Effect of an activated carbon filter on the microbial quality of water.

Recently, there has been growing concern that microbial health hazards can be increased by the use of activated carbon filters in domestic water systems. The present study was undertaken to investigate the effect of carbon filters on the microbial content of water. Results indicated that the microbial content of filtered and unfiltered water increased to about the same level on overnight standing and, in both cases, was reduced by flushing the next day. In addition, the use of activated carbon for the filtration of contaminated well water over a period of 11 weeks had no effect on the total or coliform count. Under use conditions, activated carbon filters were found to have no significant effect on the number of bacteria present in the water.     

Pyrosequencing analysis of bacterial communities in drinking water biofilters receiving influents of different types

Biological activated carbon (BAC) filters are commonly used in the world for improvement of drinking water quality. The indigenous microbiota in BAC filters can play a crucial role in reduction or biotransformation of contaminants. Molecular analysis can enhance our understanding of ecological functions of the microbial communities in drinking water BAC filters. In this study, three laboratory-scale drinking water BAC filters receiving influents of different types were constructed. Differences of bacterial communities in the three BAC filters were characterized using 454 pyrosequencing analysis. Pyrosequencing analysis illustrated the usefulness in elucidating the bacterial community structure in drinking water biofilter. High bacterial diversity in granular activated carbon (GAC) samples from each BAC biofilter was observed. Proteobacteria was the largest bacterial phylum in each GAC sample, with a marked shift of the proportions of Alpha-, Beta-, and Gammaproteobacteria. The levels of dissolved organic carbon and ammonia nitrogen in the influents could affect the bacterial diversity and community composition in the BAC biofilters. This work might add some new insights into microbial community and its influential factors in drinking water biofilters.     

Effects of activated carbon and bacteriostatic filters on microbiological quality of drinking water

Three activated carbon filters for point-of-use water treatment were tested in laboratory and field studies for chemical removal and microbiological effects on water. All removed free available chlorine in municipally treated water to below the limit of detection, but removed only about 50 to 70% of the total available chlorine and 4 to 33% of the total organic carbon. Standard plate count bacteria in the effluent increased steadily with time for 3 weeks and remained elevated over the 8-week period of the study. Total coliform bacteria were found to persist and proliferate on the filters for several days after transient contamination of the influent water. Silver-containing activated carbon filters suppressed total coliform but not total bacterial growth. Pseudomonas aeruginosa was recovered from the effluents of all filters at some time during the tests.     

Effects of activated carbon and bacteriostatic filters on microbiological quality of drinking water.

Three activated carbon filters for point-of-use water treatment were tested in laboratory and field studies for chemical removal and microbiological effects on water. All removed free available chlorine in municipally treated water to below the limit of detection, but removed only about 50 to 70% of the total available chlorine and 4 to 33% of the total organic carbon. Standard plate count bacteria in the effluent increased steadily with time for 3 weeks and remained elevated over the 8-week period of the study. Total coliform bacteria were found to persist and proliferate on the filters for several days after transient contamination of the influent water. Silver-containing activated carbon filters suppressed total coliform but not total bacterial growth. Pseudomonas aeruginosa was recovered from the effluents of all filters at some time during the tests.     

油田外排水对干旱戈壁区人工湿地土壤微生物生物量的影响

为研究油田外排水对干旱戈壁区人工湿地土壤微生物生物量的影响,选择干旱戈壁区某油田外排水形成的湿地内坝内、内外坝间、外坝边缘土壤,及不受排水影响的对照土壤,采用磷脂脂肪酸(PLFA)方法,分析外排水对土壤细菌、真菌、放线菌生物量的影响。结果表明:湿地内坝内、内外坝间、外坝边缘土壤与对照土壤的pH和容重均无显著差异,内外坝间的土壤含水量、电导率、溶解性全盐和全碳含量最高,显著高于内坝内土壤;除含水量外,对照土壤的主要物理性质和养分特征与湿地内坝内、内外坝间、外坝边缘的土壤无显著差异。土壤总微生物量、细菌和真菌生物量从湿地内坝内至外坝边缘逐渐增加。土壤总微生物量、细菌、真菌、放线菌与全氮含量均呈显著正相关,丛枝菌根真菌与全碳呈显著正相关,真菌、丛枝菌根真菌与总石油烃呈显著正相关。研究结果表明,油田外排水增加了湿地外坝边缘的土壤微生物量。     

长期模拟升温对崇明东滩湿地土壤微生物生物量的影响

以崇明东滩芦苇湿地为对象,采用开顶室生长箱(Open top chambers OTCs)原位模拟大气升温试验,研究了连续升温8a对崇明东滩湿地0—40cm土层土壤微生物生物量碳氮含量的影响。结果表明:连续升温显著提高了崇明东滩湿地土壤微生物生物量碳氮含量,从土壤表层到深层(0—10,10—20,20—30,30—40cm),微生物生物量碳分别增加了39.32%、70.79%、65.20%、74.09%,微生物生物量氮分别增加了66.46%、178.27%、47.24%、64.11%。但升温对土壤微生物生物量的影响因不同土层和不同季节并未表现出统一的规律,长期模拟升温显著提高4月0—20cm土层和7月0—40cm土层微生物生物量碳氮含量,对10月0—40cm土层微生物生物量碳含量没有影响,但是显著提高了10月0—40cm土层微生物生物量氮含量,同时,微生物生物量碳氮比在7月也显著提高。相关分析表明:无论在升温条件还是在对照条件下,土壤温度、含水量、总氮与土壤微生物生物量碳氮及微生物生物量碳氮比均无相关关系,升温条件下,有机碳与微生物生物量碳氮含量以及微生物生物量碳氮比呈显著正相关,但是在对照条件下有机碳与微生物生物量碳氮含量以及微生物生物量碳氮比呈显著负相关。因此,土壤有机碳是影响土壤微生物生物量碳氮含量对长期模拟升温响应的重要生态因子。     

Long-term microbial community dynamics at two full-scale biotrickling filters treating pig house exhaust air

In this study, the microbial community structure of two full-scale biotrickling filters treating exhaust air from a pig housing facility were evaluated using 16S metabarcoding. The effect of inoculation with activated sludge of a nearby domestic waste water treatment plant was investigated, which is a cheap procedure and easy to apply in practice. The study was performed at a three-stage and a two-stage full-scale biotrickling filter; of which, only the latter was inoculated. Both biotrickling filters evolved towards a rather similar community over time, which differed from the one in the activated sludge used for inoculation. However, the bacterial population at both biotrickling filters showed small differences on the family level. A large population of heterotrophic bacteria, including denitrifying bacteria, was present in both biotrickling filters. In the non-inoculated biotrickling filter, nitrite-oxidizing bacteria (NOB) could not be detected, which corresponded with the incomplete nitrification leading to high nitrite accumulation observed in this system. Inoculation with the wide spectrum inoculum activated sludge had in this study a positive effect on the biotrickling filter performance (higher ammonia removal and lower nitrous oxide production). It could thus be beneficial to inoculate biotrickling filters in order to enrich NOB at the start-up, making it easier to keep the free nitrous acid concentration low enough to not be inhibited by it.     

Biofilm formation in drinking water affected by low concentrations of phosphorus

Abstract: There are geographical regions where microbial growth in drinking waters is limited by phosphorus instead of organic carbon. In these drinking waters even a low amount of phosphorus can strongly enhance microbial growth. The formation of biofilm can be limited by low availability of phosphorus in drinking waters with low content of phosphorus. The formation of biofilms on polyvinyl chloride plates was studied in laboratory experiments with water containing 48 microg/L assimilable organic carbon and 0.19 microg/L microbially available phosphorus. We found that low additions of phosphate (1-5 microg/L PO4(3-)-P) to water increased microbial growth in the water and in the biofilm. The effect of phosphorus on microbial growth could be detected by determining either the microbial cell production or the content of ATP in biofilms. Also, in steady-state biofilms, microbial concentrations were higher with phosphorus addition as enumerated by heterotrophic plate counts on R2A-agar and acridine orange direct counting. This work confirms the earlier findings of the importance of phosphorus for microbial growth in humic-rich drinking waters.     

Polaromonas and Hydrogenophaga species are the predominant bacteria cultured from granular activated carbon filters in water treatment

Aim:  Identification of the predominating cultivable bacteria in granular activated carbon (GAC) filters used in a variety of water treatment plants for selecting representative strains to study the role of bacteria in the removal of dissolved organic matter.
Methods and Results:  Bacterial isolates were collected from 21 GAC filters in nine water treatment plants treating either ground water or surface water with or without oxidative pretreatment. Enrichment of samples in dilute liquid medium improved culturability of the bacteria by approximately log unit, to 9% up to 70% of the total cell counts. Genomic fingerprinting and 16S rDNA sequence analysis revealed that most (68%) of the isolates belonged to the Betaproteobacteria and 25% were identified as Alphaproteobacteria . The number of different genera within the Betaproteobacteria was higher in the GAC filters treating ozonated water than in the filters treating nonozonated water. Polaromonas was observed in nearly all of the GAC filters (86%), and the genera Hydrogenophaga , Sphingomonas and Afipia were observed in 43%, 33% and 29% of the filter beds, respectively. AFLP analysis revealed that the predominating genus Polaromonas included a total of 23 different genotypes.
Conclusions:  This study is the first to demonstrate that Polaromonas , which has mainly been observed in ultraoligotrophic freshwater environments, is a common component of the microbial community in GAC filters used in water treatment.
Significance and Impact of the Study:  The predominance of ultraoligotrophic bacteria in the GAC filters indicates that very low concentrations of substrates are available for microbial growth. Polaromonas species are suited for further studies on the nutritional versatility and growth kinetics enabling the modelling of biodegradation processes in GAC filters.     

Soil Water Content and Organic Carbon Availability Are Major Determinants of Soil Microbial Community Composition

Exploration of environmental factors governing soil microbial community composition is long overdue and now possible with improved methods for characterizing microbial communities. Previously, we observed that rice soil microbial communities were distinctly different from tomato soil microbial communities, despite management and seasonal variations within soil type. Potential contributing factors included types and amounts of organic inputs, organic carbon content, and timing and amounts of water inputs. Of these, both soil water content and organic carbon availability were highly correlated with observed differences in composition. We examined how organic carbon amendment (compost, vetch, or no amendment) and water additions (from air dry to flooded) affect microbial community composition. Using canonical correspondence analysis of phospholipid fatty acid data, we determined flooded, carbon-amended (+C) microcosm samples were distinctly different from other +C samples and unamended (–C) samples. Although flooding without organic carbon addition influenced composition some, organic carbon addition was necessary to substantially alter community composition. Organic carbon availability had the same general effects on microbial communities regardless of whether it was compost or vetch in origin. In addition, flooded samples, regardless of organic carbon inputs, had significantly lower ratios of fungal to bacterial biomarkers, whereas under drier conditions and increased organic carbon availability the microbial communities had higher proportions of fungal biomass. When comparing field and microcosm soil, flooded +C microcosm samples were most similar to field-collected rice soil, whereas all other treatments were more similar to field-collected tomato soil. Overall, manipulating water and carbon content selected for microbial communities similar to those observed when the same factors were manipulated at the field scale.     

Effect of Elevated CO2 and Drought on Soil Microbial Communities Associated with Andropogon gerardii

Our understanding of the effects of elevated atmospheric CO2, singly and In combination with other environmental changes,on plant-soil interactions is incomplete. Elevated CO2 effects on C4 plants, though smaller than on C3 species, are mediated mostly via decreased stomatal conductance and thus water loss. Therefore, we characterized the interactive effect of elevated CO2 and drought on soil microbial communities associated with a dominant C4 prairie grass, Andropogon gerardii Vitman. Elevated CO2 and drought both affected resources available to the soil microbial community. For example, elevated CO2 increased the soil C:N ratio and water content during drought, whereas drought alone decreased both. Drought significantly decreased soil microbial biomass. In contrast, elevated COz increased biomass while ameliorating biomass decreases that were induced under drought. Total and active direct bacterial counts and carbon substrate use (overall use and number of used sources) increased significantly under elevated CO2. Denaturing gradient gel electrophoresis analysis revealed that drought and elevated CO2, singly and combined, did not affect the soil bacteria community structure.We conclude that elevated CO2 alone increased bacterial abundance and microbial activity and carbon use, probably in response to increased root exudation. Elevated CO2 also limited drought-related impacts on microbial activity and biomass,which likely resulted from decreased plant water use under elevated CO2. These are among the first results showing that elevated CO2 and drought work in opposition to modulate plant-associated soil-bacteria responses,which should then Influence soil resources and plant and ecosystem function.     

Heterogeneity of microbial community structures inside the up-flow biological activated carbon (BAC) filters for the treatment of drinking water

Filtration using biological activated carbon (BAC) performs well in the removal of biodegradable dissolved organic carbon from water sources. The application of ozonation followed by up-flow BAC filtration has gained increasing attention in the world scale. In this study, a pilotscale up-flow BAC filtration system was constructed for the treatment of polluted lake water. The operational results indicated that this BAC filtration system could effectively remove organic matter. Spatial heterogeneity of the microbial community structure inside the BAC filtration system was identified using bacterial 16S rRNA clone library analysis. A marked decrease of microbial diversity in the BAC filtration system was observed along the flow path. Alphaproteobacteria, Gammaproteobacteria and Acidobacteria were found to be the major bacterial groups in the BAC filters. Moreover, Novosphingobium aromaticivorans-like microorganisms were detected. This work might add some new insights towards microbial communities in regards to BAC filtration for the treatment of drinking water.     

蚂蚁筑巢对西双版纳热带森林土壤微生物生物量碳及熵的影响

蚂蚁筑巢能够改变热带森林土壤理化环境,从而对土壤微生物生物量碳及熵的时空动态产生重要影响.本研究以西双版纳高檐蒲桃热带森林群落为对象,采用氯仿熏蒸法对蚂蚁巢地和非巢地土壤微生物生物量碳及熵时空动态进行测定.结果表明: 1)蚁巢地平均微生物生物量碳及熵(1.95 g·kg^-1,6.8%)显著高于非巢穴(1.76 g·kg^-1,5.1%);蚁巢地和非蚁巢地土壤微生物生物量碳呈单峰型时间变化趋势,而土壤微生物熵呈“V”型变化格局.2)蚁巢地和非巢地土壤微生物生物量碳及熵均具有明显的垂直变化:微生物生物量碳随土层加深显著降低,微生物熵则沿土层加深显著升高,但蚁巢微生物生物量碳及熵的垂直变化较非巢穴显著. 3)蚂蚁筑巢引起了巢内水分和温度的显著改变,进而影响土壤微生物生物量碳及熵的时空动态.土壤水分分别解释微生物生物量碳及熵的66%～83%和54%～69%,而土壤温度分别解释土壤微生物生物量碳及熵的71%～86%和67%～76%. 4)蚂蚁筑巢引起土壤理化性质变化对土壤微生物生物量碳和熵产生重要影响.蚁巢土壤微生物生物量碳与土壤有机碳、温度、全氮、含水率呈极显著正相关,与容重、硝态氮,水解氮呈显著正相关,与土壤pH呈极显著负相关;除土壤微生物熵与pH呈显著正相关外,与其他土壤理化指标均呈显著负相关.土壤总有机碳、全氮和温度对微生物生物量碳的贡献最大,而土壤总有机碳和全氮对微生物熵的负作用最小.因此,蚂蚁筑巢能够显著改变微生境(如土壤水分与温度)及土壤理化性质(如总有机碳及全氮),进而调控热带森林土壤微生物生物量碳及熵的时空动态.     

Effects of Soil Organic Matter Properties and Microbial Community Composition on Enzyme Activities in Cryoturbated Arctic Soils

Enzyme-mediated decomposition of soil organic matter (SOM) is controlled, amongst other factors, by organic matter properties and by the microbial decomposer community present. Since microbial community composition and SOM properties are often interrelated and both change with soil depth, the drivers of enzymatic decomposition are hard to dissect. We investigated soils from three regions in the Siberian Arctic, where carbon rich topsoil material has been incorporated into the subsoil (cryoturbation). We took advantage of this subduction to test if SOM properties shape microbial community composition, and to identify controls of both on enzyme activities. We found that microbial community composition (estimated by phospholipid fatty acid analysis), was similar in cryoturbated material and in surrounding subsoil, although carbon and nitrogen contents were similar in cryoturbated material and topsoils. This suggests that the microbial community in cryoturbated material was not well adapted to SOM properties. We also measured three potential enzyme activities (cellobiohydrolase, leucine-amino-peptidase and phenoloxidase) and used structural equation models (SEMs) to identify direct and indirect drivers of the three enzyme activities. The models included microbial community composition, carbon and nitrogen contents, clay content, water content, and pH. Models for regular horizons, excluding cryoturbated material, showed that all enzyme activities were mainly controlled by carbon or nitrogen. Microbial community composition had no effect. In contrast, models for cryoturbated material showed that enzyme activities were also related to microbial community composition. The additional control of microbial community composition could have restrained enzyme activities and furthermore decomposition in general. The functional decoupling of SOM properties and microbial community composition might thus be one of the reasons for low decomposition rates and the persistence of 400 Gt carbon stored in cryoturbated material.     

Performance comparison of experimental constructed wetlands with different filter media and macrophytes treating industrial wastewater contaminated with lead and copper

The aim of this study was to investigate the treatment efficiency of passive vertical-flow wetland filters containing different macrophytes (Phragmites and/or Typha) and granular media with different adsorption capacities. Gravel, sand, granular activated carbon, charcoal and Filtralite (light expanded clay) were used as filter media. Different concentrations of lead and copper sulfate were added to polluted urban stream inflow water to simulate pretreated mine wastewater. The relationships between growth media, microbial and plant communities as well as the reduction of predominantly lead, copper and five-day biochemical oxygen demand (BOD5) were investigated. An analysis of variance showed that concentration reductions (mg l(-1)) of lead, copper and BOD5 were significantly similar for the six experimental wetlands. Microbial diversity was low due to metal pollution and similar for all filters. There appears to be no additional benefit in using adsorption media and macrophytes to enhance biomass performance during the first 10 months of operation.     

Use of activated carbon as a support medium for H<Subscript>2</Subscript>S biofiltration and effect of bacterial immobilization on available pore surface

The use of support media for the immobilization of microorganisms is widely known to provide a surface for microbial growth and a shelter that protects the microorganisms from inhibitory compounds. In this study, activated carbon is used as a support medium for the immobilization of microorganisms enriched from municipal sewage activated sludge to remove gas-phase hydrogen sulfide (H₂S), a major odorous component of waste gas from sewage treatment plants. A series of designed experiments is used to examine the effect on bacteria-immobilized activated carbon (termed biocarbon) due to physical adsorption, chemical reaction, and microbial degradation in the overall removal of H₂S. H₂S breakthrough tests are conducted with various samples, including microbe-immobilized carbon and Teflon discs, salts-medium-washed carbon, and ultra-pure water-washed carbon. The results show a higher removal capacity for the microbe-immobilized activated carbon compared with the activated carbon control in a batch biofilter column. The increase in removal capacity is attributed to the role played by the immobilized microorganisms in metabolizing adsorbed sulfur and sulfur compounds on the biocarbon, hence releasing the adsorption sites for further H₂S uptake. The advantage for activated carbon serving as the support medium is to adsorb a high initial concentration of substrate and progressively release this for microbial degradation, hence acting as a buffer for the microorganisms. Results obtained from surface area and pore size distribution analyses of the biocarbon show a correlation between the available surface area and pore volume with the extent of microbial immobilization and H₂S uptake. The depletion of surface area and pore volume is seen as one of the factors which cause the onset of column breakthrough. Microbial growth retardation is due to the accumulation of metabolic products (i.e., sulfuric acid); and a lack of water and nutrient salts in the batch biofilter are other possible causes of column breakthrough.     

黑土肥沃耕层构建效应

东北黑土区粘重的耕地土壤,经多年不合理耕作后产生了较厚的“犁底层”,成为该地区农业生产的主要限制因子.本研究利用田间试验,分析了构建肥沃耕层对作物产量、土壤物理性质、土壤含水量和微生物数量的影响.结果表明：肥沃耕层构建后,土壤形成了一个深厚的耕层,作物产量增加.与常规耕作法相比,向20～35 cm土层施用秸秆和有机肥使土壤容重分别降低了9.88%和6.20%,总孔隙度分别增加了9.58%和6.02%,饱和导水率分别增加了167.99%和73.78%,表明肥沃耕层的构建能够有效地改善土壤的通气透水性,提高大气降水的入渗能力;向“犁底层”施用秸秆和有机肥处理0～100 cm土层土壤含水量和水分利用效率均显著高于常规耕作法,该处理玉米出苗率与0～35 cm土层土壤含水量之间呈显著正相关关系.肥沃耕层的构建由于增加了土壤中的有机碳源和透气性,从而增加了土壤中的微生物数量.     

水分对武夷山草甸土壤有机碳激发效应的影响

水分是影响土壤有机碳激发效应的重要因子,但水分如何影响山地草甸土有机碳激发效应尚不清楚.本试验以武夷山高海拔(2130 m)山地草甸土为研究对象,通过室内添加13C标记的葡萄糖结合控制土壤水分(30％FWC和60％ FWC,FWC为田间持水量),进行为期126 d的室内培养试验,定期测定CO2浓度和13C-CO2丰度值...     

Impact of Carbon and Flooding on the Metabolic Diversity of Microbial Communities in Soils

The assumption that carbon and soil water content are major determinants of microbial community structure and function is rarely questioned because of substantial evidence of the impacts of these variables on specific populations and functions. The significance of carbon and water for metabolic diversity at the microbial community level was tested on the field scale in agricultural plots varying in carbon inputs and in whether they were flooded. Surface soils in which rice straw was incorporated or burned and which were flooded or unflooded were sampled at monthly intervals three times during the flooded winter period (January to March) and again 1 month postdraining. Biomass carbon and nitrogen were not affected by treatments, active bacterial counts showed slight increases, and respiration rates were increased by carbon inputs and flooding. Biolog microplates were inoculated with soil extracts to quantify the metabolic diversity of the soil microbial community. Canonical correspondence analysis and the Monte Carlo permutation testing showed that differences in substrate utilization patterns were significantly related (P < 0.001) to carbon and flooding treatments. Biolog substrates whose metabolism was altered by the treatments were consistent across dates and tended to be positively related (utilization enhancement) to carbon inputs and negatively related to winter flooding. The importance of carbon as an environmental variable increased over time after straw treatment, whereas the importance of water became evident after flooding and decreased after drainage. The effect of long-term rice straw incorporation on substrate utilization patterns at another field site was consistent with these results despite the dissimilarities of the two soils.     

黑土肥沃耕层构建效应

东北黑土区粘重的耕地土壤,经多年不合理耕作后产生了较厚的“犁底层”,成为该地区农业生产的主要限制因子.本研究利用田间试验,分析了构建肥沃耕层对作物产量、土壤物理性质、土壤含水量和微生物数量的影响.结果表明：肥沃耕层构建后,土壤形成了一个深厚的耕层,作物产量增加.与常规耕作法相比,向20～35 cm土层施用秸秆和有机肥使土壤容重分别降低了9.88%和6.20%,总孔隙度分别增加了9.58%和6.02%,饱和导水率分别增加了167.99%和73.78%,表明肥沃耕层的构建能够有效地改善土壤的通气透水性,提高大气降水的入渗能力;向“犁底层”施用秸秆和有机肥处理0～100 cm土层土壤含水量和水分利用效率均显著高于常规耕作法,该处理玉米出苗率与0～35 cm土层土壤含水量之间呈显著正相关关系.肥沃耕层的构建由于增加了土壤中的有机碳源和透气性,从而增加了土壤中的微生物数量.