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

Abstract

, Ray, M.B., Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation, Water Research (2017Research ( ), doi: 10.1016Research ( /j.watres.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The present study examines the relationship between the degree of solubilization and biodegradability of 11 wastewater sludge as a result of low-temperature thermal pre-treatment. The main effect of thermal pre-12 treatment is the disintegration of cell membranes and thus solubilization of organic compounds. There is 13 an established correlation between chemical oxygen demand (COD) solubilization and temperature of 14 thermal pre-treatment, but results of thermal pre-treatment in terms of biodegradability are not well 15 understood. Aiming to determine the impact of low temperature treatments on biogas production, the 16 thermal pre-treatment process was first optimized based on an experimental design study on waste 17 activated sludge in batch mode. The optimum temperature, reaction time and pH of the process were 18 determined to be 80 o C, 5 hr and pH 10, respectively. All three factors had a strong individual effect (p < 19 0.001), with a significant interaction effect for temp.pH 2 (p = 0.002). Thermal pre-treatments, carried out 20 on seven different municipal wastewater sludges at the above optimum operating conditions, produced 21 increased COD solubilization of 18.3 ± 7.5 % and VSS reduction of 27.7± 12.3 % compared to the 22 untreated sludges. The solubilization of proteins was significantly higher than carbohydrates. Methane 23 produced in biochemical methane potential (BMP) tests, indicated initial higher rates (p = 0.0013) for the 24 thermally treated samples (k hyd up to 5 times higher), although the ultimate methane yields were not 25 significantly affected by the treatment. 26 Process Optimization and Effects on Solubilization and Anaerobic

Pre-treatments to enhance the biodegradability of waste activated sludge: Elucidating the rate limiting step

“…However, in other cases, higher COD solubilization did not result in a higher biogas production, but sometimes in the same or even lower biogas production (Dhar et al, 2012;Haug et al, 1978;D.-H. Kim et al, 2013;J. Kim et al, 2013b;Nazari et al, 2016;Sapkaite et al, 2017). Since COD solubilization is apparently not an accurate parameter to predict the effectiveness of subsequent biogas production (Sapkaite et al, 2017), until now, batch or (semi)continuous, anaerobic digestion methods are the only useful and accurate tools to assess the effect of pre-treatments on the anaerobic biodegradability of WAS.…”

“…The operational parameters are temperature and application time. Its main effect is the disintegration of cell membranes and a concomitant solubilization of organic compounds (Nazari et al, 2016).…”

Nano‐layered TiO2 for effective bacterial disintegration of waste activated sludge and biogas production

“…3 Various pretreatment processes, such as thermal treatment, biological treatment, chemical treatment, ultrasonic treatment, microwave treatment, and combinative treatment, such as chemo-sonic treatment, thermo-sonic treatment, and thermo-chemo-sonic treatment, are available. 4,5 Among them, biological pretreatment has quite a few benefits, which include minimum energy input, an eco-friendly process without pollution, and less harsh working conditions. 6 In addition, the complex high molecular weight and nexus interlace of extracellular polymeric substances (EPSs) protect the sludge from unfavorable conditions.…”

Thermal Effects

“…generally Nazari et al (2017). investigated the relationship between the degree of solubilization and biodegradability of wastewater sludge in AD due to low-The results showed that MSW was successfully processed after carrying out a feedstock pretreatment.…”