Graduation Semester and Year
Summer 2025
Language
English
Document Type
Thesis
Degree Name
Master of Science in Civil Engineering
Department
Civil Engineering
First Advisor
Dr. Hyeok Choi
Second Advisor
Dr. Srinivas Prabakar
Third Advisor
Dr. Xiujuan Chen
Abstract
Municipal wastewater sludge is a valuable resource rich in carbohydrates and nutrients (particularly nitrogen (N) and phosphorus (P)), which requires significant sludge management effort. Thermal hydrolysis process (THP), as a pretreatment of anaerobic digestion process (ADP), is one of the effective methods of sludge treatment that increases digestion rates later, improves the breakdown of sludge components (biodegradability), and enhances dewatering properties. High-temperature hydrolyzed sludge is typically cooled down by passing through cooling heat exchangers (CHEs) and blending with digested sludge before entering ADP. The rheological and thermal properties of sludge are greatly changed over THP, CHEs, and ADP, and thus knowledge on the property changes would significantly help the design and operation of the unit processes. In addition, revealing the behavior of N and P nutrients would help achieve the overall sludge management goal. As a result, the main objective of this study was to understand the changes of the comprehensive properties of sludge over the sludge management system. Sludge was taken monthly over a year from the Central Regional Wastewater System, Dallas, TX at 5 different sampling locations, so-called mixed sludge, dewatered sludge after cake bin, hydrolyzed sludge, sludge before ADP, and digested sludge. The properties of the sludges were then measured, including various solid concentrations and N and P nutrients, viscosity, heat capacity, and conductivity at 20 °C. Some of the key property parameters were also measured at actual operating temperatures, and Herschel-Bulkley model parameters were estimated to reveal the fluidic behavior of some selected sludge samples. Results showed that the sludge properties changed significantly over the sampling locations. The changes were ascribed to the physical and chemical action of each unit process towards the sludge. Indeed, the rheological and thermal properties of the sludge were largely affected by its solid content, and thus the properties of the sludge were significantly different from those of clean water. The property data and findings will help make the design, operation, and maintenance of THP, CHEs, and ADP more efficient, cost-effective, and nutrient-rich and thus provide a practical framework for retrofitting municipal wastewater sludge management systems.
Keywords
Wastewater Sludge; Sludge Management; Anaerobic Digestion; Thermal Hydrolysis; Cooling Heat Exchanger; Rheological Properties; Thermal Properties; Nutrients
Disciplines
Civil and Environmental Engineering
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Saha, Prachi Rini, "CHANGES OF THE RHEOLOGICAL, THERMAL, AND NUTRIENT PROPERTIES OF MUNICIPAL WASTEWATER SLUDGE OVER THERMAL HYDROLYSIS AND ANAEROBIC DIGESTION PROCESSES" (2025). Civil Engineering Theses. 463.
https://mavmatrix.uta.edu/civilengineering_theses/463