İçme sularında giardia kistlerinin araştırılması

Abstract

Bu çalışmada içme sularında Giardia Kistleri konusu incelenmiştir. İlk bölümde, çalışmanın önemi, amaç ve kapsamı açıklanmıştır. İkinci bölümde, içme sularında biyolojik kirlenme konusu kısaca belirtilip, Giardia Kistleri ile bunların sebep olduğu Giardiasis hastalığı hakkında bilgiler sunulmuştur. Üçüncü bölümde, Giardia türlerinin çevrede ve sistemlerde varlığı, Giardia kistlerinin incelenmesi ve bu kistlerin sudan giderilmesi ile ilgili önceden yapılmış çalışmalar incelenmiştir. Dördüncü bölümde, örnek bir içme suyu arıtma tesisinde (İSKİ Kağıthane İçme Suyu Arıtma Tesisi) ve bu tesise su temin eden yüzey suyu kaynağında Giardia kistleri incelenmiştir. Giardia kistlerinin araştırılmasında Standart Methods (1989)'da belirtilen yöntem uygulanmıştır. Bu yöntem ile yapılan deneylerde ham suda bu kistler bulunamamıştır. Fakat, böylesine spesifik bir çalışmanın yıl boyunca sürdürülmesi gerektiği sonucuna varılmıştır. Ölçülen diğer parametrelerden faydalanılarak kist konsantrasyonları tahmin edilmeye çalışılmıştır. Beşinci bölümde, elde edilen sonuçlar değerlendirilerek yapılması gerekenler sıralanmıştır.

In this thesis, Giardia cysts in water systems has been studied. In the first section, the importance of this study and its aim have been explained. In the second section, information about Giardia cysts and giardiasis have been presented. Giardia is the flagellated protozoan parasite that causes significant health problems. It was first described 310 years ago by Leeuwenhoek and the first formal description of Giardia duodenalis was made by Lambl in 1859. Giardia has two forms in life cycle; the first one is the throphozoite and second is the csyst. Trophozoites are usually 10-20 um long, 5-10 um wide and 2-4 um thick. The trophozoite form has two nuclei and eight flagella. By means of these flagella, the trophozoite is able to swim actively. These flagella are bilateral symmetry. The reproduction of trophozoite is binary fission. There is no sexual stage in life cycle. The cyst forms of Giardia are elliptically shaped or ovals, range about 8-14 um long and 6.10 um wide. They contain four nuclei when mature. The cyst outer-wall protects the organism against different environmental conditions such as temperature and disinfectants. When the cyst is swallowed by a susceptible host, it probably hatches in the duodenum. Within the days after the infection, many millions of trophosoites develop and cover the small intestinal epithelial surface. Giardia is distributed almost everywhere in environment. Species of genus have been described from the small intestines of man, dogs, cats, cattle, various rodents, rabbits and other mammals and also a few species recorded from amphibian and reptiles. We dont know how many Giardia species there are and also we don't know the pathogenicity of them. The most common known species are; Giardia muris, Giardia agilis, Giardia duodenalis, Giardia cams, Giardia ardeae. Giardia duodenalis is also known as Giardia intestinalis, Giardia lamblia and Lamblia intestinalis. All species are quite similar in shape to each other. Giardiasis is one of the most common human parasite infectious disease. Malabsorption syndrome is characteristic of giardiasis. It is characteristics with substantial weight loss, general debility and consequent fatigue. The trophozoites closely adhering to the epithelial surface interfere mechanically with absorption. The immune system of the host plays a major role in pathogenesis of giardiasis. Especially the IgA is very important. Mothers milk is protective as well, because it contains antibodies of IgA. Products of lipid hydrolysis of milk in the normal digestive are toxic to Giardia. The symptoms of Giardiasis develop between one and four weeks after infection. These include explosive, watery, foul-smelling diarrhoea, gas in the stomach or intestines, nausea and, not surprisingly, a loss of appetite. Other symptoms are jaundice and vomiting. Giardia lamblia does not invade tissues; heavy cases may produce acute but not bloody diarrhoea. It causes epigastric pain especially in children. The parasites are thought to go to the bile duct and into the gall bladder. The prevalence of Giardia lamblia among adults was slightly lower than at the children and infants in the U.S. Giardia can be treated by a number of drugs, but there is no way of preventing infection except by adequate water treatment. There are three pharmaceutics to treat Giardiasis. These are guinacrine (Atabrine), metronidozale (Flagyl) and furazolidone (Furoxone). Prevention of Giardiasis depends on proper maintenanceof community water supplies, treatment systems and distribution systems. Boiling water for 20 minutes will kill the cysts. Transmission of Giardia species is by the fecal-oral route. Also there are some other routes of transmission such as beavers, dogs, cats, mice, rabbits, contaminated foods and sexual relations. The cyst forms of Giardia are able to spread out all environment. Especially fecally contamined surface waters contain the Giardia species and helped them to disperse to our environment. Giardiasis is endemic in many countries of the world including the United States. The information about giardiasis in the U.S. is available since 1920. Especially during the 70's, giardiasis were reported with increasing frequency in the U.S. 53 outbreaks of giardiasis had effected 20039 people in the U.S. during 1965-1981. It was the most common waterborne pathogen during the period 1972-1981. The giardiasis outbreaks have usually occurred primarily in the areas or populations that have depend on surface water sources. 19 outbreak have occured in Colorado. This number was more than any other state and the outbreaks of Giardiasis. Have generally occurred in small community water systems or non community systems in recreational areas. The largest waterborne outbreak of giardiasis occurred in Rome, New York between November, 1974 to June, 1975. According to the epidemiological study, 4800-5300 cases of giardiasis were estimated. According to the article or Craun, there were 3 outbreaks and 176 cases between 1961-1970, but outbreak between 1971-1988 have increased to 103 and the number of illnesses 25834. XI The presence of Giardia cysts in wastewater is primarily due to infected humans discharging the cysts into wastewater collecting systems. The most important causes of outbreaks were the use of contaminated, untreated surface or ground water or inadequately treated surface or ground water during 1981- 1988 in the U.S. Also animals may represent a source of cysts. Many giardiasis cases have occurred all around the U.S. because of the beavers and muskrats. In the third section, previous studies about the presence of Giardia species in environment and systems, detection of Giardia cysts and removal of these cysts from water have been examined. Information on the number of Giardia cysts present in sewage and water would be useful for health and cure studies. A person infected with Giardia lamblia may give 108 cysts/day to the wastewater. The cysts numbers in water and wastewater depend on the treatment systems, temperature of the water and source of the water. Activated sludge unit process was more efficient than the trickling filtration process in removing Giardia cysts from the wastewater. The range of effluent cysts concentrations from the trickling filter was much greater (4-44 cysts / 1) than the activated sludge treatment process (4 cysts / 1). The cyst concentration is higher in the colder climate than warmer climate in the raw water. According to the research of Casson and others, the higher cyst concentrations in raw wastewater were determined during the months of September through January. Also according to Sykora's studies in the Youghiogheny River, Giardia cysts concentrations increased in winter and early spring. Also in Nancy, France daily the highest concentrations of the cysts in domestic wastewater were found during the morning activities at 8-10 a.m. The highest values were observed in February and March and minimum values were observed in November. The concentrations of Giardia cysts in sewage are different range in different countries and nations; ranging from 8xl02 to l,4xl04 cysts / 1. In the U.S.; according to the Jakubowski and others' article, the highest annual geometric mean raw sewage cysts level was at the California site (3750 cysts / 1) and the lowest level was at the Pennsylvania site (683 cysts / 1) among the 1 1 different states in the country. The highest average concentration was found in the sludge samples from the Pennsylvania site, the lowest average concentrations were found in the sludges from the Illinois plant. The counts ranged between 70-30.000 cysts / 1 in sludge samples among the 11 state. In the counting technique, centrifugation may cause more than 50% cysts lost. Giardia cysts were determined in the aquatic environment of the 14 states of the U.S. and 1 Canadian province by Le Chevallier and others during 1989-1990. Their studies included 66 surface water treatment plants and Giardia cysts were detected in Xll %81 of the raw water samples. The research showed that Giardia cysts 10 times higher in industrially polluted waters than protected watersheds. Also there was a relationship between Giardia densities with fecal coliform, total coliform and turbidity. If the coliform concentration and turbidity were high, also Giardia cysts concentration was high in this study. Removing the Giardia cysts from the drinking water is the important point of treatment. There are some methods to remove these cysts. The most effective systems are filtration and disinfection. The primary data study was made by Hibler and others. In this study, cysts have been exposed to various degrees of chlorine, pHs and temperatures. Haas and Heller's research was related to Hibler' s study. Their study objective was to analyze inactivation data of Hibler using the maximum likelihood technique to determine the most suitable set of descriptors. The Horn model was found the most adequate for describing the inactivation of Giardia by free chlorine. Five of the six viable type cysts found in tap water samples were from systems that exposed to chloramination. Because chloramines react slowly with Giardia species, these microorganisms may not demonstrate the same level of destruction. Giardia cysts can pass the filters if they are inadequate for them. The most of the giardiasis outbreaks have occurred because of the filters. Giardia cysts were detected in 17% of the 83 filtered drinking water samples in the 14 states of the U.S. and 1 Canadian province. The geometric mean of the cysts concentration was 4,54 cysts per 100 liters and the range of 0,29 to 64 cysts per 100 liters. Slow sand filters have also been used to treat the Giardia cysts from drinking water. This type of filters were tried in Northern Idaho to control Giardia cysts. Results showed that if a slow sand filter is designed adequately, it can provide enough treatment for the cysts. The control in this study was analyzed by 2 methods : Microscopic Particle Analysis (MP A) and Electronic Particle Counts (EPC). The estimated filtered water cyst concentration was 0,01 cyst / 1 compared with 0,09 cyst / 1 in the raw water sample Two other filtration systems (DE Filtration and Granular Media Filtration) are also very effective to remove the cysts. The filtration flow-rate of water is very important to remove the cysts. Changes in flow-rate should be avoided to reduce the potential for the passage of cysts into filtered water. The chemical conditioning is helpful to remove the cysts from raw water. Especially alum coagulant (10-16mg/l) was more effective to remove the cysts than the polymers (0,3 mg/1). The using together these chemicals was the most effective way of the chemical conditioning. The choosing of dosage and chemical can affect the treatment. xm Diatomaceous earth filtration was evaluated for removal of Giardia muris in raw water of Shingletown, Pa. The using the 10 mg alum/g DE filter has been very effective in filtration. No Giardia cysts were detected in effluent. The effect of cationic polymers and alum on this removal was also investigated. Essentially all of the Giardia cysts were removed from water that were including 2000 cysts / 1. Immunofluorescense methods were recently developed to detect the Giardia cysts in water samples. Also cDNA probe method has been used to detect Giardia species. This method is faster and more cost-effective than the other known methods. Neither the cDNA probe nor the immunofluorescence methods have not been used to determine cyst viability. Direct count of the cysts were also used by simple centrifugation or by sucrose flotation and assayed microscopically. In the fourth section, Giardia cysts have been examined in a full-scale treatment plant and surface water supplies which are providing water to this plant. Giardia cysts should be measured and controlled in the water supplies and treatment plants. Giardia cysts have not been measured before in water resources in Turkey and they are not in the list of drinking water standard. This parameter should be seriously considered by municipalities and the private sector which provide and sell drinking water in Turkey. In the fifth section, conclusions and recommendations have been presented.