| Abstract: | In four tropical water works there are carried out investigations on the floc rising occurring during the day-hours, and especially in the hot season, in the flocculators. This phenomenon is caused by the great heating of the raw water during the day-hours, due to which between 10.00 a. m. and 10.00 p. m. a temperature difference up to 3.7 K between the influent and the effluent of the flocculators occurs during a retention period of 3.5… 5 h within the flocculators. Even temperature differences of only 1 K result in floc rising, reducing the filter run by four to seven hours. Oversaturation of the raw water with oxygen by the photosynthetic oxygen production constitutes an additional cause. As a measure against the rising and passing-on of flocs we recommend the aeration of the water at the raw water intake point, to prevent a thermal stratification during the day-hours and at the same time to remove the perhaps given oxygen oversaturation. |
