Effects of isocyanuric acid on the monochlorodimedone chlorinating rates with free chlorine and ammonia chloramine in water

Changes in monochlorodimedone (MCD) chlorinating rates with free chlorine (mixture of HOCl and OCl-) and ammonia monochloramine (NH2Cl) in water at pH 7 by the addition of isocyanuric acid (H3Cy) were determined at room temperature. Decreases in MCD absorbance at 290nm in equimolar (0.04mM) reactions of MCD and free available chlorine solutions containing H3Cy (0.01-1.60 mM) were recorded in a stopped-flow spectrophotometer. The rates indicate second-order reactions. Since the rate with free chlorine was high (> 7.6 x 10(6) M(-1) s(-1)), the amounts of free chlorine in the solutions could be distinguished from that of chlorinated cyanurates. The chlorinating rates with chlorinated cyanurates decreased with an increase in H3Cy concentrations. Plotting the rates against the molar ratio of chlorine to H3Cy showed a linear correlation and the rates with chlorinated cyanurates (H2ClCy) was estimated at 0.5 x 10(5) M(-1) s(-1). In contrast, the rates with the NH2Cl solution containing H3Cy increased with an increase in H3Cy concentrations, increasing from 1.2 x 10 to 2.7 x 10 M(-1) s(-1) by the addition of 1.55 mM H3Cy. The DPD color development rates (OD512/t1/2/M) with free available chlorine (0.015mM) declined from 1.3 x 10(5) to 0.9 x 10(5)M(-1) by the addition of 0.61 mM H3Cy.     

Changes in the swimming activity and the glutathione S-transferase activity of Jenynsia multidentata fed with microcystin-RR

We report the effects of sublethal doses of microcystin-RR (MC-RR) on the swimming activity of Jenynsia multidentata as well as the simultaneous response of its detoxication system by measuring glutathion S-transferase (GST) activities in the liver and brain of fish. MC-RR was applied on the food pellets at doses of 0.01, 0.1 and 1 microg g(-1). Swimming activity was recorded 10 min each hour over 24h by using a computer-based image processing system, which facilitates quantification of two measures of fish swimming behaviour (average velocity, movement percentage). Results show that low levels of cyanotoxin increased the swimming activity, while the highest dose used produced significant changes with respect to control group only since approximately 20 h of exposure, when the swimming activity was decreased. On the other hand, GST activity was significantly increased only in the liver and brain of fish fed with the highest MC-RR dose. Both results suggest that fish are reacting to the stress caused by low doses of MC-RR by increasing their swimming activity, raising further questions on the probable neurotoxicity of MCs, and presenting the behavioural change as a good biomarker of early toxic stress. On the other hand, fish reduced their swimming speed at the highest MC-RR dose, when the detoxication activity began, which can be hypothesized to be a reallocation of their energy, favouring detoxication over swimming activity.     

Stimulation of microbial sulphate reduction in a constructed wetland: microbiological and geochemical analysis

Microbial sulphate reduction was stimulated successfully in enclosures installed in a constructed wetland. When sucrose (2.4mM) and NH(4)Cl (600 microM) were added to water in the test enclosures, the indigenous microbial community was able to remove over 90% of the sulphate, present as a contaminant from nearby mining activity at a concentration of 384 mg x l(-1) (4mM), over 50 days. Over 90% of the sucrose was also removed. Sulphate was not reduced in control enclosures containing no added sucrose or NH(4)Cl. Fermentation of sucrose by obligate anaerobes including Clostridium sp. and Bacteriodes sp. preceded sulphate reduction in the test enclosures. Sulphate reduction was biphasic, with maximum rates noted between 2-5 and 23-27 days after the addition of the growth substrates. Relatively unbiased 16S rDNA analysis suggested that nitrogen-fixing bacteria were important constituents of the microbial community in the test enclosures at day 23, suggesting that soluble nitrogen was limiting in the amended test enclosures during the experiment.     

Estimating energy savings from behaviours using building performance simulations

Occupants’ behaviours are a major determinant of energy use in buildings. The related savings potential has been insufficiently exploited. Although research has addressed behavioural savings through real-world interventions and quantitative modelling approaches, it has not yet explored the full variety of household activities. This work proposes an integrative modelling approach of energy behaviours in the residential setting as a tool to estimate the behavioural impact of households on energy consumption. It uses building energy performance simulation (BEPS) tools to exploit the behavioural savings potential associated with usage and investment energy behaviours when using different energy services in daily household activities. Simulations have estimated significant behavioural savings potential associated with energy behaviours, which may be materialized if some forms of behaviour are induced. Investment behaviours have higher savings potential than usage behaviours, and the behavioural savings potential per energy service is proportional to the energy consumption breakdown. BEPS tools enable a quantitative estimate of the behavioural impact on energy consumption, but further improvements to these tools are needed to incorporate the complexity of behavioural dimensions. Estimating the behavioural savings potential is important for a more effective design of behaviour change interventions, which in turn will support more effective energy efficiency policies.     

Real-time biomonitoring of water contamination by cyanide based on analysis of the continuous electric signal emitted by a tropical fish: Apteronotus albifrons

A new early warning system for monitoring the quality of water was developed using the information conveyed by the continuous electric organ discharges of the tropical fish Apteronotus albifrons (Gymnotiformes, family Apteronotidae). The principle is based on the time characterisation of the electric signal emitted by the fish and uses the fact that the frequency and the form of the signal vary as a function of the physico-chemical quality of the ambient water. Eight test fish were individually confined in a heat-proof test chamber in which a continuous water current, thermo-regulated at 27°C, was maintained. The electric signal sampled over 1 s periods were amplified. The computer processed the signals and their frequencies and determined the coordinates of the points where the temperatures were recorded. The results of the A. albifrons electrical activity were then visualised on a visual display unit. Subsequent mathematical processing helped to detect unusual electrical behaviour (crossing of lower and upper bounds). To illustrate the principle of this new early warning system, the electric response of the A. albifrons exposed to cyanide was tested and compared with the detection thresholds of other biological early warning systems. A. albifrons is able to detect a cyanide concentration of 34.6 μg l⁻¹ in less than half an hour. The recorded results suggest that this new biomonitor corresponds very well with the requirements of warning stations for surface waters subject to cyanide pollution.     

Causes of Fish Mortality Along the Qatari Waters (Arabian Gulf)

Excessive fish mortality were observed along the Qatari coastline and offshore during the summer of 1996 and 1998. Massive amounts (about 40 tons) of dead fish were recorded off the eastern coast. Siganidae, Lethrinidae and Carangidae, coral reef inhabiting fish, were the main species observed dead along the beaches. Hydrographic parameters (temperature, salinity and dissolved oxygen) and main pollutants (ex ${\rm NH}_4^+$     

溴酸根在紫外和氯消毒联用工艺中的形成

以H2O-Br--Cl2/NH2Cl/ClO2为研究对象,考查UV作用下BrO3-产生的情况。结果表明:原水和去离子水背景下,Cl2/UVC联用可以氧化部分的Br-生成BrO3-;NH3可以有效的抑制BrO3-生成,并且NH2Cl/UVC作用时不生成BrO3-;ClO2/UV体系产生溴酸根能力明显弱于Cl2/UV;ClO2/UVC产生BrO3-的量高于ClO2/UVA。酸性条件同时促进BrO3-的产生和ClO2的分解,碱性条件正好相反。     

Evaluation of acoustic attenuation as an indicator of roof stability in advancing headings

A novel acoustic technique developed to monitor roof stability in advancing headings was evaluated during a field monitoring trial at the Brunswick Mine, New Brunswick, Canada. The acoustic technique uses waveforms generated by mining activity near the active face (such as rotary-percussion drilling for the installation of support or drilling blast-holes) to identify changes in the attenuation properties of the roof rock mass which are correlated to stability through conceptual models and independent experimental work. Field trial results indicate that (a) the selected frequency range of the acoustic sensors is suitable to ensure that recorded waveforms have originated within the rock mass volume of interest near the face of the active heading, (b) the waveforms generated by rotary–percussion drilling are sufficiently consistent to be considered as a stable acoustic source, and (c) observed changes in roof attenuation are consistent with what would be expected in response to the installation of support near the freshly blasted face and blast-hole drilling of the face.     

Behavioural responses to cold thermal discomfort

Heating energy demand in buildings depends in part on occupants' behavioural responses to thermal discomfort during the heating season. The understanding of this has become one of the priorities in the quest to reduce energy demand. Thermal comfort models have long been associated with occupants' behaviour by predicting their state of thermal comfort or rather discomfort. These assumed that occupants would act upon their level of discomfort through three types of response: mechanisms of thermoregulation, psychological adaptation and behavioural responses. Little research has focused on the behavioural aspect. One of the key challenges is to gather accurate measurements while using discreet, sensor-based, observation methods in order to have minimum impact on occupants' behaviour. To address these issues, a mixed-methods approach is introduced that enables the establishment of a three-part framework for mapping behaviour responses to cold sensations: (1) increasing clothing insulation level; (2) increasing operative temperature by turning the heating system on/up; and (3) increasing the frequency, duration and/or amplitude of localized behaviour responses such as warm drink intake or changing rooms. Drawing on this framework, an extended model of thermal discomfort response is introduced that incorporates a wider range of observed behaviours.     

Particulate-biofilm, expanded-bed technology for high-rate, low-cost wastewater treatment: nitrification

The performance of a particulate-biofilm, expanded-bed process for nitrification of activated sludge final effluent (ASFE) is reported for a plant receiving mixed industrial and domestic wastewater. The support material for the particulate-biofilms was glassy coke, to which the nitrifying bacteria attached and formed a highly active biofilm. An average nitrification rate of 1.7+/-0.6 kg m(expanded bed)(-3)d(-1) was recorded during operation of the bioreactor, which had a hydraulic residence time of 15 min. On average, the ASFE contained 12.6+/-3.7 g m(-3) NH3-N, which was reduced to 2.6+/-3.3 g m(-3) NH3-N. Furthermore, transfer of 10-12% of the oxygen in air was achieved using counter-current aeration. This investigation has demonstrated that a high rate of nitrification can be achieved with a particulate-biofilm, expanded-bed process. It has also demonstrated that the process can operate without backwashing and still remove particulate material from the ASFE feed.     

Oxygen consumption and activity of the white sucker (Catostomus commersoni), in lethal and nonlethal levels of the organochlorine insecticide, methoxychlor

The survival, oxygen consumption and spontaneous activity of suckers were determined at 15°C in water containing different concentrations of methoxychlor in ethanol, ethanol, and no added substances. A dynamic bioassay was used to estimate the 96 h LC50, which was found to be 0·0345 ppm. Routine oxygen consumption was determined in a continuous-flow respirometer, and the activity was recorded in separate experiments by measuring the water disturbance using silver wire electrodes.After 24 h fish exposed to untreated, ethanol-treated and 0.01 ppm methoxychlor-treated water had oxygen uptake rates which were relatively constant and near standard levels. At 0.10 ppm methoxychlor (lethal to all fish within 85 h), oxygen consumption rates were 2–3.5 × as high as those of control fish. Activity also greatly increased. The fish lost their balance along with the coordination between opercular and locomotor movements. Suckers that died in 0.04 ppm methoxychlor showed oxygen uptake rates and poisoning symptoms similar to 0.10 ppm treated fish, while those that survived this treatment had rates similar to control fish. The increase in ventilation which accompanies this hyperactivity may result in increased uptake of insecticide and thereby explain the irreversible nature of the response.     

Antimutagenic effect of neem leaves extract in freshwater fish, Channa punctatus evaluated by cytogenetic tests

Neem (Azadirachta indica), an indigenous plant commonly grown in India and its sub-continent is a multipurpose plant well known for its insecticidal and biomedical properties, however, its antimutagenic effects in vertebrate organisms are lacking. The present work is therefore, focused on possible antimutagenic potential of ethanolic extract of neem leaves evaluated on the clastogenicity induced by Pentachlorophenol (PCP) and 2, 4-dichlorophenoxyacetic acid (2,4-D) in freshwater fish, Channa punctatus used as a vertebrate model, by cytogenetic endpoints: chromosome aberration (CA) and micronucleus (MN) test. In the first set of experiment, fish were exposed by medium treatment to a single treatment of each chemical (PCP, 0.6 ppm; 2,4-D, 75 ppm; neem extract, 3 ppm) along with the controls. The chromosome preparations were made after processing kidney cells and micronucleus slides were prepared from peripheral blood at multiple duration (48, 72 and 96 h). PCP and 2,4-D when used alone, induced significant CA and MN in a time dependent manner. Neem extract did not show genotoxic potential in both assays. The maximum frequency of CA were recorded as 18.58% and 15.17%, while frequency of MN reached to 8.08% and 4.62% by PCP and 2,4-D respectively, after 96 h exposure. In the second set of experiment, three concentrations of neem extract (1, 2 and 3 ppm) were run simultaneously with the same concentration of PCP (0.6 ppm) and 2,4-D (75 ppm) for antimutagenicity estimates. In mixed treatment, neem extract significantly reduced the frequency of CA and MN. The reduction in the frequency of CA ranged from 40-75% and 45.4-83.3% and similar values for MN were 40.2-75.3% and 44.1-65.8% for PCP and 2,4-D respectively. Although the reductions were significant but not dependent on concentration and time intervals employed. Results suggested that under present experimental conditions, neem extract exhibit strong antimutagenic activity in this fish model, which could further contribute to study its benefit in humans.     

Investigation of active vibration drilling using acoustic emission and cutting size analysis

This paper describes an investigation of active bit vibration on the penetration mechanisms and bit-rock interaction for drilling with a diamond impregnated coring bit. A series of drill-off tests (DOTs) were conducted where the drilling rate-of-penetration (ROP) was measured at a series of step-wise increasing static bit thrusts or weight-on-bits (WOBs). Two active DOTs were conducted by applying 60 Hz axial vibration at the bit-rock interface using an electromagnetic vibrating table mounted underneath the drilling samples, and a passive DOT was conducted where the bit was allowed to vibrate naturally with lower amplitude due to the compliance of the drilling sample mountings. During drilling, an acoustic emission (AE) system was used to record the AE signals generated by the diamond cutter penetration and the cuttings were collected for grain size analysis. The instrumented drilling system recorded the dynamic motions of the bit-rock interface using a laser displacement sensor, a load cell, and an LVDT (linear variable differential transformer) recorded the dynamic WOB and the ROP, respectively. Calibration with the drilling system showed that rotary speed was approximately the same at any given WOB, facilitating comparison of the results at the same WOB. Analysis of the experimental results shows that the ROP of the bit at any given WOB increased with higher amplitude of axial bit-rock vibration, and the drill cuttings increased in size with a higher ROP. Spectral analysis of the AEs indicated that the higher ROP and larger cutting size were correlated with a higher AE energy and a lower AE frequency. This indicated that larger fractures were being created to generate larger cutting size. Overall, these results indicate that a greater magnitude of axial bit-rock vibration produces larger fractures and generates larger cuttings which, at the same rotary speed, results in a higher ROP.     

Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine: a new disinfection by-product

Studies have been conducted specifically to investigate the hypothesis that N-nitrosodimethylamine (NDMA) can be produced by reactions involving monochloramine. Experiments were conducted using dimethylamine (DMA) as a model precursor. NDMA was formed from the reaction between DMA and monochloramine indicating that it should be considered a potential disinfection by-product. The formation of NDMA increased with increased monochloramine concentration and showed maximum in yield when DMA was varied at fixed monochloramine concentrations. The mass spectra of the NDMA formed from DMA and 15N isotope labeled monochloramine (15NH2Cl) showed that the source of one of the nitrogen atoms in the nitroso group in NDMA was from monochloramine. Addition of 0.05 and 0.5 mM of preformed monochloramine to a secondarily treated wastewater at pH 7.2 also resulted in the formation of 3.6 and 111 ng/L of NDMA, respectively, showing that this is indeed an environmentally relevant NDMA formation pathway. The proposed NDMA formation mechanism consists of (i) the formation of 1,1-dimethylhydrazine (UDMH) intermediate from the reaction of DMA with monochloramine followed by, (ii) the oxidation of UDMH by monochloramine to NDMA, and (iii) the reversible chlorine transfer reaction between monochloramine and DMA which is parallel to (i). We conclude that reactions involving monochloramine in addition to classical nitrosation reactions are potentially important pathways for NDMA formation.     

Biomarkers in an invasive fish species, Oreochromis niloticus, to assess the effects of pollution in a highly degraded Brazilian River

Paraiba do Sul watershed is one of the most important Brazilian water bodies (5.5 million people depend on the river). It is in a critical environmental situation, polluted by industrial discharges, non-treated urban wastes, and pesticides, which have had cumulatively negative effects. This study analyzes the effects of pollution, with a biomarker approach, by using the invasive fish species, Oreochromis niloticus, as a sentinel species. The approach comprehends a general biomarker of the health of individual fish, the condition factor, a biomarker of genotoxicity, the micronuclei test; and specific biomarkers of contaminant exposure such as metallothionein (MT) and acetylcholinesterase (AChE) activity. The results revealed different effects in fish from diverse locations with varying degrees of pollution. Low AChE activities were found in fish from the region with strong agriculture activity, showing the effects of pesticides. Fish from an industrialized and heavily environmentally degraded area presented high levels of MT and low AChE activities, indicating an intricate polluted condition. It is noteworthy that fish located just upstream of the main water-treatment plant of the metropolitan area Rio de Janeiro presented high levels of MT, showing to be affected by metals. This can be an alert to public health officials. O. niloticus has proven a suitable sentinel species to assess the effects of pollutions in an aquatic system with a complex and serious polluted situation. The present study also shows the usefulness of integrating a set of biomarkers to define the exposure and the effects of anthropogenic inputs among impacted and reference sites in this water body.     

Evaluation of the impact of bioaugmentation and biostimulation by in situ hybridization and microelectrode

Three rotating disk biofilm reactors were operated to evaluate whether bioaugmentation and biostimulation can be used to improve the start-up of microbial nitrification. The first reactor was bioaugmented during start-up period with an enrichment culture of nitrifying bacteria, the second reactor received a synthetic medium containing NH(4)(+) and NO(2)(-) to facilitate concomitant proliferation of ammonia- and nitrite-oxidizing bacteria, and the third reactor was used as a control. To evaluate the effectiveness of bioaugmentation and biostimulation approaches, time-dependent developments of nitrifying bacterial community and in situ nitrifying activity in biofilms were monitored by fluorescence in situ hybridization (FISH) technique and microelectrode measurements of NH(4)(+), NO(2)(-), NO(3)(-), and O(2). In situ hybridization results revealed that addition of the enrichment culture of nitrifying bacteria significantly facilitated development of dense nitrifying bacterial populations in the biofilm shortly after, which led to a rapid start-up and enhancement of in situ nitrification activity. The inoculated bacteria could proliferate and/or survive in the biofilm. In addition, the addition of nitrifying bacteria increased the abundance of nitrifying bacteria in the surface of the biofilm, resulting in the higher nitrification rate. On the other hand, the addition of 2.1mM NO(2)(-) did not stimulate the growth of nitrite-oxidizing bacteria and did inhibit the proliferation of ammonia-oxidizing bacteria instead. Thus, the start-up of NO(2)(-) oxidation was unchanged, and the start-up of NH(4)(+) oxidation was delayed. In all the three biofilm reactors, data sets of time series analyses on population dynamics of nitrifying bacteria determined by FISH, in situ nitrifying activities determined by microelectrode measurements, and the reactor performances revealed an approximate agreement between the appearance of nitrifying bacteria and the initiation of nitrification activity, suggesting that the combination of these techniques was a very powerful monitoring tool to evaluate the effectiveness of bioaugmentation and biostimulation strategies.     

The home as enabler of more active lifestyles among older people

Inactive lifestyles have negative health consequences, while time spent sedentary (sitting and lying) is related to morbidity and premature mortality. Older adults often form the most sedentary segment of the population. Much of this behaviour may be practised at home where this group can spend extended periods. Physical activity rates among older adults are particularly low. Even household physical activities can be beneficial for this group, while they can constitute much of an older person's total activity. Despite this context, the home's role in the active and sedentary behaviours of the older population appears critically understudied. Using interview and focus group data collected from 22 older adults (healthy volunteers, stroke survivors and people with dementia), this paper begins to address this issue. Aspects of the home that aid or impede a more active, less sedentary lifestyle are identified with three presenting particular capacity in this respect discussed: steps, space within the home, and the location and form of facilities, fixtures and fittings. The crucial role health status plays in structuring this capacity is identified. Simple design recommendations, devised to support older people to lead more active lives at home, are presented.     

氯胺消毒工艺中一氯胺生成效率的影响规律

以上海市某自来水厂滤后水为研究对象,系统考察了氯胺消毒过程中氮源种类、氯氮比、pH值、反应时间、温度、G值和氯投加速率等因素对一氯胺浓度及消毒副产物(DBPs)生成量的影响。结果表明,氮源种类、Cl₂/N质量比和p H值为主要影响因素,其他为次要影响因素。与氯化铵、碳酸铵、醋酸铵和氨水这4种氮源相比,以硫酸铵为氮源可生成较高浓度的一氯胺;当pH值由6.0增大到9.0时,一氯胺浓度(以Cl₂计)由2.611 mg/L升高至4.256 mg/L;随着Cl₂/N质量比由2∶1逐渐增至8∶1,一氯胺浓度先升后降,并在5∶1时达到最大值3.831 mg/L。DBPs浓度随Cl₂/N质量比、反应时间、温度和氯投加速率的增加而升高,随G值的增大而降低;而随着pH值由6.0增加到9.0,DBPs浓度先降低后略有增加。自来水厂氯胺消毒工艺中一氯胺生成的最佳工艺条件如下:以硫酸铵为氮源,Cl₂/N质量比为(4∶1)~(5∶1),pH值为中性或碱性,反应时间为2 h,温度为25℃左右,G值为300 s-1,混匀慢速加氯。     

Identifying correlates of breaks in occupational sitting: a cross-sectional study

Office workers are commonly targeted in interventions to modify their sitting behaviour, yet there is limited evidence of the correlates of breaks in sitting to inform intervention development. This study identifies the individual, workplace and spatial configuration correlates of the frequency of breaks in sitting (number/hour) in office workers (n?=?5531) stratified by office type (private-enclosed, shared, open plan). All behaviours and potential correlates were measured via self-report using an online cross-sectional survey. Regression analyses revealed age was the only socio-demographic characteristic associated with frequency of breaks in sitting in all office types. Greater job autonomy and local connectivity were positively associated with frequency of breaks in sitting in shared and open-plan offices. In open-plan offices co-worker proximity was negatively associated with frequency of breaks in sitting. Co-worker visibility was positively associated with frequency of breaks in sitting in all office types. This study demonstrates that individual, workplace and spatial configuration factors are all associated with the frequency of breaks in sitting and that these relationships differ by office type. These observations extend prior studies that have only examined correlates at a single level (e.g. the individual). This evidence could be useful to guide future interventions in the design of workplaces to increase breaks in sitting and workers’ physical activity.     

Load Tests of Piled Raft Models with Different Pile Head Connection Conditions and Their Analyses

A series of experimental and analytical studies on the behaviours of model pile groups and model piled rafts in dry sand subjected to static vertical loading and static cyclic horizontal loading were carried out in order to investigate the influence of various pile head connection conditions between the raft and the piles on the behaviours of the foundations models and to examine the applicability of an simplified analytical method to simulate the load tests. In the load tests, the behaviours of the model foundations were investigated in detail, with particular focus on cyclic horizontal loading, and behaviour such as horizontal stiffness and the rotation of the foundation, the load proportions between the raft and the piles, and the bending moments and shear forces generated in the piles. A simplified three-dimensional deformation analysis method was used to simulate the experiments.