Genotyping of single Cryptosporidium oocysts isolated from sewage and river water.

The study was designed to genotype individual Cryptosporidium oocysts using an 18S rRNA gene-based semi-nested PCR and direct sequencing procedure. Positive PCR amplification was observed in all single C. parvum HNJ-1 oocyst samples tested. Semi-nested PCR and direct sequencing was applied to Cryptosporidium oocysts isolated from sewage and river water. The procedure could genotype 54% of FITC-stained single oocysts isolated from sewage and 32% from river water. The predominant genotype in both sewage and river water was C. parvum genotype 1, accounting for 33 and 25%, respectively, of all the FITC-stained intact Cryptosporidium oocysts present.     

Pathogen monitoring offers questionable protection against drinking-water risks: a QMRA (quantitative microbial risk analysis) approach to assess management strategies.

Risk mitigation provided by human monitoring and control over a water supply system has been consistently overlooked when estimating pathogen exposure to consumers. The Systems-Actions-Management (SAM) framework lends itself neatly to Quantitative Microbial Risk Assessment (QMRA) as one way to establish this link. The general premise is that an organisational protocol will influence how a human controller behaves, in turn influencing the system performance. For illustrative purposes, the framework was applied to a hypothetical water supply system to quantify the risk reduction offered by routine Cryptosporidium monitoring and the response to oocyst 'detects'. Our findings suggest that infrequent direct pathogen monitoring may provide a negligible risk barrier. The practice of sampling treated water to verify microbiological integrity is also dubious: oocyst densities were largely under-estimated, in part due to the spatial dispersion of oocysts in the waterbody, but predominantly from imperfect detection methods. The development of 'event-driven' monitoring schemes with barrier performance-based treatment verification methods, as promoted in new guidelines, is supported as a pressing issue to reduce the likelihood of undetected pathogen passage through a treatment plant.     

Inactivation of enteric microbes in water by electro-chemical oxidant from brine (NaCl) and free chlorine.

Oxidant solutions of mostly free chlorine can be electrochemically produced on-site from brine (NaCl) solution and used to disinfect water at the household or community level. In this study electrochemical oxidant (ECO) from brine and free chlorine were evaluated under laboratory conditions for inactivation of test microbes. Purified suspensions of Escherichia coli, the rugose strain of Vibrio cholerae, Clostridium perfringens spores, MS2 coliphage and Cryptosporidium parvum oocysts were treated with 2 mg/L or 5 mg/L solutions of ECO or free chlorine at 5 degrees C and 25 degrees C and pH 6, 8, and 10 (pH 7 and 25 degrees C only for C. parvum oocysts) for contact times <60 min. Under nearly all conditions, inactivation kinetics were more rapid for E. coli, V. cholerae, C. perfringens spores and MS2 coliphage with ECO than with free chlorine. ECO reduced E. coli, V. cholerae and MS2 by >4 log10 within 30 min and C. perfringens spores by >2 log10 within 10 min at pH 8 and 25 degrees C. Contrary to previous results, however, C. parvum oocysts were not inactivated by ECO, and the reasons for this difference are uncertain. The on-site electrolytic generation of oxidants from brine provided a convenient and inexpensive disinfectant containing free chlorine that was effective against many enteric microbes, for the treatment of household and community drinking-water supplies worldwide. However, the effectiveness of such oxidants for inactivating C. parvum oocysts was variable and sometimes ineffective.     

Elimination of viruses, bacteria and protozoan oocysts by slow sand filtration.

The decimal elimination capacity (DEC) of slow sand filters (SSF) for viruses, bacteria and oocysts of Cryptosporidium has been assessed from full-scale data and pilot plant and laboratory experiments. DEC for viruses calculated from experimental data with MS2-bacteriophages in the pilot plant filters was 1.5-2 log10. E. coli and thermotolerant coliforms (Coli44) were removed at full-scale and in the pilot plant with 2-3 log10. At full-scale, Campylobacter bacteria removal was 1 log10 more than removal of Coli44, which indicated that Coli44 was a conservative surrogate for these pathogenic bacteria. Laboratory experiments with sand columns showed 2-3 and >5-6 log10 removal of spiked spores of sulphite-reducing clostridia (SSRC; C. perfringens) and oocysts of Cryptosporidium respectively. Consequently, SSRC was not a good surrogate to quantify oocyst removal by SSF. Removal of indigenous SSRC by full-scale filters was less efficient than observed in the laboratory columns, probably due to continuous loading of these filter beds with spores, accumulation and retarded transport. It remains to be investigated if this also applies to oocyst removal by SSF. The results additionally showed that the schmutzdecke and accumulation of (in)organic charged compounds in the sand increased the elimination of microorganisms. Removal of the schmutzdecke reduced DEC for bacteria by +/-2 log10, but did not affect removal of phages. This clearly indicated that, besides biological activity, both straining and adsorption were important removal mechanisms in the filter bed for microorganisms larger than viruses.     

上海市浦东给水厂两虫去除研究

采用EPA1623法(免疫磁分离及荧光染色法)对上海市几家典型的给水厂的水源水、出厂水、管道水中贾第鞭毛虫和隐孢子虫的分布状况进行了测定分析,并对给水厂净水过程中不同操作单元对两虫的去除效果进行了研究.研究表明:上海浦东给水厂水源水中存在贾第鞭毛虫与隐孢子虫,但其密度分别维持在0～6个/10 L和0～8个/10 L的低水平,而出厂水与管道水中均未检出两虫;给水厂净水过程中,混凝沉淀对两虫具有明显的去除效果.     

Using ultraviolet light for disinfection of finished water.

Ultraviolet light is now recognised to be very effective for inactivation of Cryptosporidium parvum oocysts; however, its application for disinfection of finished water necessitates validation of UV reactors prior to their installation. Although reactor performance will likely be assessed using non-pathogenic microorganisms as biodosimetry surrogates, it would be prudent for the water industry to simultaneously measure Cryptosporidium oocysts inactivation in controlled bench-scale studies using the water matrix intended for disinfection. The likelihood of that occurring is dependent upon the availability of infectivity measurement procedures that are more user-friendly than the mouse infectivity assays currently used. This study describes a modified cell culture procedure that would enable reliable measurement of changes in oocysts' infectivity following their UV treatment. Also, a number of different biodosimetry surrogates were examined and one selected for comparing the UV doses delivered between bench-scale and full-scale biodosimetry studies. Impacts of UV disinfection on production of disinfection byproducts, effects of lamp ageing on effectiveness of disinfection and the costs associated with employing this technology were also examined.     

Quantification and genotyping of Cryptosporidium spp. in river water by quenching probe PCR and denaturing gradient gel electrophoresis.

A new detection method was developed for the simultaneous quantification and genotyping of Cryptosporidium spp. in river water. Several modifications made to the US EPA Method 1623 enabled high and stable recovery of Cryptosporidium from 40 L of river water (geometric mean = 35%, standard deviation = 8.7%). Quenching probe PCR (QProbe PCR) was used to quantify the 18S rRNA gene of Cryptosporidium spp. This method could successfully detect single oocysts in a sample, and the lower quantitation limit was as low as 2.5 oocysts/sample. In addition, denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing was used to identify the genotypes. These methods were applied to detect Cryptosporidium spp. in the Koyama River, Japan. The positive ratio was 69% (11/16) with the maximum concentration of 59 oocysts/100 L. Seven genotypes including two novel ones were identified. These results showed that this detection method could provide valuable information on Cryptosporidium in river water, both in the concentration and in the genotypes, which is essential for the precise assessment of waterborne risk to human health.     

Experimental Study on Slope Runoff,Erosion and Sediment under Different Vegetation Types

The relationships between precipitation, vegetation and erosion are important yet unresolved issues in the field of earth surface processes. Vegetation plays an important role in controlling soil erosion. Through field simulated rainfall experiments, we analyzed the characteristics, regulation of, and correlation among the slope rainfall-infiltration-runoff, erosion and sediment under different vegetation types. The results showed that the forest effectively improved soil structure, had stronger runoff and sediment regulation and was influenced less by rainfall intensity than those under other vegetative conditions. In addition, the efficiency and pattern of the regulation of runoff and sediment varied with vegetation types as did the mechanism of action. The soil and water conservation function of forest was water storage and sediment reduction by plant root systems to reduce erosion power, increase infiltration, decrease runoff and reduce flow speed. The function of grassland was direct sediment interception based on surface vegetation canopy for runoff and sediment regulation. The root contribution to runoff and sediment reduction was relatively greater than the shoot contribution under forest conditions, whereas, the effect of shoots and roots on soil loss was almost equivalent under grassland conditions. The different spatial structures of vegetation affected runoff and sediment regulation in different ways, and plant root systems were crucial for soil and water conservation. The cumulative sediment yield of the slopes increased as a statistically significant power function of cumulative runoff. The coefficient and curve shape of function were dependent on vegetation type, soil properties, rainfall intensity and surface roughness. The process of slope runoff and sediment was divided into development, active and stable stages. These stages correlated with each other to constitute a complete rainfall-runoff and erosion-sediment process, which exhibited their own features at each stage. This study furthers understanding of the relationships between vegetation, soil erosion and precipitation.     

Cold-climate vegetative buffer zones as pesticide-filters for surface runoff.

Vegetative buffer zones adjacent to watercourses can be effective filters for diffuse pollution from agriculture. Several investigations, even during snowmelt season, have shown that retention of sediments and sediment-bound nutrients in runoff water has been high through buffer zones (BZ). It is likely that BZ also can be effective filters for sediment-bound pesticides. The retention of glyphosate, propiconazole, fenpropimorph and soil particles was studied in surface runoff experiments with 5 m wide buffer zones. Volume proportional samples were collected after each runoff episode (1999-2002). The distribution coefficient (Kd) shows moderate to high adsorption of the pesticides to the experimental soil. Results show average retention efficiency of about 51%, 48%, 85% and 34% for particles, glyphosate, propiconazole and fenpropimorph, respectively. The amount of AMPA (which is a degradation product of glyphosate), entering the BZ was high; approximately the same amount as for glyphosate. The retention efficiency through the BZ for AMPA was about 67%. There were no significant differences in removal efficiency (in %) between winter with snowmelt and summer. This is possibly due to detachment of coarser aggregates during winter, which trap more easily in the BZ. The conclusion based on this study suggests BZ to be contributors to reduced pesticide input to surface waters.     

粗糙度对坡面侵蚀及泥沙分选性影响试验研究

为进一步揭示土壤侵蚀的内在规律,以某一试验小区为例,通过模拟不同地表粗糙度,分析了不同雨强条件下的坡面侵蚀产沙及泥沙颗粒粒径变化特征。结果表明:相同雨强和降雨历时下,粗糙度对坡面径流率、水流功率、径流含沙量和产沙率有显著影响;侵蚀泥沙的搬运形式与雨强和粗糙度均有关,而不同泥沙颗粒搬运方式是引起不同粗糙度坡面侵蚀产沙分异的重要原因。因此,坡面侵蚀产沙模型中应综合考虑地表粗糙度和泥沙粒径信息。研究成果可为水土保持规划设计和水土保持措施优化配置提供一定依据。     

Incorporating Influences of Shallow Groundwater Conditions in Curve Number-Based Runoff Estimation Methods

Runoff generation process in any watershed is mainly affected by precipitation, land use and land cover, existing soil moisture conditions and losses. Shallow groundwater table conditions that occur in many regions are known to affect the soil moisture retention capacity, infiltration and ultimately the runoff. A methodology that links soil moisture capacity to the shallow groundwater table or High-Water Table (HWT) using a nonlinear functional relationship within a curve number (CN)-based runoff estimation method, is proposed and investigated using single and continuous event simulation models in this study. The relationship is used to obtain an adjusted CN that incorporates the effect of change in soil moisture conditions due to HWT. The CN defined for average conditions is replaced by this adjusted CN and is used for runoff estimation. A single event model that uses Soil Conservation Service (SCS) CN approach is used for evaluation of variations in runoff depths and peak discharges based on different HWT conditions. A real-life case study from central Florida region in the USA was adopted for application and evaluation of the proposed methodology. Results from the case study application of the models indicate that HWT conditions significantly influence the magnitudes of peak discharge by as much as 43% and runoff depth by 48% as the water table height reaches the land surface. The magnitudes of increases in peak discharges are specific to case study region and are dependent on the functional form of the relationship linking HWT and soil storage capacity. Also, for specific values of HWT, an equivalency between HWT-based CN and wet antecedent moisture condition (AMC)-based CN can be established.     

Determining potential indicators of Cryptosporidium oocysts throughout the wastewater treatment process

Most research on wastewater treatment efficiency compliance focuses on physicochemical and microbial indicators; however, very little emphasis has been placed so far on determining suitable indicator organisms to predict the discharge level of pathogens from treatment plants. In this study, raw wastewater, activated sludge, and the resulting final effluents and biosolids in four municipal wastewater treatment plants (WWTPs A, B, C and D) were seasonally investigated for human-virulent water-borne pathogens Cryptosporidium parvum/hominis and Giardia duodenalis, and microsporidia (e.g. Encephalitozoon hellem, E. intestinalis, and Enterocytozoon bieneusi) between 2008 and 2009. A suite of potential microbial indicators for human-virulent protozoa and microsporidia was also determined. A combination of multiple fluorescent in situ hybridization and immunofluorescent antibody assays were applied to detect Cryptosporidium oocysts, Giardia cysts, and microsporidian spores. Escherichia coli, enterococci and Clostridium perfringens spores were cultivated in selective media. Positive correlations were found between the abundance of enterococci and E. coli and abundance of Cryptosporidium oocysts (r(s) > 0.47, p < 0.01) and Giardia cysts (r(s) > 0.44, p < 0.01) at WWTPs A-D. Cryptosporidium perfringens spores were positively correlated to Cryptosporidium oocysts (r(s) = 0.40, p < 0.01) and Giardia cysts (r(s) = 0.46, p < 0.01). There was a strong positive correlation between abundance of Giardia cysts and that of Cryptosporidium oocysts (r(s) > 0.89, p < 0.01). To sum up, a suite of faecal indicator bacteria can be used as indicators for the presence of Cryptosporidium oocysts and Giardia cysts in these activated-sludge systems (WWTPs A, B and C). Overall, Giardia duodenalis was noted to be the best Cryptosporidium indicator for human health in the community-based influent wastewater and throughout the treatment process.     

红砂岩侵蚀区典型水土流失治理模式减流减沙效应

阐明小区尺度下不同水土流失治理模式的减流减沙效应,可为大尺度上的水土流失治理提供科学依据。以红砂岩侵蚀劣地为研究对象,采用野外径流小区长期定位试验的方法,分析自然降雨下典型水土流失治理模式的减流减沙效应及其对降雨要素、降雨雨型的响应规律。结果表明:试验观测期间,裸露地表径流系数为0. 66,土壤侵蚀量为0. 07 t/hm2,生态或经济开发治理后减流减沙效应均能达90%以上。地表裸露坡面产流产沙受降雨量、雨强影响显著,生态恢复模式降低了降雨要素对坡面产流产沙过程的影响,经济开发模式受降雨量影响显著。大雨强、短历时的降雨雨型是坡面产流产沙的主要雨型,对裸露坡面产流产沙的贡献将近50%,生态或经济开发治理后该雨型对产流产沙的贡献明显提高,增幅以经济开发模式大于生态恢复模式。因此,生态恢复和经济开发均是治理红砂岩水土流失的有效途径,应将生态恢复和经济开发治理相结合,使水土流失治理模式不仅具有水土保持功能,同时提升生态服务价值,促进当地的经济发展。     

The hydrodynamic filter separator for removal of urban storm runoff.

The majority of storm runoff pollution is trapped in particles smaller than 100 microm in diameter. Solid particles smaller than 100 microm in diameter are not easily separated by conventional types of hydrodynamic separator, and remain in suspension in overflow. To overcome this problem, a HDFS (hydrodynamic filter separator) has been developed for treatment of the microparticles in urban storm runoff. We conducted a laboratory scale study on treatable potential of microparticles using HDFS that combined HDS with perlite filter. To determine the efficiency for various operation conditions, a series of experiments was performed with different solids concentrations and surface loading rate. The operation ranges of surface loading rates were 100 to 2,800 m3/m2/day, and influent solids concentrations were varied from 800 to 1,900 mg/L. Also, the particle size distribution was monitored to investigate the effects of surface loading rates on the particle size. Results indicated that the HDFS-inside type showed greater efficiency at solids separation than the other type.     

雨强和地表糙度对坡面微地形及侵蚀的影响

地表糙度是影响坡面侵蚀产沙的重要因素之一,以往研究多关注糙度对坡面产流产沙特征的影响,而较少关注不同糙度条件下坡面微地形变化和侵蚀产沙的关系。通过人工模拟降雨试验,结合Photoscan技术研究了不同雨强和地表糙度对坡面微地形及产流产沙的影响。结果表明:在试验条件下,降雨后光滑坡面和粗糙坡面4个微地形因子(地表糙度、地形起伏度、地表切割度、洼地蓄积量)数值均减小,且有随雨强增大,其减幅增大的趋势;相同雨强和降雨历时条件下,粗糙坡面微地形因子变化幅度大于光滑坡面,微地形因子变化量与侵蚀产沙量呈明显正相关;与光滑地表相比,粗糙地表只在降雨初期能有效减少产流,随着降雨时间延长,2种坡面的产流率趋于一致;在试验选取的4个雨强条件下,粗糙坡面和光滑坡面产流率均呈现先增大后趋于稳定的趋势。粗糙坡面产沙率和产流率变化规律一致,但光滑坡面产沙率表现出在产流初期迅速增大,而后呈降低并趋于稳定的趋势。研究结果可为揭示坡面土壤侵蚀机理和建立坡面侵蚀产沙模型提供参考。     

Distribution of soluble heavy metals between ionic and complexed forms in a saturated sediment as affected by pH and redox conditions

Research was undertaken to determine the effects of pH and redox potential on heavy metal speciation and on the size distribution of the organo-metal complexes in the soluble fraction of sediment-water systems. A cation exchange technique was effective in separating free and complexed metal ions. Fe, Mn and Zn differed in the extent of complexation with soluble organic matter. Under reducing conditions approximately two thirds of the soluble Fe was in a complexed form that was not sorbed in passing through the cation exchange resin. Soluble Mn on the other hand, was almost completely ionic under reducing conditions, with only a trace amount passing through the resin column. Over 90 percent of the soluble Zn was complexed under reduced conditions, with only 9 percent sorbed onto the resin. The complexed Fe and Zn were bound to soluble organic matter particles with equivalent molecular weight greater than 25,000 while Mn passed through this size filter. There were marked differences in the size distribution of the various organo-metal complexes under different redox and pH conditions. The soluble Fe was associated with both the largest and smallest size ranges of soluble organic matter. The effect of pH was most evident in the smallest size range with much more complexed iron being present at low pHs. Mn, on the other hand, was associated with only the smallest size range under all pH and redox conditions, reflecting its ionic nature. The greater solubility and mobility of Mn probably accounts for it being depleted relative to iron in Gulf Coast sediments. Hg and Pb were associated with only the largest size soluble complexes and were little affected by pH and redox conditions.     

流域植被对减缓土壤侵蚀作用的实验研究

根据河北省邢台市西部山区两个小流域实验站的水文泥沙监测资料,对不同流域在不同植被情况下,流域植被对减缓土壤侵蚀的作用进行分析,阐明流域植被对年输沙模数、地表径流含沙量以及次暴雨对输沙模数的影响等,结果表明,较好的流域植被对涵养水源、控制土壤侵蚀起重要作用。     

赣南红壤坡面不同措施径流泥沙及氮磷污染输出试验研究

选择赣南于都县左马小流域的典型红壤坡面,通过在研究区布设标准径流小区,进行了不同措施径流泥沙及氮磷污染输出的试验研究。通过径流小区的试验观测分析表明:水保林+水平竹节沟式综合水保措施实施初期,平均减流和减沙效果达到近73%,以植被增加地表覆盖度,以水平竹节沟坡面水保工程截短坡长,分段拦蓄径流泥沙,可实现保水保土目的;经果林+坡面工程或绿篱是坡地经济果业开发保持水土的重要措施,工程措施在初期发挥作用较绿篱更大;氮磷等面源污染随水土流失从坡面输出,试验区不同措施氮素输出多以径流携带为主,磷素输出均以泥沙携带为主;经果林+工程措施对径流携带氮磷拦截率较高,水保林+工程措施对泥沙携带氮磷的拦截率较高,都在75%以上。     

Analysis of soluble chemical transfer from soil to surface runoff and incomplete mixing parameter identification

A two-layer mathematical model proposed by Tong et al.(2010) was used to predict soluble chemical transfer from soil into surface runoff with ponded water on the soil surface. Infiltration-related incomplete mixing parameter g and runoff-related incomplete mixing parameter a in the analytical solution of the Tong et al.(2010) model were assumed to be constant. In this study, different laboratory experimental data of soluble chemical concentration in surface runoff from initially unsaturated and saturated soils were used to identify the variables g and a based on the analytical solution of the model. The values of g and a without occurrence of surface runoff were constant and equal to their values at the moment when the surface runoff started. It was determined from the results that g decreases with the increase of the ponded water depth, and when the initial volumetric water content is closer to the saturated water content, there is less variation of parameter g after the occurrence of surface runoff. As infiltration increases, the soluble chemical concentration in surface runoff decreases. The values of parameter a range from0 to 1 for the fine loam and sand under the controlled infiltration conditions, while it can increase to a very large value, greater than 1, for the sand under the restrained infiltration conditions, and the analytical solution of the model is not valid for experimental soil without any infiltration if a is expected to be less than or equal to 1. The soluble chemical concentrations predicted from the model with variable incomplete mixing parameters g and a are more accurate than those from the model with constant γ and a values.