Biofilm characterization of several wastewater treatment plants with rotating biological contactors in Madrid (Spain)

Ciliate communities were studied in the biofilms of three planes with rotating biological contactors (RBCs) over the period of one year. The aims of this study were: (i) to characterize ciliates to species level; (ii) to determine their abundance and spatial variation through the biological system; and (iii) to relate the spatial segregation and richness of ciliate species to plant performance. A number of species ranging from 33 to 67 were identified at the different plants. The overall best represented groups were peritrichs followed by scuticociliates (Las Matas), cyrtophorids (Boadilla) or hypotrichs (Camarma). Comparison of RBCs and activated sludge communities indicated that even though both were mainly constituted by peritrichs, differences in groups and species composition were observed.     

Removal of As(V) and As(III) from water with a PEI-modified fungal biomass.

A novel biosorbent was prepared by chemically grafting polyethylenimine (PEI) on the fungal biomass of Penicillium chrysogenum through a two-step reaction. The PEI-modified biomass was found to possess zero zeta potential at pH 10.4. Owing to the protonation of amine groups on the biosorbent surface, the biosorbent is favourable for the removal of anionic arsenic species in water. The sorption capacity for As(V) at pH 3 increased by 5.7-fold after surface modification. The sorption performances including kinetics and isotherm were investigated and several models were used to describe the experimental data. The pseudo-second-order model described the kinetic data better, while the Langmuir equation was the better model to fit the isotherm data. The corresponding thermodynamic parameters for As(V) and As(III) sorption were also calculated.     

用细菌生长潜力(BGP)评价饮用水生物稳定性

介绍了饮用水生物稳定性的测定方法,针对AOC和BDOC对操作和仪器等要求高的问题,提出可以利用细菌生长潜力(BGP)测定生物稳定性,给出了优化方法,并以BDOC为参考进行了对照试验,结果表明,BGP与BDOC具有较好的相关性,在我国一般给水厂的试验条件下可以作为生物稳定性的参考指标.     

A hydrodynamic investigation of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) redd selection at the riffle scale

High‐resolution velocity profile measurements were taken over a series of riffles on a gravel‐bed stream using a Pulse Coherent Acoustic Doppler Profiler (PCADP) to quantify the fluid structure of riffles and nests (redds) where brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) spawned. Velocity profiles were obtained on a highly discretized planometric scale ranging between 20 and 40 cm grid spacings, with vertical observations occurring every 1.6 cm. From the velocity profiles, between 15 000 and 38 000 velocity measurements were obtained over each riffle on any given day of measurement. Velocity profiles were converted to streamwise velocity magnitude, flow depth, Reynolds number, Froude number, shear stress, vertical velocity components and turbulent kinetic energy per unit area to evaluate the spatial structure of the riffles and the spatial structure of redds (pits and tailspills) relative to the surrounding riffle structure. Semi‐variograms were employed to evaluate the persistence of the fluid structure based upon the metrics evaluated. Results showed that discrete velocity observations poorly described the spatial structure of the flow system and poorly correlated with redd locations. Reynolds number analysis identified a relatively consistent fluid property for distances typically 2–3 times the longitudinal length of redds. Turbulent kinetic energy per unit area consistently identified common regions on all riffles studied that corresponded with the location selections for redds where flow was identified as essentially uni‐directional. Froude number was found to be insensitive in predicting the fluid spatial structure in wadeable flow depths and relating it to the fluid structure of redds. Results indicated that a series of metrics at varying spatial scales of turbulence may be necessary to understand the spatial complexity of redd selection. Copyright © 2011 John Wiley & Sons, Ltd.     

Use of sesame stalk biomass for the removal of Ni(II) and Zn(II) from aqueous solutions

In this study an agricultural residue, sesame stalk, was evaluated for the removal of Ni(II) and Zn(II) metal ions from aqueous solutions. Biosorption studies were carried out at different pH, biosorbent dosage, initial metal ion concentrations, contact time, and solution temperature to determine the optimum conditions. The experimental data were modeled by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Langmuir model resulted in the best fit of the biosorption data. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and to evaluate rate constants. The best correlation was provided by the second-order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The experimental results showed that sesame stalk can be used as an effective and low-cost biosorbent precursor for the removal of heavy metal ions from aqueous solutions.     

菱形销用于砂箱模板定位的设计工艺（续）

通过分析砂箱模板中的定位结构原理，阐述了我国大多数中小型企业在铸造加工中普遍采用的“一面两孔”定位法的优缺点，着重介绍了采用一圆柱销、一菱形销(砂箱全部采用固套)和平面支承实现砂箱与模板定位的原理和工艺计算，并列举了此种定位方法易于作到工艺过程中的基准统一、保证砂箱(上、下)及模板的位置精度和重复精度、避免砂箱在造型过程中不被卡死等优点。     

Nitrification and denitrification in partially aerated biological aerated filter (BAF) with dual size sand media.

A 104-mm (4-inch) diameter pilot-scale biological aerated filter (BAF) with a media depth of 2.5 m (8.3 feet) was operated with an anaerobic, anoxic and oxic zone at a temperature of 23 degrees C. The medium for the anaerobic and anoxic zones was 10 mm diameter sand while the medium for the oxic zone was 5 mm diameter sand. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 h with recirculation rates of 100, 200 and 300% in the column was above 96%. Nitrification was found to be more than 96% for 3 h HRT at 200 and 300% recirculation. Total nitrogen removal was consistent at more than 80% for 4 and 6 h HRT at 300% recirculation. For 3 h HRT and 300% recirculation, total nitrogen removal was approximately 79%. The ammonia loading rates for maximum ammonia removed were 0.15 and 0.19 kg NH3-N/m3-day for 100 and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3h with 200-300% recirculation rates with more than 96% removal of sCOD and ammonia and at least 75% removal of total nitrogen.     

Development of a spatially resolved linked hydrodynamic and exposure model (LOTOX2) for PCBs in Lake Ontario

A linked hydrodynamic–hydrophobic organic chemical mass balance and food chain bioaccumulation model, LOTOX2, was developed to support the Lake Ontario Lakewide Management Plan (LaMP) for establishing contaminant load reduction strategies. This paper describes the development of LOTOX2, including the linkage with a relatively finer-scale hydrodynamic model (the Princeton Ocean Model, POM). An important component of this development was the reconstruction of PCB loading history (1930–2005), which was used to understand historic trends and to conduct model calibration/confirmation for total PCBs (tPCBs) in the lake water, sediments, and adult lake trout using data for the last 25 years. A separate mass balance was conducted for the radioisotope cesium-137 (¹³⁷Cs) in order to develop a sorbent mass balance model for the system. Following calibration and confirmation, a diagnostic application of the model showed that the lake is not yet at steady-state with current loads. It will take more than 50 years for tPCB concentration in lake trout to decrease to a steady-state value of about 0.4 ppm if year 2005 loads remain constant. If all external loads were instantaneously eliminated in 2005, it would take approximately 40 years for the adult lake trout tPCB concentration to reach 0.05 ppm (the uniform Great Lakes protocol value for unrestricted consumption) from its current level of 0.74 ppm.     

扁平潜器微速与倒航水动力试验研究

在长条水池中进行了具有扁平外形潜器的微速与倒航运动的水动力模型空间斜拖试验，测量了具有攻角和漂角同时存在下的空间运动的三个水动力和三个水动力矩。将测量的水动力和力矩整理成空间角度攻角、漂角的变化关系曲线图，初步得到了其变化规律。最后将水动力和力矩回归成攻角和漂角双变量的表达式。     

A biological regime shift in the Bay of Quinte ecosystem (Lake Ontario) associated with the establishment of invasive dreissenid mussels

Thirty-two biological variables (taxonomic and/or functional groups) representing the four major communities, phytoplankton, zooplankton, benthos and fish, characterizing the upper Bay of Quinte (Lake Ontario) ecosystem, were assembled for the 27-year period, 1982-2008. Coincident regime shifts were detected in phytoplankton, benthos, and fish in 1995, which was just after invasive zebra mussels (Dreissena spp.) became established in the bay in 1993-1994. Two independent methods were used to detect these shifts: 1) principal components analysis followed by a Regime Shift Detector test for a change point in the running mean of the first principal component scores and (2) measurements of significant difference between pre- and post-Dreissena ecosystem structure based on measures of Bray-Curtis community similarity. Although a statistically significant shift was not detected in the zooplankton community by itself, zooplankton variables were instrumental in the overall ecosystem shift, determined for the combined four communities. All 32 variables were ranked for their individual contribution to the difference between the pre- and post-Dreissena ecosystem structures. The resolution of two distinct ecosystem structures, pre- and post-Dreissena, was greatly improved after employing a novel method of variable optimization that involved a selective and sequential removal of variables contributing least to the statistical difference between pre- and post-Dreissena ecosystem structures. The resultant 20-variable subset defined a 1995 ecosystem regime shift at very high level of statistical confidence (ANOSIM-R = 0.970).     

Chemical and biological features of a high altitude lake in the southern Alps (Laghetto Inferiore, Switzerland)

Since 1980, surveys have been performed nearly every three years on approximately 50 small high altitude alpine lakes located in the Swiss part of the Lake Maggiore watershed. On the basis of this information, since 1996 Laghetto Inferiore has been included in the Mountain Lakes Research (MOLAR) project, an extensive European cooperative research project with 23 partners. Laghetto Inferiore is located at 2074 m a.s.l.; its watershed is mainly composed of crystalline silicic rocks; it has a maximum depth of 33 m, and a theoretical renewal time of 41 days. The pH of the water is approximately 5.6; the alkalinity of the surface water is approximately 30 μmol and that of the bottom water approximately 60 μmol. Chemical studies were performed on the inputs from atmospheric deposition and the main tributary streams, the lake concentration (on a monthly basis), and the outflow. The results show that the characteristics of summer deposition (rain) differ significantly from those of winter deposition (snow). By means of a budget model it was possible to distinguish between the contribution from atmospheric deposition and the contribution from weathering. Biological studies revealed a considerable variety of phytoplankton species and a scarcity of zooplankton species. The vertical distribution of the main algal species shows a marked vertical stratification, with biomass concentrations higher in the profundal. Along this profile, the species of the same taxonomic class tend to gather in a particular depth band, while the single classes tend to be distributed at different depths, according to their specific light requirements.     

无标底招标存在问题及思考

无标底招标是招标方式的重大改革。在分析无标底招标特点的基础上,针对普洱市镇沅县靛坑河水库渠道工程无标底招标的评标过程,分析了无标底招标中存在的问题,提出了一些思考。认为对中小型水利工程,不宜采用无标底招标,而应设置标底,采用综合评分法评标较为合理。     

BNR—MBR组合工艺处理生活污水研究进展

目前城市污水处理工艺多采用生物营养盐去除工艺(BNR),引入膜生物反应器(MBR)组成BNR—MBR组合工艺,可以提高出水水质,实现水资源的回用。与传统的BNR工艺相比,组合工艺的某些运行条件和工艺参数发生了改变。概述了BNR—MBR工艺应用在生活污水处理中的工艺特征,分析和探讨了组合工艺对氮、磷的去除特性以及膜污染控制。     

Biofilm development during the start-up of a sulfate-reducing down-flow fluidized bed reactor at different COD/SO4(2-) ratios and HRT

In sulfate-reducing reactors, it has been reported that the sulfate removal efficiency increases when the COD/SO4(2-) ratio is increased. The start-up of a down-flow fluidized bed reactor constitutes an important step to establish a microbial community in the biofilm able to survive under the operational bioreactor conditions in order to achieve effective removal of both sulfate and organic matter. In this work the influence of COD/SO4(2-) ratio and HRT in the development of a biofilm during reactor start-up (35 days) was studied. The reactor was inoculated with 1.6 g VSS/L of granular sludge, ground low density polyethylene was used as support material; the feed consisted of mineral medium at pH 5.5 containing 1 g COD/L (acetate:lactate, 70:30) and sodium sulfate. Four experiments were conducted at HRT of 1 or 2 days and COD/SO4(2-) ratio of 0.67 or 2.5. The results obtained indicated that a COD/SO4(2-) ratio of 2.5 and HRT 2 days allowed high sulfate and COD removal (66.1 and 69.8%, respectively), whereas maximum amount of attached biomass (1.9 g SVI/L support) and highest sulfate reducing biofilm activity (10.1 g COD-H2S/g VSS-d) was achieved at HRT of 1 day and at COD/sulfate ratios of 0.67 and 2.5, respectively, which suggests that suspended biomass also played a key role in the performance of the reactors.     

Dietary niche and growth rate of the nonnative tubenose goby (Proterorhinus semilunaris) in the Lake Superior basin

The tubenose goby (Proterorhinus semilunaris) entered the Great Lakes in the 1990s via ballast water, but remains poorly studied within North America, making it difficult to predict its effects on native ecosystems. Dietary breadth and somatic growth rate have important ramifications for survival, competitiveness, and dispersal ability of a fish species, and thereby its ecological impact. We studied diet and growth of age-0 tubenose goby within the St. Louis River, a tributary to Lake Superior that contains the largest population within the Lake Superior basin. We sampled tubenose gobies from shallow, vegetated habitats during summer and fall. Stomach contents were identified and weighed to measure fullness and dietary breadth between seasons and several locations. We aged fish based on otolith daily increments to model somatic growth. Diet was dominated by isopods and amphipods, and dietary breadth was low and not significantly different between locations and seasons. Tubenose goby diet strongly overlapped with that of tadpole madtom (Noturus gyrinus), a native, demersal species. We tested several candidate growth models; the Gompertz growth function was the most parsimonious model among those examined. The model demonstrates that tubenose goby obtains a small maximum size and is short-lived. We conclude that tubenose goby presents a unique risk to the Great Lakes and other freshwater bodies because their life history is typical of invasive species, their diet overlaps with native fish, and because they occupy shallow, vegetated habitat which functions as both nursery and foraging habitat for many native fishes.     

Fish and Macroinvertebrate Communities in Tributary Streams of Eastern Lake Erie with and without Round Gobies (Neogobius melanostomus, Pallas 1814)

Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams.     

Light availability and growth of wildcelery (Vallisneria americana) in upper Mississippi River backwaters

Large beds of Vallisneria americana declined in the backwaters of the Upper Mississippi River after a drought that occurred between 1987 and 1989. One hypothesis for this decline is that low light availability may have decreased net photosynthesis to the extent that overwintering tubers were not formed. Following the decline, light availability remained low. To determine what light levels would be necessary for the re-establishment of Vallisneria in the Upper Mississippi River, the long-term growth of plants in a backwater lake and in an experimental pond was measured while the surface and subsurface light were monitored continuously. Plants grown from tubers transplanted to 0·5, 1·0 and l·5m depth in the lake grew and produced tubers only at 0·5m depth (9% of surface light). At 1·0 m, light availability was less than 1% of the surface light. Plants grown from tubers in experimental ponds with four shade treatments (2, 5, 9 and 25% of surface light) for the same growing period produced replacement-weight tubers in 9% light. For a longer growing season, plants also produced replacement-weight tubers in treatments with at least 5% of surface light. An average light-extinction coefficient of 4·64 m^?1 was calculated for the backwater lake based on continuous data collected during 94 days during the growing season from eight widely separated sites. Using equations based on the average extinction coefficient for the lake and average leaf lengths of plants grown in experimental ponds, we predict that in years with comparable turbidity, plants grown from locally collected tubers will grow and produce replacement tubers only at depths of 0·8 m or less.