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Vermicomposting utilizes the synergistic effect of earthworms with microorganisms to accelerate the stabilization of organic matter in biowastes. Nevertheless, the exact mechanism behind the maturity of vermicompost and the growth of earthworms exposed to biochar of varying particle sizes remains unclear. This study presents an investigation of the effect of biochar particle size on earthworm (Eisenia fetida) survival, microbial diversity, and the quality of vermicompost products. To address these issues, pelletized dewatered sludge samples from a municipal sewage treatment plant were amended with pine-based biochar with particle sizes of 1–2 mm, 25–75 μm, 200 nm, and 60 nm as the substrate for vermicomposting. This study revealed that the addition of millimeter-scale biochar and micron-scale biochar significantly promoted the degradation of organic matter since the organic matter in the treatment with 1–2 mm biochar at the end of the vermicomposting experiment decreased by 12.6%, which was equivalent to a 1.9-fold increase compared with that of the control. Excessive nanopowdering of nanobiochar significantly affected the survival of earthworms and led to 24.4–33.3% cumulative mortality, while millimeter-scale (mm) biochar and micron-scale (μm) biochar achieved zero mortality. The findings of this study could be used for evaluating the potential impact of nanoscale biochar to earthworms and guiding biochar-augmented vermicomposting. Highlights: The addition of 1–2 mm biochar resulted in a 1.9-fold greater reduction in organic matter compared to the control group. The introduction of 25–75 μm biochar led to a significant 94% increase in earthworm cocoons. The cumulative mortality rates of 200 nm and 60 nm biochar amendment reached peaks of 33.3% and 24.4% at first week, respectively. Earthworms excrete mucus that effectively removes attached nanobiochar. [ABSTRACT FROM AUTHOR]

Conventional anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) yields significant quantity of digestate with high nitrogen content, posing considerable disposal challenges. The spotlight has recently been cast upon producing easily biodegradable carbon sources by hydrolysis for synergistic wastewater treatment. However, the hydrolysis during its transportation and storage prior to treatment has been commonly overlooked. This study endeavors to investigate the untapped potential for further hydrolysis and acidification of in-field OFMSW upon arriving at the treatment facilities, aiming to release more organic carbon into the hydrolysate to serve as a carbon source for biological denitrification. Results showed that lactic acid occupied about 83% of dissolved organic carbon in homogenized slurry upon its arrival at treatment facilities, and limited the bioprocess for further acidification. A remarkable volatile fatty acids (VFAs) production rate of 366 g/kg VS was achieved through enhanced acidification of OFMSW's solid fraction, effectively breaking down proteins and hemicellulose. Notably, about 50% of chemical oxygen demand in the hydrolysate consisted of high-quality carbon sources, including VFAs and lactic acid. In the described OFMSW treatment park with the context of processing 1000 t OFMSW daily, optimizing this method could save approximately 4600 USD/day by eliminating the need for external carbon sources. Surplus hydrolysate can be further digested to produce biogas without negatively impacting biomethane potential. Highlight: High content of lactic acid in HS limited further acidification. Satisfactory VFAs yield of 366 g VFAs/kg VS was achieved in SF. Protein and hemicellulose in SF were effectively degraded. Fortified hydrolysis and acidification improved the bio-availability of carbon. [ABSTRACT FROM AUTHOR]

The importance and urgency of domestic solid waste (DSW) source segregation in universities is self-evident. Although many universities have carried out waste management, however, a comprehensive summary for successful implementation work of DSW segregation is lacking. This study summarizes the mechanism of DSW segregation in Chinese university based on questionnaire survey, on-site inquiry and sampling analysis in a comprehensive university in Shanghai. Questionnaire survey show that it is critical for encouraging students to participate in waste segregation to build convenient segregation facilities and humanized segregation reward and punishment method. The strengthened publicity and education due to the advantages in environmental discipline, easy-operating waste dumping site/facility as well as personalized solutions for different functional areas (teaching building) were considerably important strategies for implementing efficient waste segregation. The recyclables that were collected by intelligent recycling device and mobile recycling enterprise were dominated by paper, and the amounts increased dramatically during the graduation season. Therefore, the university correspondingly increased the collection frequencies of waste and the number of segregation guiders in the period to decrease the potential risk of fire safety. The study could provide a valuable reference for efficient implementation of waste segregation on university/college in China. [ABSTRACT FROM AUTHOR]

By iterating the Bolyai-Rényi transformation T(x) = (x + 1)2 (mod 1), almost every real number x ∈ [0, 1) can be expanded as a continued radical expression x = − 1 + x 1 + x 2 + ... + x n + ... with digits xn ∈ {0, 1, 2} for all n ∈ ℕ. For any real number n ∈ [0, 1) and digit i ∈ {0, 1, 2}, let rn(x, i) be the maximal length of consecutive i's in the first n digits of the Bolyai-Rényi expansion of x. We study the asymptotic behavior of the run-length function rn(x, i). We prove that for any digit i ∈ {0, 1, 2}, the Lebesgue measure of the set D (i) = { x ∈ [ 0 , 1) : lim n → ∞ r n (x , i) log n = 1 log θ i } is 1, where θ i = 1 + 4 i + 1 . We also obtain that the level set E α (i) = { x ∈ [ 0 , 1) : lim n → ∞ r n (x , i) log n = α } is of full Hausdorff dimension for any 0 ⩽ α ⩽ ∞. [ABSTRACT FROM AUTHOR]

Biochar and humic substances are prevalent redox pools in the environment, which is critical to electron transfer in geochemical cycles and pollution control processes. The dissolution of biochar and the sorption of humic substances on biochar have the potential to redistribute redox substances, consequently altering the redox properties of solid and liquid phases. However, studies have often focused on either sorption or dissolution separately, overlooking the mutual effects and not involving redox properties. Herein, molecular interactions between biochar and humic acid (HA) and variations in their redox properties were elucidated using UPLC Orbitrap MS and mediated electrochemical measurement. The dissolution of biochar was far greater than the sorption of HA constituents, and HA enhanced the dissolution of biochar through molecular exchange. But preferential sorption of oxygenated aromatics to pine char (pi500) mainly by hydrogen bonding and higher saturated molecules to starch char (st700) mainly by hydrophobic interactions caused the oxygenated functional groups on biochar to increase (1 ~ 1.5 times). Thus the Electron exchange capacities (EEC) of pi500 and st700 turned to 1 ~ 3 times, and the EEC of HA decreased ca. 50%. Absorption (partition) caused more sorption of HA constituents to pi500 than to st700, while larger surface area resulted in higher EEC of st700 with sorbed HA. The enrichment of redox constituents on biochar is promising for its long-term use in waste reclamation and pollution control. The findings can aid in the understanding of variations in redox properties under interactions between pyrolytic and natural organic matter. Highlights: The dissolution of biochar was far more than the sorption of HA constituents. Dissolution of biochar was enhanced by humic acid through molecular exchange. Sorbed redox constituents increased biochar EEC to 1~3 times. Oxygenated aromatics were sorbed to pine biochar mainly by hydrogen bonding. Higher saturated molecules were sorbed to starch biochar mainly by hydrophobic interactions. [ABSTRACT FROM AUTHOR]

Elemental composition is a key parameter in solid waste treatment and disposal. This study has proposed a method based on infrared spectroscopy and machine learning algorithms that can rapidly predict the elemental composition (C, H, N, S) of solid waste. Both noise and moisture spectral interference that may occur in practical application are investigated. By comparing two feature selection methods and five machine learning algorithms, the most suitable models are selected. Moreover, the impacts of noise and moisture on the models are discussed, with paper, plastic, textiles, wood, and leather as examples of recyclable waste components. The results show that the combination of the feature selection and K-nearest neighbor (KNN) approaches exhibits the best prediction performance and generalization ability. Particularly, the coefficient of determination (R2) of the validation set, cross validation and test set are higher than 0.93, 0.89, and 0.97 for predicting the C, H, and N contents, respectively. Further, KNN is less sensitive to noise. Under moisture interference, the combination of feature selection and support vector regression or partial least-squares regression shows satisfactory results. Therefore, the elemental compositions of solid waste are quickly and accurately predicted under noise and moisture disturbances using infrared spectroscopy and machine learning algorithms. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) has been studied for centuries, but its operation still mainly relies on physicochemical indicators. Recent advanced molecular biological tools can unveil the nature of the AD process since microbial activity is directly related to digester performance. The paper summarized up-to-date microbiological and molecular biological analysis techniques applied in AD, including PCR-based techniques, electrophoresis, next-generation sequencing, MS-based techniques, and visualization-based techniques. In addition, the paper also reviewed the techniques that link microbial identity and activity to ecological function. Molecular biological techniques can identify microbial activity and AD process disturbance, but research on on-site analysis of microbial communities for a full-scale system is lacking. One of the most suitable methods for studying microbial communities in anaerobic digesters is fluorescence in situ hybridization, which does not require preparative isolation and cultivation. Another very important method is the use of physiological fluorescent probes to reveal the functional characteristics of methanogenic communities by CTC (5-cyano-2,3-ditolyl tetrazolium chloride)/DAPI (4'-6 diamino-2 phenylindole), which is a very rapid, sensitive and informative assay. These methods, together with the application of confocal laser microscopy, and the study of polyphosphate granules and Co-factor 420 of the microbial communities allow us a very effective and targeted functional-molecular control of the processes in anaerobic digesters. [ABSTRACT FROM AUTHOR]

Background: The interaction among microorganisms in the anaerobic digestion of food waste (ADFW) reactors lead to the degradation of organics and the recycling of energy. Viruses are an important component of the microorganisms involved in ADFW, but are rarely investigated. Furthermore, little is known about how viruses affect methanogenesis. Results: Thousands of viral sequences were recovered from five full-scale ADFW reactors. Gene-sharing networks indicated that the ADFW samples contained substantial numbers of unexplored anaerobic-specific viruses. Moreover, the viral communities in five full-scale reactors exhibited both commonalities and heterogeneities. The lab-scale dynamic analysis of typical ADFW scenarios suggested that the viruses had similar kinetic characteristics to their prokaryotic hosts. By associating with putative hosts, a majority of the bacteria and archaea phyla were found to be infected by viruses. Viruses may influence prokaryotic ecological niches, and thus methanogenesis, by infecting key functional microorganisms, such as sulfate-reducing bacteria (SRB), syntrophic acetate-oxidizing bacteria (SAOB), and methanogens. Metabolic predictions for the viruses suggested that they may collaborate with hosts at key steps of sulfur and long-chain fatty acid (LCFA) metabolism and could be involved in typical methanogenesis pathways to participate in methane production. Conclusions: Our results expanded the diversity of viruses in ADFW systems and suggested two ways that viral manipulated ADFW biochemical processes. 3DQb7S-2dM-gGjfqAhcADy Video Abstract [ABSTRACT FROM AUTHOR]

This NOTE summarizes process, practical case, and perspectives of intelligent bioconversion via insect (housefly larvae) for treating food waste based on Special Session of 3R International Scientific Conference on Material Cycles and Waste Management (3RINCs 2022). The applied intelligent bioconversion technology could not only achieve efficient reduction and recycling (insect protein and material for organic fertilizer) of food waste, also save the cost of operation, as well as diminish potential environmental risk caused by odor emission. Key technologies including I-smart algorithms and automatic guided vehicle (AGV) system have in situ-demonstrated considerable efficiency in optimization of operation conditions in the bioconversion process of food waste. In addition, studies on carbon emission for intelligent bioconversion and fluctuation effect of feedstock properties on process performance are required to achieve sustainable development of the technology. All in all, the NOTE is expected to provide a reference for smooth and efficient promotion of intelligent bioconversion of perishable (food) waste via insect in terms of practical application. [ABSTRACT FROM AUTHOR]

With urbanization, municipal solid waste (MSW) transfer station as an important link in the process of refuse collection and transportation is closer to residents' living areas. At present, studies on airborne antibiotic resistance genes (ARGs) generated during MSW management are still few and not comprehensive enough. In this study, metagenomics and high-throughput sequencing methods were used to analyze the composition and content of bioaerosol and airborne ARGs in the waste reception hall and the top vent of three MSW transfer stations. 265 ARG subtypes were detected. The main subtypes were bacA, multidrug_transporter, mexW, sul2 and macB, and the main types were multidrug resistance genes and bacitracin resistance genes. Different microbes and ARGs showed diverse release characteristics, but in general, the concentration of bacteria and ARGs at the top vent of the transfer station was higher than that in the waste reception hall, and fungi were more sensitive than bacteria when passing through the odor treatment system connecting between the top vent and the waste reception hall. For ARGs, daily intake of a worker was calculated to be 1.08 × 1010–2.79 × 1010 copies d− 1 and environmental release was 2.88 × 109–9.49 × 109 copies m− 3. Therefore, control measures for airborne ARGs and pathogenic microorganisms are urgently needed to ensure the health of workers and surrounding residents. [ABSTRACT FROM AUTHOR]

Chemically enhanced solid–liquid separation (CES) of digestate can improve its membrane filterability but potentially influence the environmental features of the separated solid fraction, thus hindering its possible agricultural reuse. In this study, the effects were assessed of different dosages of polyaluminum chloride (PAC), epichlorohydrine-dimethylamine with ethylendiamine (DEED) and polyacrilamides (PAM) on CES of digestate from biowaste in terms of Total Suspended Solid (TSS) mitigation in the liquid fractions and resulting environmental quality of the solid fractions. Results from lab-scale trials showed that applied chemicals significantly increased the centrifugation efficiency with achieving minimum TSS concentration of 2347 ± 281 mgTSS/L (up to 90% improved TSS mitigation). Also, performed treatments led to almost complete removal of P and Heavy Metals (HMs) from the liquid fractions after centrifugation. Conditioned solid fractions showed higher Al (reaching 20 g kg−1 TS), organic carbon and nitrogen content (up to 324 mgTOC kg−1 TS and 44.1 mgTKN kg−1 TS, respectively) due to residual PAC, DEED and PAM. However, achieved concentrations of HMs guaranteed full consistency with EU regulation limits established for agricultural reuse of organic soil amendments. Further, leaching tests performed on the treated solid fractions indicate higher chlorides and soluble Al concentrations in the water extracts (up to 4.6 g L−1 and 2.3 g L−1, respectively), but lower HMs leachability from the digestates undergone CES. Nevertheless, water extracts from treated biosolids were characterized by higher phytotoxicity, likely related with direct Al toxicity and increased salinity due to chemicals addition. Accordingly, the effects on soil–plant system should be better investigated when agricultural reuse of CES-treated solid fraction of digestate is foreseen. [ABSTRACT FROM AUTHOR]

Background: Biological treatment technology is good for the recovery of resources and energy from municipal solid waste (MSW) and cutting down biodegradable components in landfill waste. Recently, the aerobic biological treatment of MSW has increased in rural areas of China. These facilities are usually open setup and close to nearby residents, and complaints tend to be received regarding odorous gases. A semi-in-vessel setup facility was built in recent years, and its impact on the environment and personnel is not clear. Results: Ammonia was the predominant compound released from the windrow and its concentration was one order of magnitude higher than those of other compounds. Terpenes and reduced sulfur compounds (RSCs) persisted throughout the entire active fermentation process, with only slight decreases. The biofilter pool had a greater odor impact on the surrounding neighborhood than the waste unloading and sorting operation. The concentrations of most compounds were reduced by the biofilter pool. Ten major substances that caused odors at the facility were analyzed, where most comprised RSCs. The odor impact of the facility was low, but it was associated with a carcinogenic risk to the operators, thereby indicating the need to improve personal protection. Conclusions: Large amounts of ammonia and volatile organic compounds were released from the composting units, but they had a low odor impact on the environment because of the semi-in-vessel setup. The odor impact of the facility was low but it was associated with a carcinogenic risk to the operators. This technology can be popularized in rural areas. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon (HPC) materials contain organized pores having different scales of diameters. These materials exhibit surprisingly high performance in various applications due to the functional combination of hierarchical pores. This paper reviews the preparation of HPC from waste and biomass, and their potential applications. Biomass with naturally organized hierarchical structure, such as wood, grass and nut shell, have been widely used as raw materials, from which, hierarchical porosity can be formed through simple pyrolysis-activation. Influences of the types and dosages of activating agent, as well as the pyrolysis/activation conditions on the specific surface area, pore volume and hierarchical porous structure of the structured biomass-based HPC are discussed. For non-structured raw materials such as sucrose, pitch and plastics, novel technologies have been developed to prepare HPC; these include hard-/soft-template methods, hydrothermal carbonization, chemical vapor deposition, spray pyrolysis and autogenic pressure carbonization. The approaches to design or control the structures and properties of HPC made from non-structured materials are also reviewed. Moreover, advanced applications of HPC in energy storage, deionization, adsorption and catalysis are summarized. [ABSTRACT FROM AUTHOR]

Let φ : N → (0 , 1 ] be a positive function and T β be the beta-transformation for any β > 1 . We prove that the set E (0 , φ) = { β > 1 : | T β n 1 - 0 | < φ (n) for infinitely many n ∈ N } is of zero or full Lebesgue measure in (1 , + ∞) according to ∑ φ (n) < + ∞ or not. As an application, we determine the exact Lebesgue measure of the set E (0 , { l n }) = { β > 1 : | T β n 1 - 0 | < β - l n for infinitely many n ∈ N } , where { l n } n ≥ 1 is a sequence of non-negative real numbers. [ABSTRACT FROM AUTHOR]

Let β > 1 and x ∈ [0, 1) be two real numbers. For any y ∈ [0, 1), the maximal run-length function rx(y, n) (with respect to x) is defined to be the maximal length of the prefix of x's β-expansion which appears in the first n digits of y's. In this paper, we study the metric properties of the maximal run-length function and apply them to the hitting time, which generalises many known results. In the meantime, the fractal dimensions of the related exceptional sets are also determined. [ABSTRACT FROM AUTHOR]

Incorporation of biochar into soil has been proposed as a strategy for enhancing soil fertility and rice production. A pot trial was carried out to investigate the effects of the dissolvable fraction of biochar in the Yangtze River estuary, China. Soil in plastic pots was incorporated with straw biochar at five different rates: 0%, 5%, 10%, 15%, and 20% (w/wet weight). The rice height, tiller number, and grain yield were recorded; soils and surface water were sampled, and key chemical properties were investigated. Rice grain yield was improved by 29.1–34.2%, and the grain-to-straw ratio was promoted by 8.0–26.1% in the treatments with 10–15% biochar incorporated compared with the control. Soil total organic carbon and total nitrogen contents increased 65.7–242.8% and 22.9–75.3% in the biochar-amended treatments, respectively. Meanwhile, the soil dissolved organic carbon contents increased by 13.4–25.3% in biochar-amended treatments. Higher amounts of added biochar resulted in increased soil electrical conductivity but had no significant effect on soil pH. The major anion was Cl−, and the main cations were K+ and Na+ in the mudflat soil. Addition of 10–15% straw biochar to soil for agronomic purposes is a potentially sustainable ecologically technology. [ABSTRACT FROM AUTHOR]

Background: Anaerobic digestion of easily degradable biowaste can lead to the accumulation of volatile fatty acids, which will cause environmental stress to the sensitive methanogens consequently. The metabolic characteristics of methanogens under acetate stress can affect the overall performance of mixed consortia. Nevertheless, there exist huge gaps in understanding the responses of the dominant methanogens to the stress, e.g., Methanosarcinaceae. Such methanogens are resistant to environmental deterioration and able to utilize multiple carbon sources. In this study, transcriptomic and proteomic analyses were conducted to explore the responses of Methanosarcina barkeri strain MS at different acetate concentrations of 10, 25, and 50 mM. Results: The trend of OD600 and the regulation of the specific genes in 50 mM acetate, indicated that high concentration of acetate promoted the acclimation of M. barkeri to acetate stress. Acetate stress hindered the regulation of quorum sensing and thereby eliminated the advantages of cell aggregation, which was beneficial to resist stress. Under acetate stress, M. barkeri allocated more resources to enhance the uptake of iron to maintain the integrities of electron-transport chains and other essential biological processes. Comparing with the initial stages of different acetate concentrations, most of the genes participating in acetoclastic methanogenesis did not show significantly different expressions except hdrB1C1, an electron-bifurcating heterodisulfide reductase participating in energy conversion and improving thermodynamic efficiency. Meanwhile, vnfDGHK and nifDHK participating in nitrogen fixation pathway were upregulated. Conclusion: In this work, transcriptomic and proteomic analyses are combined to reveal the responses of M. barkeri to acetate stress in terms of central metabolic pathways, which provides basic clues for exploring the responses of other specific methanogens under high organics load. Moreover, the results can also be used to gain insights into the complex interactions and geochemical cycles among natural or engineered populations. Furthermore, these findings also provide the potential for designing effective and robust anaerobic digesters with high organic loads. [ABSTRACT FROM AUTHOR]

Acid crisis characterized by acid accumulation and/or low pH is a common reason for the failure of anaerobic digestion (AD), which is usually applied for wastewater and waste treatment. Acid-tolerant methanogens are rarely reported to be active in the artificial anaerobic digester. In this study, we observed that the thermophilic methanogenesis by a consortium in the form of flocs and not granules could still be recovered during long-term operation at acetate concentration of up to 104 mM and pH 5.5 by adjusting the pH gradually or directly to pH 5.5 or 5.0. The acclimation process involving the gradual decrease in pH could enhance the resistance of the consortium against extreme acidification. The stable isotopic signature analysis of biogas revealed that Methanosarcina , which produced methane through acetoclastic methanogenesis (AM) pathway, was the predominant methane producer when the pH was decreased gradually to 5.0. Meanwhile, the abundance of Coprothermobacter increased with a decrease in pH. Contrastingly, when directly subjected to an environment of pH 5.5 and 104 mM acetate (15.84-mM free acetic acid) after a 42-day lag phase, Methanothermobacter was the predominant methanogen. Methanothermobacter initiated methane production through the hydrogenotrophic pathway and formed syntrophic relationship/consortium with the potential acetate-oxidizing bacteria, Thermacetogenium and Coprothermobacter. Comparative metagenomic and metatranscriptomic analysis on this self-adapted and acid-tolerant consortium revealed that the genes, such as GroEL, DnaK, CheY, and flagellum-related genes (FlaA, FlgE, and FliC) from Anaerobaculum , Thermacetogenium , and Coprothermobacter were highly overexpressed in response to system acidification. Microbial self-adaptation patterns (community structure adjustment, methanogenesis pathway shift, and transcriptional regulation) of thermophilic methanogenic consortium to gradual and sudden acidification were evaluated by integrated stable isotopic signature and comparative meta-omic approaches. The study elucidated the acid-resistant mechanism of thermophilic methanogenic consortium and deepened our knowledge of the function, interaction, and microbial characteristics of Methanosarcina , Methanothermobacter , and Coprothermobacter under extreme acidic environment. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Increasing the degradation ratio of organic matter is one of the key challenges for sludge anaerobic digestion. The conventional solution is by directly treating the raw sludge so as to enhance the sludge degradation. In contrast, the target of the present study was digested sludge enriching in refractory organic matter. The method proposed to improve the organic degradation of digested sludge uses ultrasound combined with linear alkylbenzene sulfonate (LAS) to control flocs re‐flocculation. RESULTS: Gas production of the sludge treated with the highest ultrasound energy (360 W, 20 min) was only 57.7 ± 0.3 mL‐CH4 g‐1‐VSadded, and the sludge treated with lower ultrasound energy (120 W, 20 min) with LAS had the highest gas production, up to 92.5 ± 8.5 mL‐CH4 g‐1‐VSadded. Meanwhile, the total VS degradation of 120 W, 20 min with LAS was up to 69.6 ± 5.2%. And the gas production of 360 W, 5 min with LAS was 27.1% higher than that of 360 W, 5 min without LAS. CONCLUSION: These results revealed that digested sludge treated by ultrasonication could be further degraded, and the addition of LAS could significantly improve the re‐digestion performance with less energy. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The present study investigated the independent roles of biofilm and external power supply for volatile fatty acids degradation and methane production in the microbial electrolysis cell. Reactors were operated in fed-batch mode in the presence of graphite felt (GF) or titanium rod (Ti) as electrodes, in open circuit (OC, without applied voltage) or closed circuit (CC) conditions, i.e. R1 (Ti + CC), R2 (GF + CC) and R3 (GF + OC). The first-order kinetic analysis of acetate degradation indicated that the presence of GF biofilm and applied voltage in R2 improved the degradation rate of acetate by 23% as compared to R1, while it was only a 7% increment in R3 with GF biofilm. The degradation of butyrate was accelerated by 12% in the first 24 h, whereas there was no enhancement of the propionic acid digestion. Generally, methane yields from the three reactors followed the sequence: R2 > R1 > R3, indicating the positive effect of external power supply on methane generation. Highthroughput sequencing revealed that Geobacter sp. could be enriched on conductive GF even without electric stimulation. The clustered Geobacter and Methanosarcina in R2 presented the potential to promote interspecies electron transfer and accelerate substrate utilization and methane production. [ABSTRACT FROM AUTHOR]

Background: This study aimed at producing C6-C8 medium-chain carboxylates (MCCAs) directly from gaseous CO using mixed culture. The yield and C2-C8 product composition were investigated when CO was continuously fed with gradually increasing partial pressure. Results: The maximal concentrations of n-caproate, n-heptylate, and n-caprylate were 1.892, 1.635, and 1.033 mmol L-1, which were achieved at the maximal production rates of 0.276, 0.442, and 0.112 mmol L-1 day-1, respectively. Microbial analysis revealed that long-term acclimation and high CO partial pressure were important to establish a CO-tolerant and CO-utilizing chain-elongating microbiome, rich in Acinetobacter, Alcaligenes, and Rhodobacteraceae and capable of forming MCCAs solely from CO. Conclusions: These results demonstrated that carboxylate and syngas platform could be integrated in a shared growth vessel, and could be a promising one-step technique to convert gaseous syngas to preferable liquid biochemicals, thereby avoiding the necessity to coordinate syngas fermentation to short-chain carboxylates and short-tomedium-chain elongation. Thus, this method could provide an alternative solution for the utilization of waste-derived syngas and expand the resource of promising biofuels. [ABSTRACT FROM AUTHOR]

Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N incorporation and the high mobility of vacancies under growth temperatures of 950-1000°C. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing. [ABSTRACT FROM AUTHOR]

Given a positive integer M and a real number $$q >1$$ , a q -expansion of a real number x is a sequence $$(c_i)=c_1c_2\ldots $$ with $$(c_i) \in \{0,\ldots ,M\}^\infty $$ such that It is well known that if $$q \in (1,M+1]$$ , then each $$x \in I_q:=\left[ 0,M/(q-1)\right] $$ has a q-expansion. Let $$\mathcal {U}=\mathcal {U}(M)$$ be the set of univoque bases $$q>1$$ for which 1 has a unique q-expansion. The main object of this paper is to provide new characterizations of $$\mathcal {U}$$ and to show that the Hausdorff dimension of the set of numbers $$x \in I_q$$ with a unique q-expansion changes the most if q 'crosses' a univoque base. Denote by $$\mathcal {B}_2=\mathcal {B}_2(M)$$ the set of $$q \in (1,M+1]$$ such that there exist numbers having precisely two distinct q-expansions. As a by-product of our results, we obtain an answer to a question of Sidorov (J Number Theory 129:741-754, 2009) and prove that where $$q'=q'(M)$$ is the Komornik-Loreti constant. [ABSTRACT FROM AUTHOR]

This research focused on the inhibitory effects of Ca on the aerobic biological treatment of landfill leachate containing extremely high Ca concentrations. When the Ca concentration in leachate to be treated was more than 4500 mg l−1, the total organic carbon removal rate was significantly reduced and the processing time to achieve the same removal efficiency was 1.4 times that in the control treatment without added Ca. In contrast, the total nitrogen and ammonia nitrogen (NH4+–N) removal efficiencies were positively related to the Ca concentration, increasing from 65.2% to 81.2% and from 69.2% to 83.7%, respectively, when the dosage of added Ca increased from zero to 8000 mg l−1. During aerobic treatment, the reductions of solution Ca concentration were in the range of 1003–2274 mg l−1 and were matched with increases in the Ca content in the residual sludge. The inhibition threshold of Ca in the leachate treated by the activated sludge process appeared to be 4500 mg l−1, which could be realized by controlling the influent Ca concentration and using an appropriate sludge return ratio in the activated sludge process. [ABSTRACT FROM AUTHOR]

The addition of various amounts of biochar to anaerobic digestion of food wastes at different ratios of inoculum to substrate (ISR) was investigated to evaluate the effect of biochar as a functional additive and to optimize the additive dosage of biochar. The biochar treatments at ISR 2, 1, and 0.8 shortened the lag phase of digestion by −20.0%–10.9%, 43.3%–54.4%, and 36.3%–54.0%, and raised the maximum methane production rate by 100%–275%, 100%–133.3%, and 33.3%–100%, respectively, compared to control without biochar. Biochar also enhanced the degradation rate of dissolved organics and volatile fatty acids. Furthermore, the amount of biochar with best effectiveness at ISR = 2, 1, and 0.8 was 2.5, 0.625, and 0.5 g g−1-waste, respectively. Therefore, the effectiveness of biochar depended on the additive amount of biochar and at the same time the inoculum amount, implying a complementary role of abiotic biochar to biotic inoculum. [ABSTRACT FROM AUTHOR]

With the increasing use of municipal solid waste incineration (MSWI) and more stringent limits on landfilling of organic waste, more MSWI bottom ash is being landfilled, and the proportion of inorganic wastes in landfills is increasing, causing the increased Ca concentrations in landfill leachate. In this research, the inhibition effect of Ca concentration on the anaerobic treatment of landfill leachate was studied using a biochemical methane potential experiment. Slight inhibition of methane production occurred when the addition of Ca concentration was less than 2000 mg/L. When the addition of Ca concentration was between 6000 and 8000 mg/L, methane production was significantly reduced (to 29.4-34.8 % of that produced by the BLK reactor), and the lag phase was increased from 8.55 to 16.32 d. Moreover, when the dosage of Ca concentration increased from zero to 8000 mg/L, reductions in solution Ca concentration increased from 929 to 2611 mg/L, and the proportion of Ca in the residual sludge increased from 22.58 to 46.87 %. Based on the results, when the dosage of Ca concentration was less than 4000 mg/L, the formation of Ca precipitates on the surface of sludge appeared to prevent mass transfer and was the dominant reason for the reduction in methane production and sludge biomass. At higher Ca concentrations (6000-8000 mg/L), the severe inhibition of methane production appeared to be caused by the toxic effect of highly concentrated Ca on sludge as well as mass transfer blockage. [ABSTRACT FROM AUTHOR]

An integrated approach was applied to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities (an aerobic biological treatment plant and an anaerobic landfill site), identify their precise sources, and distinguish the interactive influences between them. Seven odor families were investigated, including alcohols, terpenes, carbonyls, aromatics, volatile fatty acids (VFAs), sulfur compounds, and ammonia. Principal components analysis, characteristic molecular ratios, and ternary diagrams were used to differentiate the interactive influence of the odor sources. Among typical biotic compounds, terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs. Ratios ofp-cymene at sampling locations related to the biological treatment plant (aerobic status) were between 0.00 and 0.25, whereas those at landfill-related sampling points (anaerobic status) were between 0.25 and 1.0. The molecular ratio of terpenes was also found to be an appropriate means to differentiate between homologous and similar odor sources such as an aerobic biological treatment plant and anaerobic landfill. Implications: The aim of this work is to identify the key odorants comprising emissions from different zones in two adjacent waste treatment facilities, identify their precise sources, and distinguish the interactive influences between them. The emission of gaseous pollutants greatly affects the living quality of nearby residents, and odor complaints are becoming a major problem. In this study we utilized various pretreatment and analytical methods to obtain integrated emission information of gaseous pollutants. The results showed terpenes were found to be more suitable as odor markers for their better fingerprinting character than sulfur compounds and VFAs. [ABSTRACT FROM AUTHOR]

Rice straw is one of the most abundant agricultural wastes, and has potential as the feedstock for biofuel production. In this study, rice straw was pretreated with 1.5 % (m/m) sulfuric acid at 121 °C for 60 min and then subjected to consolidated bioprocessing (CBP) by Clostridium thermocellum at 55 °C. The composition, morphology, surface area and cellulose crystal structure of rice straw were determined to evaluate effects of the pretreatment on physicochemical characteristics of rice straw, and CBP performance was evaluated by the production of H and ethanol. The results showed that 90 % of hemicellulose was removed, the Brunauer-Emmett-Teller surface area was increased by 5.2-fold, amorphous cellulose lost, and lignin amount increased by 53 % after the pretreatment. The maximum H2 productions from unpretreated (Unpre) and pretreated (Pre) rice straw were 33.3 and 35.7 mmol L, respectively, the values were 0.6 and 0.8 g L respectively for ethanol. Over the first 4 days, the H2 productions from Unpre and Pre made up 46.2 and 70.6 % of their maximum H productions respectively, and the values were about 62.6 and 70.5 % for ethanol. The differences of physicochemical characteristics and metabolic pathways between Unpre and Pre both contributed to the different accelerating effects of the pretreatment on H2 and ethanol production. [ABSTRACT FROM AUTHOR]

The effect of different concentrations of ammonia (1.0-7.0 g/L) during mesophilic anaerobic digestion with fiber or liquid digestate as inoculum was examined. Evolution of microbial community within fiber and liquid digestates was quantitatively assessed by the intact lipid analysis methods and qualitatively by DNA fingerprint methods in order to determine their resistance to ammonia inhibition. The results showed that an increased level of total ammonia nitrogen prolonged the lag phase of fiber digestates while reduced the metabolic rate of liquid digestates. Fiber digestates had 19.6-50.9-fold higher concentrations of phospholipid fatty acids (PLFA) compared to liquid digestates, whereas concentrations of phospholipid ether lipids (PLEL) in the fiber digestates were only 2.91-17.6-fold higher compared to liquid digestates. Although the cell concentration in liquid fraction was far lower than that in the fiber one, the ammonia-resistant ability and the methanization efficiency of the liquid digestate was superior to the fiber digestate. The bacterial profiles were affected more by the type of digestate inoculum compared to the concentration of ammonia. Principal component analysis indicated that the lipids technique was superior to the DNA technique for bacterial quantification but detected less archaeal diversity. [ABSTRACT FROM AUTHOR]

The effect of straw on natural solar sludge drying was investigated. As the thickness of the stack increased, the rate of water removal per unit area slightly increased and the rate of water removal per unit volume rapidly decreased. The rate of water removal increased as the accumulation of solar energy increased but decreased as the relative humidity increased. On the 23rd day, the moisture content of the dewatered sludge and the chopped straw mixture decreased from 75.2 to 45.1% at a thickness of stack of 30 cm, with an average water evaporation rate of 7.2 kg/m2d. [ABSTRACT FROM AUTHOR]

We study the distribution of the orbits of real numbers under the beta-transformation $T_{{\it\beta}}$ for any ${\it\beta}>1$. More precisely, for any real number ${\it\beta}>1$ and a positive function ${\it\varphi}:\mathbb{N}\rightarrow \mathbb{R}^{+}$, we determine the Lebesgue measure and the Hausdorff dimension of the following set: $$\begin{eqnarray}E(T_{{\it\beta}},{\it\varphi})=\{(x,y)\in [0,1]\times [0,1]:T_{{\it\beta}}^{n}x-y<{\it\varphi}(n)\text{ for infinitely many }n\in \mathbb{N}\}.\end{eqnarray}$$ [ABSTRACT FROM AUTHOR]

To precisely control the application of methyl fluoride (CH3F) for analysis of methanogenic pathways, the influence of 0–10% CH3F on bacterial and archaeal communities in a thermophilic methanogenic sludge was investigated. The results suggested that CH3F acts specifically on acetoclastic methanogenesis. The inhibitory effect stabilized at an initial concentration of 3–5%, with around 90% of the total methanogenic activity being suppressed, and a characteristic of hydrogenotrophic pathway in isotope fractionation was demonstrated under this condition. However, extended exposure (12 days) to high concentrations of CH3F (>3%) altered the bacterial community structure significantly, resulting in increased diversity and decreased evenness, which can be related to acetate oxidation and CH3F degradation. Bacterial clone library analysis showed that syntrophic acetate oxidizing bacteria Thermacetogenium phaeum were highly enriched under the suppression of 10% CH3F. However, the methanogenic community did not change obviously. Thus, excessive usage of CH3F over the long term can change the composition of the bacterial community. Therefore, data from studies involving the use of CH3F as an acetoclast inhibitor should be interpreted with care. Conversely, CH3F has been suggested as a factor to stimulate the enrichment of syntrophic acetate oxidizing bacteria. [ABSTRACT FROM AUTHOR]

The sludge digestate stabilized by mesophilic anaerobic digestion was further degraded through thermophilic anaerobic digestion using 0-10 % (v/v) of thermophilic, proteolytic Coprothermobacter proteolyticus, and/or methanogenic granular sludge. The results demonstrated that the temperature shift to thermophilic condition promoted abiotic solubilization of proteins and reactivated the fermentative bacteria and methanogens indigenous in the sludge digestate, resulting in a final methane yield of 6.25 mmol-CH/g-volatile suspended solid (VSS) digestate. The addition of C. proteolyticus accelerated the hydrolysis and fermentation of proteins and polysaccharides in the digestate during the early stage of thermophilic anaerobic digestion and stimulated methane production by syntrophic cooperation with methanogenic granular sludge. In the treatment with granular sludge and inoculated with 10 % (v/v) of C. proteolyticus, a final methane yield of 7 mmol-CH/g-VSS digestate was obtained, and 48.4 % proteins and 27.0 % polysaccharides were degraded. The dissolved proteins were contributed by abiotic factor, C. proteolyticus, and indigenous digestate bacteria, respectively, by around 16, 28, and 56 %. [ABSTRACT FROM AUTHOR]

Cellulose is the most abundant biopolymer on Earth. Optimising energy recovery from this renewable but recalcitrant material is a key issue. The metaproteome expressed by thermophilic communities during cellulose anaerobic digestion was investigated in microcosms. By multiplying the analytical replicates (65 protein fractions analysed by MS/MS) and relying solely on public protein databases, more than 500 non-redundant protein functions were identified. The taxonomic community structure as inferred from the metaproteomic data set was in good overall agreement with 16S rRNA gene tag pyrosequencing and fluorescent in situ hybridisation analyses. Numerous functions related to cellulose and hemicellulose hydrolysis and fermentation catalysed by bacteria related to Caldicellulosiruptor spp. and Clostridium thermocellum were retrieved, indicating their key role in the cellulose-degradation process and also suggesting their complementary action. Despite the abundance of acetate as a major fermentation product, key methanogenesis enzymes from the acetoclastic pathway were not detected. In contrast, enzymes from the hydrogenotrophic pathway affiliated to Methanothermobacter were almost exclusively identified for methanogenesis, suggesting a syntrophic acetate oxidation process coupled to hydrogenotrophic methanogenesis. Isotopic analyses confirmed the high dominance of the hydrogenotrophic methanogenesis. Very surprising was the identification of an abundant proteolytic activity from Coprothermobacter proteolyticus strains, probably acting as scavenger and/or predator performing proteolysis and fermentation. Metaproteomics thus appeared as an efficient tool to unravel and characterise metabolic networks as well as ecological interactions during methanisation bioprocesses. More generally, metaproteomics provides direct functional insights at a limited cost, and its attractiveness should increase in the future as sequence databases are growing exponentially. [ABSTRACT FROM AUTHOR]

Biogas recirculation was conducted to improve the performance of two thermophilic anaerobic sequenced batch reactors (ASBRs), in which high concentrations of volatile fatty acids (VFAs) were accumulated. To accelerate degradation of VFAs, facilitating acetate consumption via syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis (SAO-HM) was expected to be effective. Hence, to promote the SAO-HM pathway, hydrogen was removed to create low hydrogen partial pressure (pH2) in reactor RH, yet in reactor RB, hydrogen was not treated. The performance of RB and RH on VFAs degradation and methane production processes was compared at steady stage; the VFAs and soluble microbial products (SMP) in the effluents were monitored. The results showed that lowpH2intensified the SAO reaction, thereby accelerating conversion of acetate to methane, as well as acetate production from glucose and VFAs. Glucose fermentation type was also influenced. VFAs and SMP in the effluents were reduced after the introduction of biogas mixing, which proceeded much faster in RH with lowpH2. Recirculation of low hydrogen biogas with SAO-HM pathway being promoted should be more effective to alleviate high acid level stress and to improve the reactor performance. [ABSTRACT FROM AUTHOR]

Ventilation is very important during the biodrying process because it affects the biodrying efficiency and secondary pollution. In this study, three ventilation modes—intermittent negative ventilation (IN), continuous negative ventilation (CN) and intermittent positive ventilation (IP)—were used to provide the same amount of total air during biodrying of municipal solid waste (MSW). During the entire 16-day experiment, 68.4%, 68.7% and 67.2% of water contained in the initial waste was removed under IN, CN and IP trials respectively. The ratio of water loss to volatile solid loss was used to evaluate the biodrying efficiency, with values of 5.35, 5.93 and 4.82 being observed for IN, CN and IP trials respectively. The total organic carbon concentrations of the leachate generated from the biodrying of waste were as high as 25,000 mg/l, while those of the condensate were not higher than 3500 mg/l. During the entire process, the average ammonia concentrations of leachate and condensate were 1350 mg/l and 2140 mg/l respectively. From the aspect of biodrying efficiency, continuous negative ventilation was the most preferable ventilation mode for biodrying of MSW, while special care should be taken to prevent aqueous pollution if it is used in a MSW treatment plant. [ABSTRACT FROM AUTHOR]

To test the dose effect of ammonium (NH) fertilization on soil methane (CH) oxidation by methanotrophic communities, batch incubations were conducted at a wide scale of NH amendments: 0, 100, 250, 500, and 1,000 mg N kg. Denaturing gradient gel electrophoresis and real-time quantitative PCR analysis were conducted to investigate the correlation between the CH oxidation capacity and methanotrophic communities. Immediately after the addition of NH, temporal inhibition of CH oxidation occurred, and this might have been due to the non-specific salt effect (osmotic stress). After a lag phase, the CH oxidation rates of the soils with NH fertilization were promoted to levels higher than those of the controls. More than 100 mg N kg of NH addition resulted in the reduction of type II/type I MOB ratios and an obvious evolution of type II MOB communities, while less than 100 mg N kg of NH addition induced nearly no change of methanotrophic community compositions. The NH-derived stimulation after the lag phase was attributed to the improvement of N availability for type I MOB. Compared with the controls, 100 mg N kg of NH addition doubled the CH oxidation peak value to more than 20 mg CH kg h. Therefore, an appropriate amount of leachate irrigation on the landfill cover layer might efficiently mitigate the CH emissions. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO and HO absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO electrode, notwithstanding the number of hydroxyl radicals produced on PbO is higher than that on the BDD surface. [ABSTRACT FROM AUTHOR]

To understand the influence patterns and interactions of three important environmental factors, i.e. soil water content, oxygen concentration, and ammonium addition, on methane oxidation, the soils from landfill cover layers were incubated under full factorial parameter settings. In addition to the methane oxidation rate, the quantities and community structures of methanotrophs were analyzed to determine the methane oxidation capacity of the soils. Canonical correspondence analysis was utilized to distinguish the important impact factors. Water content was found to be the most important factor influencing the methane oxidation rate and Type II methanotrophs, and the optimum value was 15% (w/w), which induced methane oxidation rates 10- and 6- times greater than those observed at 5% (w/w) and 20% (w/w), respectively. Ambient oxygen conditions were more suitable for methane oxidation than 3% oxygen. The addition of 100 mg-N·kg of ammonium induced different effects on methane oxidation capacity when conducted at low or high water content. With regard to the methanotrophs, Type II was sensitive to the changes of water content, while Type I was influenced by oxygen content. Furthermore, the methanotrophic acidophile, Verrucomicrobia, was detected in soils with a pH of 4.9, which extended their known living environments. [ABSTRACT FROM AUTHOR]

pH and volatile fatty acids both might affect the further hydrolysis of particulate solid waste, which is the limiting-step of anaerobic digestion. To clarify the individual effects of pH and volatile fatty acids, batch experiments were conducted at fixed pH value (pH 5–9) with or without acetate (20 g/L). The hydrolysis efficiencies of carbohydrate and protein were evaluated by carbon and nitrogen content of solids, amylase activity and proteinase activity. The trend of carbohydrate hydrolysis with pH was not affected by the addition of acetate, following the sequence of pH 7>pH 8>pH 9>pH 6>pH 5; but the inhibition of acetate (20 g/L) was obvious by 10%–60%. The evolution of residual nitrogen showed that the effect of pH on protein hydrolysis was minor, while the acetate was seriously inhibitory especially at alkali condition by 45%–100%. The relationship between the factors (pH and acetate) and the response variables was evaluated by partial least square modeling (PLS). The PLS analysis demonstrated that the hydrolysis of carbohydrate was both affected by pH and acetate, with pH the more important factor. Therefore, the inhibition by acetate on carbohydrate hydrolysis was mainly due to the corresponding decline of pH, but the presence of acetate species, while the acetate species was the absolutely important factor for the hydrolysis of protein. [ABSTRACT FROM AUTHOR]

Sewage sludge biochars were obtained at different pyrolysis temperatures from 300°C to 900°C and their macro- and microscale properties were analyzed. The biochar's plant-available nutrients and humus-like substances in the water-extractable phase and fixed nutrients in the solid fraction were evaluated for their potential agronomic implications. FT-IR, Raman, XRD, XPS, and SEM techniques were used to investigate the chemical structure, functional groups, and microcrystal structure on the surface of the biochar. The results revealed minor chemical changes and dramatic mass loss in the biochar obtained at 300-500°C, whereas significant chemical changes in the biochar were obtained at 600-900°C. The concentrations of plant-available nutrients as well as fulvic- and humic-acid-like materials decreased in the biochar samples obtained at higher temperatures. These results implied that the biochar samples pyrolyzed at 300-500°C could be a direct nutrient source and used to neutralize alkaline soil. The surface area and porosity of the biochar samples increased with temperature, which increased their adsorption capacity. Rearrangement occurred at higher temperature 600-900°C, resulting in the biochar becoming increasingly polyaromatic and its graphite-like carbon becoming organized. [ABSTRACT FROM AUTHOR]