Application of a pathogenicity marker found in Escherichia coli for the assessment of irrigation water quality.

A polymerase chain reaction (PCR)-based method was developed to differentiate between pathogenic and nonpathogenic Escherichia coli (E. coli). A pathogenicity marker, linked to the deletion of the ygfB gene, was identified in 80% of the clinical E. coli isolates tested. This marker, combined with the malic acid dehydrogenase gene, formed the duplex PCR that was subsequently used to screen E. coli isolates recovered from two secondary wastewater treatment plants (STPs) and a river site. All waters samples are used to irrigate dairy farm pasture in the West Gippsland region of Victoria, Australia. Results from three consecutive months of sampling (December 2001 and January and February 2002) indicated that Longwarry STP showed 8, 8, and 0% pathogenic E. coli; Pakenham STP showed 0, 12.5, and 33%; and the Bunyip river site showed 20, 12, and 25% respectively.     

Constructed wetlands for mitigation of atrazine-associated agricultural runoff

Atrazine was amended into constructed wetlands (59-73x14x0.3 m) for the purpose of monitoring transport and fate of the pesticide to obtain information necessary to provide future design parameters for constructed wetlands mitigation of agricultural runoff. Following pesticide amendment, a simulated storm and runoff event equal to three volume additions was imposed on each wetland. Targeted atrazine concentrations were 0 microg/l (unamended control), 73 microg/l, and 147 microg/l. Water, sediment, and plant samples were collected weekly for 35 days from transects longitudinally distributed throughout each wetland and were analyzed for atrazine using gas chromatography. Between 17 and 42% of measured atrazine mass was within the first 30-36 m of wetlands. Atrazine was below detection limits (0.05 microg/kg) in all sediment and plant samples collected throughout the duration of this study. Aqueous half lives ranged from 16 to 48 days. According to these data, conservative buffer travel distances of 100-280 m would be necessary for effective runoff mitigation.     

Constructed wetlands as a component of the agricultural landscape: mitigation of herbicides in simulated runoff from upland drainage areas

Constructed wetlands are a recommended practice for buffering pollutant source areas and receiving waters. A wetland consisting of a sediment trap and two treatment cells was constructed in a Mississippi Delta lake watershed. A 3-h simulated runoff event was initiated (2003) to evaluate fate and transport of atrazine and fluometuron through the wetland. Water samples were collected during a runoff simulation and then afterward at selected intervals for 21 d, and analyzed for the herbicides. Breakthrough patterns for herbicide concentrations in water samples during the first 20 h after simulated runoff showed peak concentrations in the first 6 h, with gradual tailing as the herbicide pulse was diluted in the second, excavated (deeper) cell. Atrazine and fluometuron concentrations in the first (shallower, non-excavated) cell averaged 12- and 20-fold greater, respectively, than those in the second cell following simulated runoff, indicating entrapment in the first cell. Atrazine and fluometuron concentrations in the shallower cell decreased 32% and 22%, respectively, 9 d following simulated runoff, indicating either degradation or sorption to soil or wetland flora. In the excavated cell, concentrations were even lower, and atrazine declined more rapidly than fluometuron. Results indicate constructed wetlands can improve downstream water quality though sequestration or processing of pollutants.     

Source apportionment of visual impairment during the California regional PM10/PM2.5 air quality study

Gases and particulate matter predictions from the UCD/CIT air quality model were used in a visibility model to predict source contributions to visual impairment in the San Joaquin Valley (SJV), the southern portion of California's Central Valley, during December 2000 and January 2001. Within the SJV, daytime (0800–1700 PST) light extinction was dominated by scattering associated with airborne particles. Measured daytime particle scattering coefficients were compared to predicted values at approximately 40 locations across the SJV after correction for the increased temperature and decreased relative humidity produced by “smart heaters” placed upstream of nephelometers. Mean fractional bias and mean fractional error were ?0.22 and 0.65, respectively, indicating reasonable agreement between model predictions and measurements. Particulate water, nitrate, organic matter, and ammonium were the major particulate species contributing to light scattering in the SJV. Daytime light extinction in the SJV averaged between December 25, 2000 and January 7, 2001 was mainly associated with animal ammonia sources (28%), diesel engines (18%), catalyst gasoline engines (9%), other anthropogenic sources (9%), and wood smoke (7%) with initial and boundary conditions accounting for 13%. The source apportionment results from this study apply to wintertime conditions when airborne particulate matter concentrations are typically at their annual maximum. Further study would be required to quantify source contributions to light extinction in other seasons.     

Escherichia coli and total coliforms in water and sediments at lake marinas

Escherichia coli, a fecal coliform, and total coliforms were monitored between September 1999 and October 2001 in five marinas at Lake Texoma, located on the Oklahoma and Texas border. The general trend was that densities of E. coli were lower in the summer season due to the lower loading of fecal material into Lake Texoma and the ecological conditions of the lake, such as more vigorous grazing by protozoa and less viability of E. coli at an elevated temperature. The densities of total coliforms greatly increased in the summer. E. coli levels increased with depth, and the bottom water samples had higher densities of E. coli mainly due to their association with particles. There was a direct relationship between amount of gasoline sold, which was related to recreational boating activity, and the resuspension of E. coli. This indicated that recreational boating activity in lake marinas may have resuspended bottom sediments with bound E. coli, and the presence of E. coli in marinas was not an indication of recent fecal contamination. E. coli were detected in the largest densities at the boat dock points, followed by the gasoline filling station, and marina entrance. In addition, enumeration of bacteria in bottom sediment showed that the densities of E. coli and total coliforms in sediment were much higher compared to those in lake water.     

Physiological parameters of plants as indicators of water quality in a constructed wetland

Introduction  

Increasing demand for water has stimulated efforts to treat wastewater for reuse in agriculture. Decentralized facilities for wastewater treatment became popular as a solution to remote and small communities. These systems mimic natural wetlands, cleaning wastewater as they flow through a complex of filter media, microbial fauna, and vegetation. The function of plants in constructed wetlands (CWs) has not been fully elucidated yet.     

2种人工湿地的水力停留时间及净化效果

以复合垂直流人工湿地(IVCW)和水平潜流人工湿地(HSCW)为研究对象,研究了2种湿地运行的季节性最佳水力停留时间(HRT)参数,并监测了2种湿地在最佳HRT参数下运行时对污水的净化效果。结果显示:(1)在IVCW中,最佳HRT在春、秋季为8～10 h;夏季为6 h;冬季为12 h。在HSCW中,最佳HRT在春、秋季为10～12 h;夏季为6～8h;冬季为24～36 h。(2)2种湿地对COD的去除率均无显著的季节性差异;湿地进水中NH4+-N/TN比值与TN去除率显著负相关;不同季节下IVCW对TN的去除效果均高于HSCW。(3)水温对TN、TP去除率的影响在IVCW中比HSCW中的明显;水温高时,2种湿地中的TN去除率较高,IVCW中的TP去除率也较高,但HSCW中的TP去除率则较低,它们间均未达到显著的相关性。     

人工湿地系统微生物去除污染物的研究进展

人工湿地污水处理系统具有净化效果显著、建设和运行费用低廉、管理简便等优点,近年来越来越受到人们的重视。人工湿地是利用介质、植物和微生物构成的复合系统来处理污水。微生物在人工湿地系统净化污水过程中发挥着重要作用。介绍了人工湿地系统中微生物去除污染物的研究进展,重点讨论了人工湿地对污染物和特殊有机污染物的去除以及系统基质中微生物的种群和活性等内容,并结合我国研究现状展望了该领域的研究前景。人工湿地系统微生物对污染物去除将成为人工湿地生态系统服务功能评价、人工湿地生态系统健康与稳定的诊断的重要组成部分。     

Sanitation assessment of wastewater treated by stabilization ponds for potential reuse in agricultural irrigation sanitation assessment.

Wastewater reuse has become an important alternative to agricultural irrigation; on the other hand, it poses concern with regard to public health. Total coliform and Escherichia coli concentration, presence of helminth eggs and Salmonella, and physical-chemical parameters were evaluated in raw and treated wastewater. Chemical and biochemical oxygen demand removal efficiency was 74.6 and 77.9%, respectively. As for organic nitrogen, total phosphorus, and total suspended solids, total efficiency removal was 17.4, 12.5, and 32.9%, respectively. The average density of total coliforms and E. coli was 3.5 x 10(9) and 1.8 x 10(8) MPN/100 mL and 1.1 x 10(7) MPN/100 mL and 3.9 x 10(5) MPN/100 mL for raw and treated wastewater, respectively. Ascaris eggs were observed in 80.8% of the samples collected, and viable eggs in 42.3% of the samples. Salmonella was detected in 36.4% of the samples. The values observed in treated wastewater did not show the adequate bacteriological quality, as recommended by World Health Organization (Geneva, Switzerland). Therefore, additional measures should be taken to achieve an improved microbiological and parasitological quality.     

Influence of vegetation in mitigation of methyl parathion runoff

A pesticide runoff event was simulated on two 10 m x 50 m constructed wetlands (one non-vegetated, one vegetated) to evaluate the fate of methyl parathion (MeP) (Penncap-M). Water, sediment, and plant samples were collected at five sites downstream of the inflow for 120 d. Semi-permeable membrane devices (SPMDs) were deployed at each wetland outflow to determine exiting pesticide load. MeP was detected in water at all locations of the non-vegetated wetland (50 m), 30 min post-exposure. MeP was detected 20 m from the vegetated wetland inflow 30 min post-exposure, while after 10d it was detected only at 10 m. MeP was measured only in SPMDs deployed in non-vegetated wetland cells, suggesting detectable levels were not present near the vegetated wetland outflow. Furthermore, mass balance calculations indicated vegetated wetlands were more effective in reducing aqueous loadings of MeP introduced into the wetland systems. This demonstrates the importance of vegetation as sorption sites for pesticides in constructed wetlands.     

Long-term efficiency and stability of wetlands for treating wastewater of a lead/zinc mine and the concurrent ecosystem development

A constructed wetland system in Guangdong Province, South of China has been used for treating Pb/Zn mine discharge since 1985. The performance in the purification of the mine discharge and the concurrent ecosystem development within the system during the period of 1985-2000 has been studied. The untreated wastewater contained rather high concentrations of cadmium (Cd) (0.05 mg L(-1)), lead (Pb) (11.5 mg L(-1)), and zinc (Zn) (14.5 mg L(-1)), which greatly exceed the upper limits for industrial wastewater discharge in China. The constructed wetland system effectively removed Cd by 94.00%, Pb by 99.04%, Zn by 97.30%, and total suspended solids (TSS) by 98.95% from the mine discharge over a long period (over 16 years) leading to significant improvement in water quality; it was also found that there were no significantly annual or monthly variations in pH values, As, Cd, Hg, Pb, and Zn concentrations in water collected from the outlet of the wetland. Moreover, diversity and abundance of living organisms, including protozoan, higher plants, terrestrial animals, and birds, increased gradually. The 16-year monitoring results showed a reciprocal relationship, at a certain extent, between restoration of the wetland ecosystem, in other words, the maturity of the wetland, and the long-term efficiency and stability on purifying heavy metal-contaminated wastewater.     

Investigation of the soil radon variation during the winter months in Sapporo, Japan

Soil radon was measured from late October 2000 to January 2001 at three test sites on the campus of Hokkaido University in Sapporo, Japan. Factors affecting radon concentrations were investigated with relation to meteorological data, as well as soil 226Ra content, mineral composition, water content, and pH, Eh and conductivity. Soil radon varied with time and with sampling site appreciably, in a manner unaltered by the surface geology. However, the ratio of radon isotopes (220Rn/222Rn) in the soil was constant within each sampling site, regardless of varying concentration of these nuclides during the monitoring period. Snow covering on the soil surfaces may affect the 222Rn concentration.     

Transport of Escherichia coli and solutes during waste water infiltration in an urban alluvial aquifer

Recharge of waste water in an unconsolidated poorly sorted alluvial aquifer is a complex process, both physically and hydrochemically. The aim of this paper is to analyse and conceptualise vertical transport mechanisms taking place in an urban area of extensive wastewater infiltration by analysing and combining the water balance, the microbial (Escherichia coli) mass balance, and the mass balance for dissolved solutes. For this, data on sediment characteristics (grain size, organic carbon, reactive iron, and calcite), groundwater levels, and concentrations of E. coli in groundwater and waste water were collected. In the laboratory, data on E. coli decay rate coefficients, and on bacteria retention characteristics of the sediment were collected via column experiments. The results indicated that shallow groundwater, at depths of 50 m below the surface, was contaminated with E. coli concentrations as high as 10(6) CFU/100 mL. In general, E. coli concentrations decreased only 3 log units from the point of infiltration to shallow groundwater. Concentrations were lower at greater depths in the aquifer. In laboratory columns of disturbed sediments, bacteria removal was 2-5 log units/0.5 cm column sediment. Because of the relatively high E. coli concentrations in the shallow aquifer, transport had likely taken place via a connected network of pores with a diameter large enough to allow bacterial transport instead of via the sediment matrix, which was inaccessible for bacteria, as was clear from the column experiments. The decay rate coefficient was determined from laboratory microcosms to be 0.15 d(-1). Assuming that decay in the aquifer was similar to decay in the laboratory, then the pore water flow velocity between the point of infiltration and shallow groundwater, coinciding with a concentration decrease of 3 log units, was 0.38 m/d, and therefore, transport in this connected network of pores was fast. According to the water balance of the alluvial aquifer, determined from transient groundwater modelling, groundwater flow in the aquifer was mainly in vertical downward direction, and therefore, the mass balance for dissolved solutes was simulated using a 1D transport model of a 200 m column of the Quaternary Alluvium aquifer. The model, constructed with PHREEQC, included dual porosity, and was able to adequately simulate removal of E. coli, cation-exchange, and nitrification. The added value of the use of E. coli in this study was the recognition of relatively fast transport velocities occurring in the aquifer, and the necessity to use the dual porosity concept to investigate vertical transport mechanisms. Therefore, in general and if possible, microbial mass balances should be considered more systematically as an integral part of transport studies.     

Possible use of constructed wetland to remove selenocyanate,arsenic, and boron from electric utility wastewater

Wetland microcosms were used to evaluate the ability of constructed wetlands to remove extremely high concentrations of selenocyanate (SeCN-), arsenic (As), and boron (B) from wastewater generated by a coal gasification plant in Indiana. The wetland microcosms significantly reduced the concentrations of selenium (Se), As, B, and cyanide (CN) in the wastewater by 64%, 47%, 31%, and 30%, respectively. In terms of the mass of each contaminant, 79%, 67%, 57%, and 54% of the Se, As, B, and CN, respectively, loaded into the microcosms were removed from the wastewater. The primary sink for the retention of contaminants within the microcosms was the sediment, which accounted for 63%, 51%, and 36% of the Se, As, and B, respectively. Accumulation in plant tissues accounted for only 2-4%, while 3% of the Se was removed by biological volatilization to the atmosphere. Of the 14 plant species tested, cattail, Thalia, and rabbitfoot grass were highly tolerant of the contaminants and exhibited no growth retardation. Environmental toxicity testing with fathead minnow (Pimephales promelas) larvae confirmed that the water treated by the wetland microcosms was less toxic than untreated water. The data from the wetland microcosms support the view that constructed wetlands could be used to successfully reduce the toxicity of aqueous effluent contaminated with extremely high concentrations of SeCN-, As, and B, and that a pilot-scale wetland should therefore be constructed to test this in the field. Cattail, Thalia, and rabbitfoot grass would be suitable plant species to establish in such wetlands.     

Analysis of PM10, PM2.5, and PM2 5-10 concentrations in Santiago, Chile, from 1989 to 2001

Daily particle samples were collected in Santiago, Chile, at four urban locations from January 1, 1989, through December 31, 2001. Both fine PM with da < 2.5 microm (PM2.5) and coarse PM with 2.5 < da < 10 microm (PM2.5-10) were collected using dichotomous samplers. The inhalable particle fraction, PM10, was determined as the sum of fine and coarse concentrations. Wind speed, temperature and relative humidity (RH) were also measured continuously. Average concentrations of PM2.5 for the 1989-2001 period ranged from 38.5 microg/m3 to 53 microg/m3. For PM2.5-10 levels ranged from 35.8-48.2 microg/m3 and for PM10 results were 74.4-101.2 microg/m3 across the four sites. Both annual and daily PM2.5 and PM10 concentration levels exceeded the U.S. National Ambient Air Quality Standards and the European Union concentration limits. Mean PM2.5 levels during the cold season (April through September) were more than twice as high as those observed in the warm season (October through March); whereas coarse particle levels were similar in both seasons. PM concentration trends were investigated using regression models, controlling for site, weekday, month, wind speed, temperature, and RH. Results showed that PM2.5 concentrations decreased substantially, 52% over the 12-year period (1989-2000), whereas PM2.5-10 concentrations increased by approximately 50% in the first 5 years and then decreased by a similar percentage over the following 7 years. These decreases were evident even after controlling for significant climatic effects. These results suggest that the pollution reduction programs developed and implemented by the Comisión Nacional del Medio Ambiente (CONAMA) have been effective in reducing particle levels in the Santiago Metropolitan region. However, particle levels remain high and it is thus imperative that efforts to improve air quality continue.     

Partitioning and source diagnostics of polycyclic aromatic hydrocarbons in rivers in Tianjin, China

Water, suspended particulate matter (SPM), and sediment samples were collected from ten rivers in Tianjin and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), dissolved organic carbon (DOC), particulate organic carbon (POC) in SPM and total organic carbon (TOC) in sediment. The behavior and fate of PAHs influenced by these parameters were examined. Generally, organic carbon was the primary factor controlling the behavior of the 16 PAH species. Partitioning of PAHs between SPM and water phase was studied, and K(OC) for some PAH species were found to be significantly higher than the predicted values. The source of PAHs contamination was diagnosed by using PAH isomer ratios. Coal combustion was identified to be a long-term and prevailing contamination source for sediment, while sewage/wastewater source could reasonably explain a short-term PAHs contamination of SPM.     

复合垂直流与潜流人工湿地沿程脱氮除磷对比研究

针对复合垂直流和潜流人工湿地对COD、TP、NH_4~+-N、NO~3~--N和TN的沿程去除规律进行了对比研究.结果表明,夏季复合垂直流人工湿地的去除效果均好于潜流人工湿地.对于复合垂直流人工湿地,污染物的去除主要集中在下行流池,且在进水端0～20 cm对COD、TP、NH_4~+-N和TN都有快速降解的过程.对于潜流人工湿地,进水端0～40 cm主要是COD和TP的快速降解沉淀,之后硝化作用逐渐加强,潜流人工湿地沿程均会发生反硝化作用,TN浓度基本呈均匀下降趋势.     

Sulphur transformation and deposition in the rhizosphere of Juncus effusus in a laboratory-scale constructed wetland

Sulphur cycling and its correlation to removal processes under dynamic redox conditions in the rhizosphere of helophytes in treatment wetlands are poorly understood. Therefore, long-term experiments were performed in laboratory-scale constructed wetlands treating artificial domestic wastewater in order to investigate the dynamics of sulphur compounds, the responses of plants and nitrifying microorganisms under carbon surplus conditions, and the generation of methane. For carbon surplus conditions (carbon:sulphate of 2.8:1) sulphate reduction happened but was repressed, in contrast to unplanted filters mentioned in literature. Doubling the carbon load caused stable and efficient sulphate reduction, rising of pH, increasing enrichment of S(2-) and S(0) in pore water, and finally plant death and inhibition of nitrification by sulphide toxicity. The data show a clear correlation of the occurrence of reduced S-species with decreasing C and N removal performance and plant viability in the experimental constructed wetlands.     

Hydroponic root mats for wastewater treatment—a review

Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs.