The impact of hydroxyl radical (*OH) on the molecular weight distribution of natural organic matter (NOM) was investigated. *OH was generated via the photolysis of hydrogen peroxide (H2O2) by ultraviolet (UV) radiation of 254 nm, also known as UV/ H2O2 advanced oxidation (AO). Additionally, the impact of combined membrane and UV/H2O2 treatment on the molecular weight distribution of NOM was studied. High performance size exclusion chromatography (HPSEC) was used to determine the apparent molecular weight (AMW) distribution of chromophoric NOM (CNOM). Prior to AO, 33% of the CNOM in the water had AMW greater than 1400 Da. Meanwhile, lower AMW CNOM made up smaller amounts of the CNOM, with CNOM of AMW less than 450 Da making up 5% of the total. Under the AO conditions typically applied in drinking water treatment applications, NOM was not mineralized but was partially oxidized resulting in significant reduction in aromaticity. *OH preferentially reacted with higher AMW CNOM and the fragmentation of high AMW CNOM led to the formation of smaller AMW CNOM. Ultrafiltration removed all CNOM greater than 1400 Da AMW and a large portion of other high AMW fractions. In the absence of high AMW CNOM, *OH reacted more readily with all AMW fractions leading to a reduction in concentration of most AMW fractions. Whereas *OH reacted nonspecifically with all AMW fractions, the reaction rate between *OH and CNOM was observed to be dependent on molecular size.
, 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
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