Performance and microbial population variation in a plug‐flow A2O process treating domestic wastewater with low C/N ratio

BACKGROUND: In this study, a plug‐flow A²O (anaerobic/anoxic/oxic) reactor, with a working volume of 52.5 L, was employed to investigate the performance of biological nutrients removal and microbial population variations when treating low C/N ratio domestic wastewater. RESULTS: Results showed that TN removal was significantly affected by the shortage of carbon source while phosphorus removal was only slightly affected. The effluent soluble orthophosphate‐phosphorus (SOP) concentration was lower than 0.50 mg L^?1 but the TN concentration was over 20 mg L^?1 when the C/N ratio was 4.43. There was denitrifying phosphorus removal in the anoxic reactor and this was enhanced by increasing the volume ratio of anoxic reactor and maintaining appropriate mixed liquor recycle rate. More than 60% of the SOP were removed in anoxic reactors by denitrifying phosphorus removal when the volume ratio of anaerobic/anoxic/oxic was 1/1.4/1.6 and the mixed liquor recycle rate was 250%. The TN concentration of effluent decreased to 11.34 mg L^?1 and SOP concentration was still lower than 0.5 mg L^?1 in this condition. The main microorganisms found in the process by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and the functional biodiversity are discussed. CONCLUSION: Traditional design and operating parameters of A²O are not appropriate for treating low C/N wastewater. Enhancing the denitrifying phosphorus removal ratio in an A²O process is an effective way to increase the removal rate of N and P from low C/N wastewater. Copyright © 2010 Society of Chemical Industry     

Batch treatment of liquid fraction of pig slurry by intermittent aeration: process simulation and microbial community analysis

BACKGROUND: Manure treatment in intensive livestock farming is required to reduce the risk of negative environmental impacts by nitrogen disposal. Biological removal through intermittent aeration in a single bioreactor is a suitable method for this purpose. The characteristic operation based on the alternation of oxic/anoxic phases confers these systems with certain particularities in terms of process modelling and of understanding the microbial interactions. RESULTS: The performance of a sequencing batch reactor (SBR) treating raw liquid fraction of pig slurry (LFPS) under loading rates of 0.13 g N L^?1 d^?1 was studied. Three different aeration strategies were applied: (1) constant airflow; (2) dissolved oxygen (DO) set‐point; and (3) DO‐based real‐time control. The comparatively low aeration intensity applied throughout the third strategy resulted in the process being performed mainly via nitrite, implying a reduction on the requirements of organic carbon and oxygen. However, a decrease in the nitrification rate was observed under those conditions. Experimental results were satisfactorily simulated by a mathematical model focused on organic carbon and nitrogen removal. Microbial community structure analysis through denaturing gradient gel electrophoretic profiling of 16S rDNA genes showed that the aeration exerted a strong influence on the dominant microbial populations. The presence of the ammonia‐oxidizing species Nitrosomonas europaea, and of denitrifying bacteria related to Thauera sp. and Ralstonia sp., was detected in the strategy at low DO. CONCLUSION: Dependence of model statement and parameter values on the bioreactor operational patterns and piggery wastewater composition was evidenced. Oxygen limitation was responsible for a significant microbial shift in SBR treating LFPS. Copyright © 2009 Society of Chemical Industry     

Characterization of microbial communities in a fluidized-pellet-bed bioreactor for wastewater treatment

In order to make clear the microbiological characteristics of the fluidized-pellet-bed bioreactor (FPB) which is a newly developed wastewater treatment device to perform coagulation, particle pelletization, biological degradation and solid-liquid separation in a single unit, the method of denaturing gradient gel electrophoresis (DGGE) was applied in this study paying attention to the microbial diversity of the granular sludge. Spread plate method was also used for enumeration of aerobic bacteria in unit weight of granular sludge. As a result, slight difference was found between the total aerobic bacteria at the bottom, middle, and top sections though the dissolved oxygen (DO) concentration decreased from about 3.5 mg/L at the bottom inlet to 0.23 mg/L at the top of the FPB bioreactor. From the DGGE finger printing, 17 common species were identified from all these sections, and certain specific species were also identified from each section. The comparability of the microbial communities in the three sections was 83.1%, indicating a very stable structure of the microbial communities. The 16 S rRNA sequence analysis results revealed that the 18 operational taxonomic units (OTUs) obtained all belong to Eubacteria. Among them 11 are Proteobacteria, 3 are Actinobacteria, 2 are low G + C gram-positive bacteria and the remaining 2 belong to other bacteria branches. The dominant microbial communities are typical aerobes or facultative anaerobes commonly encountered in conventional activated sludge.     

Assessment of the presence and dynamics of fungi in drinking water sources using cultural and molecular methods

A comparison of different isolation techniques and culture media for detection of filamentous fungi and yeasts in the aquatic environment revealed that the use of membrane filtration with the media dichloran rose bengal chloramphenicol (DRBC) optimized fungi detection in terms of abundance and variety in three untreated water sources with very different characteristics (surface water, spring water, and groundwater). The diversity of the fungi population captured by direct DNA extraction of fungi collected by membrane filtration was compared with the isolates obtained after selective growth using different culture media through amplification of the internal transcribed spacer gene and denaturing gradient gel electrophoresis (DGGE). The Czapek-Dox agar, Sabouraud dextrose agar, and DRBC media showed closer similarities to those obtained by the uncultured biomass for the different water sources. Based on these data and the best enumeration results, DRBC is recommended for the assessment of fungi in water sources using culture-based methods. DGGE was also used to monitor temporal variations in the fungal population structure and showed that each water matrix possessed a distinct population profile as well as that changes in the fungal community can be expected in the different matrices throughout the year.     

Characterizing Soy Sauce Moromi Manufactured by High‐Salt Dilute‐State and Low‐Salt Solid‐State Fermentation Using Multiphase Analyzing Methods

Present study was to characterize the physiochemical properties, free amino acids (FAAs), volatiles and microbial communities of various moromi, respectively sampled from different stages of high‐salt dilute‐state (HSDS) and low‐salt solid‐state (LSSS) fermentation, using multiphase analyzing methods. Phospholipid fatty acids (PLFA) analysis indicated that Gram‐positive bacteria were dominant bacteria and fungi were principal microbes. For DGGE analysis, dominant microbes in moromi were mainly fell into Weissella, Tetragenococcus, Candida, Pichia, and Zygosaccharomyces. During fermentation, the dominant microbes shifted from nonhalophilic and less acid‐tolerant species to halophilic and acid‐tolerant species. Total of 15 FAAs and 44 volatiles were identified in moromi, mainly Glu, Asp, Tyr, and acids, alcohols, esters, aldehydes, respectively. Odor activity values analysis suggested that the final moromi of LSSS fermentation had more complicated odors than that of HSDS fermentation. Conclusively, technological parameters, microbial communities, raw materials and fermentation process may result in the discrepancy of HSDS and LSSS moromi.     

跌水式人工湿地处理溢流雨污水的效能

为改善汉江水电站库区水质,考察了跌水式人工湿地应用于合流制排水系统雨季溢流污染的治理情况,以维护附近生态环境平衡.通过与普通湿地的比较,发现3级跌水式湿地对COD、氨氮、总氮及总磷的去除率均高于普通湿地,分别高13.1%、7.9%、6.1%和6.0%.跌水型湿地具有较好的溶解氧梯度,而普通湿地末端容易形成厌氧环境.Biolog微平板试验的结果表明,跌水型湿地中的微生物对糖类及其衍生物、氨基酸及其衍生物、脂肪酸及脂类、代谢中间产物及次生代谢物的利用程度更高.PCR-DGGE分子图谱技术分析表明,跌水型湿地的微生物种群普遍比普通湿地的微生物群落结构组成丰富,且特有的功能微生物与污染物去除相关.     

Characterization of microbial community during Asian dust events in Korea

An Asian dust event, also sometimes known as a Yellow Sand event, is a seasonal meteorological phenomenon affecting East Asia, typically in the early spring. Because of the significant ecological and health effects of these events on East Asia, and the large amount of dust that is transported from the desert in China to Korea and Japan, these events have been receiving increased attention. It is likely that these storms often provide long-range transport to various microorganisms. However, despite a certain level of attention to the chemical analysis of these storms, microbiological studies of Yellow Sand dust have been scarce. We collected a total of 30 microbiological air samples using a PM_2.5 cyclone sampler in Seoul, Korea from April 2007 to March 2008. Six of these samples were collected during Yellow Sand events, while 24 were from non-Yellow Sand events. Chemical analysis was performed on the samples using a thermal–optical transmittance (TOT) method. Total nucleic acids were also extracted, and the 16S rDNA was amplified by PCR and analyzed by denaturing gradient gel electrophoresis (DGGE). Dendrogram analysis, based on DGGE, indicated that the microbial profiles from the Yellow Sand were distinctive from those of the non-Yellow Sand samples. Microorganisms identified in Yellow Sand samples included Aquabacterium sp., Flavobacteriales bacterium sp., Prevotellaceae bacterium sp., and others, whereas microorganisms in non-Yellow Sand samples included Propionibacterium sp., Bacillus sp., Acinetobacter sp., and others. These results suggest that, as a result of Yellow Sand events, humans in the affected regions are exposed to communities of microorganisms that might cause various adverse health effects.