A crucial measurement in wastewater treatment, it represents the volume occupied by a settled mass of solids after a specific settling period, typically 30 minutes. It is determined by dividing the settled sludge volume (in mL/L) by the mixed liquor suspended solids concentration (in mg/L, converted to g/L). The resulting value, usually expressed in mL/g, provides an indication of the settling characteristics of activated sludge. For example, a value of 100 mL/g indicates that one gram of solids occupies a volume of 100 mL after settling.
This determination is valuable for assessing and controlling the performance of secondary clarifiers in wastewater treatment plants. Optimizing clarifier performance is essential for achieving effluent quality standards and preventing solids washout, which can negatively impact receiving water bodies. Historically, this measurement has been a key operational parameter, providing a relatively simple and readily available means to evaluate sludge settleability, guiding adjustments to plant operating conditions to maintain optimal treatment efficiency.
