Evaluation of changes in activated sludge and sewage sludge quality by FTIR analysis and laser diffraction
Paweł Wiercik, Magdalena Kuśnierz, M. Kabsch-Korbutowicz, Anita Plucińska, Przemysław Chrobot
Abstract
ABSTRACT Fourier transform infrared (FTIR) spectroscopy and laser diffraction are commonly applied methods to assess the quality of activated and digested sludge. However, the effect of particle size on FTIR data has never been thoroughly explored. There is also scarce literature on the application of FTIR spectroscopy in conjunction with laser diffraction to investigate changes in the composition and structure of the raw, untreated activated and sewage sludge. In this paper, laser diffraction and FTIR analyses were applied to evaluate the composition, structure and properties of particles in suspensions of activated, thickened and digested sludge samples collected at Janówek Wastewater Treatment Plant (WWTP) located in Wrocław, Poland. FTIR analyses led to the identification of characteristic compounds in the aforementioned types of sludge and processes which they had undergone, for example, decarboxylation and deamination. Laser diffraction tracked the changes in the size and structure of particles in the suspension. Thickened sludge suspensions, which had the largest active surface and the lowest compactness, were characterized by the highest sorption capacity and catalytic activity. The conducted research has shown that the intensity of infrared (IR) absorption is size dependent – smaller particles in the suspension had a higher absorbance intensity in a given wavenumber ranges than larger ones.