Evaluation of denitrification in an urban stream receiving wastewater effluent

Urban streams often contain elevated concentrations of nitrogen (N) which can be amplified in systems receiving effluent from wastewater treatment plants (WWTP). In this study, we evaluated the importance of denitrification in a stream draining urban Greensboro, NC, USA, using two approaches: (1) natural abundance of ¹⁵N–NO₃⁻ in conjunction with background NO₃⁻–N concentrations along a 7 km transect downstream of a WWTP; and (2) C₂H₂ block experiments at three sites and at three habitat types within each site. Overall lack of a longitudinal pattern of δ¹⁵N–NO₃⁻ and NO₃⁻–N, combined with high concentrations of NO₃⁻–N suggested that other factors were controlling NO₃⁻–N flux in the study transect. However, denitrification did appear to be significant along one portion of the transect. C₂H₂ block experiments showed that denitrification rates were much higher downstream of the WWTP compared to upstream, and showed that denitrification rates were highest in erosional and depositional areas downstream of the WWTP and in erosional areas upstream of the plant. Thus, the combination of the two methods for evaluating denitrification provided more insight into the spatial dynamics of denitrification activity than either approach alone. Denitrification appeared to be a significant sink for NO₃⁻–N upstream of the WWTP, but not downstream. Approximately 46% of the total NO₃⁻–N load was removed via denitrification in the upstream, urban section of the stream, while only 2.3% of NO₃⁻–N was lost downstream of the plant. This result suggests that controlling NO₃⁻–N loading from the plant could result in considerable improvement of downstream water quality.     

In situ toxicity tests of fishes in acid waters

Toxicity of waters within the North Branch of the Moose River to various life stages of lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis), creek chub (Semotilus atromaculatus), and blacknose dace (Rhinichthys atratulus) were examined in situ. Study sites were selected that were expected to range from toxic to favourable water quality. For example, pH varied from 4.25 to 7.17, inorganic monomeric Al ranged from ND (< 0.01 mg/l) to 0.40 mg/l, and Ca, from 0.41 to 4.27 mg/l.Toxicity tests were conducted at times when the life stages would naturally occur in these waters and were continued until a range of mortality was observed at the various sites. These experiments suggested that the extent of the drainage system that is toxic to fish increases during snowmelt and major runoff events. Summer base flow water quality was generally the least toxic.Critical life stages were upon hatching and as early feeding fry. In general, young of the year fish were the most tolerant life stage tested. Yearling and adult fish, however, were very sensitive. Blacknose dace were the most sensitive fish of the four species tested, and brook trout were the most tolerant.Hydrogen ion (H⁺) concentration was the most toxic variable in the majority of tests. Inorganic monomeric Al was the most toxic in several, and the combination of H⁺ and Al seemed to cause increased toxicity in many instances. A three-variable model employing hours of exposure, H⁺ concentration, and inorganic monomeric Al predicted mortality quite well. A simple two-variable model using H⁺ and color was nearly as good (R² from 0.49 to 0.94).Documented differences in toxicity among sites and species agreed with observed patterns of fish distribution. These in situ results indicated that laboratory estimates of safe levels of pH and concentrations of Al can result in mortality of fishes in surface waters subject to acidification.     

Value of laboratory tests in employer-sponsored health risk assessments for newly identifying health conditions: analysis of 52,270 participants

Background

Employer-sponsored health risk assessments (HRA) may include laboratory tests to provide evidence of disease and disease risks for common medical conditions. We evaluated the ability of HRA-laboratory testing to provide new disease-risk information to participants.

Methodology/Principal Findings

We performed a cross-sectional analysis of HRA-laboratory results for participating adult employees and their eligible spouses or their domestic partners, focusing on three common health conditions: hyperlipidemia, diabetes mellitus, and chronic kidney disease. HRA with laboratory results of 52,270 first-time participants were analyzed. Nearly all participants had access to health insurance coverage. Twenty-four percent (12,392) self-reported one or more of these medical conditions: 21.1% (11,017) self-identified as having hyperlipidemia, 4.7% (2,479) self-identified as having diabetes, and 0.7% (352) self-identified as having chronic kidney disease. Overall, 36% (n = 18,540) of participants had laboratory evidence of at least one medical condition newly identified: 30.7% (16,032) had laboratory evidence of hyperlipidemia identified, 1.9% (984) had laboratory evidence of diabetes identified, and 5.5% (2,866) had laboratory evidence of chronic kidney disease identified. Of all participants with evidence of hyperlipidemia 59% (16,030 of 27,047), were newly identified through the HRA. Among those with evidence of diabetes 28% (984 of 3,463) were newly identified. The highest rate of newly identified disease risk was for chronic kidney disease: 89% (2,866 of 3,218) of participants with evidence of this condition had not self-reported it. Men (39%) were more likely than women (33%) to have at least one newly identified condition (p<0.0001). Among men, lower levels of educational achievement were associated with modestly higher rates of newly identified disease risk (p<0.0001); the association with educational achievement among women was unclear. Even among the youngest age range (20 to 29 year olds), nearly 1 in 4 participants (24%) had a newly identified risk for disease.

Conclusions/Significance

These results support the important role of employer-sponsored laboratory testing as an integral element of HRA for identifying evidence of previously undiagnosed common medical conditions in individuals of all working age ranges, regardless of educational level and gender.     

Progress in remediation and revegetation of the barren Jales gold mine spoil after in situ treatments

A series of single extractions and short-term plant tests were performed in order to test a variety of inexpensive mineral amendments for the in situ inactivation of trace elements on the fine-grained spoil of the former gold mine of Jales, Portugal. Based on the results of these tests, mesocosms (lysimeters) were constructed and a small-scale semi-field trial was carried out since 1998. The long-term effect of steelshots (SS, iron grit), beringite (B), and municipal compost (C) as spoil amendments was investigated. Vegetation establishment on the treated spoils was successful with Holcus lanatus L. in year 1 and Pinus pinaster Ait. in year 2. Therefore, a detailed monitoring program was implemented for determining the sustainability of trace elements in situ inactivation by C (5%), CB (5% compost combined with 5% beringite), CSS (5% compost combined with 1% steelshots), and CBSS (5% compost combined with 5% beringite and 1% steelshots) treatments (all amendments are expressed by soil dry weight) and of the revegetation. After 3 years, revegetation was excellent in the CSS treatment, and successful for the CBSS. Volunteer plant species became established in treated spoils during year 2. In contrast, the trees planted on the C treated spoil declined from year 2 and some died. In year 3, the trees on the CB treatment started to decline. Arsenic and zinc exposure are suggested to explain the negative effects on pine growth. In agreement with results of single extractions, compost addition in the spoil increased long-term arsenic percolation. Lead leaching was also enhanced. The CBSS and CSS treatments were the most effective for limiting water-soluble As and decreasing long-term metal leaching.     

A comparison of bacterial,ciliate and macroinvertebrate indicators of stream ecological health

We evaluate the reliability of communities of bacteria and ciliated protozoa as indicators of freshwater ecological health. Samples of epilithic biofilm were taken from 18 freshwater streams, impacted by varying types and degrees of catchment modification. Communities of bacteria and ciliates were characterised using DNA fingerprinting techniques (automated ribosomal intergenic spacer analysis and terminal restriction fragment length polymorphism, respectively) and macroinvertebrate data also obtained, for comparison. Similar to the macroinvertebrates, the taxa richness of ciliate communities was reduced in more developed stream catchments; significant differences in the evenness of ciliate communities were also detected. We could identify no significant relationship between the richness of bacterial taxa and the percentage catchment development. However, a significant trend was detected between bacterial community structure and the predominant catchment land use (rural vs. urban) using a Bray–Curtis measure of similarity, a relationship not detected for the ciliate and macroinvertebrate communities. These findings indicate that stream bacterial, ciliate and macroinvertebrate communities each respond differently to various catchment conditions and highlight the potential of microbial communities to provide novel, alternative indicators of stream ecosystem health.     

Proteome changes in the initial bacterial colonist during ecological succession in an acid mine drainage biofilm community

Proteomes of acid mine drainage biofilms at different stages of ecological succession were examined to understand microbial responses to changing community membership. We evaluated the degree of reproducibility of the community proteomes between samples of the same growth stage and found stable and predictable protein abundance patterns across time and sampling space, allowing for a set of 50 classifier proteins to be identified for use in predicting growth stages of undefined communities. Additionally, physiological changes in the dominant species, Leptospirillum Group II, were analysed as biofilms mature. During early growth stages, this population responds to abiotic stresses related to growth on the acid mine drainage solution. Enzymes involved in protein synthesis, cell division and utilization of 1- and 2-carbon compounds were more abundant in early growth stages, suggesting rapid growth and a reorganization of metabolism during biofilm initiation. As biofilms thicken and diversify, external stresses arise from competition for dwindling resources, which may inhibit cell division of Leptospirillum Group II through the SOS response. This population also represses translation and synthesizes more complex carbohydrates and amino acids in mature biofilms. These findings provide unprecedented insight into the physiological changes that may result from competitive interactions within communities in natural environments.     

树叶凋落物在受酸性矿山废水污染溪流中的分解

为了解华南地区酸性矿山废水对溪流中树叶分解的影响,在广东省大宝山矿区附近的1条受酸性矿山废水污染（pH值为2．7—3．4且富含多种重金属元素）的3级溪流中,利用2种孔径（5ram的网袋和0．1ram的布袋）的分解网袋对2种树叶（人面子和蒲桃）进行了为期101d的树叶分解研究。结果表明,人面子树叶网袋和布袋中的树叶干重剩余率分别为39％和48％,而蒲桃树叶网袋和布袋中的干重剩余率仍保持较高的水平,分别为61％和70％。根据指数衰减模型计算出树叶分解的半衰期,人面子树叶在网袋和布袋中的分解半衰期分别为57d和69d,而蒲桃树叶则分别为14-4d和217d。蒲桃树叶的分解速率明显比人面子树叶慢。在网袋中定殖的底栖动物主要是集食者,其中优势类群为摇蚊幼虫,占底栖动物个体总数的99％。摇蚊种群在网袋中的数量波动对2种树叶分解速率的影响并不明显。结果表明,受酸性矿山废水的影响,底栖动物群落的多样性大为减少。同时由于各种金属氧化物在树叶表面的不断沉淀,使树叶处于缺氧状态,抑制了微生物的活动,导致树叶分解速率大为降低。     

Resource dynamics and detritivore production in an acid stream

1. Life history patterns and production of eight shredder‐detritivore species were studied in relation to the detritus dynamics of a small acidic stream in England. Mean annual detritus inputs (direct and lateral sources combined) were approximately 400 g m^?2 year^?1 and showed significant seasonal and annual variation. 2. Detritus standing stock did not increase significantly during times of high input, reflecting low retention efficiency. However, the mean detritus standing stock was relatively large (108 g m^?2) reflecting a slow decomposition rate typical of acid streams. 3. Four species were univoltine with highly synchronous patterns of emergence and recruitment (Leuctra inermis, Leuctra hippopus, Capnia vidua and Amphinemura sulcicollis). Two species were univoltine with extended patterns of emergence and recruitment (Nemoura cinerea, Potamophylax cingulatus). Leuctra nigra was apparently semivoltine, while Protonemura meyeri showed two successive cohorts in the second year of the study, suggesting either bivoltinism or cohort splitting. 3. Secondary production of the dominant shredders was 1.67 g m^?2 year^?1 in 1997 and 1.99 g m^?2 year^?1 in 1998, which is low compared with other small European streams. This was probably because of an impoverished invertebrate community and poor food quality associated with acid conditions. Food availability probably did not account for the low production as the detritus standing stock far exceeded the estimated shredder ingestion of 42–50 g m^?2 year^?1. 4. Despite low overall shredder production, species‐specific production was high, possibly because of competitive release in this species‐poor acid stream. Periods of high production and growth showed no relationship with detritus availability but were closely related to life history.     

Comparative life cycle assessments of incineration and non-incineration treatments for medical waste

Background, aim, and scope  Management of the medical waste produced in hospitals or health care facilities has raised concerns relating to public health, occupational safety, and the environment. Life cycle assessment (LCA) is a decision-supporting tool in waste management practice; but relatively little research has been done on the evaluation of medical waste treatment from a life cycle perspective. Our study compares the environmental performances of two dominant technologies, hazardous waste incineration (HWI) as a type of incineration technology and steam autoclave sterilization with sanitary landfill (AL) as a type of non-incineration technology, for specific medical waste of average composition. The results of this study could support the medical waste hierarchy. Materials and methods  This study implemented the ISO 14040 standard. Data on steam autoclave sterilization were obtained from an on-site operations report, while inventory models were used for HWI, sanitary landfill, and residues landfill. Background data were from the ecoinvent database. The comparative LCA was carried out for five alternatives: HWI with energy recovery efficiencies of 0%, 15%, and 30% and AL with energy recovery efficiencies of 0% and 10%. Results  The assumptions on the time frame for landfill markedly affect the impact category scores; however, the orders of preference for both time frames are almost the same. HWI with 30% energy recovery efficiency has the lowest environmental impacts for all impact categories, except freshwater ecotoxicity. Incineration and sanitary landfill processes dominate global warming, freshwater aquatic ecotoxicity, and eutrophication of incineration and non-incineration alternatives, respectively. Dioxin emissions contribute about 10% to human toxicity in HWI without energy recovery alternatives, and a perturbation analysis yielded identical results. As regards eutrophication, non-incineration treatments have an approximately sevenfold higher impact than incineration treatments. Discussion  The differences between short-term and long-term time frame assumptions mainly are decided by heavy metals dissolved in the future leachate. The high heat value of medical waste due to high contents of biomass, plastic, and rubber materials and a lower content of ash, results in a preference for incineration treatments. The large eutrophication difference between incineration and non-incineration treatments is caused by different N element transformations. Dioxin emission from HWI is not the most relevant to human toxicity; however, large uncertainties could exist. Conclusions  From a life cycle perspective, the conventional waste hierarchy, implying incineration with energy recovery is better than landfill, also applies to the case of medical waste. The sanitary landfill process is the key issue in non-incineration treatments, and HWI and the subsequent residues landfill processes are key issues in incineration treatments. Recommendations and perspectives  Integrating the medical waste hierarchy and constructing a medical waste framework require broader technologies to be investigated further, based on a life cycle approach. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Highly effective reduction of fecal indicator bacteria counts in an ecologically engineered municipal wastewater and acid mine drainage passive co-treatment system

Passive co-treatment of municipal wastewater and synthetic acid mine drainage in a laboratory-scale, four-stage continuous flow reactor system was examined for changes in fecal indicator bacteria (FIB) counts. Raw municipal wastewater (MWW) from the City of Norman, Oklahoma was mixed at a 2:1 ratio with high-strength synthetic acid mine drainage and introduced to the system. The MWW contained varying concentrations of total coliforms (TC), fecal coliforms (FC), Escherichia coli, and fecal streptococci (FS). Initial concentrations ranged from 6 to 13, 0.6 to 6, 3 to 5, and 0.1 to 0.7 million cfu/100 mL, for TC, FC, E. coli, and FS, respectively. During the 6.6-day system residence time, a 100% reduction of all FIB was observed. However, FIB exhibited evidence of sub-lethal injury with slower colony formation rates on standard growth media after 81 h of retention. Extending standard incubation periods resulted in higher concentrations of all FIB in each treatment stage, except the final stage where only E. coli and TC counts increased. Although this co-treatment regime reduced FIB concentrations more effectively than conventional active or passive MWW treatment systems, further work can be done to optimize the efficiency of treating these wastes simultaneously.     

Uncertainty in ecological status assessments of lakes and rivers using diatoms

The EU’s Water Framework Directive requires all surface water bodies to be classified according to their ecological status. As biological communities show both spatial and temporal heterogeneity, expressions of ecological status will, inevitably, have an element of uncertainty associated with them. A consequence of this environmental heterogeneity is that there is a risk that status inferred from one or more samples is different to the true status of that water body. In order to quantify the scale of temporal uncertainty associated with benthic diatoms, replicate samples were collected from sites across the ecological status gradient in lakes and rivers in the UK. Variability (expressed as standard deviation of temporal replicate samples from a single site) could be described using a polynomial function and this was then used to calculate the risk of placing a water body in the wrong ecological status class. This risk varied depending on the distance from the class boundaries and the number of replicates. Based on these data, we recommend that ecological status is determined from a number of samples collected from a site over a period of time.     

Effects of spring acid episodes on macroinvertebrates revealed by population data and in situ toxicity tests

1. While streams in Europe and North America are now recovering chemically from chronic acidification, severe episodic acidification continues to threaten sensitive biota. To appraise further the biological importance of episodic acidification, we surveyed the distribution of the mayfly Baetis alpinus in streams in the Southern Alps (Canton Ticino, Switzerland) in relation to runoff acidity during spring floods. Moreover, to improve mechanistic understanding, in situ toxicity assays were carried out on nymphal B. alpinus during low flows and spring floods, both in streams prone to acid episodes and in well‐buffered controls. 2. Streams surveyed for invertebrates represented three groups which contrasted in susceptibility to episodic acidity. Group one included streams that were acid (alkalinity <0) in spring; group two streams were susceptible to acid episodes because of low base‐flow alkalinity (<200 μeq L^?1); and group three streams were well‐buffered and unlikely ever to be acid. The abundance of B. alpinus was similar among groups during stable flows in winter and summer, but was significantly lower in groups one and two following spring snowmelt. 3. During the bioassays, control streams remained circumneutral to alkaline (pH >6.4). By contrast, episodic streams were circumneutral at low flows, but became acid (pH 4.5–5.6 and total dissolved aluminium to 276 μg L^?1) during intense spring snowmelt. After 15‐day exposures, nymphal B. alpinus survival in the circumneutral control streams exceeded 92% irrespective of flow. In the episodic streams, survival matched the controls during low flows, but declined significantly to 10–20% during acid episodes in spring. Shorter exposure (2–4 days) to pH 5.5–5.7 did not cause significant mortality either during the exposure or over the following 7 days, indicating that B. alpinus might recover from short acid episodes. 4. Our data suggest that the spring distribution of B. alpinus in acid sensitive parts of the Alps directly reflects the toxicity of acid runoff during snowmelt. Our study illustrates that even mild episodic acidification can have significant consequences in Alpine streams for one of the most important invertebrate indicators of acidity.     

Prokaryotic and eukaryotic community structure affected by the presence of an acid mine drainage from an abandoned gold mine

The acid mine drainage that originates in the abandoned gold mine in San Luis, Argentina, is released into La Carolina stream. The aim of this study was to determine the influence of this mine drainage on the physicochemical parameters of the area studied and on both prokaryotic and eukaryotic community structure. In addition, specific relationships between microbial taxonomic groups and physicochemical parameters were established. The drainage that flows into La Carolina stream acidifies the stream and increases its sulfate, Zn, Cd and Te concentrations. Microbial analysis showed that prokaryotic community structure is mainly affected by pH values. Actinobacteria and Gammaproteobacteria were abundant in samples characterized by low pH values, while Nitrospirae, Chloroflexi, Deltaproteobacteria, Thaumarchaeota and Euryarchaeota were associated with high concentrations of heavy metals. Otherwise, Alphaproteobacteria was present in samples taken in sunlit areas. Regarding eukaryotic community structure, the sunlight had the greatest impact. Inside the mine, in the absence of light, fungi and protists members were the most abundant microorganisms, while those samples taken in the presence of light displayed algae (green algae and diatoms) as the most abundant ones. After receiving the mine drainage, the stream showed a decrease in the diatom abundance and green algae predominated.

     

土壤生物工程在河道坡岸生态修复中应用与效果

土壤生物工程是一项采用存活植物构筑边坡结构,稳定河道（流）坡岸和生态修复的工程技术.本文简要讨论了土壤生物工程的原理和活枝扦插、柴笼、灌丛垫以及复合工程等基本种植技术;介绍了我国第一个采用土壤生物工程修复河道坡岸的示范工程,对比了工程实施后河道坡岸10个月来的坡岸土壤剪切力、生境条件和生物多样性变化.研究和示范工程表明,采用土壤生物工程方法可以稳定坡岸、改善坡岸的栖息地质量、修复河道的生态环境.土壤生物工程方法可以在我国各类岸（边）坡的生态修复中广泛运用.     

人工湿地污水处理工艺设计关键及生态学问题

人工湿地污水处理系统是一种经济高效的污水生态处理技术方式．然而,湿地污水处理技术在性能上仍须有待发展与完善,尤其需要对其处理工艺参数进行不断改进和系统优化．本文针对人工湿地污水处理工程中有关水力停留时间、水传导因素、表面负荷率和工程构筑物设计等技术参数,概括性地剖析、探讨了国内外人工湿地污水处理工艺的设计关键及其主要技术内涵,给出了一些重要的优化模型与最佳数值;与此同时,分析、提出了利用生态学方法克服人工湿地工程运行中所涉及的野生生物管理与蚊蝇控制等问题。     

Performance of and methanogenic communities involved in an innovative anaerobic process for the treatment of food wastewater in a pilot plant

In this study, dual-cylindrical anaerobic digesters were designed and built on the pilot plant scale for the improvement of anaerobic digestion efficiency. The removal efficiency of organics, biogas productivity, yield, and microbial communities was evaluated as performance parameters of the digester. During the stable operational period in the continuous mode, the removal efficiencies of chemical oxygen demand and total solids were 74.1 and 65.1%, respectively. Biogas productivities of 63.9 m³/m³-FWW and 1.3 m³/kg-VS_removed were measured. The hydrogenotrophic methanogen orders, Methanomicrobiales and Methanobacteriales, were predominant over the aceticlastic methanogen order, Methanosarcinaceae, probably due to the tolerance of the hydrogenotrophs to environmental perturbation in the field and their faster growth rate compared with that of the aceticlastics.     

Detection of Acidithiobacillus ferrooxidans in acid mine drainage environments using fluorescent in situ hybridization (FISH)

An important microorganism of acid mine drainage (AMD) and bioleaching environments is Acidithiobacillus ferrooxidans which oxidizes ferrous iron and generates ferric iron, an oxidant. Most investigations to understand microbial aspects of sulfide mineral dissolution have focused on understanding physiological, metabolic, and genetic characteristics of A. ferrooxidans. In this study, a 16S rRNA oligonucleotide probe designated S-S-T.ferr-0584-a-A-18, and labeled at the 5'-end with indocarbocyanine dye (CY3), was used in a fluorescent in situ hybridization (FISH) procedure on pure cultures of nine isolates of A. ferrooxidans. These isolates were recovered from acid mine drainage and mining environments. The probe was also used to detect cells of A. ferrooxidans, recovered from AMD samples, growing on FeTSB and FeSo solid media in a FISH procedure. In addition, the presence of cells of A. ferrooxidans in an environmental water sample from an AMD site in Copper Cliff, Ontario, Canada was analyzed using the FISH technique. Probe specificity was first confirmed with A. ferrooxidans ATCC 19859 (positive control) and Acidithiobacillus thiooxidans ATCC 19377, Acidiphilium acidophilum ATCC 27807, and Lactobacillus plantarum ATCC 8014 (negative controls). Positive and negative control cells were also used to determine optimal stringency conditions for hybridizations with the probe. Cells of the nine isolates of A. ferrooxidans stained positive, although the fluorescent signal varied in intensity from isolate to isolate. Colonies of A. ferrooxidans from the environmental water sample of the AMD site were recovered only on FeTSB solid medium after 22 days of incubation. The probe was able to detect cells of A. ferrooxidans in a FISH procedure. However, no cells of A. ferrooxidans were detected in the AMD water sample without cultivation. Thus, probe S-S-T.ferr-0584-a-A-18 hybridized effectively with cells of A. ferrooxidans recovered from pure cultures but failed to directly detect cells of A. ferrooxidans in the AMD site.