[From the second European drinking water guideline to the new drinking water regulations]. / Von der 2. Europäischen Trinkwasser-Richtlinie zur neuen Trinkwasser-Verordnung.

The new drinking water regulations, effective 1.1.2003, introduced several new and hygienically important changes. The term "drinking water" has changed to "water for human consumption". The change of the term gives a remarkable extension of the scope of the drinking water regulations. One of the consequences is that the water in buildings in which the water is delivered to the public has now to be controlled as well. The planned measures may help to promote good consequences in case of accidents. The need for treatment makes it necessary to control raw water to a higher degree than before. In case of microbial contamination the water has to be treated by filtration. Disinfection may no longer be the only treatment to ensure a safe drinking water supply. The adherence to the technical rules demanded by the new drinking water regulations may convey much additional security to water supply.

Role of disinfection in suppressing the spread of pathogens with drinking water: possibilities and limitations.

Transmission of pathogens with drinking water is a widespread problem, which affects not only the countries with low hygienic standards but the industrialized countries as well. The pathogens are excreted by man or animals and are picked up orally. Chlorination of drinking water has been introduced to the water supply in the beginning of the 19th century in order to stop the spreading of pathogens especially typhoid fever by drinking water. Despite the worldwide use of chlorine for disinfection of drinking water, water-mediated disease outbreaks occur again and again. Disinfection of drinking water with chlorine has undoubtedly contributed to the reduction of typhoid fever mortality. However, it must be clear that other factors play an important role in the mortality drop. Filtration of water is a long-known and very effective process for eliminating pathogens from the drinking water. Pathogens in particles cannot be killed sufficiently by a chemical disinfectant. Even small fecal particles have to be eliminated reliably from the water by filtration. Disinfection of drinking water cannot replace filtration. The disinfection should be used to minimize the residual risk due to the presence of pathogens in the water but cannot be used for bringing fecally contaminated water into a hygienically sound condition.

Giardia and Cryptosporidium in backwash water from rapid sand filters used for drinking water production.

Backwash water from rapid sand filters of a treatment plant using surface water from small rivers for drinking water production was examined with the aim of determining the degree of their potential contamination with Giardia cysts and Cryptosporidium oocysts. Simultaneous investigations were carried out for both protozoans from November 1993 to February 1994. Water samples were concentrated by continuous flow centrifugation (11 backwash water samples) or by using polypropylene cartridge filters (12 raw water samples and 39 backwash water samples). Parasites were identified by the direct immunofluorescence assay. Ten out of 12 raw water samples tested were positive for Giardia (range: 2-103/ 100 L) and 8 out of 12 were positive for Cryptosporidium (range: 0.8-109/100L). Eight of 11 backwash water samples collected by continuous flow centrifugation were positive for Giardia (range: 3-86/100 L) or Cryptosporidium (range: 1-69/100 L). Out of 39 samples collected using cartridge filters, 34 were positive for Giardia (range: 1.4-374/100 L) and 33 for Cryptosporidium (range: 0.8-252/100 L). Overall, Giardia, Cryptosporidium, or both were detected in 92% of the backwash water samples. The results have clearly shown that backwash waters were contaminated with Giardia and Cryptosporidium and the supernatant returned to the raw water after the sedimentation process was not free from cysts and oocysts.

Recovery efficiency of Cryptosporidium from water with a crossflow system and continuous flow centrifugation: a comparison study.

A crossflow system and continuous flow centrifugation were tested with regard to the recovery rate of Cryptosporidium oocysts from water. Equal volumes of tap water were contaminated with specific numbers of oocysts. With the crossflow system, an average recovery of 9.8% was obtained when using a concentration of 2 x 10(2) oocysts/L. Recovery rates achieved with the continuous flow centrifuge were more satisfactory: Starting with a concentration of 80 oocysts/L, we obtained an average recovery of 12.9%. The technique of continuous flow centrifugation was found to be more efficient for collection of Cryptosporidium oocysts from water than the crossflow system.

[The intraoral bacterial colonization of temporary denture plastics]. / Intraorale Bakterienbesiedlung von temporären Kunststoffen.

Plastic materials used for temporary crowns and bridges in prosthetic dentistry are investigated with regard to the possibility of their microbial colonization. For this purpose four different kinds of materials, i.e. Resincap, Trim, Snap (Polyalcylmethacrylate) and Protemp (Bisphenol-A-Glycidyl-Methacrylate) were chose. With the help of 10 test persons in vivo experiments were carried out. After a period of two weeks it could be verified, that the bacteria have a stronger affinity to Protemp than to Polyalcylmethacrylate. The hypothesis, that the different intensity of colonization is due to the roughness of certain surfaces could be confirmed by additional experiments.

Chemical, bacteriological and biological examination and evaluation of sediments from drinking water reservoirs--results from the first sampling phase.

Between September 1992 and April 1993, samples of sediment were taken from a total of 16 drinking water reservoirs from seven water suppliers. Five different types of raw water were examined, samples being taken with varying frequency. The comparison of surface reservoir water and ground water constituted a central aim in this first series of investigations. The composition of the sediment was determined in terms of its chemical, bacteriological and biological characteristics. It was established that the deposits that normally accumulate in the course of an operating period contain, in addition to the familiar mass-determinant inorganic constituents such as iron, manganese and calcium compounds, in some cases considerable quantities of organic substances. Total organic carbon (TOC) contents of up to 11 weight-% were found. Besides an increased concentration of heavy metals, in particular cadmium, nickel and zinc, were measured in some sediments. The bacteriological examination of the sediments, in accordance with the German drinking water regulation (TrinkwV) showed, in part, very high colony counts. However, there was apparently no influence on the effluent water as the reservoir was emptied. The microscopical examination showed independent of the raw water source the sediments being colonized by invertebrates. Up to 9000 organisms per litre of fresh sediment were recorded. The predominant group of animals, in terms of numbers, was the rotifers followed by threadworms. The comparison of water from impounding reservoirs and ground water made evident that the presence of organisms in reservoir sediments is not restricted to the use of surface water.

[Microbial contamination of wash water in automatic washing and disinfection machines]. / Mikrobielle-Kontaminationen von Spülwasser in Reinigungs- und Desinfektionsautomaten.

Samples were taken from the water containing tube system of 7 cleaning and disinfection machines located at the university clinics. The machines were used for the treatment of medical tools. The samples were bacteriologically examined. The results showed systemic contaminations of the tubes of all tested machines. The well known positive effect of common ion-exchangers on bacterial growth was not the only reason for the high degree of microbial contaminations. Partial bacterial growth on the inner sides of the water tubes was detected. The reason was the use of bacteriological objectionable tube materials. Recontamination of the post treated medical tools is possible at any time by the last washing water. Preceding sterile filtration showed as supposed no effect. Consequences for the use of cleaning and disinfection machines are discussed.

[Drinking water and parasites]. / Trinkwasser und Parasiten.

Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum, Isospora belli, Balantidium coli, and Microsporidia spp. are cosmopolitan parasites. They often cause diarrheal diseases. The waterborn transmission of all these parasites is possible (41). Surface water supplies used for drinking water are potential sources of contamination. Giardia lamblia and Cryptosporidium spp. have received great attention in industrialized countries during the last years because they are the etiological agents of waterborne diseases. The life cycles of Giardia lamblia and Cryptosporidium are described with a special reference to drinking water technologies aimed at removing these parasites.

Influence of geometrical parameters in different irradiation vessels on UV disinfection rate.

Possible differences in the disinfection rate of two irradiation concepts, e.g. irradiation in cuvettes and petri dishes, were examined and quantified on a UV laboratory irradiation plant unit. In addition the geometrical parameters of the irradiation vessels and mixing of the bacterial suspension during UV irradiation were considered. The results showed differences in disinfection rates of more than 2 log between different sample areas in the vessels. The mixing caused an improvement of the disinfection rates in unfavourable irradiation areas of the cuvettes and in contrast a deterioration in all irradiation areas in the petri dishes.

[Legionella in membrane expansion vessels]. / Legionellen in Membran-Druckausdehnungsgefässen.

Membrane expansion vessels (MEV) are installed between cold drinking water supply and hot water system to compensate pressure changes and water losses. An elastic membrane inside the MEV divides a gas pressurized compartment from a water filled compartment, which--in case of flow-through type of MEV--is directly coupled to the water current. While heating the system the expanding water enters the last mentioned compartment. When cooling down, the water is flowing out. Thus MEVs may prevent water losses. Bacteriological investigations of two DEVs of the flow-through type showed the following results: 1. While 5 samples taken from the cold water supply did not yield Legionella, all 7 samples from the outlets of both DEVs tested positive for Legionella (average 21 CFU/ml). 2. In each of 4 samples taken from the outlet of a DEV, total colony counts exceeded the guide value of 100 colonies/ml demanded in the German Drinking Water Act (average 724 colonies/ml at 20 degrees C, 921 colonies/ml at 36 degrees C). 3. Swab and contact culture from one of the membrane indicated excessive surface colonization with Legionella. The findings show the necessity to include MEVs in investigations of hot water systems for Legionella.

Photoreactivation of E. coli depending on light intensity after UV irradiation.

Interest in the disinfection of drinking water by UV rays has been growing in recent years. Since the beginning of the 40's it has been known that, by means of certain repair mechanism, microorganisms are able to restore lesions on DNA. These processes are more or less clarified. However there is no secure knowledge about the degree of possible repair. Photoreactivation induced by light of 350-600 nm is one of these repair mechanisms. Thus the effect of light exposure on disinfection results with E. coli after UV disinfection was examined. E. coli ATCC 11229 were cultivated, washed, suspended and irradiated by means of UV rays from a mercury low-pressure lamp. After UV disinfection, the bacterial suspension was illuminated by fluorescent light. The degree of photoreactivation could be influenced by illumination intensity. The speed of reactivation decreased with the distance of the probes to the illumination source and increased with the period of time of illumination. After a 4 log reduction of the colony count (10(6)/ml-10(2)/ml) through UV rays, the reduction rate could be decreased to only 1 log (10(5)/ml) after UV disinfection and illumination. In probes kept in darkness for the same period there was no change in the count of reproductive bacteria. It seems to be necessary to take photoreactivation into consideration with the UV disinfection of drinking water.

[Effect of the reflection of UV rays in the disinfection of drinking water]. / Einfluss der Reflexion von UV-Strahlen bei der Desinfektion von Trinkwasser.

The disinfection of drinking water by means of UV-rays represents an interesting alternative to chemical disinfection. However, several questions still remain to be answered, making the disinfection of drinking water by means of UV-radiation appear unsafe. The regulations concerning the disinfection performance of UV-systems are still presenting difficulties. Within the course of comparative experiments in the laboratory and using a flow-through reactor on the disinfection effectiveness of UV-radiation, it has been shown that the reflection of UV-rays can have a considerable influence on the disinfection effectiveness. In order to be able to make reliable statements on the dose-effect relation it is necessary, therefore, to record exactly the radiation applied, including the reflected proportion.

Studies on the lethal effect of ultraviolet light on Trichomonas vaginalis.

Following cultivation in Asami medium, centrifugation and resuspension in saline or in water from a medicinal spring, Trichomonas vaginalis trophozoites were exposed to well-defined doses of ultraviolet (UV) light (254 nm). We used 24- and 48-h-old trichomonads at concentrations of 1 x 10(5) and 5 x 10(4) trophozoites/ml in a total volume of 20 ml for these studies. The apparatus for UV irradiation was especially constructed for batch experiments. After irradiation at doses ranging from 80 to 160 mJ/cm2, the mobility of the parasites was reduced and morphological alterations appeared: rounding of the cells, vacuolization of the cytoplasm and even cytolysis. A dose of 401.7 mJ/cm2 killed 99.8% of the 48-h-old trichomonads when irradiation occurred in saline at a cell density of 1 x 10(5) trichomonads/ml and 98.9% when irradiation was done at a cell density of 5 x 10(4) trichomonads/ml. A dose of 362.1 mJ/cm2 killed only the more sensitive 24-h-old trichomonads. In mineral water, 241 mJ/cm2 was sufficient to kill up to 99.5% of the 48-h-old trichomonads. When 48-h-old trichomonads that had been exposed to a radiation dose of 160-240 mJ/cm2 were subcultured, they lost their ability to propagate. At a dose of 80 mJ/cm2, both the trichomonads that had been harvested during the log phase and the 48-h-old organisms suspended in mineral water lost their ability to propagate on subculture. These results indicate that 24-h-old trichomonads were more sensitive than 48-h-old organisms. Furthermore, the experiments demonstrated that a higher dose of UV radiation must be applied to T. vaginalis trophozoites than to the more sensitive bacterial strain Escherichia coli ATCC 11229 so as to achieve comparable killing results.

Ultraviolet disinfection of drinking water. 1. Communication: Inactivation of E. coli and coliform bacteria.

The inactivation of E. coli and coliform bacteria by UV rays was tested in a laboratory unit. The strains investigated were E. coli ATCC 11229, C. freundii ATCC 8090, E. cloacae ATCC 13047 and K. pneumoniae ATCC 4352. The irradiation dose was determined by a modified potassium ferrioxalate actinometer according to Calvert and Pitts. In consequence with the investigations E. cloacae ATCC 13047 proved to be the most UV resistant and K. pneumoniae ATCC 4352 to be the most UV sensitive microorganism.

[Solvents in drinking water from a thermostatic mixing battery]. / Lösemittel im Trinkwasser aus einer Thermostatmischbatterie.

In a hospital an odour of organic solvent could be smelled when a special thermostatic water mixer has been used. At no other water tap in the house a similar smell could be recognized. After stagnation overnight or after weekends the disgusting smell has been rather strong. The odour of organic solvent disappeared when the water had been running for some time. The organic compound in the drinking water has been identified and the thermostatic water mixer could be revealed as the source of the contamination. Further investigations of other thermostats showed a variety of alcoholic compounds which were used as thermostatic fluids.

[Microbial contamination of water by pipe and tube materials. 3. Behavior of E. coli, Citrobacter freundii and Klebsiella pneumoniae]. / Mikrobielle Kontamination des Wassers durch Rohrund Schlauchmaterialien. 3 Mitteilung: Verhalten von E. coli, Citrobacter freundii und Klebsiella pneumoniae.

Materials water comes into contact with can promote the microbial growth as it could be shown before. The reaction of an unspecific microorganism flora and of Legionella pneumophila in pipes and hoses has been described in the two previous communications. The investigation with L. pneumophila has shown that even a pathogen organism can grow upon the materials. Therefore it was of special interest to prove whether indicator organisms for the testing of drinking water can grow in pipes and hoses as well. Escherichia coli, Citrobacter freundii and Klebsiella pneumoniae grew after the experimental contamination for many weeks on the rubber hose until the test was finally stopped, in the other pipes and hoses (glass, high-grade steel, PVC, PE, PA, PTFE and silicone) E. coli could be found for maximal 7 weeks, Citrobacter freundii for 1 week and Klebsiella pneumoniae for maximal 3 weeks. In the copper pipe the organisms could be found only for a few days.

[Microbial contamination of drinking water by a polyamide feedpipe]. / Mikrobielle Kontamination des Trinkwassers durch eine Polyamid-Pumpensteigleitung.

An incident is described with high colony counts in the drinking water from a well. The well was disinfected with sodium hypochlorite for several times, but without permanent success. After that the search for the reason of the high colony counts started. It turned out that the polyamide rising-pipe produced the microbial growth. Besides the colony increase in the water there was a microbial growth upon the surface of the polyamide pipe as well. When a high grade steel pipe was installed instead of the polyamide pipe there was no colony increase in the water any more.

UV disinfecting experiments with E.coli and actinometric determination of the irradiation intensity.

The UV disinfection of E. coli was carried out and additionally an actinometric determination of the irradiation intensity was made. This kind of proceeding renders it possible--in regard to the time of exposure--to set up a dose-effect-relation for the UV disinfection of water.