title: Microbial-based evaluation of foaming events in full-scale wastewater treatment plants by microscopy survey and quantitative image analysis.
abstract: Activated sludge systems are prone to be affected by foaming occurrences causing the sludge to rise in the reactor and affecting the wastewater treatment plant (WWTP) performance. Nonetheless, there is currently a knowledge gap hindering the development of foaming events prediction tools that may be fulfilled by the quantitative monitoring of AS systems biota and sludge characteristics. As such, the present study focuses on the assessment of foaming events in full-scale WWTPs, by quantitative protozoa, metazoa, filamentous bacteria, and sludge characteristics analysis, further used to enlighten the inner relationships between these parameters. In the current study, a conventional activated sludge system (CAS) and an oxidation ditch (OD) were surveyed throughout a period of 2 and 3 months, respectively, regarding their biota and sludge characteristics. The biota community was monitored by microscopic observation, and a new filamentous bacteria index was developed to quantify their occurrence. Sludge characteristics (aggregated and filamentous biomass contents and aggregate size) were determined by quantitative image analysis (QIA). The obtained data was then processed by principal components analysis (PCA), cross-correlation analysis, and decision trees to assess the foaming occurrences, and enlighten the inner relationships. It was found that such events were best assessed by the combined use of the relative abundance of testate amoeba and nocardioform filamentous index, presenting a 92.9 % success rate for overall foaming events, and 87.5 and 100 %, respectively, for persistent and mild events.
authors.affiliation: Instituto Politécnico de Coimbra, ISEC, Rua Pedro Nunes, Quinta da Nora, 3030-199, Coimbra, Portugal.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Leal
authors.affiliation: Instituto Politécnico de Coimbra, ISEC, Rua Pedro Nunes, Quinta da Nora, 3030-199, Coimbra, Portugal. lpamaral@isec.pt.|CEB-Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057, Braga, Portugal. lpamaral@isec.pt.
authors.forename: António Luís
authors.initials: AL
authors.lastname: Amaral
authors.affiliation: CERNAS-Center of Studies on Natural Resources, Environment and Society, Instituto Politécnico de Coimbra, ESAC, Bencanta, 3045-601, Coimbra, Portugal.
authors.forename: Maria de Lourdes
authors.initials: Mde L
authors.lastname: Costa
mesh_terms: D001419:Bacteria; D018533:Biomass; D008853:Microscopy; D012722:Sewage / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000382:microbiology*
chemical_list: D012722:Sewage; D062065:Wastewater
keywords: Activated sludge systems; Decision trees; Filamentous bacteria; Filamentous bacteria index; Principal components analysis; Protozoa and metazoa; Quantitative image analysis