Release 2.83
Liquid Stream Fundamentals: Sedimentation
Sedimentation is one of the processes most commonly used in wastewater treatment and in many cases the last barrier before the effluent leaves the water resource recovery facility (WRRF). Despite being vital components of the WRRF, sedimentation processes are sometimes overlooked. This fact sheet discusses the key design and operational considerations for the sedimentation processes and their role in achieving optimal plant performance.
Description: Liquid Stream Fundamentals: Sedimentation
Sections
Description: Liquid Stream Fundamentals: Sedimentation
Sedimentation refers to the physical process where gravity forces account for the separation of solid particles that are heavier than water (specific gravity > 1.0). The common sedimentation unit processes in a wastewater liquid treatment train include grit removal, primary sedimentation, secondary sedimentation and tertiary sedimentation. This fact sheet primarily focusses on the primary and...
PublisherWater Environment Federation
Word count434
Description: Liquid Stream Fundamentals: Sedimentation
Generally, clarifiers in a wastewater treatment plant are designed to serve four main functions discussed below.
PublisherWater Environment Federation
Word count137
Description: Liquid Stream Fundamentals: Sedimentation
Primary sedimentation is one of the key processes for TSS and BOD removal in the liquid treatment train and for reducing the load to the downstream biological process(es). Primary sedimentation is principally governed by discrete settling (Type I) along with minimal flocculation/flocculent (Type II) settling (Griborio et. al, 2014). Compression settling (Type IV) occurs in the sludge blanket...
PublisherWater Environment Federation
Word count1,180
Description: Liquid Stream Fundamentals: Sedimentation
The purpose of secondary clarifiers is to separate the incoming biomass from the biological reactors into clarified effluent and thickened sludge. For processes such as trickling filters and rotating biological contactors, the solids are typically settled and wasted, similar to primary sedimentation. For activated sludge, it is necessary to recycle most of the settled solids and return settled...
PublisherWater Environment Federation
Word count1,594
Description: Liquid Stream Fundamentals: Sedimentation
Geometry features of clarifiers can have a significant impact on clarifier performance and capacity and should therefore be carefully selected. This section discusses some of the main geometry features pertinent to both primary and secondary clarifiers.
PublisherWater Environment Federation
Word count3,330
Description: Liquid Stream Fundamentals: Sedimentation
While clarifiers are not instrumentation-intensive unit processes, some instrumentation-based controls can be useful for regulating and monitoring clarifier performance. One of the most commonly used instrumentation devices are sludge blanket readers/trackers (e.g. light emitting analyzers, ultrasonic analyzers, optical sensors). Sludge blanket measurement devices are mostly used in secondary...
PublisherWater Environment Federation
Word count172
Description: Liquid Stream Fundamentals: Sedimentation
Operation and control of clarifiers can range from completely manual to completely automated. In either scenario, the key operator responsibilities for clarifier operation are controlling RAS/primary sludge flow rates to maintain clarifier blankets and prevent solids carryover in the effluent, especially during high flows. Additionally, attention should be paid to monitoring flows, influent TSS,...
PublisherWater Environment Federation
Word count132
Description: Liquid Stream Fundamentals: Sedimentation
Clarifier design is complex and the resources for design and evaluation range from design standards (such as the Ten State Standards, local, state and federal standards) and literature guidelines (WEF MOP 8, Metcalf and Eddy, etc.) to limiting solids flux theory and sophisticated mathematical models (computational fluid dynamics, CFD). Since design standards and some literature-based resources do...
PublisherWater Environment Federation
Word count356
Description: Liquid Stream Fundamentals: Sedimentation
WEF Municipal Resource Recovery Design Committee
PublisherWater Environment Federation
Word count244