[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)]

Abstract

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.