FROM THE PREFACE
The processes used to remove water from biosolids and change their form from a liquid to a damp solid are critical to the operation of other downstream processes in wastewater treatment. An ideal dewatering operation would capture all of the biosolids solids at minimum cost and the resultant dry biosolids solids or cake would be capable of being handled without causing unnecessary problems. Process reliability, ease of operation, and compatibility with the treatment plant environment are also optimum.
This text is designed to provide a detailed look at several dewatering options. It must be pointed out, however, that this text takes a strong, biased view toward centrifugation as the dewatering process that is most reliable, maintenance free, cost effective, and capable of producing the highest quality end-product when compared to the other options in a holistic manner.
Therefore, the underlying theme of this text is wrapped around the premise that it is better to centrifuge it!
Having said this, it must also be pointed out that all major biosolids dewatering processes are discussed in this text, in detail. Several examples of actual operating systems are presented, and preventive maintenance and cost considerations are presented and discussed.
In recent years there has been a tendency in some technical texts like this one to focus on the theoretical and laboratory analyses of dewatering operations. While such research and documented findings can lead to improved understanding of the scientific and engineering concepts associated with dewatering biosolids, this text is presented in such a fashion so as to be user-friendly. It is an operator's text that can also afford the decision-maker the opportunity to make informed choices about selecting a dewatering system for his/her plant use.
Dewatering Biosolids will be of interest to people in all aspects of wastewater plant operation. Useful as a handbook for operators, this plain language text is also of importance to anyone considering altering or adapting their wastewater operating system.
Table of Contents
Preface - Acknowledgements
Part I: Introduction
Biosolids: Introduction - What's in a Name? - Key Terms and Calculations - Importance of Biosolids Management - Sources of Solids and Biosolids from Wastewater Treatment - Composition of Biosolids - Solids Concentration
Objectives of Dewatering Biosolids:Introduction - Dewatering's Role in Wastewater Treatment Processes - Dewatering Processes
Biosolids Characteristics Affecting Dewatering: Introduction - Characteristics Affecting Dewatering
Part II: Dewatering Processes
Gravity/Low Pressure Dewatering: Introduction - Advantages and Disadvantages of Gravity/Low Pressure Dewatering Devices - Operational Factors and Variables - Gravity Dewatering
Biosolids Lagoons: Introduction - Biosolids Lagoon Operation - Biosolids Lagoons: Final Thoughts
Drying Beds: Introduction: Natural Dewatering Techniques - Sand Drying Beds - Paved Drying Beds - Artificial Media Drying Beds: Wedgewire & Wedgewater Types - Vacuum-Assisted Drying Beds - Innovative Natural Methods of Dewatering Biosolids - Freeze-Assisted Drying Beds - Dewatering Using Aquatic Plants - Emerging Technologies
Pressure Filtration: Introduction - Pressure Filtration: Process Description - Pressure Filtration - A Typical Mechanical Biosolids Dewatering Process: Plate & Frame Press - Biosolids Cake Conveyor System - Acid Wash System - Auxiliary/Support Systems
Vacuum Filtration: Introduction - Vacuum Filter Description - Vacuum Filter Operational Process Variables
Belt Press Filtration: Introduction - Belt Filter Press Description and Operation - Technology of the Future: Belt Filter Presses
Centrifugation: Introduction - Process Description - History of Biosolids Centrifugation - Theory of Centrifugation - Process Parameters: Centrifugation - Testing & Optimizing Performance - Solid-Bowl Centrifuges - Solid Bowl Centrifuge Components - Centrifuge Operation - Centrifuge Maintenance Requirements
Part III: Chemicals Used for Dewatering
Lime: Introduction - Lime - Biosolid Lime Conditioning Process: Filter Process
Ferric Chloride: Introduction - Typical Ferric Chloride Feed System (Belt Filter Press)
Polymer: Introduction - Typical Polymer Feed System (Vacuum Filtrate) - Polymer Dosage for Optimum Performance in Dewatering
Safety Considerations when Using Chemicals: Introduction - Wastewater Treatment and OSHA's HAZCOM Program (29 CFR 1910.1200) - Safety Considerations for Chemicals Used in Dewatering Biosolids
Part IV: Dewatering Selection Considerations
Cost Considerations: Introduction - Cost Considerations