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Copyright of Paint & Coatings Industry (0253-4312) is the property of Paint & Coatings Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The yield of green energy from solid-state anaerobic co-digestion (SSAD) has recently been enhanced by incorporating innovative pretreatment methods and nanoparticles. However, the environmental consequences of employing new processes have not been fully examined. In this study, the environmental impacts of three high-methane-yielding scenarios including SSAD of corn stover blended with dairy manure (DM) denoted as (SYM1), calcium hydroxide-pretreated corn stover (CpCS) blended with DM (SYM2), and the CpCS blended with DM and nanoparticles (SYM3) were assessed and compared the baselines of solid-state and semi-solid-state anaerobic digestion using a life cycle assessment (LCA) approach. The approach investigated the best management practices that would result in high methane yield and low environmental impact. Results of the life cycle assessment indicate the inclusion of calcium hydroxide and nanoparticle has minimal negative environmental impact. There was an environmental gain in GWP when corn stover was co-digestion with DM (SYM1) relative to DM mono-digestions (baselines) and the carbon footprint of SYM1 was less by more than 85% compared to SYM2 and SYM3. However, the large volume of untreated corn stover harnessed for SYM1 scenario resulted in over 75% fossil fuel depletion compared to the other scenarios. The surplus methane from the SYM3 (at least twofold of other scenarios and baselines) in conjunction with being the least with the environmental implication makes the scenario the most attractive option for on-farm practice capable of harnessing the growing organic waste volume. These outcomes can guide trade-off between pretreatment and nanoparticle application to reduce solid-state anaerobic digestion's negative environmental impact. [ABSTRACT FROM AUTHOR]

Copyright of Coatings & Protection / Tuceng yu Fanghu is the property of Coating & Protection Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In this study, a high frequency monitoring method was used to assess how semi-continuous feeding affects H2S production in high solid anaerobic digestion. The results showed that H2S characteristics at a monitoring frequency of 1 point/3 h were different to that of 1 point/24 h, its concentration decreased from 3449 ± 227 mg/m3 at 0 h to 298 ± 45 mg/m3 at 3 h. H2S concentration was negatively correlated with volatile fatty acids (VFAs), and oxidation reduction potential (ORP). 72–82% of H2S reduction in the first 3 h resulted from the introduction of O2 during feeding, and 18–28% of that was closely related to the production of a large quantity of soluble acidic matter, such as VFAs. A more accurate H2S release model was established according to the content of VFAs. Totally, this study implies that feed carrying air is a promising method for in situ control of H2S production in anaerobic digestion. Graphical Abstract

The fermentation system with high solid materials for food waste (FW) is uneven in nutrition and easy to produce volatile acid accumulation, which causes the reaction system to acidify and affects the normal operation of fermentation. This study evaluated the effect of the co-substrate percentages (FW:CB = 9:1, FW:CB = 8:2, FW:CB = 7:3) and the initial total solid contents (12%, 15%, 18%) on the co-fermentation acidification performance of FW and cardboard waste (CB). The maximum methane production was obtained when mono-fermenting FW had high solids contents (1.4 L/kg). The methane production increased and then decreased with the increasing percentages of CB. Under the conditions of FW:CB = 8:2, the maximum methane production could reach 3.4 L/kg. The lower methane production (1.8 – 2.5 L/kg) with high percentages of CB (FW:CB = 7:3) was translated into higher yields of caproic acid (up to 26%), which indicated that lower percentages of CB had a stabilization effect due to the higher buffering capacities in co-fermentation. As a result, this study demonstrated new possibilities for using CB percentages to control the production of high added-value biogas in dry co-fermentation of FW. HIGHLIGHTS High-solid anaerobic co-fermentation of food waste and waste cardboard was studied.; Co-fermentation results in rapid degradation and stabilization of amylase.; Anaerobic co-fermentation of waste can adjust the nutritional balance of the system.; Addition of cardboard increases buffer capacity, and methane production is 3.4 L/kg.; Food and cardboard waste co-fermentation are classified as butyric acid fermentation.;

In this study, a high frequency monitoring method was used to assess how semi-continuous feeding affects H2S production in high solid anaerobic digestion. The results showed that H2S characteristics at a monitoring frequency of 1 point/3 h were different to that of 1 point/24 h, its concentration decreased from 3449 ± 227 mg/m3 at 0 h to 298 ± 45 mg/m3 at 3 h. H2S concentration was negatively correlated with volatile fatty acids (VFAs), and oxidation reduction potential (ORP). 72–82% of H2S reduction in the first 3 h resulted from the introduction of O2 during feeding, and 18–28% of that was closely related to the production of a large quantity of soluble acidic matter, such as VFAs. A more accurate H2S release model was established according to the content of VFAs. Totally, this study implies that feed carrying air is a promising method for in situ control of H2S production in anaerobic digestion. [ABSTRACT FROM AUTHOR]

The gradual increase in cattle farming has led to a huge production of cattle manure (CM), but the conventional treatment methods are less efficient. In this study, the treatment method of anaerobic digestion (AD) of high-solids CM by combining nanobubble water (NBW) with different gases was proposed to present a new idea for the reduction, harmlessness, and resourcefulness of CM. It was found that the performance of the digester with added NBW was better than the control. Among them, the cumulative methane yield T-Air: 227.09 mL g−1 VS added and T-CO 2 : 226.12 mL g−1 VS added increased by 17.72 % and 17.22 %, respectively, compared with the control T: 192.90 mL g−1 VS added under thermophilic conditions. Under mesophilic conditions, M-Air: 162.39 mL g−1 VS added increased by 9.68 % compared with control M: 148.05 mL g−1 VS added. Microbial communities analyzed at the genus level revealed that the relative abundance of bacteria favorable to hydrolysis and acid-producing processes, such as Defluviitalea , Haloplasma , and Bacillus , increased to varying degrees. Moreover, the relative abundance of archaea favorable for methanogenesis, such as Methanoculleus , Methanobrevibacter , and Methanosarcina , also increased to varying degrees. Therefore, the addition of NBW promoted the hydrolysis of high-solids CM, enhanced the stability of the reaction, improved the methanogenic performance, and increased the RA of favorable genera, which ultimately led to a better performance of the AD of high-solids CM. [Display omitted] • Compared with control, NBW increased CH 4 production by 5–17 %. • Compared with control, NBW contributes to the production/transformation of VFAs. • Incorporation of NBW improves stability of high solids anaerobic digestion. • Compared with control, NBW increased the RA of hydrolytic acidification-associated bacteria. • Compared with control, NBW increased the RA of methanogenic-associated archaea. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a promising technology for the treatment of chicken manure but its application has limitations due to the inhibition induced by high concentration of ammonium nitrogen. In this study, the methane yield and methanogenic pathway of high solid anaerobic digestion of chicken manure, and their response to total ammonium nitrogen (TAN) variations with and without ammonia stripping were investigated through 194 days' continuously fed experiment. The results obtained show a 20% reduction in the TAN and a 30% reduction of volatile fatty acids by a moderate in-situ ammonia stripping. Methane yield increased by 34% and the enhanced acetoclastic and hydrogenotrophic methanogenic activities were significant. Firmicutes, Bacteroidetes, and Cloacimonetes were dominant at a TAN range of 5.8–6.8 g/L. Methanosarcina sp. was the dominant archaea and its relative abundance increased with in-situ ammonia stripping. The shifts of methanogenic pathway with and without stripping was quantified by 2–13C stable isotope probing and was consistent with the microbial community's changes. The positive effects achieved by in-situ ammonia stripping set the foundation for its use in the anaerobic digestion process of nitrogen-rich and high solid materials during treatment management. • Moderate in situ stripping reduced TAN by 20% and VFAs by 30%. • Stripping increased both methane yield and methanogenic activities. • The microbial communities were identified by high throughout sequencing. • The methanogenic pathway was quantified by 2–13C isotope probing. [ABSTRACT FROM AUTHOR]

Enzymatic hydrolysis at high solids loading has the potential to reduce both capital and operational expenditures. Here, pretreatment of rice straw (PRS) with dilute acid was carried out at a pilot scale (250 kg per day) at 162°C for 10 min and 0.35% acid concentration, followed by enzymatic hydrolysis at different total solids loadings. It showed that although the total sugar concentration increased from 48 to 132 g/l, glucan conversion reduced by 27% (84–66.2%) with increasing solids from 5 to 20% in batch mode. Therefore, two different fed-batch approaches were evaluated to improve the glucan conversion by the sequential addition of a substrate and/or enzyme. At 20% solid loadings and a 3 filter paper units/g enzyme dosage, the highest glucan conversion obtained was 66% after 30 h of hydrolysis in batch mode. However, in an optimized fed-batch approach, the glucan yield was improved to 70% by simply dividing the substrate feeding into three batches, that is, 50% at 0 h, 25% each after 4 h, and 8 h of hydrolysis reaction. The addition of surfactant (Ecosurf E6) further improved the conversion to 72% after 30 h. The role of critical factors, that is, inhibitors, enzyme–lignin binding, and viscosity, was investigated during the course of hydrolysis in the batch and fed-batch approaches. This study suggests a sustainable approach for improved hydrolysis at high solids loadings by fine-tuning a simple process.

• Fe2+ and Ni2+ enhanced long term methanogenic performance at TAN of 6.8/L. • Both acetoclastic and hydrogenotrophic methanogenic activity was increased. • The microbial communities was identified by high throughout sequencing. • Hydrogenotrophic methanogens were out-competed with trace elements addition. High solid anaerobic digestion (AD) is a promising technology for the treatment of organic waste in terms of efficient bioenergy production and digestate volume reduction. However, the high solid AD of chicken manure has been a challenge due to the inhibition effects caused by high ammonia levels. In this study, the addition of 280 mg/L Fe2+ and 2 mg/L Ni2+ has been proven to enhance the microbial activity and to overcome inhibition under the stressed environment. The mesophilic digesters feeding with total solid around 150 g/kg operated at an organic loading rate of 4.8 g/(L d) based on volatile solid and a 20-day hydraulic retention time. The total ammonia-nitrogen reached around 6.8 g/L in control and Fe-Ni digesters. The results from the 147-day continuously-fed experiment provided an increment of 34% methane production and a 29% reduction of volatile fatty acids against control. The acetoclastic and hydrogenotrophic methanogenic activity was increased by 89% and 40% respectively. The high throughout sequencing results showed an increased percentage of Methanosarcina sp., which may have contributed to the shifting of the methanogenic pathway towards acetoclastic methanogenesis. The positive effects of Fe2+ and Ni2+ supplementation obtained in this study lay the foundation for its use in AD of nitrogen rich materials. [ABSTRACT FROM AUTHOR]

Highlights • Highly effective DESs took only 6 min at 120 °C to remove 79% xylan and 82% lignin. • Ternary DESs were effective for biomass fractionation at 35% solid loading. • Rapid deconstruction led to concentrated sugar hydrolysate with 78.4% glucose yield. • Low enzyme loading of 5 mg protein/solid was used for hydrolysis at 20% solids. • Lignin properties were affected by constitutes of ternary DESs. Abstract Ternary deep eutectic solvents (DESs) were developed to enable rapid and high-solid biomass pretreatment as well as concentrated sugar hydrolysate production. Six ternary DESs constituted choline chloride (ChCl) or guanidine hydrochloride (GH) as a hydrogen bond acceptor (HBA), ethylene glycol (EG) or propylene glycol (PG) or glycerin (GLY) as a polyol-based hydrogen bond donor (HBD), and p -toluenesulfonic acid (PTSA) as an acidic HBD. GH-EG-PTSA was the most effective, evidenced by 79% xylan and 82% lignin removal in only 6 min at 120 °C and 10 wt% solid loading. Even at 35 wt% solid loading, both GH-EG-PTSA and ChCl-EG-PTSA still removed more than 60% xylan and lignin in 30 min. Using a 20% solid loading and a low enzyme loading of 5 mg protein/g solid, 128 g/L glucose and 20 g/L xylose was obtained, with a glucose yield of 78.4%. Overall, this study demonstrated novel and high-performance ternary DESs for effective lignocellulose deconstruction. [ABSTRACT FROM AUTHOR]

The effects of temperature and pH on volatile solid (VS) degradation and CH 4 production of anaerobic digestion treating high-solid municipal dewatered sludge was studied. There were two single-phase reactors in Group 1: 35 and 55 °C reactors. In Group 2 (G2), acidification phase temperature was 55 °C or 70 °C and digestion phase temperature was 35 °C or 55 °C. G3 was set on the basis of G2 with the initial pH adjusted to 10.0. VS degradation ratio and CH 4 generation ratio of G2 and G3 were higher than G1. In G2, acidification reactors did not show much difference on VS degradation and CH 4 generation. Higher VS degradation ratio with higher CH 4 generation ratio was get in extreme thermophilic/thermophilic-mesophilic systems. In G3, pH adjustment only promoted VS degradation and CH 4 generation in acidification reactors when compared to G2, but the two ratios of the whole systems was not further enhanced. [ABSTRACT FROM AUTHOR]

Performance of continuous mesophilic high solids anaerobic digestion (HSAD) was simulated using Anaerobic Digestion Model No. 1 (ADM1), under different conditions (solids concentrations, sludge retention time (SRT), organic loading rate (OLR), and type of sludge). Implementation of ADM1, using the proposed biochemical parameters, proved to be a useful tool for the prediction and control of HSAD as the model predicted the behavior of the tested sets of data with considerable accuracy, especially for SRT more than 13 days. The model was then used to investigate the possibility of changing the existing conventional anaerobic digestion (CAD) units in Gabal El Asfar water resource recovery facility into HSAD, instead of establishing new CAD units, and results show that the system will be feasible. HSAD will produce the same bioenergy combined with a decrease in capital, operational, and maintenance costs. [ABSTRACT FROM AUTHOR]

Metagenomic comparisons of microbial profiles were conducted to investigate differences between the samples from steady (Day 42), ammonium-adjusting (Day 63), and ammonium-stressed (Day 102) periods during the 110-day operation of a high solid anaerobic digester of sewage sludge. Comparing to the steady period, biogas production was slightly inhibited after ammonium adjustment, during which the microbes showed higher abundance in 6 of the total 22 ammonium-related genes. In addition, among the 19 amino-acid-related genes, 9 genes involved in amino acid generation and utilization were reduced, which partially revealed the reason of deterioration of volatile solids (VSs) degradation following ammonium stress. Furthermore, although the acetoclastic pathway was to some extent inhibited with the decrease of biogas amount and content, no enhancement of genes involved in hydrogenotrophic methanogenesis was observed, elucidating the distinct role of ammonium stress in directing bacterial community structure toward the enhanced syntrophic acetate oxidation reaction. [ABSTRACT FROM AUTHOR]

The aim of this work was to examine the improvement of anaerobic biodegradability of organic fractions of poplar leaf from codigestion with swine manure (SM), thus biogas yield and energy recovery. When poplar leaf was used as a sole substrate, the cumulative biogas yield was low, about 163 mL (g volatile solid (VS)) after 45 days of digestion with a substrate/inoculum ratio of 2.5 and a total solid (TS) of 22 %. Under the same condition, the cumulative biogas yield of poplar leaf reached 321 mL (g VS) when SM/poplar leaf ratio was 2:5 (based on VS). The SM/poplar leaf ratio can determine C/N ratio of the cosubstrate and thus has significant influence on biogas yield. When the SM/poplar leaf ratio was 2:5, C/N ratio was calculated to be 27.02, and the biogas yield in 45 days of digestion was the highest. The semi-continuous digestion of poplar leaf was carried out with the organic loading rate of 1.25 and 1.88 g VS day. The average daily biogas yield was 230.2 mL (g VS) and 208.4 mL (g VS). The composition analysis revealed that cellulose and hemicellulose contributed to the biogas production. [ABSTRACT FROM AUTHOR]

In the present study, the feasibility of hygienic treatment and energy recovery of dead animals (pork as an experimental alternative) by high solid co-digestion with vinasse under mesophilic condition was investigated. A lab-scale digester was operated for 125 days with SRT of 20 days. The volatile solid (VS) reduction, biogas yield, and CH 4 content finally achieved stability after two obvious fluctuations, and were 55 ± 1%, 0.40 ± 0.02 m 3 /kg VS feed and 68%, respectively. Meanwhile, the shifts of microbial communities of the samples taken on typical days with different performance (day 40 (stable), day 65 (deteriorated), day 75 (in recovery), day 90 (recovered) and day 110 (stable)) were monitored by the application of pyrosequencing technology and the bioinformatical analysis with QIIME 1.8. In consequence, the details of changes in bacterial and archaeal communities elaborately explained the intrinsic reasons for the deterioration and recovery of the digester, and provided the proofs for the feasibility of hygienic treatment and energy recovery of dead animals by high solid co-digestion with vinasse under mesophilic condition. [ABSTRACT FROM AUTHOR]

Different mixture ratio of household organic waste (HOW) and cow manure (CM) were investigated for biogas production. The objective was to explore possible significant synergistic effect obtained from the combination of these different substrates in Reactor 1 – 4 (R 1 – 4 ) batch experiment. The highest methane yield, 247 mL/g VS was obtained from R 3 and 243 mL/g VS in R 4 . Co-digestion in R 4 increased to 9% for CM and 78% for HOW in methane production. The results clearly demonstrate synergistic effect from nutrient balanced that improves the stability of anaerobic process. [ABSTRACT FROM AUTHOR]

The converter dust of different particle sizes was used as fillers for preparing high solid coating, to study the surface morphology and particle sizes of dust on the coating film properties. The results show that: with the converter dust particle diameter in 20~60?m, the particle size < 20 μm dust accounted for 50%, and the grain size meet the size of pigments and fillers for general coating (multi control in 50~60μm) requirement; when the dust particle size was 250 mesh, the coating surface shrinkage is smaller, the performance is best. [ABSTRACT FROM AUTHOR]

To obtain eco-friendly high solid and excellent anti-corrosive polyaspartic (PAS) coating, a novel self-thixotropic nanofiller, hydrogenated castor oil modifying graphene oxide (HMGO) nanosheet, was fabricated and blended into the PAS coating to enhance its corrosion resistance. The self-thixotropic HMGO nanosheets were synthesized from 3-aminopropyltriethoxysilane (APTES) modified graphene oxide sheets by grafting the hydrogenated castor oil (HCO) with long alkyl chain molecular structure. HMGO could form a three-dimensional hydrogen network, separating and stabilizing the nanosheets in the polyaspartic coating matrix homogeneously, so that the HMGO/polyaspartic nanocomposite coating did not contain free low molecules or free inorganic nanofillers. Electrochemical impedance spectroscopy (EIS) and salt spray testing of HMGO/polyaspartic nanocomposite coatings with 86 wt% high solids have shown that corrosion protection properties have been significantly improved with the addition of self-thixotropic HMGO nanofiller. Compared with other nanofillers, including graphene oxide and APTES modified graphene oxide, HMGO nanosheets presented an impressive improvement in corrosion resistance of polyaspartic coatings. The superiority of HMGO/polyaspartic nanocomposite coating is owing to the self-thixotropic effect of HMGO promoted homogeneous distribution and high compatibility of HMGO nanosheets in polyaspartic polymer matrix. • Preparation of high-solid anticorrosive coating with self-thixotropic HMGO and polyaspartic resin • The HMGO nanofillers are fabricated by modified graphene oxide grafting hydrogen castor oil. • HMGO nanofillers exhibit excellent rheology, dispersion and hydrophobic properties. • Robust and long-term anticorrosion property of coating are achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] SSF process with delayed inoculation eliminates problems related to typical SSF. [•] Gradual feeding of prehydrolysed medium enabled increase final ethanol concentration. [•] In fed-batch SSF with delayed inoculation ethanol yield from cellulose was 0.37g/g. [ABSTRACT FROM AUTHOR]

Anaerobic membrane bioreactors (AnMBR) were a promising technology to treat high-strength wastewater; however, inorganic precipitation trigged membrane fouling was an obstacle when treating leachate produced from the organic fraction of municipal solid waste. A flat sheet submerged AnMBR was therefore operated for 61 days to treat leachate with total solids in reactor reaching 57 g/L. The results obtained in this study found that approximately 95%, 74%, and 84% of the Ca, Mg, and P were removed through the formation of complex precipitates. Calcite was the dominant precipitation form. There were 17.4 mg-Ca/cm2, 1.3 mg-P/cm2, and 0.4 mg-Mg/cm2 residues attached to the membrane surface. Those materials were removed by immersing in a 2% citric acid solution and thus the membrane filtration ability was completely recovered. By the end, the concentration of inorganic materials inside the AnMBR accumulated to 42 g/L, accounting for 73% of the total solids. The trans-membrane pressure slightly increased from 3.1 kPa to 4.2 kPa indicating the sustainability of this high-solids type AnMBR. The chemical precipitation induced 91% removal of phosphors from leachate. Conclusively, this study may provide new insights into the formation of membrane fouling in a leachate treatment AnMBR. [Display omitted] •The AnMBR can sustain the high inorganic solids when treating OFMSW leachate; •Mass balance of Ca, P, and Mg explained the precipitation formation; •Calcite was the dominant precipitation form; •Around 91% phosphorus was anaerobically removed in the AnMBR. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of extracellular polymeric substances based on high-solid anaerobic digestion was investigated by gel filtration chromatography (GFC) and three-dimensional excitation and emission matrix (EEM) The organic matters of Extracellular Polymeric Substances (EPS) in the sludge decreased 24% and shifted from the tightly bound EPS (TB-EPS) fraction to the Slime fraction during anaerobic digestion. The raw sludge and the digestate had opposite molecular weights (MW) distribution in EPS fractions. From the fluorescence spectra result, tyrosine-like substances were converted to tryptophan-like substances, and more humic-like substance in Slime fration was produced with the reduction of the protein-like substance during anaerobic digestion. [Copyright &y& Elsevier]

Enzymatic hydrolysis of high-solid biomass (>10% w/ w dry mass) has become increasingly important as a key step in the production of second-generation bioethanol. To this end, development of quantitative real-time assays is desirable both for empirical optimization and for detailed kinetic analysis. In the current work, we have investigated the application of isothermal calorimetry to study the kinetics of enzymatic hydrolysis of two substrates (pretreated corn stover and Avicel) at high-solid contents (up to 29% w/ w). It was found that the calorimetric heat flow provided a true measure of the hydrolysis rate with a detection limit of about 500 pmol glucose s. Hence, calorimetry is shown to be a highly sensitive real-time method, applicable for high solids, and independent on the complexity of the substrate. Dose-response experiments with a typical cellulase cocktail enabled a multidimensional analysis of the interrelationships of enzyme load and the rate, time, and extent of the reaction. The results suggest that the hydrolysis rate of pretreated corn stover is limited initially by available attack points on the substrate surface (<10% conversion) but becomes proportional to enzyme dosage (excess of attack points) at later stages (>10% conversion). This kinetic profile is interpreted as an increase in polymer end concentration (substrate for CBH) as the hydrolysis progresses, probably due to EG activity in the enzyme cocktail. Finally, irreversible enzyme inactivation did not appear to be the source of reduced hydrolysis rate over time. [ABSTRACT FROM AUTHOR]

High solid thick polyurethane coatings are one of the best choices for pipeline coatings. In this research electrochemical impedance spectroscopy (EIS) has been used to assess the degradation of a high solid polyurethane pipeline coating. Physical and electrochemical properties of coating were interpreted via analysis of equivalent circuits. The mechanism and kinetic of electrochemical systems were assessed by measuring the variations in resistance, capacitance and percentage of water uptake through coating. Electrochemical impedance spectroscopy measurements showed that this coating has very good protection efficiency and after 3 months immersion in 5%NaCl solution, resistant and capacitance of coating reach ∼107 Ω cm2 and 10-12 F cm-2 respectively. Furthermore cathodic disbonding test was carried out in accordance to ASTM G8 for 30 days. After this time duration only 1·53 mm disbonding was observed around the created hole. The coated panels were evaluated in salt fog (ASTM B117) and 100% humidity cabinet (ASTM D2247). After 1000 h exposure in salt fog and 100% relative humidity cabinet no blister, chalking, rust or coating delamination was observed. The results revealed that the coating has very high protection efficiency and could be a very good alternative for conventional coatings in pipeline protection against corrosion. [ABSTRACT FROM AUTHOR]

• MAD and TAD of high-solids containing sludge were comprehensively compared. • The response of microbial community composition to sludge properties was monitored. • TAD performed better than MAD in biogas production and VTS reduction. • Ammonia inhibition was the main risk for high-solids TAD of sludge. • Microbial analysis based on RNA datasets more accurately reflected the AD process. This study involved a comparison between mesophilic (MAD) and thermophilic anaerobic digestion (TAD) of municipal sludge with high (10%) solids content; the reactor performance and the response of total and active microbial communities to changes in sludge properties were monitored. Both TAD and MAD were stably maintained. TAD performed better than MAD in biogas production and volatile total solids reduction upon feeding sludge 1. TAD was slightly inhibited by ammonia, whereas the performance of MAD was improved when sludge 2 was used as the feedstock. Alpha- and beta-diversity analyses revealed significant differences in the microbial community based on DNA and RNA datasets, indicating that not all microbes function in AD. The active microbial community diversity and composition in MAD and TAD were also driven by sludge properties. Moreover, MAD showed significantly higher richness and diversity of the active microbial community compared with TAD, regardless of changes in sludge properties. [ABSTRACT FROM AUTHOR]

High free ammonia nitrogen (FAN) is regarded as a main factor that inhibits biogas production in high solid anaerobic digestion systems with dewatered sludge. Two mesophilic semi-continuous anaerobic digesters fed with dewatered sludge (input total solids=15%) were operated and their performance under different FAN concentrations by two regulation methods including pH reduction and total ammonia nitrogen (TAN) promotion were investigated. Results showed that when FAN was elevated from (400±174) mg·L -1 to (526±25) mg·L -1 with the increase of TAN, the daily biogas yield declined from (11.9±0.3) L·d -1 to (10.3±0.2) L·d -1 . Meanwhile, volatile solids (VS) reduction rate decreased by 33.7%. When FAN dropped from (330±99) mg·L -1 to (47±13) mg·L -1 due to pH reduction, daily biogas yield declined from (14.4±1.1) L·d -1 to (10.8±0.3) L·d -1 and VS reduction rate decreased by 26.9%. The system performance was not enhanced with the reduction of FAN. With the stop of pH regulation, FAN gradually raised again to 300 mg·L -1 and digester performance recovered to the same as the situation before regulation. The result suggested that inhibition occurred during pH reduction. By 16S rRNA pyrosequencing analysis on bacterial and archaeal diversity and quantitative PCR analysis aiming at methanogens, it was found that bacterial community structure both changed obviously with obvious performance decline in the two digesters. Excessive FAN (>500 mg·L -1 ) could change the main bacteria species which degrade protein from Tepidimicrobium and Proteiniborus to Anaerobranca . On the other hand, some carbohydrate and protein degrading bacteria were also inhibited by pH reduction for FAN control, leading to the decline of hydrolysis rates of organic matters. As a result, the shortage of substrate supply for the methanogens weakened the biogas production of the digestion system.