Urban water reuse: microbial pathogens control by direct filtration and ultraviolet disinfection.

Physicochemical treatment efficiency for unrestricted urban water reuse was evaluated at a conventional activated-sludge wastewater treatment plant (WWTP). Pilot plant set-up consisted of an alum coagulation step, granular media upflow flocculation and direct downflow dual-media filtration followed by ultraviolet disinfection (dose of 95 mJ cm⁻²). Optimum aluminum sulfate dosage of 10 mg L⁻¹ and coagulation pH 7.0 were preset based on bench scale tests. Under WWTP stable operation, water quality met United States Environmental Protection Agency (USEPA) suggested guidelines for unrestricted urban reuse regarding turbidity (mean value 1.3 NTU) and suspended solids (mean value 2.1 mg L⁻¹). When WWTP overall plant performance dropped from 90 to 80% (although BOD value stayed below 6 mg O2 L⁻¹, suggesting unrestricted reuse), solids breakthrough in filtrate was observed. Microorganism removal rates were: total coliforms 60.0%, Escherichia coli 63.0%, Giardia spp. 81.0%, and helminth eggs 62.5%; thus organisms still remained in filtrate. Ultraviolet (UV) disinfection efficiency was 4.1- and 3.8-log for total coliforms and E. coli, respectively. Considering low UV efficiency obtained for helminths and the survival of protozoa and helminths in the environment, effluent quality presents risk to public health if destined for unrestricted urban reuse.

Virus, protozoa and organic compounds decay in depurated oysters.

AIMS: (1) Evaluate the dynamic of the depuration process of Crassostrea gigas oysters using different ultraviolet doses with different amounts of contaminants (virus, protozoa and organic contaminants) and (2) investigate the morphological changes in the oysters' tissues produced by the depuration procedures. METHODS: The oysters were allocated in sites with different degrees of contamination and analyzed after 14 days. Some animals were used as positive controls by artificial bioaccumulation with HAdV2 and MNV1 and subjected to depuration assays using UV lamps (18 or 36 W) for 168 h. The following pollutants were researched in the naturally contaminated oysters, oysters after 14 days in sites and oysters during the depuration processes: virus (HAdV, HAV, HuNoV GI/GII and JCPyV), by (RT) qPCR; protozoa (Cryptosporidium and Giardia species), by immunomagnetic separation and immunofluorescence; and organic compounds (AHs, PAHs, LABs, PCBs and organochlorine pesticides-OCs), by chromatography. Changes in the oysters' tissues produced by the depuration processes were also evaluated using histochemical analysis by light microscopy. In the artificially bioaccumulated oysters, only HAdV2 and MNV1 were investigated by (RT) qPCR before the depuration procedures and after 96 and 168 h of these procedures. RESULTS: At 14 days post-allocation, HAdV was found in all the sites (6.2 × 105 to 4.4 × 107 GC g(-1)), and Giardia species in only one site. Levels of PCBs and OCs in the oyster's tissues were below the detection limit for all samples. AHs (3.5 to 4.4 µg g(-1)), PAHs (11 to 191 ng g(-1)) and LABs (57 to 751 ng g(-1)) were detected in the samples from 3 sites. During the depuration assays, we found HAdV, Giardia and Cryptosporidium species until 168 h, independent of UV treatment. AHs, PAHs and LABs were found also after 168 h of depuration (36 W and without UV lamp). The depuration procedures did not produce changes in the oysters' tissues. In the artificially contaminated and depurated oysters, we detected HAdV until 168 h and MNV1 until 96 h of depuration. CONCLUSION: The applied depuration treatments were unable to eliminate the protozoa or to degrade the HAdV genomes but were able to degrade the MNV1 genomes. Similarly, the UV water treatment was not efficient for aliphatic hydrocarbons, PAHs and LABs, as their concentrations were equivalent or higher to the concentrations of the control samples and samples from depuration tanks without UV treatment.

Practical time-gated luminescence flow cytometry. II: experimental evaluation using UV LED excitation.

In the previous article [Part 1 (8)], we have modelled alternative approaches to design of practical time-gated luminescence (TGL) flow cytometry and examined the feasibility of employing a UV LED as the excitation source for the gated detection of europium dye labelled target in rapid flow stream. The continuous flow-section approach is well suited for rare-event cell counting in applications with a large number of nontarget autofluorescent particles. This article presents details of construction, operation and evaluation of a TGL flow cytometer using a UV LED excitation and a gated high-gain channel photomultiplier tube (CPMT) for detection. The compact prototype TGL flow cytometer was constructed and optimised to operate at a TGL cycle rate of 6 kHz, with each cycle consisting of 100 micros LED pulsed excitation and approximately 60 micros delay-gated detection. The performance of the TGL flow cytometer was evaluated by enumerating 5.7 microm Eu(3+) luminescence beads (having comparable intensity to europium-chelate-labeled Giardia cysts) in both autofluorescence-rich environmental water concentrates and Sulforhodamine 101 (S101) solutions (broadband red fluorescence covering the spectral band of target signals), respectively. The prototype TGL flow cytometer was able to distinguish the target beads, and a maximum signal to background ratio of 38:1 was observed. Neither the environmental water concentrates nor S101 solution contributed to the background in the TGL detection phase. The counting efficiency of the TGL flow cytometer was typically >93% of values determined using conventional counting methods.

Effect of solar disinfection on viability of intestinal protozoa in drinking water.

The effect of solar disinfection on the viability of intestinal protozoa Giardia lamblia, Microsporidia sp., Cryptosporidium parvum, Cyclospora cyatenensis and Entamoeba histolytica in drinking water was studied as compared to chlorine disinfection. The protozoa were collected from stool samples, to infect to the distilled water. Chlorinated water samples were prepared at concentration of 4 ppm, and the parasites were incubated overnight at room temperature with the treated water. Sun treatment was applied for 2 exposures (6 & 24 hrs), in summer and winter. Sun treated water samples were put in tubes and exposed to sun. The 2 disinfection methods were tested in plastic and glass test tubes. Parasites viability was assessed by viability assay using trypan blue stain (0.4%), and bioassay infectivity tests in experimentally laboratory bred mice. Results proved that all parasites' viability was not affected by chlorine, following solar disinfection treatment, parasites became dark blue in colour and deformed by trypan blue stain. High parasites death was recorded for all parasites except Microsporidia sp. Bioassay infectivity test showed a statistically significant reduction in mean number of all parasites in intestinal sections compared to controls. The best results were tubes exposure to sun for 24 hrs in summer, where G. lamblia, C. parvum and C. cyatenensis were inactivated or absence in intestinal sections. No statistically significant difference was between the use of plastic and glass tubes, either in chlorine or sun treated parasites. So, solar disinfection proved a simple, cheap and effective means for improving water for human use, particularly in developing countries.

Evaluation of activated sludge treatment and the efficiency of the disinfection of Giardia species cysts and Cryptosporidium oocysts by UV at a sludge treatment plant in Campinas, south-east Brazil.

Among many waterborne diseases the giardiasis and cryptosporidiosis are of particular public health interest, because Giardia cysts and Cryptosporidium oocysts can persist for long periods in the environment, and both pathogenic protozoa have been implicated as the cause of many outbreaks of gastroenteritis in the last 25 years. In order to evaluate the efficiency of cysts and oocysts' removal by the activated sludge process, and by UV reactor in inactivating cysts and oocysts in one wastewater treatment plant (WWTP) of Campinas, three sampling points were selected for study: (1) influent, (2) treated effluent without UV disinfection and (3) treated effluent with UV disinfection. Giardia spp. cysts prevailed with higher density in the three different sample types. Cryptosporidium spp. oocysts were observed in only two samples of influent and just one sample of treated sewage with UV disinfection. In the animal infectivity assay for Giardia spp, one mouse of the UV treated group revealed trophozoites in intestinal scrapings. The results of the present study indicate that treatment by activated sludge process delivered a reduction of 98.9% of cysts and 99.7% of oocysts and UV disinfection was not completely efficient regarding the inactivation of Giardia cysts in the case of the WWTP studied.

Batch solar disinfection inactivates oocysts of Cryptosporidium parvum and cysts of Giardia muris in drinking water.

AIM: To determine whether batch solar disinfection (SODIS) can be used to inactivate oocysts of Cryptosporidium parvum and cysts of Giardia muris in experimentally contaminated water. METHODS AND RESULTS: Suspensions of oocysts and cysts were exposed to simulated global solar irradiation of 830 W m(-2) for different exposure times at a constant temperature of 40 degrees C. Infectivity tests were carried out using CD-1 suckling mice in the Cryptosporidium experiments and newly weaned CD-1 mice in the Giardia experiments. Exposure times of > or =10 h (total optical dose c. 30 kJ) rendered C. parvum oocysts noninfective. Giardia muris cysts were rendered completely noninfective within 4 h (total optical dose >12 kJ). Scanning electron microscopy and viability (4',6-diamidino-2-phenylindole/propidium iodide fluorogenic dyes and excystation) studies on oocysts of C. parvum suggest that inactivation is caused by damage to the oocyst wall. CONCLUSIONS: Results show that cysts of G. muris and oocysts of C. parvum are rendered completely noninfective after batch SODIS exposures of 4 and 10 h (respectively) and is also likely to be effective against waterborne cysts of Giardia lamblia. SIGNIFICANCE AND IMPACT OF THE STUDY: These results demonstrate that SODIS is an appropriate household water treatment technology for use as an emergency intervention in aftermath of natural or man-made disasters against not only bacterial but also protozoan pathogens.

Measurement of action spectra of light-activated processes.

We report on a new experimental technique suitable for measurement of light-activated processes, such as fluorophore transport. The usefulness of this technique is derived from its capacity to decouple the imaging and activation processes, allowing fluorescent imaging of fluorophore transport at a convenient activation wavelength. We demonstrate the efficiency of this new technique in determination of the action spectrum of the light mediated transport of rhodamine 123 into the parasitic protozoan Giardia duodenalis.

Low pressure ultraviolet studies for inactivation of Giardia muris cysts.

AIMS: The research was initiated to confirm earlier ultraviolet (u.v.) light inactivation studies performed on Giardia cysts using excystation as the viability indicator. Following this, a comparison of in vitro excystation and animal infectivity was performed for assessing cyst viability after exposure to low-pressure u.v. irradiation. METHODS AND RESULTS: Cysts of Giardia muris were inactivated using a low-pressure u.v. light source. Giardia muris was employed as a surrogate for the human pathogen Giardia lamblia. Cyst viability was determined by both in vitro excystation and animal infectivity. Cyst doses were counted using a flow cytometer for the animal infectivity experiments. Using in vitro excystation as the viability indicator, fluences as high as approximately 200 mJ cm(-2) did not prevent some cysts from excysting, thus verifying earlier work. Using animal infectivity, u.v. fluences of 1.4, 1.9 and 2.3 mJ cm(-2) yielded log10 reductions ranging from 0.3 to >or= 4.4. CONCLUSIONS: Results indicate that in vitro excystation is not a reliable indicator of G. muris cyst viability after u.v. disinfection. Very low doses of u.v. light rendered G. muris cysts non-infective in the mouse model employed. SIGNIFICANCE AND IMPACT OF THE STUDY: Data presented represent the only complete u.v. inactivation curve for G. muris. This research provides evidence that u.v. can be an effective barrier against Giardia spp. in the treatment of drinking water supplies.

Studies on the resistance/reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts exposed to medium-pressure ultraviolet radiation.

The ex vivo and in vivo reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts after exposure to different doses of ultraviolet (UV) radiation was determined using animal infectivity. The infectivity of UV-treated parasites stored for 1-4 days (G. muris) or 1-17 days (C. parvum) at room temperature in the dark was similar to that of organisms administered immediately after UV treatment, indicating that the parasites did not reactivate ex vivo. In contrast, we observed in vivo reactivation of G. muris in three of seven independent animal infectivity experiments, when parasites were treated with relatively low doses of medium-pressure UV (<25 mJ/cm(2)). Our observations indicate that G. muris cysts and C. parvum oocysts exposed to medium-pressure UV doses of 60 mJ/cm(2) or higher did not exhibit resistance to and/or reactivation following treatment. This suggests that when appropriate doses of UV are used, significant and permanent inactivation of these parasites may be achieved.

Inactivation of Giardia lamblia cysts by ultraviolet irradiation.

Giardia lamblia cysts were found to be resistant to high doses of germicidal ultraviolet radiation.