Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation

Laleh Nazari; Zhongshun Yuan; Domenico Santoro; Siva Sarathy; Dang Ho; Damien Batstone; Chunbao Charles Xu; Madhumita B Ray

doi:10.1016/j.watres.2016.11.055

Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation

Water Res. 2017 Apr 15:113:111-123. doi: 10.1016/j.watres.2016.11.055. Epub 2016 Dec 3.

Authors

Laleh Nazari¹, Zhongshun Yuan¹, Domenico Santoro², Siva Sarathy², Dang Ho², Damien Batstone³, Chunbao Charles Xu⁴, Madhumita B Ray⁵

Affiliations

¹ Department of Chemical & Biochemical Eng., Western University, London, ON, N6A 5B9, Canada.
² Department of Chemical & Biochemical Eng., Western University, London, ON, N6A 5B9, Canada; Trojan Technologies, London, ON, N5V 4T7, Canada.
³ Advanced Water Management Centre, The University of Queensland, Brisbane, QLD, 4072, Australia.
⁴ Department of Chemical & Biochemical Eng., Western University, London, ON, N6A 5B9, Canada. Electronic address: cxu6@uwo.ca.
⁵ Department of Chemical & Biochemical Eng., Western University, London, ON, N6A 5B9, Canada. Electronic address: mbhowmic@uwo.ca.

PMID: 28208104
DOI: 10.1016/j.watres.2016.11.055

Abstract

The present study examines the relationship between the degree of solubilization and biodegradability of wastewater sludge in anaerobic digestion as a result of low-temperature thermal pre-treatment. The main effect of thermal pre-treatment is the disintegration of cell membranes and thus solubilization of organic compounds. There is an established correlation between chemical oxygen demand (COD) solubilization and temperature of thermal pre-treatment, but results of thermal pre-treatment in terms of biodegradability are not well understood. Aiming to determine the impact of low temperature treatments on biogas production, the thermal pre-treatment process was first optimized based on an experimental design study on waste activated sludge in batch mode. The optimum temperature, reaction time and pH of the process were determined to be 80 °C, 5 h and pH 10, respectively. All three factors had a strong individual effect (p < 0.001), with a significant interaction effect for temp. pH² (p = 0.002). Thermal pre-treatments, carried out on seven different municipal wastewater sludges at the above optimum operating conditions, produced increased COD solubilization of 18.3 ± 7.5% and VSS reduction of 27.7 ± 12.3% compared to the untreated sludges. The solubilization of proteins was significantly higher than carbohydrates. Methane produced in biochemical methane potential (BMP) tests, indicated initial higher rates (p = 0.0013) for the thermally treated samples (k_hyd up to 5 times higher), although the ultimate methane yields were not significantly affected by the treatment.

Keywords: Degradability; Methane production rate; Process optimization; Solubilization; Thermal treatment; Waste activated sludge.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anaerobiosis
Biological Oxygen Demand Analysis
Methane / metabolism
Sewage / chemistry*
Temperature
Wastewater*

Substances

Sewage
Waste Water
Methane