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Microwave enhanced advanced oxidation treatment of organic slurries Saha, Moutoshi


Microwave enhanced advanced oxidation process (MW-AOP) has been applied to treat different organic slurries that include sewage sludge, source separated organics (SSO), fats, oils and grease (FOG), and dairy manure (unscreened and liquid portion). The present research aimed at treatment of organic wastes to produce more suitable substrate for subsequent energy and resource recovery. In this study, MW-AOP effectively treated three sludge types: primary, a mixture of primary and secondary, and secondary sludge. Secondary sludge showed higher treatment efficiency than primary or mixed sludge. This study explored the impact of solids concentrations on the sludge treatment efficiency. Treatment of sludge with high solids content would allow to handle larger amounts of sludge at a given period and reduce heating cost per unit of sludge treated. MW-AOP was successful to treat thickened secondary sludge with up to 8% total solids content. MW-AOP treatment efficiency of SSO and FOG increased with higher temperature and hydrogen peroxide dosage. Fatty acids, compounds with carbonyl group and/or hydroxyl group in both initial and treated FOG samples were identified by gas chromatography-mass spectrometry. MW-AOP broke down long chain fatty acids in FOG by peroxidation mechanism. Treated SSO and FOG contained more soluble organics, volatile fatty acids, nutrients and lower molecular weight compounds and became less inhibitory to microorganisms. They became more suitable for subsequent anaerobic digestion. Unscreened dairy manure was treated with batch scale MW-AOP system at different pH conditions. Liquid portion of dairy manure was also treated with pilot scale continuous flow 25 kW MW-AOP system at different hydrogen peroxide dosage and pH conditions. Sets without acidification did not show any increase in ortho-P release for both batch and pilot scale system. To achieve high phosphorous release, better solids disintegration, and better settling and supernatant quality, a combination of microwave heating with high hydrogen peroxide dosage and acidic condition was required.

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Attribution-NonCommercial-NoDerivatives 4.0 International