Nitrifying and heterotrophic population dynamics in biofilm reactors: effects of hydraulic retention time and the presence of organic carbon

Abstract

Two biofilm reactors operated with hydraulic retention times of 0.8 and 5.0 h were used to study the links between population dynamics and reactor operation performance during a shift in process operation from pure nitrification to combined nitrification and organic carbon removal. The ammonium and the organic carbon loads were identical for both reactors. The composition and dynamics of the microbial consortia were quantified by fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes combined with confocal laser scanning microscopy, and digital image analysis. In contrast to past research, after addition of acetate as organic carbon nitrification performance decreased more drastically in the reactor with longer hydraulic retention time. FISH analysis showed that this effect was caused by the unexpected formation of a heterotrophic microorganism layer on top of the nitrifying biofilm that limited nitrifiers oxygen supply. Our results demonstrate that extension of the hydraulic retention time might be insufficient to improve combined nitrification and organic carbon removal in biofilm reactors. r

High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors

“…Sixty-five percent of the eubacterial population was identified as AOB, while 25% was from the genus Nitrospira, a NOB. These values are higher than those with a similar control pH 7 nitrifying biofilm reactor showing 40% AOB and 20% NOB and reported values of dedicated nitrifying reactors using fluorescently labeled oligonucleotide probes (10,15,17,23,29). The low-pH reactor also presented a more uniform morphology of detected nitrifiers, with only smaller AOB cell clusters (about 10 m), while a more diverse colony structure with various bigger AOB cell clusters (from 10 to 25 m) could be observed in the pH 7 reactor.…”

Community Analysis of Ammonia and Nitrite Oxidizers during Start-Up of Nitritation Reactors

“…The composition of this community was clearly determined by continuous reinoculation from the sludge digester supernatant, which may therefore be an important factor in technical scale applications. Since many studies looked at the performance of nitrification reactors fed with synthetic wastewaters (24,25,32,35,38) important differences to the community composition and development in technical systems which are subject to continuous reinoculation may have been overlooked. Furthermore, most studies, unfortunately, did not repeat reactor experiments independently, which therefore may have led to generalized conclusions on the composition and behavior of ammonia oxidizer communities where such are not to be made.…”

“…The competitive disadvantage of nitrite oxidizers to ammonia oxidizers at 35°C has been experimentally established in sludge reactors (13,22). However, since Nitrobacter is not commonly found in wastewater treatment plants (5,24), it was interesting to study if nitritation could also be established from activated sludge at mesophilic temperatures (25 and 30°C) and at near-neutral pHs (7 and 7.5).…”

Eliminación de nutrientes mediante tratamientos biopelícula : corrientes actuales y necesidades de investigación

“…La competencia entre bacterias autótrofas y heterótrofas por los sustratos (oxígeno y nitrógeno amoniacal) y por el espacio en la biopelícula ha sido estudiado con anterioridad (Wanner & Reichert 1996) ) (Nogueira et al 2002). (Nogueira et al 2002) por ejemplo evaluó dos reactores de biopelícula trabajando con tiempos de residencia diferentes, 0.8h y 5 h para estudiar la relación entre la competencia de las bacterias con las condiciones de operación del reactor biopelícula.…”

“…(Nogueira et al 2002) por ejemplo evaluó dos reactores de biopelícula trabajando con tiempos de residencia diferentes, 0.8h y 5 h para estudiar la relación entre la competencia de las bacterias con las condiciones de operación del reactor biopelícula. Nogueira et al…”