Sewage sludge treatment by a continuous microwave enhanced advanced oxidation process

A continuous flow mode of the microwave enhanced advanced oxidation process (MW/[H.sub.2][O.sub.2]-AOP) was used for sludge treatment as opposed to a batch operation mode from past studies. The effects of pre-microwave heating, microwave irradiation and post-microwave holding on organic matter solubilization were studied. Pre-microwave healing did not improve the overall orthophosphate solubilization, but helped in organic matter solubilization. Nutrients and organic matter were found to have increased during the post-microwave holding period, indicating overall sludge solubilization can be more effective when maintained at a high temperature after treatment with the MW/[H.sub.2][O.sub.2]-AOP. It was beneficial to operate a continuous mode of the MW/[H.sub.2][O.sub.2]-AOP at a longer retention time for organic matter solubilization, and at a shorter retention time for orthophosphate solubilization. Sludge settleability was greatly improved with the microwave treatment, with or without the addition of [H.sub.2][O.sub.2]. The pre-heating of sludge before treatment with the microwave process by the means of heat exchange can be beneficial for the overall organic matter solubilization in the MW/[H.sub.2][O.sub.2]-AOP. Key words: microwave, sludge, hydrogen peroxide, advanced oxidation, dewaterability, settleability. Un mode en ecoulement continu du precede d'oxydation avancee amelioree par micro-ondes (MW/[H.sub.2][O.sub.2]-AOP) a ete utilise pour trailer des boues par rapport a un mode de fonctionnemenl par lot dans des eludes anterieures. Les effeis du chauffage avanl les micro-ondes, l'irradiation par micro-ondes et le maintien de la solubilization des matieres organiques apres les micro-ondes ont ete etudies. Le chauffage avant les micro-ondes n'a pas ameliore la solubilization globale des orthophosphates, mais a aide a la solubilization des matieres organiques. Les nutriments et les matieres organiques ont augmente durant la periode de maintien apres les micro-ondes, indiquant qu'une solubilization globale des bones peut etre plus efficace lorsqu'elles sont maintenues a une temperature elevee apres le traitement par le MW/[H.sub.2][O.sub.2]-AOP. Il a ete profitable de faire fonctionner le MW/[H.sub.2][O.sub.2]-AOP en mode continu pour un temps de retention plus eleve pour la solubilization des matieres organiques, et a un temps de retention plus court pour la solubilization des orthophosphates. La decantabilite des boues s'est grandement amelioree a la suite du traitement par micro-ondes, avec ou sans ajout de [H.sub.2][O.sub.2]. Le prechauffage des boues par echange de chaleur avant le traitement par micro-ondes peut etre avantageux pour la solubilization globale des matieres organiques dans le MW/[H.sub.2][O.sub.2]-AOP. Mots-cles : micro-ondes, boues. peroxyde d'hydrogene, oxydation avancee, centrifugalite, decantabilite.
Introduction As health and environmental regulations become more stringent on effluent qualities, nutrient removal from the wastewater via biological nutrient removal (BNR) processes have increased its popularity among wastewater treatment [...]