Sub-lethal effects of several metallic salts—organic compounds combinations upon the heterotrophic microflora of a natural water

The effects of several sub-lethal combinations of the metallic salts Ag₂SO₄, CuCl₂, HgCl₂ and ZnCl₂ with the organic compounds -cysteine and albumin upon the heterotrophic activity of the microflora of a natural water are studied. This heterotrophic activity technique is based upon the uptake and mineralization of a radioactivity labelled metabolite by the indigenous microflora of the Simon Fraser University reflecting pool water. Data analysis by Michaelis—Menten enzyme kinetics equations allows the estimation of the maximum rate of heterotrophic activity as well as a determination of the turnover time of the nutrient in question. The addition of a sub-lethal combination of Cu²⁺ and Zn²⁺ to a sample of the pool water decreases heterotrophic activity to approximately the same extent as the additive decrease caused by these two cations added separately to samples of this water. Cu²⁺ and Zn²⁺ treated water samples do not recover the pre-metallic salt treatment activity following a 3-day incubation. Both -cysteine and albumin have no protective effect upon heterotrophic activity inhibition caused by Hg²⁺ and Ag⁺ respectively, at the concentrations used.     

Modeling of heterotrophic bacteria counts in a water distribution system

Heterotrophic plate count (HPC) constitutes a common indicator for monitoring of microbiological water quality in distribution systems (DS). This paper aims to identify factors explaining the spatiotemporal distribution of heterotrophic bacteria and model their occurrence in the distribution system. The case under study is the DS of Quebec City, Canada. The study is based on a robust database resulting from a sampling campaign carried out in about 50 DS locations, monitored bi-weekly over a three-year period. Models for explaining and predicting HPC levels were based on both one-level and multi-level Poisson regression techniques. The latter take into account the nested structure of data, the possible spatiotemporal correlation among HPC observations and the fact that sampling points, months and/or distribution sub-systems may represent clusters. Models show that the best predictors for spatiotemporal occurrence of HPC in the DS are: free residual chlorine that has an inverse relation with the HPC levels, water temperature and water ultraviolet absorbance, both having a positive impact on HPC levels. A sensitivity analysis based on the best performing model (two-level model) allowed for the identification of seasonal-based strategies to reduce HPC levels.     

浅议地下水位大幅度下降对已有建筑物基础的不利影响

本交通过两个工程事故实例，阐明了地下水位大幅度下降对已有建筑物基础的不利影响。     

Magnetic zeolites: a new adsorbent for removal of metallic contaminants from water

In this work the adsorption features of Na Y zeolite with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as an adsorbent for metallic contaminants in water and subsequently removed from the medium by a simple magnetic process. The zeolites:iron oxide magnetic composites, were prepared by using Na Y with weight ratio of 3:1 and were characterized by powder X-ray diffraction (XRD), magnetization measurements, chemical analyses, N(2) adsorption isotherms and M?ssbauer spectroscopy. Nitrogen adsorption isotherms showed that the surface area decreased from 505 m(2)g(-1) for the pure Na Y to 353 m(2)g(-1) for the Na Y:Fe oxide 3:1 composite. The adsorption isotherms of metal ions Cr(3+), Cu(2+) and Zn(2+) from aqueous solution onto the composites also showed that the presence of iron oxide does not affect the adsorption capacity.     

工艺参数对陶瓷透水砖性能影响的研究

采用煤渣、废瓷粒等工业废渣为骨料,以石灰石、白云石、长石、高岭土、石英和瓷石粉的混合料为高温粘结剂制备陶瓷透水砖,研究工艺参数对透水砖性能的影响。结果表明,随着煤渣用量的增加或成型压力的降低,透水砖的透水性能提高而机械强度降低。通过DTA-TG分析确定了在800℃保温4 h的优化烧成制度,有效避免了黑心和变形缺陷的产生。FE-SEM显微照片表明,合理的煤渣颗粒级配能使煤渣粗颗粒间形成孔径为0.5～1.5 mm的大气孔,而煤渣颗粒本身由于其中可燃物燃烧形成了孔径为数十个微米的微孔,这种特殊的结构赋予透水砖强度高、透水好的性能。     

引水隧道竖井的联系控制测量

通过对竖井附近地面导线网平面联系测量的分析,提出了利用全站仪进行竖井的联系控制测量方法,达到快速准确地将竖井地面导线网点的坐标传递到竖井下面的效果。     

多次冻融盐条件下含水量对盐渍盐胀量的影响

介绍了温度、含盐量、含水量是影响公路盐胀的主要因素，针对此情况通过室内模拟自然界温度变化，分析了不同含水量对盐胀量的影响，得出试验结果并对其进行了分析总结，以减少或避免盐胀带来的危害。     

A conductiometric technique for measuring the water velocity in salmonid spawning beds

The survival and growth of developing salmonid embryos are strongly influenced by the rate of oxygen supply to the redd. Oxygen supply is determined as the product of the groundwater velocity (apparent velocity) and dissolved oxygen content. A modified standpipe technique is presented to measure groundwater velocity. It differs from earlier colour dilution methods in that the colour solution is replaced by an electrolyte, thus allowing remote sensing of conductivity changes and dilution rates. Up to 8 standpipes in a single spawning bed may be operated simultaneously in this way and the method offers considerable advantages in allowing systematic or randomized grid sampling designs. Accuracy compares favourably with that of earlier methods.     

Characterization of raw water for the ozone application measuring ozone consumption rate.

This study was conducted to illustrate an ideal method for characterizing natural waters for ozonation processes in drinking water treatment plants. A specific instrument designed with the flow injection analysis (FIA) technique enabled us to measure accurately the ozone decomposition rate, which was found to consist of two stages: the instantaneous ozone consumption stage and the slower ozone decay stage. The ozone consumption rate was measured at the initial and secondary stages by determining certain parameters called the instantaneous ozone demand (ID) and the pseudo first-order decay rate constant (k(c)). Using the OH*-probe, the yield of OH* per consumed ozone was also measured to determine its potential to produce OH* for the oxidation of micropollutants during the ozonation process. The ozone consumption of the ID values was significant in most natural waters, and substantial amounts of OH* were found to generate during the instantaneous ozone consumption stage. This study also investigated the effects of particulates, ozone doses, and sequential ozone injection on ozone decomposition kinetics and OH* formation yield.     

Simultaneous heterotrophic and sulfur-oxidizing autotrophic denitrification process for drinking water treatment: control of sulfate production

A long-term performance of a packed-bed bioreactor containing sulfur and limestone was evaluated for the denitrification of drinking water. Autotrophic denitrification rate was limited by the slow dissolution rate of sulfur and limestone. Dissolution of limestone for alkalinity supplementation increased hardness due to release of Ca²⁺. Sulfate production is the main disadvantage of the sulfur autotrophic denitrification process. The effluent sulfate concentration was reduced to values below drinking water guidelines by stimulating the simultaneous heterotrophic and autotrophic denitrification with methanol supplementation. Complete removal of 75 mg/L NO₃-N with effluent sulfate concentration of around 225 mg/L was achieved when methanol was supplemented at methanol/NO₃-N ratio of 1.67 (mg/mg), which was much lower than the theoretical value of 2.47 for heterotrophic denitrification. Batch studies showed that sulfur-based autotrophic NO₂-N reduction rate was around three times lower than the reduction rate of NO₃-N, which led to NO₂-N accumulation at high loadings.     

Rationale for a water pollution code part 1: the waste system and the natural system

A water pollution code must quantitatively express the amount and locations of allowable waste discharge. To do this each of the steps leading to the decision on allowable waste discharge must be defined and quantified. Six of the steps are defined in this report and techniques for quantitatively representing them are discussed. The movement of materials from man's environment back into the natural environment is described by five steps: waste generation, waste treatment, waste transport, waste interaction and waste decay. The sixth step discussed in this report represents the impact of the wastes on the natural system. Two further steps in deciding allowable waste discharges will be treated in Parts II and III of this paper which will appear in the next two issues of the Journal.     

Comparison of a novel MPN method against the yeast extract agar (YEA) pour plate method for the enumeration of heterotrophic bacteria from drinking water

This study compared the Quanti-Disc most probable number (MPN) test for heterotrophic bacteria from drinking water with the widely used yeast extract agar (YEA) pour plate method. The Quanti-Disc test module contains 50 reaction wells in which a medium has been pre-deposited. The medium contains a suite of three fluorogenic enzyme substrates selected for the detection of enzymes expressed widely by heterotrophic bacteria. The MPN of heterotrophic bacteria is calculated from the number of fluorescing reaction wells after incubation of a sample. Quanti-Disc and the YEA pour plate method were compared according to guidance on comparing methods given in United Kingdom national guidance and ISO 17994:2004. The two methods were also challenged with reference strains and isolates of heterotrophic bacteria from drinking water. This indicated that heterotrophic bacteria commonly encountered in drinking water are detected by both the YEA pour plate method and Quanti-Disc. Analysis of data from split water samples (723 for 37 degrees C tests and 872 for 22 degrees C tests) from nine geographically diverse laboratories in England and Wales demonstrated that the Quanti-Disc method is equivalent to the YEA pour plate method for the analysis of heterotrophic bacteria from drinking and similar waters at 37 degrees C, and superior to YEA for the analysis at 22 degrees C. The Quanti-Disc method is a simple and efficient alternative method for the enumeration of heterotrophic bacteria from drinking water.     

4-Aminoantipyrine as a chromogenic agent for aromatic amine determination in natural water

Reaction of 4-aminoantipyrine (4-AAP) with aromatic amines was investigated. The study showed the merits and limitations of 4-AAP as a chromogenic agent for the colorimetric determination of aromatic amies in water. Maximum colour development was reached within one minute and the colour maintained its stability for 10 min. 4-AAP is not a sensitive chromogenic reagent for the determination of chloro-, nitro-, p-substituted amines nor for polycyclic aromatic amines. Molar absorptivity of the 4-AAP-dye complexes was discussed and shown to be affected by steric hinderance and lability of the lone pair of electrons of the amino nitrogen.     

Recolonization by heterotrophic bacteria after UV irradiation or ozonation of seawater; a simulation of ballast water treatment

Transport of ballast water with ships represents a risk for introduction of foreign species. If ballast water is treated during uptake, there will be a recolonization of the ballast water by heterotrophic bacteria during transport. We investigated survival and succession of heterotrophic bacteria after disinfection of seawater in the laboratory, representing a model system of ballast water treatment and transport. The seawater was exposed to ultraviolet (UV) irradiation, ozone (2 doses) or no treatment, incubated for 16 days and examined with culture-dependent and -independent methods. The number of colony-forming units (CFU) was reduced below the detection level after disinfection with UV and high ozone dose (700 mV), and 1% of the initial level for the low ozone dose (400 mV). After less than 3 days, the CFU was back or above the starting point for the control, UV and low ozone treatment, whereas it took slightly more than 6 days for the high ozone treatment. Disinfection increased substrate availability and reduced cell densities. Lack of competition and predation induced the recolonization by opportunistic bacteria (r-strategists), with significant increase in bacterial numbers and a low diversity (based on DGGE band pattern). All cultures stabilized after the initial recolonization phase (except Oz700) where competition due to crowding and nutrient limitation favoured bacteria with high substrate affinity (K-strategists), resulting in higher species richness and diversity (based on DGGE band pattern). The bacterial community was significantly altered qualitatively and quantitatively and may have a higher potential as invaders in the recipient depending on disinfection method and the time of release. These results have implications for the treatment strategy used for ballast water.     

Contribution of drinking water to the weekly intake of heterotrophic bacteria from diet in the United States

The goal of this study was to assess the relative contribution of heterotrophic bacteria from various sources in the normal diet of an average person in the United States, due to concerns regarding the potential health implications of such bacteria in household tapwater. A literature search was conducted to determine the concentration of heterotrophic plate count (HPC) bacteria in drinking water, as well as foods common to the American diet. Food items were also obtained in Tucson, AZ to further evaluate the consumption of HPC and total coliform bacteria. This was compared to a recent study on HPC bacteria in tapwater with and without POU devices mounted on the tap in Tucson, AZ households. It was determined that only 0.048-4.5% of the average consumer's total heterotrophic bacteria intake is derived from drinking water. Thus, HPC bacteria in drinking water do not represent a significant exposure of total HPC bacteria in the average diet of consumers in the United States.     

The use of adsorption-active additions of some natural minerals for raising the quality of coagulation purification of natural water

laboratory, pilot and production tests were carried out aimed at the use of powder clinoptilolite jointly with aluminum sulfate to improve the quality of purification of the Dnieper river water. The article showed the advantages of a combined use of these reagents: higher degree of purification, lower consumption of regents, and smaller volume of deposits. The research has begun to obtain composite coagulant by treating with hot sulfuric acid of clinoptilolite and aluminum hydroxide. First research has been conducted of water coagulation under laboratory conditions using composite coagulant and its efficiency was demonstrated.     

天然水中硝酸盐氮氧同位素测试技术研究进展

水环境的硝酸盐污染是一个全球性环境问题。识别水环境中硝酸盐的来源及其转化,对更好地管理水质是十分重要的。硝酸盐的稳定氮氧同位素组成可有效识别水环境中NO 3-来源及其转化。本文总结了典型的测定硝酸盐中稳定氮氧同位素组成的方法:石墨燃烧法、AgNO3-离子交换法、细菌反硝化法、亚硝酸盐去除联合细菌反硝化法、两步化学还原法、连续选择性细菌还原法,同时对这些方法的优缺点进行了评述。最后分析了检测技术中存在的共同问题及其发展方向:δ18O精确度仍有提高的潜力;把NO 3-从水中独立提取出来进行三氧同位素的测试方法还需改进和提高;水样的采集、保存有待进一步改进。     

Long-term storage of natural water samples for dissolved oxygen determination

A method for preserving natural water samples for dissolved oxygen analysis is recommended. The conventional method of using greased glass stoppers have been found to cause an increase in oxygen concentration by 12% over 1-month period as a result of evaporation of water sample through micro-gaps and concurrent intrusion of air into the water sample bottles. Sealing the sample bottles with water has been found to be the optimal storage method. It permits a 100.2 +/- 0.3% recovery of dissolved oxygen concentration from storage seawater samples over 4 months.