Abstract
Using sludge obtained from municipal sewage treatment plants, the response of viable bacterial populations during the sludge ozonation process was investigated by a combination of adenosine triphosphate (ATP) assay and propidium monoazide (PMA)-Miseq sequencing. The ATP assay was first optimized for application on sludge samples by adjusting the sludge solid contents and reaction time. PMA-modified polymerase chain reaction (PCR) was also optimized by choosing the suitable final PMA concentration. The quantity and composition of viable bacterial populations during sludge ozonation were further elucidated using the optimized ATP and PMA-modified PCR methods. The results indicated that after the sludge was exposed to ozone (O3) at 135 mg·O3/g total suspended solids (TSS), the viable biomass displayed a substantial decrease, with a reduction rate reaching 70.89%. The composition of viable bacterial communities showed a faster succession, showing that an ozone dosage of 114 mg·O3/g TSS is enough to significantly change the viable bacterial population structure. Floc-forming genera, such as Zoogloea, Ferruginibacter, Thauera and Turneriella, are sensitive to ozonation, while the relative abundances of some functional bacterial genera, including SM1A02, Nitrospira and Candidatus Accumulibacter, remained constant or increased in the viable bacterial population during sludge ozonation, indicating that they are more resistant to ozonation.
Highlights
Excess sludge produced by biological wastewater treatments has become a big problem
The interaction between bacterial cells and ozone has only been studied for Escherichia coli in pure cultures, and the results proved that membrane components are the primary targets of O3
The activated sludge process mainly depends on its viable bacterial community [7], which is responsible for the removal of COD and nitrogen and has a very high phylogenetic diversity [8,9]
Summary
Excess sludge produced by biological wastewater treatments has become a big problem. Treatment and disposal of excess sludge may account for up to 60% of the total operational costs of a wastewater treatment plant [1]. For this reason, techniques for reducing excess sludge have gained much attention, and one of the promising techniques is the sludge ozonation process [2,3,4]. The interaction between bacterial cells and ozone has only been studied for Escherichia coli in pure cultures, and the results proved that membrane components are the primary targets of O3. The activated sludge process mainly depends on its viable bacterial community [7], which is responsible for the removal of COD and nitrogen and has a very high phylogenetic diversity [8,9]
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