Nitrifying bacterial biomass and nitrification activity evaluated by FISH and an automatic on-line instrument at full-scale Fusina (Venice, Italy) WWTP

Abstract

In this study, monthly variations in biomass of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were analysed over a 1-year period by fluorescence in situ hybridization (FISH) at the full-scale Fusina WWTP. The nitrification capacity of the plant was also monitored using periodic respirometric batch tests and by an automated on-line titrimetric instrument (TITrimetric Automated ANalyser). The percentage of nitrifying bacteria in the plant was the highest in summer and was in the range of 10-15 % of the active biomass. The maximum nitrosation rate varied in the range 2.0-4.0 mg NH4 g(-1) VSS h(-1) (0.048-0.096 kg TKN kg(-1) VSS day(-1)): values obtained by laboratory measurements and the on-line instrument were similar and significantly correlated. The activity measurements provided a valuable tool for estimating the maximum total Kjeldahl nitrogen (TKN) loading possible at the plant and provided an early warning of whether the TKN was approaching its limiting value. The FISH analysis permitted determination of the nitrifying biomass present. The main operational parameter affecting both the population dynamics and the maximum nitrosation activity was mixed liquor volatile suspended solids (MLVSS) concentration and was negatively correlated with ammonia-oxidizing bacteria (AOB) (p = 0.029) and (NOB) (p = 0.01) abundances and positively correlated with maximum nitrosation rates (p = 0.035). Increases in concentrations led to decreases in nitrifying bacteria abundance, but their nitrosation activity was higher. These results demonstrate the importance of MLVSS concentration as key factor in the development and activity of nitrifying communities in wastewater treatment plants (WWTPs). Operational data on VSS and sludge volume index (SVI) values are also presented on 11-year basis observations.

Microbial Communities in Full-Scale Wastewater Treatment Systems Exhibit Deterministic Assembly Processes and Functional Dependency over Time

“…Operational strategies and the responses of microbial communities are of paramount importance in maintaining stable and efficient treatment processes, and a collapse in the system performance can occur if functional deterioration is not detected in a timely manner . In addition to online measurement of the chemical constituents, monitoring of selected functional taxa is a common approach used to determine system performance (e.g., by fluorescence in situ hybridization probes or quantitative PCR to track the presence of key genes or microorganisms responsible for contaminant removal). − However, as next-generation sequencing decreases in cost and data analysis becomes easier, we are proposing that a possible alternative to monitor and predict system performance may be to evaluate the assembly mechanism of microbial communities. Based on results of this study, the emergence of stochastic events may indicate deterioration in performance or system failure and the need for corrective measures.…”

Integrating online differential titrimetry and dynamic modelling as innovative energy saving strategy in a large industrial WWTP

“…The applicability of pH/DO-stat titration for monitoring biological processes which affect pH or dissolved oxygen concentration has been widely demostrated in the literature (Badoer et al 2015).…”

Integrating Online Differential Titrimetry and Dynamic Modelling as Innovative Energy Saving Strategy in a Large Industrial WWTP

“…The applicability of pH/DO-stat titration for monitoring biological processes which affect pH or dissolved oxygen concentration has been widely demostrated in the literature (Ficara et al, 2000;Fiocchi et al, 2008;Badoer et al, 2015).…”