Sludge reduction and volatile fatty acid recovery using microwave advanced oxidation process

Abstract

Sewage sludge was subjected to the combined microwave-hydrogen peroxide-sulfuric acid enhanced advanced oxidation process (MW-H(2)O(2)-H(+)-AOP) to evaluate the potential of reducing suspended solids in sludge. The soluble chemical oxygen demand (SCOD) and acetic acid produced were dependent on the amounts of H(2)O(2) and acid used in the process. For sewage sludge, a higher volume of H(2)O(2) addition not only favored the destruction of sludge solids, but also conserved the carbon content in the medium. Volatile fatty acid (VFA) concentrations also increased with the amount of inorganic acid in the solution. For the soluble fraction of solutions derived from microwave-treated sludge, over 96% of the total COD was in the soluble form, and up to 25% of this soluble COD was acetic acid. The presence of an inorganic acid was a stability factor in retaining the SCOD in solution, instead of the formation of carbon dioxide, resulting in reduced total COD in the solutions. By controlling the amounts of H(2)O(2) and acid addition, the MW-H(2)O(2)-H(+)-AOP could solubilize and/or reduce the sludge mass.

Microwave Enhanced Advanced Oxidation Process Application to Treatment of Dairy Manure

“…Acid also help solublize organic phosphorus and polyphosphate (Chan, et al, 2007). A trend can be seen from Figure 2, where Treatment time highly favours the release of ortho-P, with a slight increase of hydrogen peroxide.…”

“…For the sewage wastewater treatment industry, there are many applications of microwave heating on sludge treatment for reducing volume, improving dewaterability, enhancing digestibility, enhancing nutrient release, pathogen destruction, and stabilizing heavy metal (Menendez, et al, 2002;Liao, et al, 2005;Wojciechowaska 2005;Hong et al, 2006;Eskicioglu et al, 2007;Hsieh et al, 2007;Yu, et al, 2010). It has also been reported that the overall treatment efficiency could be increased with a combination of microwave heating with chemicals (thermo-chemical) for the treatment of sludge (Chan, et al, 2007;Qiao, et al, 2008). The common chemicals used on thermo-chemical process are acid, base and oxidants.…”

“…During this treatment, the suspended solids (SS) content of the slurries is also reduced. Its mechanism is assumed to be similar to the wet-air oxidation process wherein the first process involves the breakdown of large particulate organic matters, such as carbohydrate and proteins into smaller and more soluble organic components, and the second process involves the further oxidation or gasification of some of the resulting www.intechopen.com organic products (Shanableh & Shimizu, 2000;Liao, et al, 2007). The factors affecting the performance of the MW/H 2 O 2 -AOP have been identified; they are microwave temperature, hydrogen peroxide dosage, microwave intensity, reaction time, and acid addition.…”

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

“…Although the science behind the many published research articles in this area is novel and has had impact and made significant contributions of knowledge to the scientific community, the background behind the electromagnetic interaction with biomass and wastes has often been overlooked. For [201] MW (80°C) for 5 min and 34 mL/L H2O2 + 17 mL/L H2SO4 Sludge All COD was solubilised [202] MW (80°C), 5 min heating time, with 1 mL H2O2 (30%)/1 %TS dosage WAS 25% increase in SCOD [203] MW (120°C) with 0.80 g H2O2/g dry sludge WAS Optimum parameters for maximum solids' disintegration and nutrient release [204] MW (80°C) for 3 min with 1% H2O2 WAS 18% increase in COD solubilisation [205] MW (120°C) for 10 min with 1 g H2O2 (30 % v/v/ g TS ) WAS COD solubilisation increase from 3% (control) to 24% after pre-treatment. However, no significant effect of combined pre-treatment was observed on methane production and sludge dewaterability [156] MW heating (80°C) followed by addition of H2O2 and then continuous heating to 100°C…”

Effect of pre-heating on microwave enhanced advanced oxidation process

“…When MW/H 2 O 2 -AOP is operated at higher temperatures, the synergistic effect of microwave irradiation and hydrogen peroxide is enhanced. Elevated microwave temperatures (>80°C) increase the decomposition of hydrogen peroxide into hydroxyl radicals and therefore increase the oxidation rate, resulting in a higher degree of solubilisation of the substrate (Eskicioglu et al, 2008;Liao et al, 2007). Lo and Liao (2011) suggested an optimum MW temperature of 120°C for best nutrient recovery and solids disintegration from sludge and dairy manure in a batch mode MW/H 2 O 2 -AOP.…”