Advanced Search Home WEF Login UserName Password Login Instructions   Membership     Membership Renewal     My Member Info     Meetings     Subscriptions     Marketplace     Marketplace Search     Checkout     Shopping Cart   Product Qty (empty cart)     Thickening Publication: Operation of Municipal Wastewater Treatment Plants Manual of Practice-MOP 11 Sixth Edition Medium: Download Chapter Pages 76 Publisher: Water Environment Federation (WEF) Year: 2007 Order No: MOP1129 DOI: 10.2175/1-57278-232-3-29 Table of Contents Index Cover Art Frontmatter Order Additional Chapters of MOP 11 Order a Hard Copy of MOP 11 Abstract: The primary purpose of thickening sludge or biosolids is to reduce the volume of material that will be treated in processes that follow. The volume reduction benefits treatment processes that follow, such as digestion, dewatering, drying, combustion, or land application. Thickening also reduces the required capacity of downstream tanks and equipment, the quantity of chemicals required for conditioning, the heat required by digesters, and the volume of sludge (or biosolids) to be transported, dried, incinerated, or land applied. Three methods typically used to thicken at various points in the treatment stream are described briefly below: Gravity thickening concentrates through the use of gravitational force. Flotation thickening concentrates through the attachment of microscopic bubbles (most commonly air) to suspended solids (SS), thereby reducing their specific gravity to less than that of water. The air-attached particles then float to the surface for removal. This method is well suited to wastes containing high amounts of finely divided solids. The most typical thickener in this category is the dissolved air flotation (DAF) thickener. Mechanical thickening concentrates through the enhancement of gravitational forces. This can be accomplished in several ways: Centrifugal thickening, Gravity belt thickening, and Rotary drum thickening. Conditioning agents, typically polyelectrolytes (polymers) specific to the waste stream being treated, may be required to enhance the separation of free water from the charged particles. The use of conditioning agents often supplements all of the thickening methods described above. For the 6th edition of this chapter, the sections on centrifuges and dissolved air flotation have been completely rewritten to be more specific and user friendly.   Member Price:  $27.00 List Price:  $36.00 Downloadable version Thickening Continue Shopping Login for Member Pricing ©2000 Water Environment Federation Privacy, Security and Copyright Statements