title: Influence of aeration cycles on mechanical characteristics of elastomeric diffusers in biological intermittent processes: Accelerated tests in real environment.
abstract: The paper deals with the evaluation of the effect of on/off switching of diffuser membranes, in the intermittent aeration process of the urban wastewater treatments. Accelerated tests were done using two types of commercial EPDM diffusers, which were submitted to several consecutive cycles up to the simulation of more than 8 years of real working conditions. The effect of this switching on the mechanical characteristics of the membranes was evaluated in terms of pressure increment of the air operating at different flow rates (2, 3.5 and 6 m3/h/diff): during accelerated tests, such increment ranged from 2% to 18%. The intermittent phases emphasized the loss both of the original mechanical proprieties of the diffusers and of the initial pore shapes. The main cause of pressure increment was attributed to the fouling of the internal channels of the pores. Further analyses performed by scanning electron microscopy and by mechanical tests on EPDM membrane, using a traditional tensile test and a non destructive optical method, from which the Young's Modulus was obtained, supported previous conclusions. Any changes in terms of oxygen transfer parameters (KLa and SOTE%) were specifically founded by causing to the repeated on/off switching.
authors.affiliation: Dipartimento SIMAU, Facoltà di Ingegneria, Università Politecnica delle Marche, Via Brecce Bianche, 12, 60100, Ancona, Italy. Electronic address: a.l.eusebi@univpm.it.
authors.forename: Anna Laura
authors.initials: AL
authors.lastname: Eusebi
authors.affiliation: Dipartimento SIMAU, Facoltà di Ingegneria, Università Politecnica delle Marche, Via Brecce Bianche, 12, 60100, Ancona, Italy.
authors.forename: Tiziano
authors.initials: T
authors.lastname: Bellezze
authors.affiliation: Dipartimento DIISM, Facoltà di Ingegneria, Università Politecnica delle Marche, Via Brecce Bianche, 12, 60100, Ancona, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Chiappini
authors.affiliation: Dipartimento DIISM, Facoltà di Ingegneria, Università Politecnica delle Marche, Via Brecce Bianche, 12, 60100, Ancona, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Sasso
authors.affiliation: Dipartimento SIMAU, Facoltà di Ingegneria, Università Politecnica delle Marche, Via Brecce Bianche, 12, 60100, Ancona, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Battistoni
mesh_terms: D000392:Air Movements; D019149:Bioreactors; D004058:Diffusion; D010100:Oxygen; D011312:Pressure; D014865:Waste Disposal, Fluid; D062065:Wastewater
chemical_list: D010100:Oxygen; D062065:Wastewater
keywords: Activated sludge; Aeration efficiency; Air diffuser; Grid optical method; Mechanical proprieties; Pores fouling