Investigation of Low-Pressure Ultraviolet Radiation on Inactivation of Rhabitidae Nematode from Water

By Dehghani, Mohammad Hadi; Jahed, Gholam-Reza et al. | Iranian Journal of Public Health, March 2013 | Go to article overview

Investigation of Low-Pressure Ultraviolet Radiation on Inactivation of Rhabitidae Nematode from Water


Dehghani, Mohammad Hadi, Jahed, Gholam-Reza, Zarei, Ahmad, Iranian Journal of Public Health


Abstract

Background: Rhabditidae is a family of free-living nematodes. Free living nematodes due to their active movement and resistance to chlorination, do not remove in conventional water treatment processes thus can be entered to distribution systems and cause adverse health effects. Ultraviolet radiation (UV) can be used as a method of inactivating for these organisms. This cross sectional study was done to investigate the efficiency of ultraviolet lamp in the inactivation of free living nematode in water.

Methods: The effects of radation time, turbidity, pH and temperature were invistigated in this study. Ultraviolet lamp used in this study was a 11 W lamp and intensity of this lamp was 24 µw / cm^sup 2^.

Results: Radiation time required to achieve 100% efficiency for larvae nematode and adults was 9 and 10 minutes respectively. There was a significant correlation between the increase in radiation time, temperature rise and turbidity reduction with inactivation efficiency of lamp (P<0.001). Increase of turbidity up 25 NTU decreased inactivation efficiency of larvae and adult nematodes from 100% to 66% and 100% to 64% respectively. Change in pH range from 6 to 9 did not affect the efficiency of inactivation. With increasing temperature inactivation rate increased. Also the effect of the lamp on inactivation of larvae nematod was mor than adults.

Conclusions: It seems that with requiring the favorable conditions low-pressure ultraviolet radiation systems can be used for disinfection of water containing Rhabitidae nematode.

Keywords: Ultraviolet radiation, Nematode, Rhabditidae, Water

Introduction

In many developing countries, lack of healthy drinking water is one of the most challenging health problems. Undoubtedly, without healthy drinking water supply, human health and welfare will be endangered (1, 2). One of the most com-mon and dangerous pollution of water resources is biological contamination. Water can be contam-inated by various types of microorganisms such as bacteria, fungi, viruses and parasites. Among these pollutants, worms' parasitic infection is one of the most prevalent of epidemic water borne diseases around the world (2, 3). Nematodes, which are one of the species of parasitic worms, are a group of organisms in fresh water that are considered food source for invertebrates, vertebrates such as fish and number of fungi. It is estimated that hundreds of millions of nematodes can exist in an area of 4.047 m2 in 7.6 cm of drinking water's fil-ter bed (3, 4). Free living nematodes which are usually benthic or residing in wet soils live in natural aerobic places that contain bacterial food. Thus, they can be seen in sandy filters, biological wastewater treatment units and numerously in secondary effluent. Because of their active motion and chlorine resistance, they will not die in com-mon water treatment processes and can enter the water distribution systems. Most of the nematodes in drinking water treatment facilities are caused by soil runoffs and rivers with high flow that floats bed organisms or by sewage effluent (1-4). Fig. 1 shows an adult and a larva nematode.

There are various methods for water disinfection that generally divided into two categories: chemi-cal and physical. Chlorination and the use of ozone gas are common chemical methods, and heat, filtration and radiation are common physical methods (4, 5). The most common disinfection method which is used is chlorination; but with discovery of producing three halomethanes in dis-infection with chlorine, the use of ultraviolet lamps has been increased and it causes less use of chlorination in countries with high level of health.

Using UV lamps in water disinfection is relatively a new technology and has a 40-year background (5, 6). The first mercury-vapor lamp was made in 1986 which was based on electrical discharge in a low-pressure tube containing mercury vapor. Next steps in the application of UV radiation in water disinfection were development of artificial mer-cury lamps in 1901 and the use of quartz as a UV transmitter in 1906. …

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