the cells and subsequently arouse the release of the water inside EPS and cells, facilitating water-solid separation. In the case of S 2 O 8 2− /Fe 0 , the dissolution of Fe 0 particles was the rate-limiting step, due to the formation of oxide iron layer near Fe 0 metallic surface, which resulted in the slow SO 4 − · production and thus hardly promoted WAS dewaterability. The pH adjustment could accelerate Fe 0 dissolution and enhance the dewatering performance of S 2 O 8 2− /Fe 0 process to a certain degree, but the effect was unsatisfactory. Additionally, the observations regarding the dissolved organic matters and ammonium collectively revealed that except for enhancing WAS dewatering, S 2 O 8 2− /Fe 2+ oxidation could concurrently degrade COD and ammonia from WAS filtrate, lighten the burden of the subsequent sewage treatment facilities and reduce operational expense. Hence, from an environmental and economic perspective, the S 2 O 8 2− /Fe 2+ system possesses much greater promise for WAS dewatering. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cell (MEC) holds the flexible potentials for waste biorefinery, pollutants removal, CO 2 capture, and bioelectrosynthesis of clean and renewable electrofuels or valuable chemical commodities, dealing with the depletion of fossil fuels and environmental deterioration issues. Although substantial advances in process design and mechanisms exploration have greatly promoted the development of MEC platform from a concept to a technology, how to virtually utilize it in real-world scenario remains a big challenge. There are numerous technical issues ahead for MEC to be tackled towards up-scaling and real implementations. This review article presents a state-of-the-art overview of the fundamental aspects and the latest breakthrough results and accomplishments obtained from the MEC platform, with a special emphasis on mapping the key extracellular electron transfer (EET) mechanisms between electroactive microorganisms and electrode surface (including i : cells → e − anode ; and ii : cathode → e − cells ). A unified discussion of different process design: inoculation methods for rapid start-up, role of membranes, modification of cathode materials, cathodic catalysts (i.e. noble, un-noble metal catalysts and biocatalysts) as well as designs and configurations of versatile bioelectrochemical cells, is also involved. Finally, the major challenges and technical problems encountered throughout MEC researches are analyzed, and recommendations and future needs for the virtual utilization of MEC technology in real waste treatment are elaborated. [ABSTRACT FROM AUTHOR]

The dispersion of granules in upflow anaerobic sludge blanket (UASB) reactor represents a critical technical issue in methanolic wastewater treatment. In this study, the potentials of coupling a microbial electrolysis cell (MEC) into an UASB reactor for improving methanolic wastewater biodegradation, long-term process stability and biomethane recovery were evaluated. The results indicated that coupling a MEC system was capable of improving the overall performance of UASB reactor for methanolic wastewater treatment. The combined system maintained the comparatively higher methane yield and COD removal efficiency over the single UASB process through the entire process, with the methane production at the steady-state conditions approaching 1504.7 ± 92.2 mL-CH 4 L − 1 -reactor d − 1 , around 10.1% higher than the control UASB (i.e. 1366.4 ± 71.0 mL-CH 4 L − 1 -reactor d − 1 ). The further characterizations verified that the input of external power source could stimulate the metabolic activity of microbes and reinforced the EPS secretion. The produced EPS interacted with Fe 2+/3+ liberated during anodic corrosion of iron electrode to create a gel-like three-dimensional [-Fe-EPS-] n matrix, which promoted cell-cell cohesion and maintained the structural integrity of granules. Further observations via SEM and FISH analysis demonstrated that the use of bioelectrochemical stimulation promoted the growth and proliferation of microorganisms, which diversified the degradation routes of methanol, convert the wasted CO 2 into methane and accordingly increased the process stability and methane productivity. [ABSTRACT FROM AUTHOR]

Sewage sludge management is now becoming a serious issue all over the world. Anaerobic digestion is a simple and well-studied process capable of biologically converting the chemical energy of sewage sludge into methane-rich biogas, as a carbon-neutral alternative to fossil fuels whilst destroying pathogens and removing odors. Hydrolysis is the rate-limiting step because of the sewage sludge complex floc structure (such as extracellular polymeric substances) and hard cell wall. To accelerate the rate-limiting hydrolysis and improve the efficiency of anaerobic digestion, various pretreatment technologies have been developed. This paper presents an up-to-date review of recent research achievements in the pretreatment technologies used for improving biogas production including mechanical (ultrasonic, microwave, electrokinetic and high-pressure homogenization), thermal, chemical (acidic, alkali, ozonation, Fenton and Fe(II)-activated persulfate oxidation), and biological options (temperature-phased anaerobic digestion and microbial electrolysis cell). The effectiveness and relative worth of each of the studied technologies are summarized and compared in terms of the resulting sludge properties, the digester performance, the environmental benefits and the current state of real-world application. The challenge and technical issues encountered during sludge cotreatment are discussed, and the future research needs in promoting full-scale implementations of those approaches are proposed. [ABSTRACT FROM AUTHOR]

A lab-scale methanolic wastewater-fed (3000 mg COD L − 1 ) UASB reactor was operated for 235 days to evaluate the influence of the sulfidogenesis process on metabolic routes, the re-granulation of dispersed granules and long-term process performance. Various sulfidogenesis scenarios were created by stepwise decreasing the influent COD/SO 4 2− ratio from 20 to 0.5 at a fixed organic loading rate (OLR) of 12 g COD L − 1 d − 1 . It was shown that the conversion of methanol to methane was stable at a wide COD/SO 4 2− range of ≥2, attaining high biogas production rate of 3.78 ± 0.32 L L − 1 d − 1 with efficient concurrent removal of the total COD (96.5 ± 4.4%) and sulfate (56.3 ± 13.0%). The methane content in biogas remained relatively stable at 81.5 ± 1.6% for all COD/SO 4 2− ratios tested. The particle size of the granules was shown to clearly increase as the COD/SO 4 2− ratios decreased. A slight linear decline was noted in the number of electrons utilized by methane producing archaea (MPA) (from 98.5 ± 0.5% to 80.0 ± 2.4%), whereas consumption by sulfate reducing bacteria (SRB) increased (from 1.5 ± 0.5% to 20.0 ± 2.4%) with the decreasing COD/SO 4 2− ratio. According to the results of activity tests and microbial community analysis, the conversion of methanol to methane at a low COD/SO 4 2− ratio, except from Methanomethylovorans sp., depends not only on low levels of acetoclastic and hydrogenotrophic methanogens, but also on incomplete oxidizer SRB species (e.g. Desulfovibrio sp.) that utilize H 2 -CO 2 with acetate to mineralize the methanol. This serves to diversify the metabolic pathway of methanol. Further analysis through scanning electron microscopy (SEM) revealed that a lower COD/SO 4 2− ratio favored the sulfidogenesis process and diversified the microbial community inside the reactor. The benefical sulfidogenesis process subsequently invoked the formation of a sufficient, rigid [-Fe-EPS-] n network (EPS: extracellular polymeric substances), binding and immobilizing the sludge, and resulting in the re-granulation of the dispersed granules. [ABSTRACT FROM AUTHOR]

Continuous primary energy consumption has motivated the scientists of the world to search for renewable energy sources that could substitute fossil fuels. Microalgae can be an alternative substrate for renewable energy recovery. In this study, biochemical methane potential (BMP) assays were used as a tool to examine the technical potential of methane production from microalgae (MA) through co-digesting with food waste (FW) at different MA: FW ratios on volatile solids (VS). Three mathematical models (i.e. first-order kinetic, modified Gompertz, and Cone models) were also utilized to fit the experimental data, with the purpose of elucidating the biological degradation and principle kinetics of the co-digestion. The results showed that supplementing food waste significantly improved microalgae digestion performance, with the highest methane yield of 639.8 ± 1.3 mL/g VS added obtained at a MA:FW ratio of 0.2:0.8, which was 4.99-fold increase with respect to that (106.9 ± 3.2 mL/g VS added ) of the microalgae alone. Cone model had the best fitness and reliability to the experimental results and could describe the co-digestion kinetics more reasonably. Parameter analysis and synergistic impact evaluation together revealed that the improvement in methanogenesis potential ( f d ) caused by the synergy of co-digestion might be the fundamental cause for the upgraded methane production. These results validated the superiority of co-digestion as a step towards maximizing methane production from microalgae, aiding the development of multi-biomass co-disposal and ultimately bioenergy recovery techniques. [ABSTRACT FROM AUTHOR]

A lab-scale upflow anaerobic sludge blanket (UASB) has been run for 250 days to investigate the influence of influent COD/SO 4 2− ratios on the biodegradation behavior of starch wastewater and process performance. Stepwise decreasing COD/SO 4 2− ratio enhanced sulfidogenesis, complicating starch degradation routes and improving process stability. The reactor exhibited satisfactory performance at a wide COD/SO 4 2− range ⩾2, attaining stable biogas production of 1.15–1.17 L L −1 d −1 with efficient simultaneous removal of total COD (73.5–80.3%) and sulfate (82.6 ± 6.4%). Adding sulfate favored sulfidogenesis process and diversified microbial community, invoking hydrolysis–acidification of starch and propionate degradation and subsequent acetoclastic methanogenesis; whereas excessively enhanced sulfidogenesis (COD/SO 4 2− ratios <2) would suppress methanogenesis through electrons competition and sulfide inhibition, deteriorating methane conversion. This research in-depth elucidated the role of sulfidogenesis in bioenergy recovery and sulfate removal, advancing the applications of UASB technology in water industry from basic science. [ABSTRACT FROM AUTHOR]

Microbial electromethanogenesis, relying on electrochemically active biofilm on biocathode to convert carbon dioxide to methane, provides a novel approach for renewable energy storage. One key factor that governs electron exchange and methane formation efficiencies is the electrode material. To promote methane production, a biocathode via modifying plain carbon stick with a layer of graphite felt (GF) (hereafter referred as “hybrid GF-biocathode”) was developed and evaluated in a two-chamber microbial electrolysis cells (MECs). Methane production with hybrid GF-biocathode reached 80.9 mL/L at the potential of −1.4 V after 24 h of incubation with coulombic efficiency of 194.4%. The tests by flushing three substrates (CO 2 , N 2 and H 2 –CO 2 [80:20]) revealed that direct electron transfer rather than intermediate H 2 contributed more to the electromethanogenesis. Cyclic voltammetry showed that GF enhanced the microbial electrocatalysis activity and reduced the cathode overpotential needed for methane production. Scanning electron microscope and fluorescence in situ hybridization analysis confirmed that the three-dimensional GF afforded the abundant space for the growth of electroactive microorganisms and promoted the electron exchange (e.g. cathode-to-cell etc.) via severing as “artificial pili”. This study reveals that GF with the open structure and high conductivity has the substantial potential to upgrade electromethanogenesis efficiency. [ABSTRACT FROM AUTHOR]

Long-term performance of methanol biocatalysis conversion in a lab-scale UASB reactor was evaluated. Properties of granules were traced to examine the impact of methanol on granulation. Methanolic wastewater could be stably treated during initial 240 d with the highest biogas production rate of 18.6 ± 5.7 L/L d at OLR 48 g-COD/L d. However, the reactor subsequently showed severe granule disintegration, inducing granule washout and process upsets. Some steps (e.g. increasing influent Ca 2+ concentration, etc.) were taken to prevent rising dispersion, but no clear improvement was observed. Further characterizations in granules revealed that several biotic/abiotic factors all caused the dispersion: (1) depletion of extracellular polymeric substances (EPS) and imbalance of protein/polysaccharide ratio in EPS; (2) restricted formation of hard core and weak Ca-EPS bridge effect due to insufficient calcium supply; and (3) simplification of species with the methanol acclimation. More efforts are required to solve the technical deficiencies observed in methanolic wastewater treatment. [ABSTRACT FROM AUTHOR]

The feasibility of anaerobic co-digestion of waste activated sludge (WAS) and grass Egeria densa ( E.d. ) with four different WAS: E.d. ratios was evaluated for the first time under mesophilic conditions. First-order kinetic, modified Gompertz, and Cone models were employed to reveal the principle kinetics of methane-rich bioenergy production from co-digestion. The results showed that the addition of E.d. could greatly upgrade the sludge methane production, and the highest methane yield averaged 198.32 ± 2.61 mL/g VS added for WAS: E.d. ratio of 0.7: 0.3, 18.72 ± 0.14% higher respective to that of WAS alone (about 176.36 mL/g VS added ). E.d. improved the solubilization of co-substrates and avoided the build-up of volatile fatty acids (VFAs) and free ammonia ([NH 3 ]) and subsequent inhibition, inducing a stable digestion environment. Model simulation indicated Cone model best fitted the actual evolution of methane production, as evidenced by low Root Mean Square Prediction Error (rMSPE) and Akaike’s Information Criterion (AIC), as well as high Pearson’s correlation between the predicated and actual values. Additionally, the parameters analysis highlighted that the co-digestion with E.d . substantially promoted the hydrolysis rate ( k hyd ) and methanogenesis potential ( f d ) of sludge, further explaining the increased solids removal and output of methane. This study demonstrated the sustainability and attractiveness of anaerobic co-digestion of sludge and grass E.d. , providing a sound basis for cost-efficient biomass stabilization and bioenergy recovery. [ABSTRACT FROM AUTHOR]

Long-term performance of a lab-scale UASB reactor treating starch wastewater was investigated under different hydraulic retention times (HRT). Successful start-up could be achieved after 15 days’ operation. The optimal HRT was 6 h with organic loading rate (OLR) 4 g COD/L d at COD concentration 1000 mg/L, attaining 81.1–98.7% total COD removal with methane production rate of 0.33 L CH 4 /g COD removed . Specific methane activity tests demonstrated that methane formation via H 2 –CO 2 and acetate were the principal degradation pathways. Vertical characterizations revealed that main reactions including starch hydrolysis, acidification and methanogenesis occurred at the lower part of reactor (“main reaction zone”); comparatively, at the up converting acetate into methane predominated (“substrate-shortage zone”). Further reducing HRT to 3 h caused volatile fatty acids accumulation, sludge floating and performance deterioration. Sludge floating was ascribed to the excess polysaccharides in extracellular polymeric substances (EPS). More efforts are required to overcome sludge floating-related issues. [ABSTRACT FROM AUTHOR]

Biogas, generated from an expanded granular sludge bed (EGSB) reactor treating municipal solid waste (MSW) leachate, was recirculated for calcium removal from the leachate via a carbonation process with simultaneous biogas purification. Batch trials were performed to optimize the solution pH and imported biogas (CO 2 ) for CaCO 3 precipitation. With applicable pH of 10–11 obtained, continuous trials achieved final calcium concentrations of 181–375 mg/L (removal efficiencies ≈ 92.8–96.5%) in the leachate and methane contents of 87.1–91.4% (purification efficiencies ≈ 65.4–82.2%) in the biogas. Calcium-balance study indicates that 23–986 mg Ca/d was released from the bio-system under the carbonized condition where CaCO 3 precipitating was moved outside the bioreactor, whereas 7918–9517 mg Ca/d was trapped into the system for the controlled one. These findings demonstrate that carbonation removal of calcium by biogas recirculation could be a promising alternative to pretreat calcium-rich MSW leachate and synergistically to improve methane content. [ABSTRACT FROM AUTHOR]

Long-term experiments herein were conducted to investigate the effect of cefalexin (CLX) on methane production during waste activated sludge (WAS) anaerobic digestion. CLX exhibited a considerable inhibition in methane production during the initial 25 days while the negative effect attenuated subsequently and methane production recovered depending on CLX doses used (600 and 1000 mg/L). The highest methane yield reached 450 mL at 1000 mg-CLX/L after 157 days of digestion, 63.8% higher than CLX-free one. Stimulated excretion of extracellular polymeric substances (EPS) by CLX served as microbial protecting layers, creating a suitable environment for microbes’ growth and fermentation. Further examination via ultraviolet visible (UV–Vis) spectra also verified the elevated slime EPS, LB-EPS and TB-EPS indicated by UV-254 in the presence of CLX. Unlike the commonly accepted adverse effect, this study demonstrated the beneficial role of CLX in methane production, providing new insights into its true environmental impacts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combined electrical-alkali pretreatment for improving sludge anaerobic digestion was proposed. [•] Combined process enhanced the cell lysis, biopolymers releases, and thus sludge disintegration. [•] Increased solubilization of sludge increased the anaerobic hydrolysis rate. [•] Increased solubilization does not always induce an improved anaerobic digestion efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • CH 4 generation reached 298.0 mL/L/d at −1.0 V vs. Ag/AgCl with η CE of 75.8%. • Moderate EPS played a curial role in aggregation and stability of biofilm. • hdrA , ehaA , and ehbC were putative genes for direct extracellular electron transfer. • Potential extracellular electron transfer pathway for CH 4 formation was proposed. Bioeletromethanogenesis, as a cutting-edge option to capture CO 2 and produce multi-carbon biofuels, has received extensive attraction. However, how electroactive biofilm (EAB) as the biocatalyst drives CO 2 electromethanogenesis is still not well recognized. In this study, a two-chamber bioelectrochemical cell equipped with a hybrid skirt-shaped cathode was constructed and the electrocatalytic performance of EAB and the electron shuttling mechanisms involved in extracellular electron transfer (EET) were systematically studied. The EAB colonizing on biocathode showed an excellent cathodic electrocatalytic activity and the minimum charge transfer resistance. The CH 4 production rate of 298.0 ± 46.7 mL/L/d was obtained at the cathodic potential of −1.0 V vs. Ag/AgCl with the highest Coulombic efficiency of 75.8 ± 9.9%. The gel-like extracellular polymeric substances, secreted by EAB, facilitated the adhesion/aggregation of microbes and EAB development. Further analysis suggested that CO 2 electromethanogenesis exhibited a positive association with Methanobacterium (54.4%) in EAB. Moreover, metagenome analysis confirmed the presence of direct EET-related genes (i.e., hdrA , ehaA , and ehbC), which accelerated the formation of corresponding functional protein complexes (particularly heterodisulfide reductase A, HdrA) and electron exchange. The mechanism for electron shuttling process in catalyzing CO 2 electromethanogenesis was further proposed. This study provides a new insight into direct extracellular electron transfer (DEET) mechanisms of CO 2 electromethanogenesis, and is useful for promoting EAB electrocatalytic activities and CO 2 emission reduction and reuse. [ABSTRACT FROM AUTHOR]

A bioelectrochemical anammox system (BEAnS) was constructed and operated at low temperature to investigate the effect of weak electrical stimulation (continuous or intermittent) on metabolism behaviors, electrochemical activity, nitrogen removal, and spatial distribution of anammox biofilms. Results showed that the continuously stimulated biocathode exhibited the highest electron transfer system activity (34.2 ± 6.9 μg mg−1 h−1), the fastest electron transfer coefficient (0.0412 s−1), the largest current density (0.25 A cm−2), and the smallest polarization resistance (∼4 Ω). This led to an enhanced nitrogen removal of 60.6 ± 5.6% and energy recovery of 289.1 mW m−3, compared with that of the control. Confocal laser scanning microscopy and fluorescence in situ hybridization analysis confirmed that continuous weak electrical stimulation could accelerate the secretion of extracellular polymer substances, which facilitated the aggregation/adhesion of single cell and subsequent development of compact and stratified co-existing biofilms on cathode. Microbial analysis further demonstrated the proliferation of electrotrophic denitrifying microorganisms (i.e., Thauera , Hydrogenophaga , and Ignavibacterium), nitrifier (Candidatus_Nitrotoga), and denitrifier (Denitratisoma), except for anammox bacteria (i.e., Candidatus_Brocadia , and Candidatus_Jettenia), implying the critical role of weak electrical stimulation in diversifying N-degrading microbial community and creating a more robust nitrogen metabolic pathway. These findings can provide a novel insight into autotrophic electroactive anammox biofilm enrichment and their activity enhancement by weak electrical stimulation. [Display omitted] • Constructing an electro-anammox system to explore weak electrical stimulation. • Verifying a positive impact of continuous stimulation on microbial activity. • Visualizing the spatial structure of a co-existing cathode biofilm. • Revealing a synergetic electrotrophic bacteria in biocathode for nitrogen removal. [ABSTRACT FROM AUTHOR]

Abstract: The potential benefits of Fe(II)–activated persulfate (S2O8 2−) oxidation under mild temperature in enhancing the dewaterability of waste activated sludge were investigated. Capillary suction time (CST) was used to characterize sludge dewatering. Zeta potential, particle size distribution, three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy, fourier-transformed infrared (FT-IR) spectroscopy and scanning electronic microscopy (SEM) were employed to explore influencing mechanisms. The results indicated that the dewaterability was deteriorated with single thermal treatment, but significantly enhanced in the presence of Fe(II)–S2O8 2− oxidation and further advanced together with thermal treatment. EEM and FT-IR analysis indicated that combined thermal and Fe(II)–S2O8 2− oxidation pretreatment led to degrading of tyrosine and tryptophan protein-like substances in extracellular polymeric substances (EPS) and cleavage of linkages in polymeric backbone. SEM images further revealed the rupture of sludge flocs at the colloidal scale, which contributed to the release of EPS-bound water and interstitial water trapped between flocs, and subsequent enhanced dewaterability. [Copyright &y& Elsevier]

Abstract: The potential of Fe(II)-activated persulfate (S2O8 2−) oxidation on enhancing the dewaterability of sludge flocs from 3-full scale wastewater treatment plants (WWTPs) were investigated. Normalized capillary suction time (CST) was applied to evaluate sludge dewaterability. Both extracellular polymeric substances (EPS) and metabolic activity of microorganisms were determined to explore the responsible mechanism. Fe(II)–S2O8 2− oxidation effectively improved sludge dewaterability. The most important mechanisms were proposed to be the degradation of EPS incorporated in sludge flocs and rupture of microbial cells. Three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy confirmed that the powerful SO4 − from Fe(II)–S2O8 2− system destroyed the particular functional groups of fluorescing substances (i.e., aromatic protein-, tryptophan protein-, humic- and fulvic-like substances) in EPS and caused cleavage of linkages in the polymeric backbone and simultaneous destruction of microbial cells, resulting in the release of EPS-bound water, intracellular materials and water of hydration inside cells, and subsequent enhancement of dewaterability. [Copyright &y& Elsevier]

Abstract: The potential benefits of Fe(II)-activated persulfate oxidation on sludge dewatering and its mechanisms were investigated in this study. Capillary suction time (CST) was used to evaluate sludge dewaterability. Both extracellular polymeric substances (EPS) and viscosity were determined in an attempt to explain the observed changes in sludge dewaterability. The optimal conditions to give preferable dewaterability characteristics were found to be persulfate () 1.2mmol/gVSS, Fe(II) 1.5mmol/gVSS, and pH 3.0–8.5, which demonstrated a very high CST reduction efficiency (88.8% reduction within 1min). It was further observed that both soluble EPS and viscosity played relatively negative roles in sludge dewatering, whereas no correlation was established between sludge dewaterability and bound EPS. Three-dimensional excitation–emission matrix (EEM) fluorescence spectra also revealed that soluble EPS of sludge were degraded and sludge flocs were ruptured by persulfate oxidation, which caused the release of water in the intracellular pace and subsequent improvement of its dewaterability. [Copyright &y& Elsevier]

Abstract: The high organic content in sewage sludge is the main obstacle to Portland cement-based solidification/stabilization (S/S). A novel aluminate 12CaO⋅7Al2O3 was prepared as accelerator in order to improve the performance of cement-based S/S making the sludge disposal and recycling possible. The behavior of pastes fabricated with various mass ratios of aluminate/cement has been analyzed in terms of mechanical strength, hydration products, microstructure and leaching characteristics. The incorporation of aluminate significantly improved the cement-based S/S performance. The solid matrix obtained with the aluminate/cement ratio of 4/6 and binder addition of 10wt.% presented 28day-strength of 157.2kPa, in contrast, 25.1kPa or so obtained for the cement only-sludge mix. X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG-DSC) and scanning electron microscopy (SEM) analysis revealed that the presence of aluminate counteracted the interference from organic matters, favored the formation of crystalline phases viz. ettringite C6A 3H32, calcite CaCO3 and quartz, and therefore the strength development. Environmental assessment of the final products in compliance leaching tests demonstrated that the concentration of heavy metals were below the certain legal limits (GB 5085.3-2007) set in China, though the addition of aluminate slightly fell the resistance of solidified mortars to acidic environments. [Copyright &y& Elsevier]

[Display omitted] • DMC-activated PDS oxidation was used to pretreat sludge. • Pretreatment promoted the dissolution of intracellular polymers. • Methane productivity was notably enhanced by pretreatment. • Modified Gompertz model was used to simulate biodegradation kinetics. The potential of disordered mesoporous carbon (DMC) as catalyst of peroxydisulfate (PDS) to improve sludge solubilization and methane production was investigated. Results showed that DMC activated PDS (DMC/PDS) to produce sulfate radicals (SO 4 −), facilitating cells rupture and sludge matrix dissociation by degrading the carbonyl and amide groups in organic biopolymers (especially proteins, polysaccharides and humus). At the optimal DMC/PDS dosage of 0.04/1.2 g-mmol/g-VS, SCOD was increased from initial 294.0 to 681.5 mg/L, with the methane production rate of 12.6 mL/g-VS/day. Moreover, DMC could serve as electron mediator to accelerate electron transfer of microorganisms, building a more robust anaerobic metabolic environment. Modelling analysis further demonstrated the crucial role of DMC/PDS pretreatment in biological degradation and methane productivity. This study indicated that DMC/PDS pretreatment can prominently enhance the release of soluble substances and methane production, aiding the utilization of PDS oxidation technology for improving anaerobic bioconversion of sludge. [ABSTRACT FROM AUTHOR]

Anaerobic membrane bioreactor (AnMBR) has been applied as a promising technology for treating a variety of industrial wastewaters. Nevertheless, the potential of AnMBR for methanolic wastewater treatment is still not well recognized. In this study, a lab-scale AnMBR fed with low-strength methanolic wastewater was operated for 166 days with stepwise decreased HRT, and the roles of colloidal particles and soluble biopolymers in membrane fouling behaviors were elucidated comprehensively. The results showed that AnMBR showed the desirable performance and process stability with total chemical oxygen demand removal of 89.8 ± 1.1% and the highest methane production rate of 5.49 L/L-reactor/d at organic loading rate of 20.00 g-COD/L-reactor/d and hydraulic retention time of 18 h. The serious membrane fouling was observed after a period of operation at low HRT or high OLR due to the production of colloidal particles and the liberation of soluble biopolymers. Decreased particle size, and increased adhesion forces of gel-like flocs caused by the secretion of hydrophobic protein-bearing biopolymers accelerated the deposition of foulants and the formation of cake layer, inducing the easily mitigated membrane fouling. Further observations proved that the main bioconversion pathway of methanolic wastewater to biomethane was methylotrophic methanogenesis, followed by acetotrophic/hydrogenotrophic processes. Collectively, although the membrane fouling cannot be eliminated, this research confirmed the technical feasibility of AnMBR for methanolic wastewater treatment in real-world applications. Image 1 • Anaerobic membrane bioreactor was used for methanolic wastewater treatment.. • The highest methane production of 5.49 L-CH 4 /L/d was obtained at HRT 18 h. • Colloidal organics blocked membrane pores, causing severe fouling. • Methanomethylovorans was the main degrader of methanol. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mineral-activated perxymonosulfate (PMS) shows dewaterability and triclosan removal. • Iron-rich minerals are more economical than traditional sources of Fe2+. • Rheological test demonstrates that siderite/PMS can promote sludge fragmentation. • Siderite could release Fe2+ more sustainably to persistently produce free radicals. High water and pharmaceutical and care products (PPCPs) bounded in sludge flocs limit its utilization and disposal. The advanced oxidation process of perxymonosulfate (PMS) catalyzed by iron salts has been widely used in sludge conditioning. In this study, two iron-rich minerals pyrite and siderite were proposed to enhance sludge dewatering performance and remove the target contaminant of triclosan (TCS). The permanent release of Fe2+ in the activation of PMS made siderite more effective in enhancing sludge dewater with capillary suction time (CST) diminishing by 60.5 %, specific resistance to filtration (SRF) decreasing by 79.2 %, and bound water content (BWC) dropping from 37.1 % to 2.6 % at siderite/PMS dosages of 0.36/0.20 mmol/g-TSS after 20 min of pretreatment. Pyrite/PMS performed slightly inferior under the same conditions and the corresponding CST and SRF decreased by 51.5 % and 71.8 % while the BWC only declined to 17.8 %. Rheological characterization was employed to elucidate the changes in sludge dewatering performance, with siderite/PMS treated sludge showing a 48.3 % reduction in thixotropy, higher than 28.4 % of pyrite/PMS. Oscillation and creep tests further demonstrated the significantly weakened viscoelastic behavior of the sludge by siderite/PMS pretreatment. For TCS mineralization removal, siderite/PMS achieved a high removal efficiency of 43.9 %, in comparison with 39.9 % for pyrite/PMS. The reduction in the sludge solids phase contributed the most to the TCS removal. Free radical quenching assays and EPR spectroscopy showed that both siderite/PMS and pyrite/PMS produced SO 4 -· and ·OH, with the latter acting as the major radicals. Besides, the dosage of free radicals generated from siderite/PMS exhibited a lower time-dependence, which also allowed it to outperform in destroying EPS matrix, neutralizing the negative Zeta potential of sludge flocs, and mineralizing macromolecular organic matter. [ABSTRACT FROM AUTHOR]