The impact of temporal variability of excess sludge characteristics on the effects obtained in the process of its ultrasonic disintegration

ABSTRACT

This paper aimed to indicate the characteristics of excess sludge, which have the greatest impact on the effects obtained during its ultrasonic disintegration (UD). The direct and technological effects observed after sludge disintegration and anaerobic digestion (AD) depend on the factors affecting the quality of its matrix and simply on the parameters of a disintegrator. Sludge samples originate from a Central Waste Water Treatment Plant in Gliwice, and were collected after mechanical thickening by a monthly period. This approach allowed to observe the temporal changes of sludge characteristics, in a continuous manner. To evaluate the achieved disintegration effects, the following indicators were used: degree of disintegration (DD_COD) and the author's indicators describing the direct and technological effects of UD (ID_i, IT_i, IT_d), based on the changes in the sludge characteristics. Disintegration was carried out by means of an ultrasonic device equipped with a thin sonotrode. AD was conducted under mesophilic conditions for 20 days. Statistical analysis confirmed that the most important parameters of sludge, which determine obtained effects, were total and volatile solids, capillary suction time, concentration of chemical oxygen demand and pH value. The investigations have also showed that the increase in sludge temperature during its disintegration has a significant impact on the magnitude of other effects obtained in the process.

KEYWORDS:

• Sewage sludge
• ultrasonic disintegration
• disintegration effects
• disintegration indicators
• wastewater treatment plant

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Malwina Tytła http://orcid.org/0000-0003-3059-4471

Ewa Zielewicz http://orcid.org/0000-0002-7102-5796

Additional information

Funding

This work was supported by the ‘DoktoRis – Program for Innovative Silesia’ 2007–2013, co-financed by the European Union under the European Social Fund [grant number 100127]. The ultrasonic device used in this work was funded by the Ministry of Science and Higher Education [grant number 7T07G01016].