Aerobic granulation for nitrogen removal via nitrite in a sequencing batch reactor and the emission of nitrous oxide.

In this study, the granulation of nitrifying-denitrifying via nitrite process in a sequencing batch reactor (SBR) as well as N(2)O emission patterns was investigated. After 60 days of operation, 0.8 mm granules were obtained, and partial nitrification was achieved after NH(4)(+)-N was raised to 350 mg/L. Fluorescence In-Situ Hybridization (FISH) analysis indicated that a fairly large proportion of ammonia-oxidizing bacteria (AOB) was close to the surface but nitrite-oxidizing bacteria (NOB) were rarely found. Batch experiments showed that 64.0% of NH(4)(+)-N in influent was transformed into NO(2)(-)-N, which showed the granules had excellent partial nitrification ability. Inhibition of free ammonia (FA) and limited DO diffusion within granules may contribute to the development and stabilization of partial nitrification. This process did not simultaneously lead to increased N(2)O production. N(2)O emissions at the anoxic and aerobic phases were 0.06 and 13.13 mg N(2)O/cycle, respectively.

Electricity generation from mixed volatile fatty acids using microbial fuel cells.

Fermentative hydrogen production, as a process for clean energy recovery from organic wastewater, is limited by its low hydrogen yield due to incomplete conversion of substrates, with most of the fermentation products being volatile fatty acids (VFAs). Thus, further recovery of the energy from VFAs is expected. In this work, microbial fuel cell (MFC) was applied to recover energy in the form of electricity from mixed VFAs of acetate, propionate, and butyrate. Response surface methodology was adopted to investigate the relative contribution and possible interactions of the three components of VFAs. A stable electricity generation was demonstrated in MFCs after the enrichment of electrochemically active bacteria. Analysis showed that power density was more sensitive to the composition of mixed VFAs than coulombic efficiency. The electricity generation could mainly be attributed to the portion of acetate and propionate. However, the two components showed an antagonistic effect when propionate exceeded 19%, causing a decrease in coulombic efficiency. Butyrate was found to exert a negative impact on both power density and coulombic efficiency. Denaturing gradient gel electrophoresis profiles revealed the enrichment of electrochemically active bacteria from the inoculum sludge. Proteobacteria (Beta-, Delta-) and Bacteroidetes were predominant in all VFA-fed MFCs. Shifts in bacterial community structures were observed when different compositions of VFA mixtures were used as the electron donor. The overall electron recovery efficiency may be increased from 15.7% to 27.4% if fermentative hydrogen production and MFC processes are integrated.

Characteristics and mechanisms of Cu(II) biosorption by disintegrated aerobic granules.

Disintegrated aerobic granules (DAG) as an effective biosorbent had great potential to remove Cu(II) from aqueous solution. The effects of solution pH value, contact time, initial Cu(II) concentration on the biosorption were investigated. Kinetic studies indicate that pseudo-second-order model with correlation coefficients of 0.9999 best fits the Cu(II) biosorption process. Investigation of the biosorption mechanisms shows that Cu(II) biosorption is associated with a significant release of Ca(II). The adsorption capacity of extracted extracellular polymeric substances (EPS) was 2.34 times as much as that of pristine DAG, indicating the significant role of EPS in adsorption. In order to determine the role of different functional groups, DAG was chemically modified to block specific functional groups and was then used in the adsorption of Cu(II). The anionic carboxyl group, was identified as the key binding site for the cationic Cu(II). Results reveal that ion exchange is the most important biosorption mechanism but other mechanisms to some extent like electrostatic interaction, involving in functional groups, also play a part.

Direct electricity recovery from Canna indica by an air-cathode microbial fuel cell inoculated with rumen microorganisms.

Aquatic plants are widely used for phytoremediation, and effective disposal methods should be pursued for their utilization and to avoid further environmental pollution problems. This study demonstrated that, using an air-cathode microbial fuel cell (MFC) inoculated with rumen microorganisms, electricity could be directly produced with a maximum power density of 0.405 W/m(3) from Canna indica (canna), a lignocellulosic aquatic plant rich in cellulose, hemicellulose, and lignin, without pretreatment. The mechanisms of the Canna indica degradation in the MFC were elucidated through analyzing the changes of canna structure and intermediates, that is, soluble sugars and volatile fatty acids (VFAs), in the electricity generation process. The results showed that lignin was partially removed and more cellulose became exposed on the sample surface during the electricity generation in the MFC. The electron transfer in this MFC was mainly completed through electron shuttling via self-produced mediators. This work presents an attempt to understand how complex substrates like aquatic plants are decomposed in an MFC during electricity generation. It might, hopefully, provide a promising way to utilize lignocellulosic biomass for energy generation.

[Impact of phthalic acid easters on diversity of microbial community in soil].

Phthalic acid easters (PAEs) are one of the most extensive organic and poisonous pollutants. BIOLOG and ARDRA method were used to analyze the impact of PAEs on microbial diversity in soil. BIOLOG analysis shows that the increase of average well color development (AWCD) is different in soils dealt with different concentrations of PAEs. With a higher PAEs concentration, the AWCD increases more slowly and the metabolic activity decreases more quickly. Physiological metabolism activity and carbon metabolic group show obvious difference in different samples. Although metabolic groups of carbohydrates and carboxylic acids were the dominant groups in control sample and low concentration sample, the dominant group is main polyamines in middle and high concentration samples. Principal component analysis (PCA) shows the differences of carbon metabolism. Four samples could be separated by PC1. Substrates of high positive correlation coefficients with PC1 were L-asparagine, 4-hydroxy benzoic acid and D-malic acid, but D-galacturonic acid, i-erythritol, gamma-hydroxybutyric acid and glucose-1-phosphate showed high negative correlation. ARDRA analysis showed that the diversity index decreased, with the increased concentration of PAEs. In a short time, PAEs could increase the diversity of microbial genotype in soil.

Removal of fluoride by hydrous manganese oxide-coated alumina: performance and mechanism.

A novel hydrous-manganese-oxide-coated alumina (HMOCA) material was prepared through a redox process. The adsorbent was characterized by SEM, BET surface area measurement, XRD, pH(PZC) measurement, FTIR spectroscopy, and XPS. The manganese oxides were amorphous and manganese existed mainly in the +IV oxidation state. Batch and column experiments were carried out to investigate the adsorption potential of the adsorbent. Fluoride adsorption onto HMOCA followed the pseudo-second-order equation well with a correlation coefficient greater than 0.99. Both external and intraparticle diffusion contributed to the rate of transfer and removal. The adsorption of fluoride was thought to take place mainly by ion-exchange. Optimum removal of fluoride occurred in a pH range of 4.0-6.0. The maximum adsorption capacity calculated from the Langmuir model was 7.09 mg/g. The presence of HCO(3)(-), SO(4)(2-) and PO(4)(3-) had negative effects on the adsorption of fluoride. The adsorbed fluoride can be released by alkali solution. Column studies were performed and 669 bed volumes were treated with the effluent fluoride under 1.0mg/L at an influent F(-) concentration of 5.0mg/L and flow rate of 2.39 m(3)/(m(2)h) (empty bed contact time=7.5 min).