Diurnal Thermal Stratification and Floc Rising in Clariflocculators of the Tropical Water Works

摘要

AbstractIn 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 overs