Performance of an electrochemical COD (chemical oxygen demand) sensor with an electrode-surface grinding unit

An electrochemical COD (chemical oxygen demand) sensor using an electrode-surface grinding unit was investigated. The electrolyzing (oxidizing) action of copper on an organic species was used as the basis of the COD measuring sensor. Using a simple three-electrode cell and a surface grinding unit, the organic species is activated by the catalytic action of copper and oxidized at a working electrode, poised at a positive potential. When synthetic wastewater was fed into the system, the measured Coulombic yields were found to be dependent on the COD of the synthetic wastewater. A linear correlation between the Coulombic yields and the COD of the synthetic wastewater was established (10-1000 mg L(-1)) when the electrode-surface grinding procedure was activated briefly at 8 h intervals. When various kinds of wastewater samples obtained from various sewage treatment plants were measured, linear correlations (r(2)> or = 0.92) between the measured EOD (electrochemical oxygen demand) value and COD of the samples were observed. At a practical wastewater treatment plant, the measurement system was successfully operated with high accuracy and good stability over 3 months. These experimental results show that the application of the measurement system would be a rapid and practical method for the determination of COD in water industries.     

Development of electrochemical based sandwich enzyme linked immunosensor for Cryptosporidium parvum detection in drinking water

Cryptosporidium parvum is one of the most important biological contaminants in drinking water and generates significant risks to public health. Due to low infectious dose of C. parvum, remarkably sensitive detection methods are required for water and food industry analysis. This present study describes a simple, sensitive, enzyme amplified sandwich form of an electrochemical immunosensor using dual labeled gold nanoparticles (alkaline phosphatase and anti-oocysts monoclonal antibody) in indium tin oxide (ITO) as an electrode to detect C. parvum. The biosensor was fabricated by immobilizing the anti-oocysts McAb on a gold nanoparticle functionalized ITO electrode, followed by the corresponding capture of analytes and dual labeled gold nanoparticle probe to detect the C. parvum target. The outcome shows the sensitivity of electrochemical immune sensor enhanced by gold nanoparticles with a limit of detection of 3 oocysts/mL in a minimal processing period. Our results demonstrated the sensitivity of the new approach compared to the customary method and the immunosensors showed acceptable precision, reproducibility, stability, and could be readily applied to multi analyte determination for environmental monitoring.     

电化学传感法测定水中亚硝酸盐

借助于简单可控的在线电聚合方法,溴酚蓝被修饰到玻碳电极表面,制备了聚溴酚蓝修饰玻碳电极。实验表明,聚溴酚蓝薄膜对于亚硝酸盐的电化学氧化具有很好的催化作用。经实验优化,聚溴酚蓝膜的最佳厚度为聚合20圈,最佳的检测底液为pH=4.0的0.01 mol/L磷酸盐缓冲溶液。亚硝酸盐在传感器上的电化学氧化是一个双电子双质子参与的过程。在最佳检测条件下,亚硝酸盐的氧化峰电流与其浓度在0.02~109.1μmol/L范围内有良好的线性关系,检测限低至5 nmol/L(S/N=3),所制备的亚硝酸盐传感器线性范围宽、检出限低、稳定性和重现性好、抗干扰能力强,将传感器应用于东湖水样中亚硝酸盐含量的测定,结果令人满意。     

Restoration of fly ash dump through biological interventions

Field experiment on 10 ha area of fly ash dump was conducted to restore and revegetate it using biological interventions, which involves use of organic amendment, selection of suitable plant species along with specialized nitrogen fixing strains of biofertilizer. The results of the study indicated that amendment with farm yard manure at 50 t/ha improved the physical properties of fly ash such as maximum water holding capacity from 40.0 to 62.42% while porosity improved from 56.78 to 58.45%. The nitrogen content was increased by 4.5 times due to addition of nitrogen fixing strains of Bradyrhizobium and Azotobacter species, while phosphate content was increased by 10.0 times due to addition of VAM, which helps in phosphate immobilization. Due to biofertilizer inoculation different microbial groups such as Rhizobium, Azotobacter and VAM spores, which were practically absent in fly ash improved to 7.1 × 10⁷, 9.2 × 10⁷ CFU/g and 35 VAM spores/10 g of fly ash, respectively. Inoculation of biofertilizer and application of FYM helped in reducing the toxicity of heavy metals such as cadmium, copper, nickel and lead which were reduced by 25, 46, 48 and 47%, respectively, due to the increased organic matter content in the fly ash which complexes the heavy metals thereby decreasing the toxicity of metals. Amendment of fly ash with FYM and biofertilizer helped in profuse root development showing 15 times higher growth in Dendrocalamus strictus plant as compared to the control. Thus amendment and biofertilizer application provided better supportive material for anchorage and growth of the plant.     

SPATIAL ANALYSIS AND EUTROPHICATION ASSESSMENT FOR CHLOROPHYLL a IN TAIHU LAKE

Spatial structure analysis and kriging analysis have been identified to be useful tools in illustrating the spatial patterns of variables. Taihu Lake is one of the largest fresh water lakes in China, and has suffered serious eutrophication in recent years due to the rapid economic development and growing environmental pollution in the Taihu Catchment. In this paper, spatial structural analysis, kriging interpolation and eutrophication assessment were carried out for chlorophyll a in the lake. Studies show that spherical model could be applied to fit all experimental variograms. Positive nuggets were observed for three directions except NE–SW direction. The variograms show some anisotropy with anisotropic ratio falling within 1.76. The spatial structural patterns of chlorophyll a in the lake were affected by factors such as distribution of pollution sources, water flow and wind. Two-dimensional ordinary block kriging was applied for interpolation process. An eutrophication assessment map was also made based on a water-quality evaluation standard. Results show that the content of chlorophyll a in Taihu Lake was quite high. The whole lake has suffered serious eutrophication. However, the eutrophic situation varied in space. Higher contents of chlorophyll a appeared mainly in the northern part of the lake.     

Modeling of NO x Emissions from Oil Refinery Furnaces

The current paper investigates the possibility of establishing an empirically based model for predicting the emission rate of nitrogen oxides (NO _x ) from oil refinery furnaces, in order to continually track emissions with respect to environmental licence limits. Model input data were collected by direct stack monitoring using an electrochemical cell NO _x analyser, as well as a range of telemetry sensors to obtain refinery process parameters. Principal Component Analysis (PCA), in conjunction with Partial Least Squares (PLS) regression was then used to build a series of models able to predict NO _x emissions from the furnaces. The models produced were proven to be robust, with a relatively high accuracy, and are able to predict NO _x levels over the range of operating conditions which were sampled. It was found that due to structural/operational variations a separate model is usually required for each furnace. The models can be integrated with the refinery operating system to predict NO _x emission rates on a continuous basis. Two models representing structurally different furnaces are considered in this paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimating the Microbial Risk of E. coli in Reclaimed Wastewater Irrigation on Paddy Field

Microbial risk was quantified to assess human health risk as a result of exposure to E. coli in reclaimed wastewater irrigation. Monitoring data on E. coli were collected from pond water in paddy rice plots during the growing season. Five treatments were used and each was triplicated to evaluate the changes in E. coli concentrations in experiments performed in 2003 and 2004. The Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion among farmers and neighboring children. A Monte Carlo simulation (10,000 trials) was conducted to estimate the risk associated with uncertainty. In this study, risk values ranged from 10⁻⁴ to 10⁻⁸. UV-disinfected irrigation water showed a lower risk value than others, and its level was within the range of the actual paddy rice field with surface water. Agricultural activity was thought to be safer after 1–2 days, when the paddy field was irrigated with reclaimed wastewater. Also, children were found to have a greater risk of infection with E. coli. This paper should be viewed as a first step in the application of quantitative microbial risk assessment of wastewater reuse in paddy rice culture.     

Assessment of Chlorophyll-a Concentration and Trophic State for Lake Chagan Using Landsat TM and Field Spectral Data

In this study, we present the digital evaluation of Landsat TM data and field spectral measurements for retrieving chlorophyll-a (chl-a) concentration and trophic state index in Lake Chagan of Northeast China. Chl-a concentration of the lake can be estimated from the band ratio (TM4/TM3) and the field spectral data at 670 nm (absorption peak) and at 700 nm (reflectance peak). The results show that the best determination coefficient (R ²) is 0.67 from the TM data, by which chl-a distribution can be mapped. Based on chl-a determination from laboratory analysis, field spectral and TM data, the modified trophic state index (TSI_M) was applied to assess the lake’s trophic state. With the available data in Lake Chagan, each algorithm demonstrates the similar result for assessing the lake’s chl-a and trophic state. Our results indicate that Landsat TM and field spectral data could be used effectively to determine chl-a concentration and evaluate the trophic state of Lake Chagan in the study.     

Genotoxicity evaluation of water soil leachates by Ames test, comet assay, and preliminary Tradescantia micronucleus assay

Combining genotoxicity/mutagenicity tests and physico-chemical methodologies can be useful for determining the potential genotoxic contaminants in soil samples. The aim of our study was to evaluate the genotoxicity of soil by applying an integrated physico-chemical-biological approach. Soil samples were collected at six sampling points in a Slovenian industrial and agricultural region where contamination by heavy metals and sulphur dioxide (SO₂) are primarily caused by a nearby power plant. The in vitro alkaline version of the comet assay on water soil leachates was performed with Caco-2 and HepG2 cells. A parallel genotoxicity evaluation of the samples was performed by Ames test using Salmonella typhimurium and the Tradescantia micronucleus test. Pedological analyses, heavy metal content determination, and different physico-chemical analyses, were also performed utilizing standard methodology. Water leachates of soil samples were prepared according to standard methods. Since only a battery of biotests with prokaryotic and eukaryotic organisms or cells can accurately estimate the effects of (geno)toxicants in soil samples and water soil leachates, a combination of three bioassays, with cells or organisms belonging to different trophic levels, was used. Genotoxicity of all six water soil leachates was proven by the comet assay on both human cell lines, however no positive results were detected by bacterial assay, Ames test. The Tradescantia micronucleus assay showed increase in micronuclei formation for three samples. According to these results we can assume that the comet assay was the most sensitive assay, followed by the micronucleus test. The Ames test does not appear to be sensitive enough for water soil leachates genotoxicity evaluations where heavy metal contamination is anticipated.     

Modeling the Formation of Chlorination By-Products During Enhanced Coagulation

Because of increasing need to balance health risks for pathogen control and disinfection by-products (DBP) formation in drinking water supplies, water utilities are forced to closely examine and optimize their disinfection practices. This research was designed to investigate the effects of independent variables of dissolved organic carbon (DOC), ferric chloride dosage, chlorine dose, and reaction time on trihalomethanes (THMs) formation in Terkos Lake Water (TLW) of Istanbul City. A statistically-based empirical model was developed for predicting THM formation during enhanced coagulation. The R ² and F value of model were 0.762 and 460, respectively. The model was found to be statistically significant for all four variables, and model predictions appear to be most accurate for this study. A multiple linear model exhibited the best fit of data. It was observed that THM formation depended primarily on DOC removal. Model calibration, testing and validation were accomplished by using independent data set.     

The development of a novel method for directional dust monitoring

Dust monitoring using sticky pads was popularised in the 1980s. The discolouration caused by dust adhering to white adhesive material was measured with a smoke stain reflectometer. This loss of reflectance was expressed as the percentage effective area coverage (EAC%) per day. EAC% can be used as a measure of nuisance caused by dust. EAC% may also be measured with a hand-held Sticky Pad Reader (SPR). Sticky pads can be mounted on flat or cylindrical surfaces to measure dust by deposition or in flux. An alternative method was developed in the 1990s that measured total dust coverage using computer-based scanning. DustScan used a transparent adhesive film wrapped around a vertical cylinder with magnetic north marked. The sticky pad was sealed with another transparent sheet before scanning at 50 dots per inch (dpi). Dust levels were assessed by comparing the grey-scale values of pixels in the exposed area with an unexposed reference area. Insects and other extraneous material could be ‘masked out’ from the computer analysis. Dust coverage was expressed as percentage absolute area coverage (AAC%). DustScan has subsequently been developed commercially. A limited trial indicated that monitoring periods of 7–14 days were preferred to avoid dust saturation of the sticky pad. A method for calculating EAC% has been developed and shown to have a high degree of correspondence with an SPR. A trial for the Minerals Industry Research Organisation (MIRO) made comparisons between DustScan and other dust monitoring methods. Dust nuisance limits based on AAC% and EAC% are proposed.par     

Bioremediation of metal contamination

A study was initiated to evaluate the use of the fungus Aspergillus niger for bioleaching and then todetermine the effect of process steps, the tailingsconcentration and type of substrate. An oxidized miningtailing containing mainly copper (7240 mg kg^-1 tailings) was studied. A sucrose and mineral salts medium was initially used to produce citric and gluconic acids by A. niger atvarious concentrations of tailings (1, 5, 7, 10 and 15% w/v).Maximal removal of up to 60% of the copper was obtained forthe 5% tailings when the organic acid supernatant was addedto the tailings. In a single step process, A. niger wasthen grown in the presence of mining tailings at variousconcentrations. Maximum copper solubilization (63%) occurredwith 10% mining tailings using sucrose as the substrate.Other substrates were then evaluated including molasses, corncobs and brewery waste (10% mining tailings). Sucrose gavethe best results for copper removal, followed by molasses,corn cobs and brewery waste. Other experiments usingultrasound as a pretreatment showed that 80% removal of thecopper could be obtained for a 5% tailings concentration. Inconclusion, leaching of copper from mining tailings istechnically feasible using A. niger but furtherresearch will be required to increase the economic feasibilityof the process.     

Spatial Relationships Between Water Quality and Pesticide Application Rates in Agricultural Watersheds

Pesticide applications to agricultural lands in California, USA, are reported to a central data base, while data on water and sediment quality are collected by a number of monitoring programs. Data from both sources are geo-referenced, allowing spatial analysis of relationships between pesticide application rates and the chemical and biological condition of water bodies. This study collected data from 12 watersheds, selected to represent a range of pesticide usage. Water quality parameters were measured during six surveys of stream sites receiving runoff from the selected watershed areas. This study had three objectives: to evaluate the usefulness of pesticide application data in selecting regional monitoring sites, to provide information for generating and testing hypotheses about pesticide fate and effects, and to determine whether in-stream nitrate concentration was a useful surrogate indicator for regional monitoring of toxic substances. Significant correlations were observed between pesticide application rates and in-stream pesticide concentrations (p < 0.05) and toxicity (p < 0.10). In-stream nitrate concentrations were not significantly correlated with either the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.30). Neither total watershed area nor the area in which pesticide usage was reported correlated significantly with the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.14). In-stream pesticide concentrations and effects were more closely related to the intensity of pesticide use than to the area under cultivation.     

Activity monitoring for nitrifying bacteria by fluorescence in situ hybridization and respirometry

The activities of two families of nitrifying bacteria weremeasured by applied respirometer and fluorescence insitu hybridization (FISH) for the purpose of monitoring nitrogenremoval. Oxygen uptake rates (OUR) for Nitrosomonas andNitrobacter were separately measured with the dosing ofselective inhibitors during respirometric monitoring. The FISHmethod was applied to analyze microorganism communities. In 5mg NH₄ ⁺-N/L solution, the total nitrogen oxygendemand (NOD) was found to be 6,672 mg DO/L-day with ammoniaand nitrite oxidation rate of 4,512 and 2,160 mg DO/L-day,respectively. The oxygen consumption by endogenous oxidationwas 288 mg DO/L-day and the biological oxygen demand 936 mgDO/L-day. Respirometric measurements were well matched by theFISH result, which described the presence and quantity of eachnitrifying bacteria as nitrification proceeded. It was foundthat when coupled with OUR data, FISH could provide valuableinformation about the nitrogen removal process in manypractical wastewater treatment systems.     

Whole Effluent Toxicity (WET) Tests on Wastewater Treatment Plants with Daphnia magna and Selenastrum capricornutum

Whole effluent toxicity (WET) tests, with Daphnia magna and Selenastrum capricornutum, were introduced to evaluate the biological toxicities of effluents from the wastewater treatment plants (WWTPs) in Korea. In WET tests of WWTPs effluents, 33.3% (33/99) for D. magna and 92.6% (75/81) for S. capricornutum revealed greater than 1 toxic unit (TU), even though all the treatment plants investigated were operating in compliance with the regulations, as assessed using conventional monitoring methods (i.e., BOD and total concentration of N or P, etc). There were only minor differences in toxicities according to the types of influents (municipal and agro-industrial) in all treatment plants. However, the effluents treated by an activated sludge treatment process were found to exhibit significantly lower toxicity than those treated by rotating biological contactor (RBC) and extended aeration processes. The seasonal variations in the toxicity were lower in the summer compared to winter, which may have been due to the rainfall received to the sewage intake system during the former period. The impact of WET on river water was also investigated based on the discharge volume. At sites A and B, the total impact of toxicity to stream and river waters was observed to be 70.9% and 90.4% for D. magna and S. capricornutum, respectively. The other four small treatment plants (sites F, G, H and I), with relative discharging volumes between 0.001 and 0.002, contribute less than 1% to the total toxicity.     

Estimation of Heavy Metals in Different Berberis Species and Its Market Samples

Popularity of herbal drugs is increasing all over the world because of lesser side effects as compared to synthetic drugs. Besides, it costs less and easily available to poor people particularly in developing countries. But quality assurance of herbal drugs is very necessary prior to its use. Because in today's polluted environment, even herbal drugs are not safe. Berberis spp. is very important medicinal plant, having various medicinal properties. It is also included in Indian and British pharmacopoeias. Its demand is quite high in herbal drug market. So, to check the quality of market samples of this drug, ten different samples were procured from different drug markets of India for heavy metal estimation. Besides, genuine samples of four species of Berberis viz. B. aristata, B. chitria, B. lycium, B. asiatica were also collected from natural habitats to compare heavy metal concentration in both market and genuine samples. It was found that market samples were much more contaminated than genuine samples. Lead (Pb) concentration is far beyond from WHO permissible limit (10 ppm) for herbal drugs, reaching to maximum 49.75 ppm in Amritsar market sample. Likewise, concentration of all other metals like Cd, Cr and Ni were also very high in market samples as compared to genuine samples.     

Vegetation Mapping for Change Detection on an Arid-Zone River

A vegetation mapping system for change detection was tested at the Havasu National Wildlife Refuge (HNWR) on the Lower Colorado River. A low-cost, aerial photomosaic of the 4200 ha, study area was constructed utilizing an automated digital camera system, supplemented with oblique photographs to aid in determining species composition and plant heights. Ground-truth plots showed high accuracy in distinguishing native cottonwood (Populus fremontii) and willow (Salix gooddingii) trees from other vegetation on aerial photos. Marsh vegetation (mainly cattails, Typha domengensis) was also easily identified. However, shrubby terrestrial vegetation, consisting of saltcedar (Tamarix ramosissima), arrowweed (Pluchea sericea), and mesquite trees (Prosopis spp.), could not be accurately distinguished from each other and were combined into a single shrub layer on the final vegetation map. The final map took the form of a base, shrub and marsh layer, which was displayed as a Normalized Difference Vegetation Index map from a Landsat Enhanced Thematic Mapper (ETM+) image to show vegetation intensity. Native willow and cottonwood trees were digitized manually on the photomosaic and overlain on the shrub layer in a GIS. By contrast to present, qualitative mapping systems used on the Lower Colorado River, this mapping system provides quantitative information that can be used for accurate change detection. However, better methods to distinguish between saltcedar, mesquite, and arrowweed are needed to map the shrub layer.     

Fly-ash-induced oxidative stress and tolerance in Prosopis juliflora L. grown on different amended substrates

Field experiments were conducted to study the impact of metal accumulation on malondialdehyde (MDA), cysteine and non-protein thiol (NPSH) contents in the plants of Prosopis juliflora grown on the fly ash (FA) amended with soil, blue green algae (BGA) biofertilizer, farm yard manure, press mud and Rhizobium inoculation. The analysis of data revealed that the level of MDA, cysteine and NPSH was higher in the roots of the plant than leaves, which was found positively correlated with metal accumulation. An increase of 361.14, 64.25 and 305.62% in MDA, cysteine and NPSH contents, respectively was observed after 45 days in the roots of the plants grown in 100% FA as compared to 100% garden soil (GS). The level of MDA, cysteine and NPSH was found less in the plants grown on various amendments of FA showing ameliorating effect on the toxicity induced due to the accumulation of metals. The decrease in MDA, cysteine and NPSH contents was higher in Rhizobium-inoculated plants as compared to uninoculated plants grown on 100% FA. The results showed a high tolerance potential of the plant, which is further increased by inoculating the plant with FA-tolerant Rhizobium showing feasibility of using P. juliflora in environmental monitoring of FA landfills.     

Parameters affecting partitioning of 6 PCB congeners in natural sediments

Polychlorinated biphenyls (PCBs) released by bottom sediments were determined by experiments in which the sediments were artificially resuspended using sediment contaminated with PCBs in a particle entrainment simulator (PES). Sediment cores, spikedwith PCBs, were collected from the Housatonic River in Connecticut and run in the PES at simulated shear stresses from 0 to 0.6 N m^-2. Experimental results from these simulations have shown that mean concentration of PCBs in thesolid phase for sites with high volatile organic carbon (VOC) were significantly greater than samples with low VOC; the reversewas true for the water phase. In addition, on a mass load basis,the amount of PCBs found in sediment increased when shear stresses were increased from 0 to 0.6 N m^-2, beyond which shear stress did not affect mass loads in the watercolumn. Partition coefficients (K _p) were determined from PESsediment and water data for the following congeners: PCB 28, PCB 52, PCB 101, PCB 138, PCB 153, PCB 180. K _p was determined to be inversely proportional to total suspended solids (TSS), butdirectly proportional to chlorine content of the congener. Because of the strong influence of TSS and VOC concentrations onK _p values, agitation of samples using a PES better simulatedreal environmental conditions when compared to jar studies where no agitation was employed. Therefore, a device like the PES is more appropriate in obtaining K _p that would be found underreal stream flow conditions when compared to the traditionalway of measuring K _p using the jar study technique.     

Detection of hormone mimics in water using a miniturised SPR sensor

The ubiquitous presence of chemicals, both natural andsynthetic, in the environment with the potential to mimichormones that may in turn interfere with the endocrinesystem in both wildlife and humans has in the last decadebecome a major international concern. Hormone mimics orendocrine disrupting compounds (EDCs) are especiallyprevalent in surface and waste-waters and therefore, thereis a need for an at-source or at-line analytical device forthe monitoring of EDC levels.We have incorporated a miniature integrated surface plasmonresonance (SPR) liquid sensor from Texas Instruments into afield analyser and developed a competition/inhibition assayfor a model estrogenic compound in aqueous samples. Theanalyser has the potential for in situ and semi-continuous analysis of EDCs. A novel regeneration schemeemploying the use of a domestic laundry detergent has beenused to remove immobilised assay components between eachassay cycle. The resultant re-usable sensor has beendemonstrated using estrone-3-glucuronide (E3G) as a modelEDC and an anti-E3G antibody producing a current detectionrange of 10 to 150 ng mL^-1.