Flooding tolerance of Sagittaria latifolia and Sagittaria rigida under controlled laboratory conditions

Pool‐scale growing‐season water‐level reductions (drawdowns) have been implemented on the Upper Mississippi River in an effort to improve fish and wildlife habitat. Aquatic vegetation is a key habitat component, with perennial emergent species, such as Sagittaria latifolia and Sagittaria rigida, especially important. River managers have assumed the need for continuous drawdown during the growing season with limited reflooding and used this guidance in assessing the potential for an ecologically successful drawdown. However, information on the effects of growing‐season flooding episodes on survival and growth of Sagittaria is limited. To assess the flooding tolerance of S. latifolia and S. rigida, we evaluated multiple levels of timing, duration, and depth on survival and productivity of plants. Plants were produced from S. latifolia and S. rigida seeds and S. latifolia tubers; all were reared under moist‐soil or shallow‐flooded rearing conditions. Mortality of plants was low (2%) among plants from large tubers, low (7%) among seedlings (and largely associated with early flooding treatments), and modest (11%) among plants from small tubers (with no clear effects of inundation). Flooding treatments generally had a positive effect on biomass production from seedlings, particularly when treatments occurred early, were relatively shallow, and were short in duration. There were no clear effects of depth, duration, or timing components of flooding treatments on plant biomass arising from tubers. This experiment indicates that S. latifolia and S. rigida are relatively tolerant of flooding events during the growing season and may actually benefit from some level of inundation.     

Comparison of three different media for the detection of E. coli and coliforms in water.

The European Drinking Water Directive defines reference methods for the enumeration of microbiological parameters in drinking water. The method to be used for Escherichia coli and coliforms is the membrane filtration technique on Lactose TTC agar with Tergitol 7. Many technical drawbacks of the procedure, as well as its limitations regarding the recent taxonomy of coliforms, make it necessary to evaluate alternative methods. Two alternative assays, a chromogenic media (m-ColiBlu24) and a defined substrate technology-DST test (Colilert 18/Quanty Tray) were compared with the ISO standard with attention to the phenotypic characteristic of the isolates. Results showed that the ISO method failed to detect an important percentage of coliforms and E. coli while m-ColiBlu24 and Colilert 18 provided results in a shorter time allowing the simultaneous detection of E. coli and coliforms with no further confirmation steps.     

Development of procedures for rapid detection of E. coli O157:H7 from source and finished water samples.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7, the causative agent for haemolytic uraemic syndrome, has become a significant health concern, due to an increasing number of cases. The focus of this project was rapid (<8 h) detection of E. coli O157:H7 from source and finished waters samples, either directly or indirectly, by dovetailing the procedures with existing total coliform procedures. Evaluation of four immunological lateral diffusion assays determined a detection range between 1 x 10(4) and 1 x 10(6) CFU, with the Reveal E. coli O157:H7 Test System (Neogen) being the most sensitive for detecting E. coli O157:H7. Evaluation of the BAX System for molecular detection determined that as few as 10 CFU could be reproducibly detected. Coupling either of these detection procedures with organism propagation using Tryptic Soy Broth (TSB) enabled sufficient quantities of E. coli O157:H7, such that the Reveal and BAX detection methods could be used with the 8 h time frame. Examination of matrix effects on the overall procedure indicated little impact on method performance.     

The effect of water hyacinths for wastewater treatment under Cuban climatic conditions.

The purification capacity of systems using floating aquatic plants depend on the climatic conditions under which they are used. This study from Cuban conditions evaluate the effects of the organic loading rate, hydraulic loading rate and water depth on the purification capacity of water hyacinths, as well as the effect of some climatic variables on the kinetics of the treatment processes. The experimental system consisted of two consecutive tanks simulating a system of ponds in series. The water depths used were 0.5 m and 1.12 m. In the shallower system with shorter retention times and greater superficial organic loading higher removal efficiencies are obtained. With the data obtained, empirical relations were sought. From these correlations it is possible to determine the values for some parameters used in the design of aquatic treatment systems with water hyacinths. The results revealed a relationship between the purification capacity of the water hyacinth and its velocity of growth. The specific velocity of growth varied with the months of the year and was associated with the temperature and the solar radiation. A multiple correlation equation describing these relations was obtained.     

Investigation of opportunistic pathogens in municipal drinking water under different supply and treatment regimes.

Changing regulations to lower disinfectant byproducts in drinking water is forcing utilities to switch disinfection from chlorine to monochloramine. It is generally unknown whether this will impact positively or negatively on the microbiological quality of drinking water. A utility in Florida, using water with relatively high organic carbon levels from deep wells in several wellfields, made the decision to change its disinfection regime from chlorine to chloramine in order to meet the new regulations. To assess the impacts of such a change on the microbiology of its water supplies, it undertook a number of studies before and after the change. In particular, the presence of the opportunistic pathogens Legionella and Mycobacterium, and also the composition of drinking-water biofilms, were examined. A preliminary synthesis and summary of these results are presented here. Legionella species were widely distributed in source waters and in the distribution system when chlorine was the disinfectant. In some samples they seemed to be among the dominant biofilm bacteria. Following the change to monochloramine, legionellae were not detected in the distribution system during several months of survey; however, they remained detectable at point of use, although with less species diversity. A variety of mycobacteria (21 types) were widely distributed in the distribution system when chlorine was the disinfectant, but these seemed to increase in dominance after chloramination was instituted. At point of use, only four species of mycobacteria were detected. Other changes occurring with chloramination included (a) an altered biofilm composition, (b) increased numbers of total coliforms and heterotrophs and (c) nitrification of water storage tanks. The results suggested that consideration should be given to the microbiological effects of changing disinfection regimes in drinking-water and distribution system biofilms.     

充分灌与调亏灌溉条件下桃树滴灌的耗水量研究

本文研究了充分灌与调亏灌溉条件下桃树滴灌的耗水量。在田间设置有两个处理，其一是在整个生育期以蒸发量的80%进行充分灌溉；其二是在果实生长缓慢期以蒸发量的20%进行亏缺灌溉，而在其它季节以蒸发量的80%进行充分灌溉。利用石膏块土壤水分传感器和中子仪分别测量了根区土壤水势和土壤含水量的变化，并实测了果实生长量、枝条生长量和产量。利用水量平衡法得出了在上述两种滴灌条件下桃树不同生育期的日均耗水量与蒸发皿系数。与充分灌比较，调亏灌溉对产量没有影响，灌水量减少了32%，并有效抑制了枝条生长。     

Evaluating the potential of biofilm control in water supply systems by removal of phosphorus from drinking water.

Effect of microbially available phosphorus (MAP) on biofilm development in drinking water systems was investigated at the pilot-scale experiments over 3 years. Completely mixed biofilm reactors Propella (water detention time 24 h, flow rate 0.25 m s(-1), PVC pipe coupons) were used as water distribution network models. Four experimental runs were carried out with water containing different levels of phosphorus which was limiting nutrient for bacterial growth. Positive correlation between MAP in the inlet water and heterotrophic plate count (correlation coefficient 0.95) in biofilm, as well as for the total bacteria number (correlation coefficient 0.71), was observed. However, our experiments showed that removal of phosphorus down to very low levels (below detection limits of chemical method and MAP < 1 microg L(-1) was not an efficient strategy to eliminate bacterial regrowth and biofilm formation (< 51,00,000 cells/cm2) in drinking water supply systems.     

Development and validation of a FISH-based method for the detection and quantification of E. coli and coliform bacteria in water samples

Monitoring of microbiological contaminants in water supplies requires fast and sensitive methods for the specific detection of indicator organisms or pathogens. We developed a protocol for the simultaneous detection of E. coli and coliform bacteria based on the Fluorescence in situ Hybridization (FISH) technology. This protocol consists of two approaches. The first allows the direct detection of single E. coli and coliform bacterial cells on the filter membranes. The second approach includes incubation of the filter membranes on a nutrient agar plate and subsequent detection of the grown micro-colonies. Both approaches were validated using drinking water samples spiked with pure cultures and naturally contaminated water samples. The effects of heat, chlorine and UV disinfection were also investigated. The micro-colony approach yielded very good results for all samples and conditions tested, and thus can be thoroughly recommended for usage as an alternative method to detect E. coli and coliform bacteria in water samples. However, during this study, some limitations became visible for the single cell approach. The method cannot be applied for water samples which have been disinfected by UV irradiation. In addition, our results indicated that green fluorescent dyes are not suitable to be used with chlorine disinfected samples.     

Hydraulic performance of biofilters for stormwater management: first lessons from both laboratory and field studies.

In order to improve knowledge on stormwater biofiltration systems, the Facility for Advancing Water Biofiltration (FAWB) was created at Monash University in Melbourne, Australia. One of the aims of FAWB is to improve hydraulic performance of biofilters, given that there are numerous cases of infiltration devices failing after a few years of operation. Experiments were conducted in the field to evaluate the performance of existing systems, and in the lab to understand the factors that influence hydraulic behavior over time. The field experiments show that 43% of tested systems are below nominal Australian guidelines for hydraulic conductivity. The preliminary lab results show a decrease in hydraulic conductivity during the first weeks of operation (mu=66% reduction), although most remain within acceptable limits. Influences of the size of the biofilter relative to its catchment and the importance of the type of media, on the evolution of hydraulic conductivity, are examined.     

不确定条件下的多水源联合供水调度模型

本文针对城市供水调度系统中存在的不确定性与复杂性,运用区间两阶段随机规划的方法,建立了多水源联合供水调度的优化模型。该模型以供水调度系统成本最小为目标函数,引入概率分布及区间数表示不确定性,模拟了地表水源、地下水源、外来水源等多种水源联合供水过程,并对多种水源的调水目标进行优化。以区间形式给出优化结果,为决策者提供宽裕的决策空间。利用该方法,可充分考虑系统中不确定因素对系统成本的影响,更真实的反映多水源联合供水系统的实际情况。     

Removal of bromate and assimilable organic carbon from drinking water using granular activated carbon.

This study investigated the feasibility of using granular activated carbon (GAC) to remove bromate ion (BrO3-) and assimilable organic carbon (AOC) from drinking water through a rapid small-scale column test (RSSCT) method and a pilot-scale study. Results from RSSCT indicated that the GAC capacity for BrO3- removal was dependent on the GAC type, empty bed contact time (EBCT), and source water quality. The GAC with a high number of basic groups and higher pHpzc values showed an increased BrO3- removal capacity. BrO3- removal was improved by increasing EBCT. The high EBCT provides a greater opportunity for BrO3- to be adsorbed and reduced to Br- on the GAC surface. On the other hand, the presence of dissolved organic carbon (DOC) and anions, such as chloride, bromide, and sulfate, resulted in poor BrO3- reduction. In the GAC pilot plant, a GAC column preloaded for 12 months achieved a BrO3- and AOC removal range from 79-96% and 41-75%, respectively. The BrO3- amount removed was found to be proportional to the influent BrO3- concentration. However, the BrO3- removal rate apparently decreased with increasing operation time. In contrast, the AOC apparently increased during the long-term operation period. This may be a result of the contribution due to new GAC being gradually transformed into biological activated carbon (BAC), and the bacterial biomass adsorbed on GAC surface hindering BrO3- reduction by GAC either by blocking pores or adsorbing at the activated sites for BrO3- reduction.     

Development of a hybrid ozonation biofilm-membrane filatration process for the production of drinking water.

Drinking water sources in Norway are characterized by high concentrations of natural organic matter (NOM), low alkalinity and low turbidity. The removal of NOM is therefore a general requirement in producing potable water. Drinking water treatment plants are commonly designed with coagulation direct filtration or NF spiral wound membrane processes. This study has investigated the feasibility and potential of a hybrid process combining ozonation and biofiltration with a rotating disk membrane for treating drinking water with high NOM concentrations. Ozonation will oxidize the NOM content removing colour and form biodegradable organic compounds, which can be removed in biological filters. A constructed water was used in this study which is representative of ozonated NOM-containing water. A rotating membrane disk bioreactor downstream the ozonation process was used to carry out both the biodegradation as well as biomass separation in the same reactor. Maintenance of biodegradation of the organic matter while controlling biofouling of the membrane and acceptable water production rates was the focus in the study. Three operating modes were investigated. Removal of the biodegradable organics was consistent throughout the study indicating that sufficient biomass was maintained in the reactor for all operating conditions tested. Biofouling control was not achieved through shear-induced cleaning by periodically rotating the membrane disks at high speed. By adding a small amount of sponges in the membrane chamber the biofouling could be controlled by mechanical cleaning of the membrane surface during disk rotation. The overall results indicate that the system can favorably be used in an ozonation/biofiltration process by carrying out both biodegradation as well as biomass separation in the same reactor.     

含泥黄河水人工滤床技术参数的试验研究

以黄河中游柳林段滩地自然堆积砂砾石为研究对象,通过系统试验,分别对无砂混凝土板、大粒径卵石覆盖层与剔除过大过小粒径后的黄河滩地自然级配砂砾石组合的过滤体,以及细颗粒介质、土工布、砂砾石复合过滤体的技术参数进行了分析比较,提出了满足取水流量和饮用水浊度要求的人工滤床过滤体和支撑体的技术参数.研究结果表明:无砂混凝土板具有较好的拦泥作用,但淤泥会在无砂混凝土板的孔隙中大量淤积,反冲洗后渗流能力恢复率低;大粒径卵石覆盖层拦泥过滤层的拦泥效果不如无砂混凝土方案好,反冲洗后渗流能力恢复率也较低,不宜采用;0.25~1.0mm细颗粒介质与双层土工布复合过滤体,水质满足要求、渗透系数较大,又便于淤泥的机械和水清洗,是一种值得推荐的过滤体型式;等粒径介质分层填筑支撑层过渡条件好,滤层结构、渗流更为稳定,是一种值得推荐的滤床支撑层.     

解决农村饮水安全问题的思路和措施

天津蓟县饮用水不安全地区日益增多，主要是水量不达标和用水方便程度不达标。建议有关单位从技术、建设、投资、运行和行业等方面加强管理，提高饮用水的安全系数。     

Model concept for nitrate and nitrite utilization during anoxic transformation in the bulk water phase of municipal wastewater under sewer conditions.

A two-stage anoxic transformation process, involving growth of biomass utilizing two types of different electron acceptors, namely nitrate and nitrite, has been observed. The present water quality modules established for sewer processes cannot account for the two-stage process. This paper outlines the development of a model concept that enables the two-stage anoxic transformation process to be simulated. The proposed model is formulated in a matrix form that is similar to the Activated Sludge Models and Sewer Process Model matrices. The model was successfully applied to simulate changes in nitrate and nitrite concentrations during anoxic transformations in the bulkwater phase of municipal wastewater.     

蒙阴县农村饮水安全现状调查与思考

饮水安全是事关小康社会进程、和谐社会建设的一项重要工作,也是建设社会主义新农村的一个重要内容。作为一项社会公共事业,认真做好城乡特别是农村饮水安全工作,从根本上彻底解决农村饮水安全问题,是各级党委、政府义不容辞的责任。在解决农村饮水安全的工作中,要充分利用国家的扶持政策,按照工程＂规模化发展,标准化建设,市场化运作,企业化经营,专业化管理,用水户参与＂的运作思路,打破行政区域界线,强力推进区域集中供水工程,才能从根本上彻底解决农村饮水安全问题。     

预臭氧和预氯化在北方典型水质条件下的强化常规作用分析

针对北方夏季高温高藻、冬季低温低浊的水源水质特点,以北方某水厂为例,通过分析水厂18个月运行数据及现场中试研究,评估了预臭氧和预氯化强化常规处理工艺的实际应用效果,对比了预臭氧和预氯化强化过滤的差异.结果 表明,该水厂采用预臭氧强化常规工艺结合适当调整混凝剂投量的调节方式,可有效应对原水水质特点,有助于提升滤后水质,保...