Ultrasound assisted method to increase soluble chemical oxygen demand (SCOD) of sewage sludge for digestion

Antti Grönroos (Corresponding Author), Hanna Kyllönen, Kirsi Korpijärvi, Pentti Pirkonen, Teija Paavola, Jari Jokela, Jukka Rintala

    Research output: Contribution to journalArticleScientificpeer-review

    194 Citations (Scopus)


    The aim of this study was to clarify the possibilities to increase the amount of soluble chemical oxygen demand (SCOD) and methane production of sludge using ultrasound technologies with and without oxidising agents. The study was done using multivariate data analyses. The most important factors affected were discovered. Ultrasonically assisted disintegration increased clearly the amount of SCOD of sludge. Also more methane was produced from treated sludge in anaerobic batch assays compared to the sludge with no ultrasonic treatment. Multivariate data analysis showed that ultrasonic power, dry solid content of sludge (DS), sludge temperature and ultrasonic treatment time have the most significant effect on the disintegration. It was also observed that in the reactor studied energy efficiency with high ultrasound power together with short treatment time was higher than with low ultrasound power with long treatment time. When oxidising agents were used together with ultrasound no increase in SCOD was achieved compared the ultrasonic treatment alone and only a slight increase in total organic carbon of sludge was observed. However, no enhancement in methane production was observed when using oxidising agents together with ultrasound compared the ultrasonic treatment alone. Ultrasound propagation is an important factor in ultrasonic reactor scale up. Ultrasound efficiency rose linearly with input power in sludge at small distances from the transducer. Instead, ultrasound efficiency started even to decrease with input power at long distances from the transducer.
    Original languageEnglish
    Pages (from-to)115 - 120
    Number of pages6
    JournalUltrasonics Sonochemistry
    Issue number1-2
    Publication statusPublished - 2005
    MoE publication typeA1 Journal article-refereed


    • ultrasound
    • soluble chemical oxygen demand
    • SCOD
    • sewage sludge
    • sludge
    • sludge processing
    • sludge disintegration
    • oxidising agents
    • anaerobic digestion
    • wastewater treatmen
    • wastewaters


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