[Microbial emission, immission and changes in the germ count in the cooling water during operation of wet cooling towers ii. communication: measuring methods, emission values and changes in the germ count in the cooling system (author's transl)]. / Mikrobielle Emission und Immission sowie Keimzahländerungen im Kühlwasser beim Betrieb von Nass-Kühltürmen II. Mittelung: Messmethoden, Emissionswerte und Keimzahländerungen im Kühlsystem.

The second in the series "Microbial emission, immission and changes in the germ count in the cooling water of wet cooling towers" describes measuring methods and results of the measurements for determining the emission values and the changes in the germ count in the cooling system. The content of colony-forming units (KBE) in the cooling water varied widely, depending on the germ content of the surface water and the preparation of the cooling water (filtration, chemical conditioning). In summer the KBE values were as a rule higher than the values recorded in winter (factor of about 10). The introduction of cooling tower water into the surface water thus did not result in any noticeable changes in germ content, either in summer or in winter. An emission rate of 8.3 10(7) KBE/s (CSA) measured at the top of the cooling tower was the maximum emission value recorded. This resulted in a total germ content in the plume of 1.2 . 10(4) KBE/m3. In order to place this finding into perspective, it should be noted that fluctuations in the KBE values of the air of considerably more than 1000 KBE/m3 can occur because of biological release and meteorological conditions alone (see IVth communication). The KBE-P values recorded (content of particles with units which are capable of forming colonies) in the plume were of the same order as the KBE values. From this it can be concluded that the drops of cooling water which are swept away with the plume are normally only charged with individual colony-forming units. It is worth noting that the KBE values of the plume are only indirectly dependent on the KBE values of the cooling water used in the cooling tower.

[Microbial emission, immission and changes in the germ count in the cooling water during operation of wet cooling towers. IV. Communication: microbial immission in the vicinity of wet cooling towers (author's transl)]. / Mikrobielle Emission und Immission sowie Keimzahländerungen im Kühlwasser beim Betrieb von Nass-Kühltürmen IV. Mitteilung: Die mikrobielle Immission in der Umgebung von Nass-Kühltürmen.

From the emission rates of the bacterial cooling tower emission determined in field measurements (see Comm. II) the mortality rate of enterbacteria on soil, grass and solid surfaces and the mortality rate in the atmosphere taken from literature the immission rates and the long-term effect on microbial surface flora were calculated and compared with our own measurements. The values used in the calculations include large margins for error. The atmospheric germ counts determined by experiment were no higher than the calculated values; they fluctuated in terms of concentration between 20 KBE m-3 and 200 KBE m-3 in ranges which were measured in areas with little or no anthropogenic influences. The maximum long-term surface load which occurs under these assumptions is 2.3.10(5) KBE M-2. This relatively small additional load (approx. 10(-3%) would hardly be noticeable in a number of colonies of approximately 10(10) KBE m-2 normally occurring in soil and grass samples.

[Microbial emission, immission and changes in the germ count in the cooling water during operation of wet cooling towers III. communication: laboratory tests for the determination of the reduction kinetics of Escherichia coli in cooling tower plumes (author's transl)]. / Mikrobielle Emission und Immission sowie Keimzahländerungen im Kühlwasser beim Betrieb von Nass-Kühltürmen III. Mitteilung: Laboratoriumsuntersuchungen zur Bestimmung der Absterbekinetik von Escherichia coli in Kühlturmschwaden.

The present paper reports on laboratory tests for the determination of the reduction rate of micro-organisms. The investigations were carried out with a pure culture of E. coli, a germ type from the enterobacterial group. By a suitable variation of the thermodynamic parameters it was possible to simulate the conditions through which the cooling tower plume passes inside the chimney of the cooling tower and when it mixes with ambient air. The results allow the following changes in the germ counts in the plume of a wet cooling tower to be expected: 1. As long as the cooling tower plume contains droplets, the capacity of the carried germs to form colonies does not change materially. 2. In the case of unsaturated plumes we must distinguish between two situations: a) The tests in which the germ suspension was sprayed into unsaturated air without any admixture of secondary air, did not demonstrate any dependence of the reduction rate on the relative humidity. b) In contrast to this, the tests in which the germ-carrying droplets were evaporated by admixing a stream of unsaturated secondary air, showed that the capacity to form colonies clearly decreased with diminishing relative air humidity. Case b) is of importance for the dissemination and immission of germs from cooling towers, because here, too, the visible plume initially laden with drops is dried by the admixture of unsaturated ambient air.