| Gram positive foaming bacteria were genetically identified using PCR-RLB for the first time in this study. PCR-RLB was able to identify several foaming bacterial genera in one assay using a single set of primer with multiple probes attached on the membrane. Another set of PCR-RLB for Thiothrix spp. was also developed and tested. The change of signal intensity of Gordonia spp. and Thiothrix spp. populations using PCR-RLB were observed before, during and after foaming or bulking event using PCR-RLB, which demonstrates the ability of PCR-RLB to provide an early warning sign of the problematic bacteria occurrence.;The growth of G. amarae in a partial nitrifying wastewater treatment plant was inversely correlated with temperature (r = - 0.78), while it was positively correlated with solids retention time (SRT) lagged one week during their occurrence (r = 0.67). The F/M ratio and BODin increased during G. amarae's exponential and linear growth phases. Importantly, once that concentration of G. amarae had reached concentration maxima, lowering SRT did not achieve G. amarae control and elimination. Examining in multifactorial ways indicates that elimination of the foaming event can only be achieved by manipulation of the operation during the early growth phase of G. amarae when it is confined to the mixed liquors.;In partially denitrifying plant, high Thiothrix spp. concentrations were observed during period of high dissolved oxygen (DO > 0.15 mg/L) in the anoxic selector (r = 0.39, p < 0.05), which had adverse effects on denitrifying bacteria and resulted in more available substrates for Thiothrix spp. The low oxygen half-saturation coefficient of Thiothrix spp. was an advantage, which allowed Thiothrix spp. to outcompete other bacteria in the anoxic selector and created bulking incidents. High Thiothrix spp. concentrations were associated with high influent ammonia, BOD and COD concentrations. High effluent BOD, COD, and TSS concentrations had statistically positive relationship with the Thiothrix spp. concentration in the aeration tank (p < 0.01), indicating decreased performance of treatment. |
