Interaction of Operational and Physicochemical Factors Leading to Gordonia amarae-Like Foaming in an Incompletely Nitrifying Activated Sludge Plant

Abstract

eThe overgrowth of Gordonia amarae-like bacteria in the mixed liquor of an incompletely nitrifying water reclamation plant was inversely correlated with temperature (r ‫؍‬ ؊0.78; P < 0.005) and positively correlated with the solids retention time (SRT) obtained a week prior to sampling (r ‫؍‬ 0.67; P < 0.005). Drops followed by spikes in the food-to-mass ratio (0.18 to 0.52) and biochemical oxygen demand concentrations in primary effluent (94 to 298 mg liter ؊1 ) occurred at the initiation of G. amarae-like bacterial growth. The total bacterial concentration did not increase as concentrations of G. amarae-like cells increased, but total bacterial cell concentrations fluctuated in a manner similar to that of G. amarae-like bacteria in the pseudo-steady state. The ammonium ion removal rate (percent) was inversely related to G. amarae-like cell concentrations during accelerated growth and washout phases. The dissolved oxygen concentration decreased as the G. amarae-like cell concentration decreased. The concentrations of G. amarae-like cells peaked (2.47 ؋ 10 9 cells liter ؊1 ) approximately 1.5 months prior to foaming. Foaming occurred during the late pseudo-steady-state phase, when temperature declines reversed. These findings suggested that temperature changes triggered operational and physicochemical changes favorable to the growth of G. amarae-like bacteria. Fine-scale quantitative PCR (qPCR) monitoring at weekly intervals allowed a better understanding of the factors affecting this organism and indicated that frequent sampling was required to obtain statistical significance with factors changing as the concentrations of this organism increased. Furthermore, the early identification of G. amarae-like cells when they are confined to mixed liquor (10 7 cells liter ؊1 ) allows management strategies to prevent foaming.

Improving qPCR methodology for detection of foaming bacteria by analysis of broad-spectrum primers and a highly specific probe for quantification ofNocardiaspp. in activated sludge

“…The qPCR primers and probe development followed Asvapathanagul et al . (). Lastly, the Nocardia spp.…”

“…Therefore, few qPCR applications for foaming nocardioform identification and quantification have recently been reported (Asvapathanagul et al . ). All foaming organisms are acid fast (Soddell et al .…”

“…Furthermore, the high similarity among 16S rRNAs of this group is well known. The conserved nature of the 16S RNA genes of this group has made it difficult to develop genus-specific primer and probe sets in quantitative Polymerase Chain Reaction (qPCR) (Asvapathanagul et al 2012). Therefore, few qPCR applications for foaming nocardioform identification and quantification have recently been reported (Asvapathanagul et al 2012).…”

“…The conserved nature of the 16S RNA genes of this group has made it difficult to develop genus-specific primer and probe sets in quantitative Polymerase Chain Reaction (qPCR) (Asvapathanagul et al 2012). Therefore, few qPCR applications for foaming nocardioform identification and quantification have recently been reported (Asvapathanagul et al 2012). All foaming organisms are acid fast (Soddell et al 1998(Soddell et al , 2006Stratton et al 2002).…”

“…-8176). All cultures were grown in Tryptone Yeast Glucose (TYG) media suggested by USDA as described in Asvapathanagul et al (2012). Mycobacterium bovis (ATCC 19210)-extracted DNA was obtained from the U.S. Food and Drug Administration Southwest Laboratory, Irvine, CA.…”