Monitoring of the effects of additives on sludge separation properties by using sensors

Two novel sensors, Settlometer and Schlumosed, were used to evaluate the be neficial effect of three additives on sludge-settling properties. Four diff erent activated sludges were used in the study. The settling characteristic s of the sludges were evaluated in automated batch settling tests by means of the start-up time (initial lag period), initial settling velocity, stirr ed sludge volume, and final transparency of the supernatant. Different slud ges responded in distinct ways to the dosage of additives. Talc was typical ly more effective than coal in terms of improving settling velocity and red ucing sludge volume. Chemical polymer surpassed the two particulate additiv es in terms of final transparency. Furthermore, different sludge sedimentat ion parameters of a particular sludge were not affected to the same extent by a specific additive. This substantiates the need to describe settling pr operties with more than one parameter. The absolute values of the sedimenta tion properties were found to depend on the type of sensor used.