Ozonation of Primary and Digested Sludges to Enhance Methanogenesis at Chemically Enhanced Primary Treatment Facilities

RÉSUMÉ La digestion anaérobie est un processus lent qui requiert un long temps de rétention hydraulique et offre une efficacité de dégradation modérée qui requiert des digesteurs de grand volume et des coûts d'investissement relativement élevés. Le principal facteur limitant la digestion anaérobie est normalement l'hydrolyse de la matière particulaire. L'augmentation du taux d'hydrolyse permet d'augmenter la biodégradabilité de la matière particulaire et d'améliorer la performance des digesteurs anaérobies. Diverses techniques de traitement ont été étudiées pour augmenter le taux d'hydrolyse des boues en utilisant des procédés thermiques, chimiques, mécaniques et biologiques. L'ozonation est l’un des traitements chimiques préférés qui permet non seulement la réduction des boues mais qui est également efficace pour améliorer les processus de digestion anaérobie en modifiant les propriétés physico-chimiques et de biodégradabilité des boues.----------ABSTRACT Anaerobic digestion is a slow process with long hydraulic retention times and moderate degradation efficiencies which can result in large volume digesters and relatively high capital requirements. Usually, the main factor limiting anaerobic digestion is the hydrolysis of particulate matter. Improving anaerobic digestion through enhancing rate-limiting hydrolysis can increase the degradability leading to improved performance of the anaerobic digesters. A variety of treatment techniques have been studied to enhance sludge hydrolysis by using thermal, chemical, mechanical and other biological processes. Ozonation is one of the preferred chemical treatments, which not only permits sludge reduction, but is also considered to be effective in enhancing the anaerobic digestion processes by altering the physicochemical properties and biodegradability of sludge

Ozonation of Primary Sludge and Digested Sludge to Increase Methane Production in a Chemically Enhanced Primary Treatment Facility

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO2. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O3/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester