Pin Gao

Preparation and characterization of activated carbon produced from rice straw by (NH4)2HPO4 activation

Effects of different pretreatment protocols in (NH(4))(2)HPO(4) activation of rice straw on porous activated carbon evolution were evaluated. The pore structure, morphology and surface chemistry of obtained activated carbons were investigated by nitrogen adsorption, scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that pretreatment combining impregnation with (NH(4))(2)HPO(4) and preoxidation could significantly affect the physicochemical properties of prepared activated carbons. The apparent surface area and total pore volume as high as 1154 m(2)/g and 0.670 cm(3)/g were obtained respectively, when combined process of impregnation followed by preoxidation at 200°C and activation at 700°C was carried out. Meanwhile, the activated carbon yield and maximum methylene blue adsorption capacity up to 41.14% and 129.5 mg/g were achieved, respectively. The results exhibited that (NH(4))(2)HPO(4) could be an effective activating agent for producing activated carbons from rice straw.

Correlating microbial community compositions with environmental factors in activated sludge from four full-scale municipal wastewater treatment plants in Shanghai, China

Activated sludge system is an important process of domestic and industrial wastewater treatment containing highly diverse microbial communities. In this study, high-throughput sequencing was applied to examine the microbial community composition and diversity of activated sludge samples from four full-scale municipal wastewater treatment plants (WWTPs) in Shanghai. A relationship between microbial communities and environmental variables was examined. Proteobacteria was the most dominant phylogenetic group, followed by Bacteroidetes and Firmicutes. A total of 166 genera were commonly shared by all seven sludge samples, including Zoogloea, Dechloromonas, Thauera, Nitrospira, Arcobacter, etc. Besides these shared populations, certain unique bacterial populations were found abundant in individual sludge sample. Canonical correspondence analysis (CCA) indicated that influent COD and pH had the greatest influence on microbial community compositions, whereas dissolved oxygen (DO) exhibited the least influence. The operating process was likely to foster diversity of the microbial communities inhabiting the wastewater treatment facilities. Alternative operation methods including a fluctuation of anoxic, oxic, and anaerobic conditions were favorable for promoting the growth of diverse microbial populations in activated sludge systems.

Impacts of coexisting antibiotics, antibacterial residues, and heavy metals on the occurrence of erythromycin resistance genes in urban wastewater

Antibiotic resistance is a global challenge and represents a growing threat on human health worldwide. Wastewater treatment plants (WWTPs) are generally considered as hotspots for control and/or dissemination of antibiotic resistance. The role of antibiotics, antibacterial residues, and heavy metals played on the evolution and spread of antibiotic resistance is still not well understood. Here, the occurrence of antibiotics (i.e., macrolides, tetracyclines, sulfonamides, and quinolones), antibacterial residues (i.e., triclosan), as well as heavy metals (i.e., cadmium, chromium, copper, zinc, lead, and nickel) in urban wastewater was investigated. Also, the abundances of erythromycin resistance genes (ERY-ARGs) including ere(A), ere(B), mef(A)/mef(E), erm(A), erm(B), erm(C), and msr(A)/msr(B) genes were screened. A relationship between certain antibiotics, antibacterial residues, and heavy metals and ERY-ARGs was demonstrated. ERY presented significant correlations (0.883 < r < 0.929, P < 0.05) with ere(A), ere(B), and mef(A)/mef(E) genes, while tetracycline exhibited a significant correlation (r = 0.829, P < 0.05) with erm(B) genes. It is noteworthy that triclosan correlated significantly (0.859 < r < 0.956, P < 0.05) with ere(A), ere(B), mef(A)/mef(E), and erm(B) genes. In addition, significantly positive correlations (0.823 < r < 0.871, P < 0.05) were observed between zinc and lead and certain ERY-ARGs (i.e., ere(B), mef(A)/mef(E), erm(B), etc.). Further investigations should be involved to elucidate the co-selection and/or cross-selection mechanisms due to co-existence of these selective factors in urban wastewater.

From mesophilic to thermophilic digestion: the transitions of anaerobic bacterial, archaeal, and fungal community structures in sludge and manure samples.

The shift of microbial communities during a transition from mesophilic anaerobic digestion (MAD) to thermophilic anaerobic digestion (TAD) was characterized in two treatments. One treatment was inoculated with sludge and the other was inoculated with manure. In this study, methane was produced both in MAD and TAD, but TAD has slightly more methane produced than MAD. A broad phylogenetic spectrum of bacterial, archaeal, and fungal taxa at thermophilic conditions was detected. Coprothermobacter, Bacillus, Haloplasma, Clostridiisalibacter, Methanobacterium, Methanothermobacter, Saccharomycetales, Candida, Alternaria, Cladosporium, and Penicillium were found almost exclusively in TAD, suggesting their adaptation to thermophilic conditions and ecological roles in digesting the organic compounds. The characterization of the lesser-known fungal community revealed that fungi probably constituted an important portion of the overall community within TAD and contributed to this process by degrading complex organic compounds. The shift of the microbial communities between MAD and TAD implied that temperature drastically affected the microbial diversity in anaerobic digestion. In addition, the difference in microbial communities between sludge and manure indicated that different source of inoculum also affected the microbial diversity and community.

Isolation and identification of an iopromide-degrading strain and its application in an A2/O system

An iopromide (IOPr)-degrading bacterium was isolated from activated sludge of a wastewater treatment plant in Shanghai. Based on its morphology, physiological-biochemical characteristics and a phylogenetic analysis of its 16S rRNA sequence, the bacterium was identified and named as Pseudomonas sp. I-24. The optimum condition for degrading IOPr was at 30°C and pH 7.0. After 5 days, strain I-24 could degrade 30 mg/L IOPr by 99% in a basal salts medium with a 5% (V/V) inoculum and 200 mg/L starch as the primary substrate. When applied to an Anaerobic-Anoxic/Aerobic (A2/O) process, with the coexistence of other bacteria, the strain I-24 got lower (61.3%) IOPr removal, but in two A2/O systems (with and without I-24 inoculation), the CODcr removal were both approximately 95%. The trial dosed with strain I-24 showed better IOPr removal than the un-dosed one. I-24 sustained its abundance in the A2/O system during the experiment.

Modeling Dissolved Oxygen Effects on Biological Nutrient Removal in a Sequencing Batch Reactor with Activated Sludge Model 2d

The simulation software developed by C++ Build language based on activated sludge model 2d (ASM2d) was carried out to address the effects of dissolved oxygen (DO) on the behavior of biological nutrient removal in a sequencing batch reactor (SBR) system. Changes of COD, nitrogen and phosphorus concentrations could be reliably predicted according to the time arrangement of every phase adapted to the SBR conditions. Better performance of biological nutrient removal could be achieved as long as DO concentration was above 1.5 mg/L. If DO concentration was at a low level <1 mg/L, the growth and activity of microbes would be inhibited, especially for nitrifying organisms and phosphorus accumulating organisms (PAOs). Consequently, the nutrient removal performance of the process would be affected significantly. Therefore, maintaining DO concentration above 1.5 mg/L in the SBR activated sludge system was adaptive.