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Anaerobic digestion at high organic loading rate (OLR) is prone to acid inhibition that reduces methane production. In this study, effects of Fe0 (+Co/Ni) on suppressing acid inhibition and improving methane production were studied using vegetable waste as substrate at OLR of 3.0 gVS/L/d for 160 days. Results indicated additional use of Co/Ni with Fe0 did not further improve the effects of Fe0 and use of Ni suppressed considerable the effects of Fe0. These differences were supported by microbial changes caused by addition of Fe0 (+Co/Ni). Analysis of 16S rRNA genes revealed microbial community without Ni addition was more stable, a factor largely influenced by pH and ammonia nitrogen levels. Relative abundances of Methanosarcina and Methanosaeta were approximately 60% in Fe0-Ni and Fe0-Co-Ni treatments, and 90% in control, Fe0 and Fe0-Co treatments. But linear discriminant analysis effect size and network analysis indicated Methanosaeta and Methanosphaera , not Methanosarcina, were key methanogens. They functioned with acid producing Acetobacterium , and ammonia nitrogen producing Aminobacterium to convert volatile fatty acids to methane in Fe0 treatments. Actinomyces were key microorganisms that hindered methanogenesis, especially in Ni addition treatments. This work suggests addition of Fe0 in anaerobic digestion at high OLR is theoretically feasible for engineering applications. [Display omitted] • Effects of Fe0 (+Co/Ni) in methane fermentation at high OLR were investigated. • Fe0 maintained 215–250 mL methane /gVS/d and suppressed acid inhibition. • Ni weakened or minimized promoting effect of Fe0. • Methanosaeta and Methanosphaera, not Methanosarcina were the key methanogens. • Aminobacterium and Acetobacterium promoted while Actinomyces hindered MPR. [ABSTRACT FROM AUTHOR]

Tomato bacterial wilt caused by Ralstonia solanacearum is the most destructive disease impacting production. Application of bioorganic fertilizer (BOF) containing antagonistic microorganism to suppress tomato bacterial wilt disease may be a promising disease control strategy. Here, we used organic waste materials, specifically biogas residues, cattle manure and rice straw, in composting with antagonistic strain G33 isolated from the rhizosphere soil of a healthy tomato plant to produce BOF. Strain G33 was identified as Streptomyces microflavus by morphological and culturing traits and by 16S rRNA gene sequence analysis. We conducted a field experiment with control treatment, organic fertilizer and BOF-G33 to characterize suppression of tomato bacterial wilt disease. Our results indicate that the optimal combination containing (w/w) 40% biogas residues, 40% cattle manure and 20% rice straw can increase the nutrient contents of the compost product, prolong the thermophilic period and increase the decomposition rate of organic matter and the humification degree. A combination of strain G33 and mature compost produced under optimal conditions resulted in the spore number of 5.75 × 109 CFU/g on the sixth day of fermentation. Field experiments showed that BOF-G33 significantly decreased the incidence of tomato wilt; the disease biocontrol efficiency was 64.4%. In addition, application of the BOF-G33 significantly reduced the pathogenic R. solanacearum populations and increased the abundance of beneficial indigenous flora in the rhizosphere soil, which might have been the key factors in constraining the disease. In conclusion, this study showed that bioorganic fertilizer with Streptomyces microflavus G33 is a potential biocontrol agent for controlling tomato bacterial disease. • S. microflavus G33 showed strong antagonistic activity against R. solanacearum. • BOF-G33 application effectively controlled tomato bacterial wilt disease. • BOF-G33 application led to significant changes the rhizosphere microbial community. • Strain G33 had colonization capacity stably in rhizosphere soil. • The rhizosphere R. solanacearum was the key factor directly controlling the disease. [ABSTRACT FROM AUTHOR]

Wet distillers grains, as a waste biomass with a large annual output, pose a threat to the environment and food industry. Herein, artificial humic acid (AHA) was first produced from wet distillers grains in a dual-stage microwave-assisted hydrothermal process. The influence of temperature on AHA's characteristics was investigated and compared with natural humic acid (NHA) and standard humic acid (SHA). A high yield of AHA at 20.6% was obtained at 200 °C with a total reaction time of 1 h, which is 1.8–3.1 times that obtained in traditional single-stage hydrothermal process. Increasing the reaction temperature induced the formation of phenolic hydroxyl in AHA. AHA was rich in aromaticity and carboxylic acid structure, showing similar spectral characteristics to NHA. The distribution of molecular weight of AHA was mostly 5797 Da, which decreased by 15% compared to SHA. The optimal concentration of AHA to promote seedling growth was 0.2 g/L, and the root length was 2.0 times that of the control. The microwave hydrothermal process is a facile and efficient approach to preparing AHA from waste biomass with high moisture content. [Display omitted] • AHA was first produced from wet distillers grains in a dual-stage microwave HTC. • The highest yield of AHA at 20.6% was obtained at 200 °C for 1 h in the HTC. • AHA showed higher aromaticity and carboxylic acid content than natural humic acid. • Molecular weight of AHA was mostly 5797 Da, which is 15% lower than that of SHA. • 0.2 g/L of AHA increased the seedling root length to 2.0 times that of the control. [ABSTRACT FROM AUTHOR]

This study presents a novel strategy for remedying acidification and improving the removal efficiency of pollutants from digested effluent by using Zero-Valent Iron (iron scraps) in a sequencing batch reactor. Through this strategy, the pH increased from 5.7 (mixed liquid in the reactor without added ZVI) to 7.8 (reactors with added ZVI) because of Fe 0 oxidation and NO 3 − reduction. The removal efficiencies of COD increased from 11.5% to 77.5% because of oxidation of ferric ion and OH produced in chemical reactions of ZVI with oxygen and because of flocculation of iron ions. The removal efficiencies of total nitrogen rose from 1.83% to 93.3% probably because of autotrophic denitrification using electron donors produced by the corrosion of iron, as well as the favorable conditions for anammox due to iron ions. Total phosphorus increased from −25.8% to 77.1% because of the increase in pH and the precipitation with iron ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two 3D carbon felt anodes with engineering mesoscale structure are fabricated. • Power density and columbic efficiency are increased with the 3D anodes processing. • The active 3D anode biofilm is consisted of a number of functional bacteria. • The increased anode biomasses are achieved by using the 3D anodes. In this study, the engineering-oriented three-dimensional (3D) bioanode concept was applied, demonstrating that spiral-stairs-like/rolled carbon felt (SCF/RCF) configurations achieved good performances in air–cathode microbial fuel cells (ACMFCs). With the 3D anodes, ACMFCs generated significantly higher power densities of 1535 mW/m3 (SCF) and 1800 mW/m3 (RCF), compared with that of a traditional flat carbon felt anode (FCF, 315 mW/m3). The coulombic efficiency of 15.39 % at SCF anode and 14.34 % at RCF anode also is higher than the 7.93 % at FCF anode. The 3D anode ACMFCs exhibited favorable removal of chemical oxygen demand (96 % of SCF and RCF) and total nitrogen (97 % of SCF, 99 % of RCF). Further results show that three-dimensional anode structures could enrich more electrode surface biomass and diversify the biofilm microbial communities for promoting bioelectroactivity, denitrification, and nitrification. These results demonstrate that three-dimensional anodes with active biofilm is a promising strategy for creating scalable MFCs-based wastewater treatment system. [ABSTRACT FROM AUTHOR]

The performance of an autotrophic nitrogen removal process to treat digested piggery wastewater (DPW) was investigated by gradually shortening the HRT and enhancing the DPW concentration during 390 days of operation. The results showed that the total nitrogen removal rate and efficiency reached 3.9 kg-N m −3 day −1 and 73%, which were significantly higher than the levels reported previously. A high relative abundance of Nitrosomonas (4.2%) and functional microbes (12.15%) resulted in a high aerobic ammonium oxidizing activity (1.25 ± 0.1 g-N g VSS −1 d −1 ), and a good settling ability (SVI, 78.42 mL g −1 SS) resulted in a high sludge concentration (VSS, 11.01 g L −1 ), which laid a solid foundation for the excellent performance. High-throughput pyrosequencing indicated that, compared with synthetic wastewater, the DPW decreased the relative abundances of every functional group of nitrogen removal microbes, and increased relative abundances of anaerobes (15.7%), sulfur-oxidizing bacteria (9.4%) and methanogens (40.8%). [ABSTRACT FROM AUTHOR]

China has a long history of utilizing biogas technology for the treatment of waste and the production of energy. This paper reviews the development and technology of the three types of biogas digesters used in China: household-scale digesters, biogas septic tanks, and biogas plants for the treatment of municipal, industrial, and agricultural waste. The structure of household-scale digesters is simple and practical; the basic type is the fixed-dome digester, also called the hydraulic digester. The biogas septic tank for sewage treatment is a combination of the traditional digester, an anaerobic filter, and a facultative filter. Biogas plants apply several different processes depending on the type of waste treated. The treatment of municipal waste biogas is conducted using the completely stirred tank rector (CSTR). The upflow anaerobic sludge blanket (UASB) is the most common technology used in the anaerobic treatment of industrial wastewater, followed by the CSTR and the anaerobic contact (AC) process. The treatment of agricultural waste mainly employs traditional hydraulic digesters, while newer biogas plants use advanced anaerobic processes such as CSTR and UASB as well as upflow solids reactors (USR) and upflow blanket filter (UBF) reactors. Biogas plants for agricultural waste are classified as small, medium, large and super large based on the scale of biogas production and digester volume. Although small-scale biogas plants are the most common, large-scale biogas plants produce the largest biogas output. With the changes associated with socio-economic development, the growth of household-scale digesters will slow down in the future. As central sewage treatment networks become more widespread, biogas septic tanks will be confined to villages and small towns. The development of biogas plants holds the most growth potential for the future. [ABSTRACT FROM AUTHOR]

This paper presents mass flow and energy balance as well as an economic analysis for a biogas plant in a rice–wine–pig system at a practical rather than laboratory scale. Results showed feeding amount was 65.30 t d −1 (total solid matter (TSM) 1.3%) for the normal temperature continuous stirred tank reactor (CSTR), and 16.20 t d −1 (TSM 8.4%) for the mesophilic CSTR. The digestion produced 80.50 t d −1 of mass, with 76.41 t d −1 flowing into rice fields and 4.49 t d −1 into composting. Energy consumption of this plant fluctuated with seasons, and surplus energy was 823, 221 kWh/year. Thus, biogas plant was critical for material recycling and energy transformation of this agro-ecosystem. The economic analysis showed that the payback time of the plant was 10.9 years. It also revealed application of biogas as a conventional energy replacement would be attractive for a crop–wine–livestock ecosystem with anaerobic digestion of manure. [ABSTRACT FROM AUTHOR]

The effects of temperature on biogas production and the heating strategy for anaerobic digestion of swine wastewater were investigated. Through a kinetic model, the maximum volumetric rate of biogas production ( R pmax ) for digestion at 15, 20, 25, 30, and 35 °C were found to be 0.282, 1.189, 1.464, 1.789, and 2.049 L L −1 d −1 , respectively. The temperature–activity coefficient of R pmax was 1.332 at 15–20 °C, 1.043 at 20–25 °C, 1.041 at 25–30 °C, and 1.028 at 30–35 °C. Anaerobic digestion appeared to be more sensitive to temperature variation within 15–20 °C than to variation within 20–35 °C. In terms of energy input–output ratio and total annual cost, the optimal heating strategy is an increase in the fermentation temperature from 15 to 20 °C. [ABSTRACT FROM AUTHOR]