Approved Abstracts


Author(s): Rubio-Bellido M; Lara Moreno A; Madrid F; Villaverde J; Morillo E;
Presenter: Esmeralda Morillo

Nonylphenol (NP), contaminant of emerging concern due to its role as endocrine disruptor, is accumulated in sewage sludge as a result of the biodegradation of nonylphenol ethoxylates (NPEs) used as nonionic surfactants in a large variety of industrial and domestic applications. Since a great part of sewage sludge produced is valorized as amendment in agriculture in many countries, the main objective of this study was to obtain more environmentally friendly biosolids to be used as organic amendment to prevent contamination of soils and the environment. The aim of this particular work was to obtain NP-degrading bacteria from NP enrichment cultures of sewage sludge, in order to test their ability to degrade this contaminant, in a search for strains appropriated for bioremediation of NPEs in sewage sludge. The isolated bacteria obtained will be tested for NP biodegradation first in solution, and the best ones on sewage sludge.
Three fresh sewage sludge samples collected from different Waste Water Treatment Plants (WWTPs) and one composted biosolid collected from a sludge composting plant, all of them located in Seville (Southwest Spain), were selected to isolate bacterial consortia, using NP as the only source of carbon and energy. New NP enrichment cultures were performed on each consortium to isolate the different NP degrading bacteria present in them. In total, 17 bacterial strains were isolated and their taxonomic identification carried out by comparison with NCBI database (National Centre for Biotechnology Information).
A total of 17 bacterial strains belonging to eight different genera were isolated from NP enrichment cultures of sewage sludge, and most of them had not been previously described as NP-degrading bacteria, such as: Shewanella putrefaciens, Aeromonas salmonicida, Alcaligenes faecalis, Bacillus safensis, Enterobacter bugandensis, Pseudochrobactrum saccharolyticum. Only Pseudomonas putida and Ochrobactrum anthropi had been previously used as NP-degraders.
Biodegradation experiments in solution were carried out during 120 days, and only 0.62% of NP was degraded in absence of consortia or isolated bacteria. On the contrary, when using the four consortia obtained for inoculation, 100% NP was removed by three of them, presenting DT50 ≤ 3 days, and the fourth one reached about 90% of NP removal and a DT50 of only 1,9 days.
All the bacterial genera obtained were also used in biodegradation experiments in solution, demonstrating their effectiveness to degrade NP, even those six novel bacterial strains that had not been previously described as NP-degraders. The isolated bacteria reached an extent of NP biodegradation in the range 74% - 99%, with DT50 values < 1.4 days for three of them (O. anthropic, S. putrefaciens, A. faecalis), < 8 days for P. saccharolyticum and E. bugandensis, and between 19 and 26 days for the other three genera. The study of their effectivity for NP degradation adsorbed on sewage sludge is currently under study.

Keywords: Nonylphenol; Sewage sludge; bioremediation




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