Fate of viruses in artificial wetlands

Little is known about the ability of wetlands to remove disease-causing viruses from municipal wastewater. In this study we examined the survival of several indicators of viral pollution (indigenous F-specific bacteriophages, seeded MS2 bacteriophage, and seeded human poliovirus type 1) applied in primary municipal wastewater to artificial wetland ecosystems. Only about 1% of the indigenous F-specific RNA bacteriophages survived flow through the vegetated wetland beds at a 5-cm-day-1 hydraulic application rate during the period from June through December 1985. The total number of indigenous F-specific bacteriophages (F-specific RNA and F-specific DNA phages) was also reduced by about 99% by wetland treatment, with the mean inflow concentration over the period of an entire year reduced from 3,129 to 33 PFU ml-1 in the outflow of a vegetated bed and to 174 PFU ml-1 in the outflow of an unvegetated bed. Such superior treatment by the vegetated bed demonstrates the significant role of higher aquatic plants in the removal process. Seeded MS2 bacteriophage and seeded poliovirus were removed more efficiently than were the indigenous bacteriophages, with less than 0.2% of MS2 and 0.1% of the poliovirus surviving flow at the same hydraulic application rate. The decay rate (k) of MS2 in a stagnant wetlands (k = 0.012 to 0.028 h-1) was lower than that for flowing systems (k = 0.44 to 0.052 h-1), reflecting the enhanced capacity for filtration or adsorption of viruses by the root-substrate complex (and associated biofilm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Fate and distribution of arsenic in laboratory-scale subsurface horizontal-flow constructed wetlands treating an artificial wastewater

Knowledge regarding the fate, accumulation and distribution of arsenic inside constructed wetlands is still insufficient. Based on a complete mass balance analysis, the aim of this study was to investigate the fate and distribution of As in distinct wetland compartments and different segments along the wetland gradient. Experiments were carried out in laboratory-scale wetland systems, two planted with Juncus effusus and one unplanted, using an As-containing artificial wastewater. The obtained results revealed that the planted wetlands have a substantially higher As-mass retention capacity (59–61% of the total As inflow) than wetlands without plantation (only 44%). However, different loads of organic carbon within the inflowing artificial wastewater showed no remarkable influence on As-mass retention in the planted wetlands. Nearly 47–52% of the total inflowing As mass was found to be retained within the first half of the planted wetlands and this retention decreased step by step along the flow path. In contrast, only 28% of the total inflowing As mass was retained within the first half of the unplanted wetland. In general, a different fate and distribution of As was observed inside the planted and unplanted wetlands. Higher As concentrations were exhibited by the plant roots (51.5–161.5 mg As kg^?1 dry wt.) compared to the shoots (1.1–6.4 mg As kg^?1 dry wt.). Analysis of the total As-mass balance in the planted wetlands revealed that nearly 44–49% of the total inflowing As was recovered or concentrated within the plant roots, only 1% was sequestered within the plant shoots, 7–10% were entrapped or deposited within the gravel bed sediments, 2–3% were retained in the standing pore water, 39–41% were flushed out as outflow and the remaining 1–2% is still considered to be unaccountable. Total As accumulation in the plant shoots made a small contribution to the mass balance, and plant root biomass was found to be the most important compartment for As retention. In contrast, nearly 11% of the total inflowing As were found in the sediment, 2% in the standing pore water, 57% in the outflow and a substantially higher portion (nearly 30%) remained unaccountable in the unplanted bed, which might be released as volatile As compounds or lost from the system due to various unknown reasons. The results indicate that plants have a remarkable effect on As retention and stability of already retained As; hence planted wetlands might be a suitable option for treating As-contaminated wastewater.     

模拟人工湿地处理污水的试验研究

运用自行设计的人工湿地模拟装置处理人工污水,研究了污水在系统中的净化动态和最佳停留时间,并初步探讨了pH、Eh和气温对净化效率的影响。试验结果表明,有树系统5天内的净化率分别为:BOD_594.8％,总氮93.0％,总磷95.0％,氨氮99.5％。当Pb、Cd浓度分别在2500mg/L和250mg/L以内时,系统对Pb、Cd的净化率为99.9％以上,并可在3小时内基本完成。即使在“土壤”含Pb量达2.86g/kg和含Cd量达0.29g/kg的情况下,系统对Pb、Cd的净化率仍可达96.2—98.5％。     

Waterbird use of artificial wetlands in an Australian urban landscape

With the loss of natural wetlands, artificial wetlands are becoming increasingly important as habitat for waterbirds. We investigated the relationships between waterbirds and various biophysical parameters on artificial wetlands in an Australian urban valley. The densities (birds per hectare) of several species were correlated (mostly positively) with wetland area, and correlations were observed between certain species and other physical and water chemistry variables. Waterbird community structure, based on both abundance (birds per wetland) and density data, was most consistently positively correlated with the relative amount of wetland perimeter that was vegetated, surface area, distance to nearest wetland, public accessibility and shoreline irregularity. We also compared the relative use of the two types of urban wetlands, namely urban lakes and stormwater treatment wetlands, and found for both abundance and density that the number of individuals and species did not vary significantly between wetland types but that significant differences were observed for particular species and feeding guilds, with no species or guild being more abundant or found in greater density on an urban lake than a stormwater treatment wetland. Designing wetlands to provide a diversity of habitat will benefit most species.     

Fate of 130 hemagglutinins from different influenza A viruses

In this study, we use our probabilistic models to analyze 130 hemagglutinins from different influenza A virus in order to gain the insight into their fate. The results provide three lines of evidence regarding the H5, H6, and H9 hemagglutinins: (i) the H5 hemagglutinins are more sensitive to mutations, this is the current state of the H5, H6, and H9 hemagglutinins; (ii) the H5 hemagglutinins had experienced more mutations in the past, this is the history of the H5, H6, and H9 hemagglutinins; and (iii) the H6 hemagglutinins has a bigger potential towards future mutations, this is the future of the H5, H6, and H9 hemagglutinins. Furthermore, this study gives two clues on the mutation tendency that is a degeneration process and the species susceptibility that is the chickens and ducks.     

Fate of metallic engineered nanomaterials in constructed wetlands: prospection and future research perspectives

Metallic engineered nanomaterials (ENMs) undergo various transformations in the environment which affect their fate, toxicity and bioavailability. Although constructed wetlands (CWs) are applied as treatment systems for waste streams potentially containing metallic ENMs, little is known about the fate and effects of ENMs in CWs. Hence, literature data from related fields such as activated sludge wastewater treatment and natural wetlands is used to predict the fate and effects of ENMs in CWs and to analyze the risk of nanomaterials being released from CWs into surface waters. The ENMs are likely to reach the CW (partly) transformed and the transformations will continue in the CW. The main transformation processes depend on the type of ENM and the ambient environmental conditions in the CW. In general, ENMs are expected to undergo sorption onto (suspended) organic matter and plant roots. Although the risk of ENMs being released at high concentrations from CWs is estimated low, caution is warranted because of the estimated rise in the production of these materials. As discharge of (transformed) ENMs from CWs during normal operation is predicted to be low, future research should rather focus on the effects of system malfunctions (e.g. short-circuiting). Efficient retention in the CW and increasing production volumes in the future entail increasing concentrations within the CW substrate and further research needs to address possible adverse effects caused.     

盐城自然保护区两种人工湿地模式评价

在用能值分析对盐城自然保护区两种人工湿地研究的基础上 ,对其可持续发展提出了建议。在缓冲区建立以获取经济效益为目的的鱼塘是必要的 ,它为自然保护事业的发展提供了足够的资金反馈 ;为了减轻由于湿地开发带来的珍禽的生境压力 ,在核心区的边缘必须建立以招鸟为目的的水禽湖。水禽湖对鱼塘的面积比须在 0 .1 9和 8.0 0之间。当比例是0 .1 9时 ,系统获得最大经济效益 2 .1 3× 1 0 3US＄ /a.hm2 ,当比例是 8.0 0时 ,系统获得最大生态效益 1 .1 8× 1 0 3US＄ /a.hm2当比例是 0 .3 1时 ,系统获得相等的生态和经济效益 ,其和是 3 .79× 1 0 2 US＄ /a.hm2 比例 0 .3 1是保护区较优的选择。在此模式运作几年后 ,鱼塘须被改成水禽湖 ,且被划入核心区进行严格管理 ,核心区被扩大。同时 ,建议在江苏省“海上苏东”发展计划对海涂湿地大力开发的同时 ,必须建立一定比例的适于珍禽栖息活动的人工湿地 ,扩大自然保护规模 ,以保护珍贵的生物多样性资源。     

Fate of human enteric viruses, coliphages, and Clostridium perfringens during drinking-water treatment.

The elimination of human enteric viruses, coliphages, and Clostridium perfringens was studied during a conventional complete drinking-water treatment process. The respective concentrations (geometric mean) of these microorganisms in 100-L samples of river water were, respectively, as follows: viruses, 79 mpniu (most probable number of infectious units) per 100 L, coliphages, 6565 pfu (plaque-forming units) per 100 L. and clostridia, 11,349 cfu (colony-forming units) per 100 L. After predisinfection, flocculation with alum, and settling, human enteric viruses were not detected in any of the 100-L samples (less than 4 mpniu/100 L), but coliphages were detected in 7 of 14 samples and clostridia in 15 of 16 samples. In filtered water samples, human enteric viruses were detected in 2 of 31 samples, coliphages in 10 of 33, and clostridia in 17 of 33. Finished water was free of human enteric viruses (0/162 samples), but coliphages were detected in one sample (1.5 pfu/100 L) and clostridia in three, at 1.0, 4.1, and 7.0 cfu/100 L. It thus appears that coliphages and clostridia, which are present in larger numbers than viruses in river water and which may have similar resistance to drinking-water treatments, may be useful for estimating the level of treatment attained when large volumes of water (1000 L or greater) are sampled.     

Phospholipid-based artificial viruses assembled by multivalent cations

Self-assembled DNA delivery systems based on cationic lipids are simple to produce and weakly hazardous in comparison with viral vectors, but possess a significant toxicity at high doses. Phospholipids are in contrast intrinsically safe; yet their association with DNA is problematic because of unfavorable electrostatic interactions. We achieve the phospholipid-DNA complexation through the like-charge attraction induced by cations. Monovalent cations are inappropriate due to their poor binding affinity with lipids as inferred from electrophoretic mobility, whereas x-ray diffractions reveal that with multivalent cations, DNA is complexed within an inverted hexagonal liquid-crystalline phase. Coarse-grained Monte Carlo simulations confirm the self-assembly of a DNA rod wrapped into a lipid layer with cations in between acting as molecular glue. Transfection experiments performed with Ca2+ and La3+ demonstrate efficiencies surpassing those obtained with optimized cationic DOTAP-based systems, while preserving the viability of cells. Inspired by bacteriophages that resort to polycations to compact their genetic materials, complexes assembled with tetravalent spermine achieve unprecedented transfection efficiencies for phospholipids. Influence of complex growth time, lipid/DNA mass ratio, and ion concentration are examined. These complexes may initiate new developments for nontoxic gene delivery and fundamental studies of biological self-assembly.     

Nonviral gene delivery: Towards artificial viruses

Several limitations to nonviral gene delivery have been overcome. Small nanometric particles have been obtained by condensation ofDNA with a polymerizable cation followed by DNA template-directed homopolymerization of the vector. Targeting of specific cell types has been achieved by using polyethylenimine (PEI), a cationic polymer, coupled to cell ligands such as galactose or small RGD peptide that allows cell entry by a receptor-mediated endocytosis pathway. Escape of the DNA complexes from the endosomes is favored by the ‘proton sponge’ effect as a consequence of the high buffering capacity of PEI. The last barrier to gene delivery, i.e. the nuclear membrane, can be crossed at the level of the nuclear pore complexes, by using nuclear localization signal DNA molecule conjugates. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of the diversity of root-associated bacteria in Phragmites australis and Typha angustifolia L. in artificial wetlands

Common reed (Phragmites australis) and narrow-leaved cattail (Typha angustifolia L.) are two plant species used widely in artificial wetlands constructed to treat wastewater. In this study, the community structure and diversity of root-associated bacteria of common reed and narrow-leaved cattail growing in the Beijing Cuihu Wetland, China, were investigated using 16S rDNA library and PCR–denaturing gradient gel electrophoresis methods. Root-associated bacterial diversity was higher in common reed than in narrow-leaved cattail. In both plant species, the dominant root-associated bacterial species were Alpha, Beta and Gamma Proteobacteria, including the genera Aeromonas, Hydrogenophaga, Ideonella, Uliginosibacterium and Vogesella. Acidobacteria, Actinobacteria, Nitrospirae and Spirochaetes were only found in the roots of common reed. Comparing the root-associated bacterial communities of reed and cattail in our system, many more species of bacteria related involved in the total nitrogen cycle were observed in reed versus cattail, while species involved in total phosphorus and organic matter removal were mainly found in cattail. Although we cannot determine their nutrient removal capacity separately, differences in the root-associated bacterial communities may be an important factor contributing to the differing water purification effects mediated by T. angustifolia and P. australis wetlands. Thus, further work describing the ecosystem functions of these bacterial species is needed, in order to fully understand how effective common reed- and narrow-leaved cattail-dominated wetlands are for phytoremediation.     

Treatment of an artificial sulphide containing wastewater in subsurface horizontal flow laboratory-scale constructed wetlands

In general, treatment wetlands seem to be a potential method of tackling the sulphide problem of post-treatment of anaerobic digester effluents.Because of insufficient practical experience and lack of knowledge of sulphide removal, sulphur transformation was investigated, particularly in horizontal subsurface flow constructed wetlands (depth of 35 cm) under laboratory-scale conditions with artificial wastewater.The plants affected a clear stimulation of the sulphide and ammonia removal rates. Sulphide concentration in the range of 1.5–2.0 mg l⁻¹ was tolerated by the plants and completely removed in the planted model wetlands; sulphide concentration of >2.0 mg l⁻¹ caused instabilities in sulphide and nitrogen removal. Area-specific sulphide removal rates of up to 94 mg sulphide m⁻² d⁻¹ were achieved in the planted beds at hydraulic retention times of 2.5 d. Sulphate affected the sulphide removal. While in the unplanted control bed an almost stable removal in the range of 150–300 mg N m⁻² d⁻¹ was observed variations of hydraulic retention time, sulphide and sulphate concentrations influenced the ammonia removal rate within the planted beds in a broader range (600–1400 mg N m⁻² d⁻¹).These results showed that nitrification, sulphide oxidation, denitrification and sulphate reduction can occur simultaneously in the rhizosphere of treatment wetlands caused by dynamic redox gradients (aerobic–anaerobic) conditions.     

Fate of bacterial indicators,viruses and protozoan parasites in a wastewater multi-component treatment system

The extent of reduction in selected microrganisms was tested at a multi-component wastewater treatment plant that treats sewage for a potential re-use in agriculture. The aim of the investigation was to evaluate possible reciprocal correlation among the different microrganisms and to compare the removal of two encysted pathogenic protozoa with that of microbial indicators, Clostridium perfringens spores, enteroviruses and bacteriophages. Samples collected included the raw wastewater, the chlorinated effluent and the effluent after an ultraviolet light treatment. All of the raw sewage samples were positive for Cryptosporidium oocysts and Giardia cysts, as well as for the other microorganisms tested but the bacteriophage B40-8. The data obtained confirm the removal efficiency of the entire process for indicator bacteria but also show the low and variable removal efficiency for the other microbial parameters, such as Giardia and Cryptosporidium, enteroviruses and Clostridium perfringens spores. Reciprocal correlation between Cryptosporidium and Giardia (oo)cysts and the other microbial groups was not demonstrated. The results confirm the resistance of Clostridium perfringens spores, enteroviruses and protozoa to chlorination and demonstrate the relative persistence of these organisms in the effluents even during the ultraviolet light treatment. The yields also emphasise the influence of the analytical method for the determination of protozoan parasites.     

Transmission of avian influenza A viruses among species in an artificial barnyard

Waterfowl and shorebirds harbor and shed all hemagglutinin and neuraminidase subtypes of influenza A viruses and interact in nature with a broad range of other avian and mammalian species to which they might transmit such viruses. Estimating the efficiency and importance of such cross-species transmission using epidemiological approaches is difficult. We therefore addressed this question by studying transmission of low pathogenic H5 and H7 viruses from infected ducks to other common animals in a quasi-natural laboratory environment designed to mimic a common barnyard. Mallards (Anas platyrhynchos) recently infected with H5N2 or H7N3 viruses were introduced into a room housing other mallards plus chickens, blackbirds, rats and pigeons, and transmission was assessed by monitoring virus shedding (ducks) or seroconversion (other species) over the following 4 weeks. Additional animals of each species were directly inoculated with virus to characterize the effect of a known exposure. In both barnyard experiments, virus accumulated to high titers in the shared water pool. The H5N2 virus was transmitted from infected ducks to other ducks and chickens in the room either directly or through environmental contamination, but not to rats or blackbirds. Ducks infected with the H7N2 virus transmitted directly or indirectly to all other species present. Chickens and blackbirds directly inoculated with these viruses shed significant amounts of virus and seroconverted; rats and pigeons developed antiviral antibodies, but, except for one pigeon, failed to shed virus.     

Effect of plant and artificial aeration on solids accumulation and biological activities in constructed wetlands

In constructed wetlands, solids accumulation may have two consequences with opposing effects on treatment efficiency: it decreases the longevity by reducing void space and it enhances biological activity by favoring biofilm development. The goal of our study was to estimate the effect of plants (presence and species) and artificial aeration on solids accumulation (volatile and inorganic). The horizontal and vertical distribution of solids was sampled using solids traps in 12 constructed wetland mesocosms (5 years old). Microbial density and activity were estimated in the biological fraction of the sampled solids. The effect of plant presence reduced accumulated solids by 26% and sulphide content by 50% sulphide content. There was more solids accumulation in Typha angustifolia units than in Phragmites australis. Also, T. angustifolia generated more biological activities at the surface and close to the inlet while conditions were more homogeneous throughout P. australis units. Aeration (1) stimulated biofilm development at the inlet of planted beds, (2) seemed to reduce mineral matter accumulation and (3) generated the same pattern of activities in planted beds enabling to reach a total nitrogen removal rate of up to 0.65 g N m^?2 d^?1.     

Fate of heavy metals in vertical subsurface flow constructed wetlands treating secondary treated petroleum refinery wastewater in Kaduna,Nigeria

This study examined the performance of pilot-scale vertical subsurface flow constructed wetlands (VSF–CWs) planted with three indigenous plants, i.e. Typha latifolia, Cyperus alternifolius, and Cynodon dactylon, in removing heavy metals from secondary treated refinery wastewater under tropical conditions. The T. latifolia-planted VSF–CW had the best heavy metal removal performance, followed by the Cyperus alternifolius-planted VSF–CW and then the Cynodon dactylon-planted VSF–CW. The data indicated that Cu, Cr, Zn, Pb, Cd, and Fe were accumulated in the plants at all the three VSF–CWs. However, the accumulation of the heavy metals in the plants accounted for only a rather small fraction (0.09–16%) of the overall heavy metal removal by the wetlands. The plant roots accumulated the highest amount of heavy metals, followed by the leaves, and then the stem. Cr and Fe were mainly retained in the roots of T. latifolia, Cyperus alternifolius, and Cynodon dactylon (TF < 1), meaning that Cr and Fe were only partially transported to the leaves of these plants. This study showed that VSF–CWs planted with T. latifolia, Cyperus Alternifolius, and Cynodon dactylon can be used for the large-scale removal of heavy metals from secondary refinery wastewater.     

Fate of ochratoxin A in brewing.

The fate of ochratoxin A in brewing was investigated by adding (3H)ochratoxin A to the raw materials at 1- and 10-mug/g levels during mashing in a conventional microbrewing process. The results indicated that large portions (28 to 39%) of the added toxin were recovered in spent grains, with less recovery in the yeast (8 to 20%) and beer (14 to 18%). About 38 and 12% of the added toxin at levels of 1 and 10 mug/g, respectively, were degraded during brewing.     

Effect of artificial aeration and macrophyte species on nitrogen cycling and gas flux in constructed wetlands

Constructed wetlands (CWs) are efficient at removing excessive nutrients from wastewaters. However, this removal often results in the flux of important greenhouse gases (GHG), such as nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) that could mitigate the environmental benefits of CWs. We studied the efficiency of artificial aeration and 2 different macrophyte species (Phragmites australis, Typha angustifolia) on the removal and transformations of nitrogen and GHG gas flux using CW mesocosms supplied with 60 L m^?2 d^?1 of wastewater. Removal of total nitrogen (TN) and dissolved organic nitrogen (DON) was generally high in all beds but resulted in a net production of oxidized nitrogen (NO_y) in aerated CW mesocosms as compared to ammonium (NH₄⁺) in non-aerated units. Aerated units emitted less N₂O when planted with P. australis or left unplanted. Aerated beds and planted mesocosms had lower CH₄ fluxes than non-aerated units and unplanted beds, respectively. Our study suggests that planted systems with artificial aeration have the overall best performances in that they lead to a reduction of GHG flux and promote the release of NO_y over NH₄⁺ in their effluents.     

Response of soil microbial respiration of tidal wetlands in the Yangtze River Estuary to different artificial disturbances

To clarify the effects of artifical disturbances on the soil microbial respiration (SMR) of existed tidal wetlands, the SMR of three typical areas in Chongming Dongtan and Jiuduansha of the Yangtze River Estuary, China, were evaluated. The causes of the differences in the SMR were also evaluated by analyzing the microbial activity factors and community structure, as well as the physical-chemical characteristics of the different wetland soils. The results showed that the SMR of the existed wetlands in the area of siltation promotion was significantly higher (P < 0.01) than that of the natural area. Different agricultural practices on the inner land also affected the SMR of the tidal wetlands. Overall, the results indicated that the difference in soil microbial characteristics between the artificially disturbed and natural tidal wetlands may be the primary cause of their different SMR. Path analysis indicated that the correlation between soil bacterial diversity and SMR were especially strong. Phylogenetic analysis showed that the bacterial microbial community structure in wetland soil that had been subject to artificial disturbance was changed due to the alteration of the soil physicochemical characteristics, and Pseudomonas sp., Bacillus sp., Uncultured Lactococcus sp. and Streptococcus sp., which have high heterotrophic metabolism or stress tolerance capability, became the dominant bacterial flora in the artificially disturbed wetland soil, ultimately strengthening the SMR. This may be the essential cause of the higher SMR in wetland soils that have been subjected to artificial disturbance, resulting in a low organic carbon accumulation capability.