Abstract
In this paper, characteristics of solid-liquid separation of raw wastewater with a drum screen and prevention methods against clogging in the screen's slits by bacterial slime or scaly deposit were studied with pilot-scale equipment.
The results are summarized as follows : judging from filtration rate per unit length to the rotating axis of drum screen and clogging in the slits, wedge-wire was the most suitable material for the drum screen. Through the experiment with two brushes to prevent from clogging, in the case of the wedge-wire drum screen with 100 microns' slits, clogging had not occurred for six months without maintenance. Average SS removal ratio and BOD removal ratio were 30% and 22%, respectively. Separated sludge was discharged from the drum screen automatically and the water content of the sludge was at the low levels of 86.5% to 92.5%. Besides, the proposed formulas enabled to calculate the maximum flowrate of the drum screen. The required area and volume of the drum screen were compared with those of the conventional primary sedimentation tank.
