Abstract
Filtration and sedimentation properties have been investigated using various activated sludges prepared under the artificially controlled culture condition, to clarify the effects of organic loading on solid-liquid separation properties of activated sludge in wastewater treatment process. In microfiltration of mixed liquor containing activated sludge, the dynamic behaviors were well described by the Ruth filtration rate equation. It was revealed that the filter cake composed of activated sludge has extremely high compressibility. Therefore, membrane filtration of activated sludge should be conducted at relatively low pressure, because increase in the filtration pressure does not necessarily lead to increase in the filtration rate. Also, the filtration rate and the initial sedimentation velocity of mixed liquor are highly dependent on the characteristics of activated sludge. On the basis of the experimental data of the average specific filtration resistance, sludge volume index (SVI) and the area mean diameter of activated sludge, a correlation between solid-liquid separation properties and floc size of activated sludge was clarified. In addition, floc size of activated sludge was greatly influenced by biochemical oxygen demand (BOD) loading of the wastewater. From these results, it is clear that solid-liquid separation properties of activated sludge are closely related to the BOD loading of wastewater.
