Detection of Giardia cysts at low concentrations in water using nuclepore membranes

A filtration procedure was devised to recover Giardia cysts from water using 5 μm Nuclepore membranes (110 mm in dia). Cysts taken from a beaver (Castor canadensis) were added to 100 l. of untreated stream water and recovered by filtration. Cysts were washed from the membrane, concentrated by centrifugation and microscopically examined. Recovery efficiencies averaged 53% at cyst concentrations between 0.5 and 45 cysts l⁻¹. Maximum cyst recovery was observed at filtration pressures of 40–60 kPa. The advantages offered by this method over cartridge filtration methods include higher recovery efficiencies at low cyst concentrations and simpler, more rapid laboratory procedures.     

Removal of Giardia and Cryptosporidium in drinking water treatment: a pilot-scale study

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern for public health. The aim of this study is to examine both parasites in the water samples taken from three pilot-scale plant processes located in southern Taiwan, to upgrade the current facilities. Three processes include: conventional process without prechlorination (Process 1), conventional process plus ozonation and pellet softening (Process 2), and integrated membrane process (MF plus NF) followed conventional process (Process 3). The detection methods of both parasites are modified from USEPA Methods 1622 and 1623. Results indicated that coagulation, sedimentation and filtration removed the most percentage of both protozoan parasites. The pre-ozonation step can destruct both parasites, especially for Giardia cysts. The microfiltration systems can intercept Giardia cysts and Cryptosporidium oocysts completely. A significant correlation between water turbidity and Cryptosporidium oocysts was found in this study. The similar results were also found between three kinds of particles (phi=3-5,5-8 and 8-10 microm) and Cryptosporidium oocysts.     

Analysis of nitroaromatics in aqueous samples by capillary supercritical fluid chromatography

The extraction and analysis of nitroaromatics from aqueous environmental samples was examined. Two extraction methods; liquid‐liquid extraction with dichloromethane as extracting solvent and solid phase extraction with C₁₈ cartridge were carried out to determine the selectivity and extraction efficiencies of each method. In this investigation, eight nitroaromatics were selected as the test compounds. The extracts were then analysed using capillary supercritical fluid chromatography with flame ionization detection and with carbon dioxide as mobile phase. Satisfactory separation of the eight nitroaromatics including three pairs of isomers could be achieved. Detection limits in the range of 5 to 40 ppm were obtained using this system. Higher extraction efficiencies were obtained using the liquid‐liquid extraction method compared to the solid phase extraction method.     

Development Of An Air Cleaner Based On Gas Absorption Membranes

The aim of the present study is to demonstrate the technical feasibility of the membrane absorber as an air cleaner with small-scale modules. Six small-scale membrane modules with different fibre lengths and fibre diameters have been investigated. Each module has been tested as a membrane absorber treating air with 4 different chemicals, formaldehyde, nitrogen dioxide, ammonia and acetone, with tap water. The pressure drop and the filtration efficiency has been measured at different flow rates. From these results the optimal membrane module has been selected for the following reasons: low pressure drop, small required membrane surface area and high filtration efficiency. The experiments were continued with the selected module for ETS in a test room. Water soluble compounds were removed with an efficiency of at least 95%. The efficiency was inconsistent for NO, (not expected) and low for hydrocarbons (as expected). The sensory filtration efficiency was also measured with two different methods, the threshold method and the decipol method. Both efficiencies were about 50%. Recommendations for future research are given.     

Comparative performance of membrane filters vs. high-surface area filtration cartridges for the determination of element concentrations in freshwater systems

Interdisciplinary studies on trace element cycles in aquatic environments may require the simultaneous use of small- and large-scale filtration devices to collect all the necessary sample aliquots for the different scientific objectives (e.g. trace element and organic carbon analysis, chronic toxicity testing, and characterization of colloidal matter). This study compares the performance of membrane filters (MF, Millipore-approx. surface area 0.002 m2) and two large-surface area filtration cartridges (Calyx, MSI and Polypro, CUNO approx. surface area 1 m2) in three freshwater systems with contrasting characteristics. Membrane filters and filtration cartridges fractionate water samples in a comparable way except for some elements (Al, Mn, Pb, and Ti) and when dealing with high-turbidity, organic-rich matrices. Estimation of the actual filters' pore size using the single particle counting technique gives cut-offs of 0.2-0.3, 0.7 and 2 microm for membrane filters, Polypro cartridge and Calyx cartridge respectively, explaining many of the differences observed between membrane and cartridge filters. Direct involvement of filter manufacturers to determine actual filter cut-offs during environmental applications would be highly beneficial to increase the comparability of the measurements of filterable element concentrations. Better harmonization of filtration procedures (filter type, actual filter cut-off, in situ vs. ex situ filtration) among laboratories in different countries is also necessary in order to improve consistency of environmental databases.     

A comparison of current methods of poliovirus concentration from tap water

The efficiency of concentration of poliovirus from Jerusalem tap water was investigated for several types of “electronegatively-charged” and “electropositively-charged” microporous filters. In addition, the efficiency of organic flocculation as a procedure for reconcentrating poliovirus from filter eluates was investigated. The Balston and Cox filters had similar recovery efficiencies from tap water, with recovery of approx. 90% of the input virus, both after filtration and after organic flocculation. Decreasing the concentration of beef extract in the eluent from 3 to 1% did not negatively influence virus recovery. However, recovery of low virus numbers from large volume samples by Cox filters was variable. Balston filters were used in a series of high volume experiments to test the efficacy of the tentative standard method for virus recovery using a proportioner pump with two additive pumps. The method was inefficient without a simple modification, the addition of a second mixing chamber, which increased the virus recovery to an acceptable level. The Zeta Plus electropositively-charged type of filter had a high efficiency of virus recovery in the eluate, but approximately half of the virus was lost during organic flocculation. This may indicate the need for modification of the organic flocculation method when used with filters.     

Filtration behaviors of Giardia and Cryptosporidium--ionic strength and pH effects

The laboratory-scale filtration tests of Giardia cysts and Cryptosporidium oocysts in both 2 mm-phi glass beads and 2 mm-phi polystyrene beads filters were conducted to investigate their filtration behaviors. The protozoan parasites were used as target particles, while the chemical system altered by changing the electrolyte concentration and pH. The results significantly indicate that ionic strength have a positive effect on the removal efficiencies for Giardia cysts and Cryptosporidium oocysts. The removal efficiency of two filters for Giardia cysts slightly decreased from pH 2.4 to 8.7 and decreased significantly in pH as pH up to 8.7, while that for Cryptosporidium slightly rippled beyond pH 8.7, and with the decrease in pH up to pH 8.7. The experimental collision efficiencies from the interactions between colloids and the filter media were calculated with a semi-empirical approach of the single sphere model and clean-bed filtration theory. The results also indicated that experimental collision efficiencies for (oo)cysts corresponded to the (oo)cysts removal efficiencies in all trials, and oocysts exhibits higher collision efficiencies than cysts.     

Detection of Toxoplasma gondii oocysts and surrogate microspheres in water using ultrafiltration and capsule filtration

While reports on waterborne infections with Toxoplasma gondii are emerging worldwide, detection of this zoonotic parasite in water remains challenging. Lack of standardized and quantitative methods for detection of T. gondii oocysts in water also limits research on the transport and fate of this pathogen through aquatic habitats. Here, we compare the ability of hollow-fiber ultrafiltration and capsule filtration to concentrate oocysts in spiked tap water, fresh surface water, and seawater samples. Detection of T. gondii oocysts in concentrated samples was achieved using molecular methods, as well as visually via epifluorescent microscopy. In addition to oocysts, water samples were spiked with T. gondii surrogate microspheres, and detection of microspheres was performed using flow cytometry and epifluorescent microscopy. Results demonstrate that both water concentration methods followed by microscopy allowed for quantitative detection of T. gondii oocysts and surrogate microspheres. For T. gondii oocysts, microscopy was more sensitive than TaqMan and conventional PCR, and allowed for detection of oocysts in all water samples tested. Compared with flow cytometry, microscopy was also a more cost-efficient and precise method for detection of fluorescent surrogate microspheres in tap, fresh and seawater samples. This study describes a novel approach for quantitative detection of T. gondii oocysts in drinking and environmental water samples. The techniques described for concentrating and detecting surrogate microspheres have broad application for evaluating the transport and fate of oocysts, as well as the efficiency of water treatment methods for removal of T. gondii from water supplies.     

提高过滤浓缩阶段对两虫回收率的试验研究

针对美国EPA1623检测方法中过滤浓缩、免疫磁分离和荧光免疫镜检这3个主要步骤进行了分段回收率的研究。结果表明,过滤浓缩为导致两虫回收率损失的关键步骤,因此对过滤浓缩中的洗脱和分离过程进行了相应的改进和替代。以超声洗脱替代振荡洗脱,用滤膜抽滤/超声洗脱替代离心分离,构成优化的过滤浓缩工艺,具有较高的回收率,操作简单且成本较低。其对卵囊和孢囊的初始回收率分别为61%和55%,远高于EPA1623方法的最低要求,适宜作为国内自来水厂的常规检测方法。     

Size selective continuous flow filtration method for detection of Cryptosporidium and Giardia

We describe a size selective continuous flow filtration method for detecting Cryptosporidium oocyst and Giardia cyst in finished water. Twenty liters of finished water spiked with Cryptosporidium oocysts (110) and Giardia cysts (60) were filtered through macro (5.0–10.0 μm) and micro (3.0 μm) pore-sized polycarbonate-track-etch (PCTE) membrane filters housed into two separate 47 mm diameter filter holders joined with a stainless steel nipple. The macro-pore-sized filters removed larger unwanted particles while allowing the Cryptosporidium oocysts and Giardia cysts to pass through, these being subsequently captured on the micro-pore-sized filter. The eluted oocysts and cysts were transferred onto the well-slide, stained by IFA and examined microscopically. The mean recovery efficiencies obtained for Cryptosporidium oocysts using the filter pairs of macro 5 μm and micro 3 μm, macro 8 μm and micro 3 μm, and macro 10 μm and micro 3 μm were 67.3%, 77.2–85.0% and 76.9–82.2%, respectively. Whereas the recovery rates for Giardia cysts using the same filter pairs were 0, 55 and 77.1%. The filter pair having the pore size of macro 10 μm and micro 3 μm was found to be most efficient in the simultaneous detection of Cryptosporidium and Giardia in the finished water. This method is simple, easy, rapid and economical.     

Assessment of the presence and dynamics of fungi in drinking water sources using cultural and molecular methods

A comparison of different isolation techniques and culture media for detection of filamentous fungi and yeasts in the aquatic environment revealed that the use of membrane filtration with the media dichloran rose bengal chloramphenicol (DRBC) optimized fungi detection in terms of abundance and variety in three untreated water sources with very different characteristics (surface water, spring water, and groundwater). The diversity of the fungi population captured by direct DNA extraction of fungi collected by membrane filtration was compared with the isolates obtained after selective growth using different culture media through amplification of the internal transcribed spacer gene and denaturing gradient gel electrophoresis (DGGE). The Czapek-Dox agar, Sabouraud dextrose agar, and DRBC media showed closer similarities to those obtained by the uncultured biomass for the different water sources. Based on these data and the best enumeration results, DRBC is recommended for the assessment of fungi in water sources using culture-based methods. DGGE was also used to monitor temporal variations in the fungal population structure and showed that each water matrix possessed a distinct population profile as well as that changes in the fungal community can be expected in the different matrices throughout the year.     

Determination of 1-aminopropan-2-one, a dissolved sewage component, in water samples

A new method for the determination of 1-aminopropan-2-one (APR) in water samples was developed. APR was synthesised as its hydrochloride and derivatized with 2,4-dinitrophenylhydrazine (DNPH) for determination by high-pressure liquid chromatography with ultraviolet detection (UV-HPLC). APR was determined in water samples at pH 12 using a gas-stripping chamber, connected to a cartridge containing DNPH. Acidified water samples were injected into the gas-stripping chamber and a solution of NaOH added to bring the solution to pH 12. APR was volatilised and stripped from solution and passed onto the cartridge under a constant stream of nitrogen gas. Gas flow rates were carefully controlled to allow maximum contact of APR with DNPH on the cartridge. When the reaction time had elapsed, the cartridge was disconnected and the derivative eluted with a fixed volume of acetonitrile and injected onto the HPLC, where the APR hydrazone was resolved isocratically with a mobile phase consisting of acetonitrile and water (60:40). The HPLC was calibrated using standard solutions of the APR hydrazone. Recoveries of APR from standard samples were 90-100% at the 10 microM level and the detection limit for the method was calculated as 18 nM. Detection of APR in urine and primary-treated sewage samples (41 nM and 1.225 microM, respectively) confirmed the applicability of the technique to analysis of environmental samples.     

Sensitive detection of sample interference in environmental qPCR

Sample interference in environmental applications of quantitative PCR (qPCR) can prevent accurate estimations of molecular markers in the environment. We developed a spike-and-recovery approach using a mutant strain of Escherichia coli that contains a chromosomal insertion of a mutant GFP gene. The method was tested in water samples by separately reducing extraction efficiency or adding humic acids and ethanol, compounds that often contaminate environmental DNA extracts, and analyzing qPCR amplification of the spiked E. coli control and human fecal Bacteroides markers (HF183 and HF134). This approach, coupled with previously developed kinetic outlier detection (KOD) methods, allowed sensitive detection of PCR inhibition at much lower inhibitor concentrations than alternative approaches using Cq values or amplification efficiencies. Although HF183 was more sensitive to the effects of qPCR inhibitors than the E. coli control assay, KOD methods correctly identified inhibition of both control and HF183 assays in samples containing as little as 0.1 ng humic acids per reaction or 5% ethanol. Because sigmoidal modeling methods allow distinction of qPCR inhibition from poor DNA recovery, we were able to simultaneously identify qPCR-inhibited reactions and estimate recovery of nucleic acids in environmental samples using a single control assay. Since qPCR is currently used to estimate important water quality parameters that have serious economic and human health outcomes, these results are timely. While we demonstrate the methods in the context of water quality regulation, they will be useful in all areas of environmental research that use qPCR.     

A Pilot UK Evaluation of a Rapid Defined Substrate Method for Enumeration of Total Coliforms and Escherichia coli in Water

A simple rapid method for determining total coliforms and Escherichia coli in drinking water was evaluated in a preliminary pilot-scale study at three independent laboratories by comparison with the standard membrane filtration technique. No significant difference was found between the two methods.
The method is based on defined substrate technology. It gives confirmed results within 24 h and requires only limited equipment. It was considered particularly suitable for weekend and emergency use and for on-site testing at remote sampling points.     

BAC滤池对浊度和颗粒数的控制研究

传统的贾第鞭毛虫和隐孢子虫（简称“两虫”）检测方法存在诸多不足，为此选用浊度和颗粒数作为“两虫”的替代指标，以对浊度和颗粒物的去除率来衡量生物活性炭（BAC）滤池对“两虫”的控制效果。试验结果表明：采用颗粒数表征滤后水水质比采用浊度更适宜。过滤初期颗粒数从峰值降到50个／mL以下所需的时间比浊度降到0．1NTU所需的时间多1h左右。正常过滤期间BAC滤池进水浊度一般在0．1NTU以下，经过BAC滤池处理后，浊度得到进一步降低，平均去除率为52．7％。炭层对浊度的去除率为56．4％，其出水浊度基本上都低于0．05NTU，而砂层对浊度不但没有去除能力，反而使出水浊度平均上升了约3．7％。炭层对颗粒物的平均去除率为33．3％，砂层对颗粒物的平均去除率为8．5％。     

Quantification of aqueous cyanogen chloride and cyanogen bromide in environmental samples by MIMS

Membrane introduction mass spectrometry (MIMS) was developed and verified for the direct quantification of cyanogen chloride (CNCl) and cyanogen bromide (CNBr) in environmental samples without any sample workup. Factors including the membrane temperature and the liquid flow rates were examined for system optimization. The MIMS method provided linear responses for three orders of magnitude of concentrations. The instrument detection limits of CNCl and CNBr were 1.2 and 3.8 microg/L, respectively, and the method detection limits of CNCl and CNBr were both 1.7 microg/L. Effects of pH and the water matrix including synthetic water, saline water, natural surface water, and wastewater, on the responses were also examined. A pH ranging from 3 to 10 did not affect the quantification. The average recoveries of CNCl and CNBr in the water matrixes tested were 98.5% and 92.7%, respectively. The use of the MIMS method in on-line monitoring of the formation of cyanogen halide was demonstrated in chlorination of aqueous solutions containing glycine and bromide ions. The results indicated the important role of bromide ions in cyanogen halide speciation.     

Biological black water treatment combined with membrane separation

Separate treatment of black (toilet) water offers the possibility to recover energy and nutrients. In this study three combinations of biological treatment and membrane filtration were compared for their biological and membrane performance and nutrient conservation: a UASB followed by effluent membrane filtration, an anaerobic MBR and an aerobic MBR. Methane production in the anaerobic systems was lower than expected. Sludge production was highest in the aerobic MBR, followed by the anaerobic MBR and the UASB-membrane system. The level of nutrient conservation in the effluent was high in all three treatment systems, which is beneficial for their recovery from the effluent. Membrane treatment guaranteed an effluent which is free of suspended and colloidal matter. However, the concentration of soluble COD in the effluent still was relatively high and this may seriously hamper subsequent nutrient recovery by physical-chemical processes. The membrane filtration behaviour of the three systems was very different, and seemed to be dominated by the concentration of colloidals in the membrane feed. In general, membrane fouling was the lowest in the aerobic MBR, followed by the membranes used for UASB effluent filtration and the anaerobic MBR.     

Survie in vitro de Yersinia dans les eaux d'alimentation et recuperation par filtration sur membraneIn vitro survival of Yersinia strains in drinking water and recovery by membrane filtration

This study was undertaken to determine the survival characters and optimal parameters for the recovery of Yersinia from drinking water samples. Experiments were done by artificial contamination of 4 different water samples with 4 Yersinia strains.

The strains tested along this study are: Y. enterocolitica 4052, 0:3 and 4360, 0:9, Y. enterocolitica intermedia 3953, 0:17 and Y. pseudotuberculosis 0:1. The water samples are characterized by an increasing mineralization: Distillated water, Gerardmer water (-30,300 ω cm⁻¹—Hardness = 1° Français), Nancy water (-4500 ω cm⁻¹—H = 10°) and Vittel water (-730 ω cm⁻¹, H = 71°).

Total mineralization does not significantly affect the survival of Yersinia at 20°C, but causes a dramatic decrease of the Yersinia strains at 4°C for the most mineralized water. There is no pH effect from alkaline, neutral and acidic values until pH 4.4 but Yersinia is greatly affected by more acidic pH.

The previous stay of Yersinia strains in artificially contaminated water causes a reduction of kinetic growth during cultivation on peptone-water but does not change the recovery rate by filtration method.

The recovery rate of the filtration method using cellulose acetate membranes (mean porosity = 0.45 μm) is very poor, ranging from 0 to 8%. The efficiency is significantly higher with the aid of polyester membranes treated by laser (Nucleopore−0.40 μm) ranging from 12 to 53% according to the mineralization of the water. The best recovery rate is obtained with the moderately mineralized water.

These results can explain the poor results obtained with the use of water bacteriology classical methods for the search of Yersinia.

Thus the best results can be predicted from the concentration of fairly mineralized water by filtration on polyester membrane at neutral, alkaline or weakly acidic pH.     

A hybridized photocatalysis-microfiltration system with iron oxide-coated membranes for the removal of natural organic matter in water treatment: Effects of iron oxide layers and colloids

A photocatalysis/microfiltration (MF) hybrid system, with the coating of a membrane using iron oxide particles (IOPs), was investigated with respect to natural organic matter (NOM) removal and membrane permeability during the treatment of various surface waters. A comparison of the performance between bare (uncoated) and IOP-coated membranes employed for the photocatalytic hybrid system was made. Due to the additional adsorption of NOM onto IOPs on the membrane surface, the IOP-coated membrane system always achieved greater DOC removal efficiencies during photocatalysis/MF. Particularly, the influence of colloidal particles that were present in different water sources with respect to membrane fouling was explored. Colloidal fouling occurred to both bare and IOP-coated membranes, but the interaction of colloids with IOP coating layers was in close association with the characteristics of colloids, such as size distribution, resulting in opposing fouling behaviors with varying water sources. The IOP-coated membrane was able to control fouling properly when a relatively large size of colloidal particles existed in raw water, but not for the case of small colloids. The IOP coat layer may become denser as small colloids penetrate into it, therefore leading to further fouling. The analysis of the hydraulic filtration resistances revealed that such fouling was virtually reversible in being removed by backwashing processes. Scanning electron microscopic observations, however, visualized the existence of several foulants remaining at the membrane surface after backwashing when feed water, containing a relatively large portion of small-sized colloids, was supplied.     

Evaluation of the lactose Tergitol-7, m-Endo LES, Colilert 18, Readycult Coliforms 100, Water-Check-100, 3M Petrifilm EC and DryCult Coliform test methods for detection of total coliforms and Escherichia coli in water samples

In this study we compared the reference membrane filtration (MF) lactose Tergitol-7 (LTTC) method ISO 9308-1:2000 with the MF m-Endo LES method SFS 3016:2001, the defined substrate chromogenic/fluorogenic Colilert 18, Readycult Coliforms and Water Check methods, and ready-made culture media, 3M Petrifilm EC and DryCult Coli methods for the detection of coliforms and Escherichia coli in various water samples. When the results of E. coli detection were compared between test methods, the highest agreement (both tests negative or positive) with the LTTC method was calculated for the m-Endo LES method (83.6%), followed by Colilert 18 (82.7%), Water-Check (81.8%) and Readycult (78.4%), whereas Petrifilm EC (70.6%) and DryCult Coli (68.9%) showed the weakest agreement. The m-Endo LES method was the only method showing no statistical difference in E. coli counts compared with the LTTC method, whereas the Colilert 18 and Readycult methods gave significantly higher counts for E. coli than the LTTC method. In general, those tests based on the analysis of a 1-ml sample (Petrifilm EC and DryCult Coli) showed weak sensitivity (39.5-52.5%) but high specificity (90.9-78.8%).