Gwy-Am Shin

Evaluation of a novel electropositive filter for the concentration of viruses from diverse water matrices

Human enteric viruses are important agents of waterborne illness. They are diffusely distributed in environmental waters, necessitating concentration of tens to hundreds of litres for effective detection. This study evaluates the novel ViroCap disposable capsule filter for concentration of coliphage MS2 and poliovirus (PV1) from deionised (DI) water and artificial seawater, as well as natural ground, surface, and seawater. Retention and recoveries for the ViroCap were compared with two well-characterised filters: the 1MDS for DI water, and the OptiCap XL for artificial seawater. The mean adsorption for MS2 by the ViroCap was 88%. Recovery of MS2 was significantly greater (p< or=0.01) than alternative filters tested: 65% from DI water and 63% from artificial seawater, compared to 30% for the 1MDS and 15% for the OptiCap for the respective matrices. Recovery of PV1 from DI water (37%) was similar to that of the 1MDS (51%). PV1 recoveries from artificial seawater were significantly greater (p< or =0.01) for the ViroCap (44%) than the OptiCap (11%). Recovery of MS2 from seeded environmental samples yielded 44% from groundwater, 53% from surface water, and 51% from seawater. ViroCap disposable filter is efficient for concentrating MS2 and PV1 from diverse matrices and is robust across a range of ionic concentrations.

Enhanced effectiveness of medium-pressure ultraviolet lamps on human adenovirus 2 and its possible mechanism

There has been growing concern over human exposure to adenoviruses through drinking water due to their apparent high resistance to UV irradiation and the anticipated widespread use of ultraviolet (UV) disinfection in drinking water treatment processes. However, most inactivation studies on adenoviruses were performed using only one type of UV technology--low-pressure (LP) UV, and little is known about the effectiveness of different UV technologies such as medium- pressure (MP) UV or other polychromatic UV technologies. In this work, the kinetics and extent of inactivation of a human adenovirus (adenovirus 2 (Ad2)) by both monochromatic LP and polychromatic MP UV were evaluated to determine the effectiveness of these UV technologies on human adenoviruses. Inactivation of Ad2 by LP UV was very slow and only 0.87 and 2.17 log(10) inactivation was achieved with UV doses of 30 and 90 mJ/cm(2), respectively. However, inactivation of Ad2 by MP UV was much faster and 2.19 and 5.36 log(10) inactivation was observed with the same UV doses (30 and 90 mJ/cm(2), respectively). It appears that MP UV is more effective against Ad2 than LP UV and the enhanced effectiveness of MP UV on Ad2 is likely due to its ability to inhibit the repair process in UV-irradiated Ad2.

Characterisation of the water quality from open and rope-pump shallow wells in rural Cambodia

An 8 month investigation into the quality of water from open and rope-pump shallow wells in rural Cambodia was conducted. Wells were analysed for indicators of the health (arsenic, fluoride, manganese, nitrate, total coliforms, E. coli, male-specific coliphage) and aesthetic (iron, chloride, conductivity, total dissolved solids, hardnesss, turbidity, pH) quality of the water, and referenced to the Cambodian Drinking Water Standard when available. The shallow aquifer was chemically less of a health risk than the deep aquifer; however, microbial contamination was considerable for both shallow well types with mean E. coli loads of 10(3) CFU/100 mL and male-specific coliphage contamination of 10(2) PFU/eluate. Temporal variation in microbial contamination was significant (p<0.05), with overall loads decreasing during the dry season. The aesthetic quality of the water was poor for all samples, but worsened during the dry season. No significant difference was observed in the quality of water from open and rope-pump wells, despite their classification as unimproved and improved respectively by the WHO/UNICEF Joint Monitoring Programme. Contaminants present in both well types may readily be removed by simple water treatment, suggesting that household treatment may be more beneficial to rural Cambodian households than shallow aquifer source improvements.

Inactivation of Giardia lamblia cysts by polychromatic UV.

Aims:  Giardia lamblia is one of the most important waterborne pathogens in the world. In this study, we determined the effectiveness of a promising alternative UV technology – a polychromatic emission from a medium‐pressure (MP) UV lamp – against G. lamblia cysts in phosphate buffered saline (PBS) and a filtered drinking water.

Reactivation of Giardia lamblia cysts after exposure to polychromatic UV light

Aims:  In this study, we determined the ability of a promising alternative UV technology – a polychromatic emission from a medium‐pressure UV (MP UV) technology – to inhibit the reactivation of UV‐irradiated Giardia lamblia cysts.

Reactivation of Giardia lamblia cysts after exposure to low-pressure UV irradiation

In this study, we determined the repair capabilities of Giardia lamblia cysts when they were exposed to low-pressure (LP) UV and then 4 different repair conditions. A UV collimated beam apparatus was used to expose shallow suspensions of G. lamblia cysts in buffered reagent water (PBS, pH 7.2) to various doses of LP UV irradiation. After UV irradiation, samples were exposed to 4 repair conditions (light and dark repair conditions with 2 temperatures (25 °C and 37 °C) for each condition). The inactivation of G. lamblia cysts by LP UV was very extensive (∼ 5 log10) even with a low dose of LP UV (1 mJ/cm(2)). More importantly, there was significant restoration of infectivity in G. lamblia cysts when they were exposed to a low dose of LP UV and then to all the repair conditions tested. Overall, the results of this study indicate that G. lamblia cysts do have the ability to repair their UV-damaged DNA when they are exposed to low doses of LP UV irradiation. This is the first study to report the presence of repair in UV-irradiated G. lamblia cysts.