Deciphering three-dimensional bioanode configuration for augmenting power generation and nitrogen removal in air-cathode microbial fuel cells.

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.

Remedying acidification and deterioration of aerobic post-treatment of digested effluent by using zero-valent iron.

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 Fe0 oxidation and NO3- 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.

Performance of autotrophic nitrogen removal from digested piggery wastewater.

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 390days of operation. The results showed that the total nitrogen removal rate and efficiency reached 3.9kg-Nm-3day-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±0.1g-NgVSS-1d-1), and a good settling ability (SVI, 78.42mLg-1SS) resulted in a high sludge concentration (VSS, 11.01gL-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%).

Enrichment and characterization of acid-tolerant nitrifying sludge.

Nitrification is an acidifying process that requires the addition of external alkalinity because of the alkaliphilic nature of the most ammonia-oxidizing bacteria. In this study, aerobic activated sludge was used as inoculum in an internal loop air-lift reactor, which resulted in successful enrichment of acid-tolerant nitrifying (ACIN) sludge at pH 6.0 by sequential addition of tea orchard soil suspension. The results showed that ACIN sludge had a remarkable acid tolerant capability with a volumetric ammonia conversion rate of 1.13 kg N m-3 day-1. ACIN sludge showed a higher maximum specific ammonia conversion rate (0.29 g N g-1 VSS day-1) than neutrophilic nitrifying sludge (0.14 g N g-1 VSS day-1) at pH 6.0 and had good resistance against pH fluctuations, with a maximum specific ammonia conversion rate (0.584 g N g-1 VSS day-1) at pH 7.5. Microbial community analysis indicated that the higher abundance of acid tolerant Nitrosospira and ammonia-oxidizing archaea laid a solid foundation for the remarkable acid-tolerant capability of ACIN sludge.

Mass flow and energy balance plus economic analysis of a full-scale biogas plant in the rice-wine-pig system.

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.

The effects of temperature, organic matter and time-dependency on rheological properties of dry anaerobic digested swine manure.

An efficient way to avoid the pollution of swine wastewater is the application of dry anaerobic digestion, which needs rheological parameter for stirring and pipe designing. The rheological properties of this kind of sludge have been studied for many decades, yet their effects only solid concentration has been investigated widely. In this paper, the influences of temperature, organic and time-dependency on the efficiency of anaerobic digested swine manure were studied. The viscosity decreased with temperature arranged from 10 to 60 °C which caused increase in protein from 7.18 to 8.49 g/kg. 60 °C can make the digested swine manure with TS from 16.6% to 21.5% reach to the same rheology state. The added peptone decreased the viscosity because of its function of water-reducing admixture and air entraining mixture. Time-dependent experiment showed the decrease of shear stress over time. The first and the second yield stress of dry anaerobic digested swine manure were evaluated through time-dependent model.

Characteristics and management of domestic waste in the rural area of Southwest China.

With its rapid development, the rural area of Southwest China has been puzzled by the waste management problem, especially for increasing solid waste and water pollution from the domestic waste. Therefore, in order to efficiently and effectively manage the domestic waste in the rural area of Southwest China, 22 villages were selected randomly to analyse the characteristics of domestic waste, the influence factors of characteristics and resident's willingness of participation in domestic waste management by questionnaires, field samplings and laboratory tests. The results of the rural area of Southwest China indicated that the generation of domestic waste was 178 g d(-1) per capita and it was mainly composed of kitchen waste, inert waste, plastics and paper with a total proportion of 81.98%. The waste bulk density, moisture, ash, combustible and lower calorific value were 107 kg m(-3), 37.04%, 25.73%, 37.23% and 8008 kJ kg(-1), respectively. These characteristics were influenced by the topography, the distance from towns or cities, the villagers' ethnicities and income sources to some extent. Moreover, the distance of 50-800 m between each collection facility and the disposal fee of around ¥5.00 per household per month could be accepted. The working hours of participation in waste management is suggested as 5 hours per day with the income of ¥1000 per capita per month. Based on the outcome of this survey, a waste management system consisting of classified collection, centralised treatment and decentralised treatment was proposed. It is important to ensure financial viability and practical considerations of this system.