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One-stage autotrophic nitrogen (N) removal, requiring the simultaneous activity of aerobic and anaerobic ammonium oxidizing bacteria (AOB and AnAOB), can be obtained in spatially redox-stratified biofilms. However, previous experience with Membrane-Aerated Biofilm Reactors (MABRs) has revealed a difficulty in reducing the abundance and activity of nitrite oxidizing bacteria (NOB), which drastically lowers process efficiency. Here we show how sequential aeration is an effective strategy to attain autotrophic N removal in MABRs: Two separate MABRs, which displayed limited or no N removal under continuous aeration, could remove more than 5.5 g N/m(2)/day (at loads up to 8 g N/m(2)/day) by controlled variation of sequential aeration regimes. Daily averaged ratios of the surficial loads of O(2) (oxygen) to NH(4)(+) (ammonium) (L(O(2))/L(NH(4))) were close to 1.73 at this optimum. Real-time quantitative PCR based on 16S rRNA gene confirmed that sequential aeration, even at elevated average O(2) loads, stimulated the abundance of AnAOB and AOB and prevented the increase in NOB. Nitrous oxide (N(2)O) emissions were 100-fold lower compared to other anaerobic ammonium oxidation (Anammox)-nitritation systems. Hence, by applying periodic aeration to MABRs, one-stage autotrophic N removal biofilm reactors can be easily obtained, displaying very competitive removal rates, and negligible N(2)O emissions.

Abstract The effects on human performance of elevated temperature causing thermal discomfort were investigated. Recruited subjects performed neurobehavioural tests examining different component skills, and addition and typing tasks that were used to replicate office work. The results show that thermal discomfort caused by elevated air temperature had a negative effect on performance. A quantitative relationship was established between thermal sensation votes and task performance. It can be used for economic calculations pertaining to building design and operation when occupant productivity is considered. The relationship indicates that optimum performance can be achieved slightly below neutral, while thermal discomfort (feeling too warm or too cold) leads to reduced performance. Consequently, it makes sense to set the PMV limits in workplaces in the range between −0.5 and 0 instead of between −0.5 and 0.5 as stipulated in the present standards.

A central composite design of response surface method was used to optimize H(2)SO(4)-catalyzed hydrothermal pretreatment of rapeseed straw, in respect to acid concentration (0.5-2%), treatment time (5-20 min) and solid content (10-20%) at 180 degrees C. Enzymatic hydrolysis and fermentation were also measured to evaluate the optimal pretreatment conditions for maximizing ethanol production. The results showed that acid concentration and treatment time were more significant than solid content for optimization of xylose release and cellulose recovery. Pretreatment with 1% sulfuric acid and 20% solid content for 10 min at 180 degrees C was found to be the most optimal condition for pretreatment of rapeseed straw for ethanol production. After pretreatment at the optimal condition and enzymatic hydrolysis, 75.12% total xylan and 63.17% total glucan were converted to xylose and glucose, respectively. Finally, 66.79% of theoretical ethanol yielded after fermentation.

Electricity generation integrated with xylose degradation was investigated in a two-chamber mediator-less microbial fuel cell (MFC). Voltage output followed saturation kinetics as a function of xylose concentration for concentration below 9.7 mM, with a predicted maximum of 86 mV (6.3 mW m(-2) or 116 mW m(-3)) and half-saturation constant (K(s)) of 0.29 mM. Xylose concentrations from 0.5 mM to 1.5 mM resulted in coulombic efficiencies and maximum voltage ranging from 41+/-1.6% to 36+/-1.2% and 55+/-2.0 mV to 70+/-3.0 mV respectively. Xylose degradation rate increased with increasing xylose concentration up to 9.7 mM and the predicted maximum degradation rate was 0.13 mM h(-1) and K(s) of 3.0 mM. Stirring by nitrogen in the anode chamber led to 99+/-2.3 mV maximum voltage (8.4+/-0.4 mW m(-2) or 153+/-7.1 mW m(-3)) and 5.9+/-0.3% coulombic efficiency at MFC running time 180 h, which were respectively 17+/-1.2% and 37+/-1.8%, higher than those without stirring. The COD removal under stirring was 22.1+/-0.3%, which was slightly lower than that of 23.7+/-0.4% under no stirring. However, stirring resulted in 59% lower xylose degradation rate. This work demonstrates that xylose can be used in the MFC for electricity production. Comparatively higher electricity generation and coulombic efficiency can be obtained by adjusting initial xylose concentration and applying stirring in the anode chamber.

The energy efficiency of microwave-assisted dilute sulfuric acid pretreatment of rape straw for the production of ethanol was investigated. Different microwave energy inputs and solid loadings were tested to find economic pretreatment conditions. The lowest energy consumption was observed when solid loading and energy input were fixed at 50% (w/w) and 54 kJ (900 W for 1 min), respectively, and amounted to 5.5 and 10.9 kJ to produce 1g of glucose after enzymatic hydrolysis and 1g ethanol after fermentation, respectively. In general, 1g ethanol can produce about 30 kJ of energy, and therefore, the energy input for the pretreatment was only 35% of the energy output. The approach developed in this study resulted in 92.9% higher energy savings for producing 1g ethanol when compared with the results of microwave pretreatments previously reported.

Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae F12 were used to ferment carbohydrates of wet exploded pre-treated wheat straw (PWS) directly to ethanol. Both microorganisms were first grown aerobically to produce cell mass and thereafter fermented PWS to ethanol under anaerobic conditions. During fermentation, soluble and insoluble carbohydrates were hydrolysed by the lignocellulolytic system of F. oxysporum. Mixed substrate fermentation using PWS and corn cobs (CC) in the ratio 1:2 was used to obtain an enzyme mixture with high cellulolytic and hemicellulolytic activities. Under these conditions, activities as high as 34300, 9100, 326, 24, 169, 27 and 254 U dm(-3) of xylanase, endoglucanase, beta-glucosidase, arabinofuranosidase, avicelase, feruloyl esterase and acetyl esterase, respectively, were obtained. The replacement of the enzyme production phase of F. oxysporum by the addition of commercially available enzymes Celluclast (R) 1.5 L FG and Novozym (R) 188 in 3:1 ratio for the treatment of PWS, resulted in a 3-fold increase in the volumetric ethanol productivity without increasing the ethanol production significantly. By direct bioconversion of 110 kg m(-3) dry matter of PWS, ethanol concentration (4.9 kg m(-3)) and yield (40 g kg(-1) of PWS) were similarly obtained by F. oxysporum and the mixed culture, while productivity rates as high as 34 g m(-3) h(-1) and 108 g m(-3) h(-1) were obtained by F. oxysporum and the mixed culture, respectively.

The effect of substrate changes on the performance and microbial community of two-chamber microbial fuel cells (MFCs) was investigated in this study. The MFCs enriched with a single substrate (e.g., acetate, glucose, or butyrate) had different acclimatization capability to substrate changes. The MFC enriched with glucose showed rapid and higher power generation, when glucose was switched with acetate or butyrate. However, the MFC enriched with acetate needed a longer adaptation time for utilizing glucose. Microbial community was also changed when the substrate was changed. Clostridium and Bacilli of phylum Firmicutes were detected in acetate-enriched MFCs after switching to glucose. By contrast, Firmicutes completely disappeared and Geobacter-like species were specifically enriched in glucose-enriched MFCs after feeding acetate to the reactor. This study further suggests that the type of substrate fed to MFC is a very important parameter for reactor performance and microbial community, and significantly affects power generation in MFCs.

The environmental profile of two municipal solid waste incineration (MSWI) technologies with semi-dry flue gas cleaning, namely grated firing incinerators (GFI) and fluidised bed incinerators (FBI) that are commonly used in China were evaluated and compared by life-cycle assessment (LCA) using the EASEWASTE model. All emissions of key pollutants as well as energy, resource and material inputs and outputs associated with the two MSWI technologies were determined and the corresponding environmental impact potentials were modelled. Incineration of MSW with a lower heating value (LHV) around 4.5 MJ kg—1 demands that auxiliary fuel is used, and both GFI and FBI caused environmental loads by contributing with environmental impact potentials in most categories except for some saving in global warming (GW100) and hazardous waste (HW). Coal combustion in FBI is a main contributor to the environmental impact potentials and thus should always be limited to a minimum. Auxiliary fuels can be avoided when the LHV of MSW is higher than 5—6 MJ kg— 1. For all scenarios, GFI saves more global warming potentials than FBI due to its higher net power generation from combustion of MSW itself. Leachate from the bunker could be sprayed into the furnace for evaporation under high temperature, as an alternative to waste-water treatment, without major changes in the environmental profile of the incinerator. The presented evaluations may contribute to a more balanced environmental assessment of the two incineration technologies with respect to incineration of MSW with low heating values as often found in Asia and China.