Effect of Sewage Sludge Alkalization and Acidification on Keratinolytic and Keratinophilic Fungi
K. Ulfig
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Institute for Ecology of Industrial Areas, 40-832 Katowice, Kossutha St. 6, Poland
Pol. J. Environ. Stud. 2005;14(5):647–653
This study aimed to determine the influence of sewage sludge alkalization and acidification on the qualitative and quantitative composition of keratinolytic and keratinophilic fungi in a model experiment. The sludge was alkalized to pH 9 with 0.5N NaOH, 0.5N KOH, 0.5N NH4OH or with 2% burnt lime mixed with powdered limestone (20g CaO + 5g CaCO3), and acidified to pH 4 with 0.5N HCl, 0.5N HNO3 or 0.5N H2SO4. The sludge with unmodified pH (6.5) served as control. The hair baiting method with four incubation temperatures (23, 29, 33, and 37°C) was used to examine fungi. The sludge alkalization with KOH, NaOH or CaO+CaCO3 increased the number of keratinolytic fungi but decreased the number of keratinophilic fungi. The inhibition of the growth of keratinolytic fungi was observed due to the sludge acidification with H2SO4 or HCl. The sludge acidification with HNO3 or HCl stimulated keratinophilic fungi to grow. Sludge acidification with HNO3 eliminated keratinolytic fungi, while acidification with H2SO4 eliminated keratinophilic fungi. Results are discussed from ecological and epidemiological points of view.