Effect of free ammonia and free nitrous acid concentration on the anabolic and catabolic processes of an enriched Nitrosomonas culture

Abstract

The effects of free ammonia (FA; NH(3)) and free nitrous acid (FNA; HNO(2)) concentrations on the metabolisms of an enriched ammonia oxidizing bacteria (AOB) culture were investigated using a method allowing the decoupling of growth and energy generation processes. A lab-scale sequencing batch reactor (SBR) was operated for the enrichment of an AOB culture. Fluorescent in-situ hybridization (FISH) analysis showed that 82% of the bacterial population in the SBR bound to the NEU probe specifically designed for Nitrosomonas europaea. Batch tests were carried out to measure the oxygen and ammonium consumption rates by the culture at various FA and FNA levels, in the presence or absence of inorganic carbon (CO(2), HCO(3) (-), and CO(3) (2-)). It was revealed that FA of up to 16.0 mgNH(3)-N . L(-1), which was the highest concentration used in this study, did not have any inhibitory effect on either the catabolic or anabolic processes of the Nitrosomonas culture. In contrast, FNA inhibited both the growth and energy production capabilities of the Nitrosomonas culture. The inhibition on growth initiated at approximately 0.10 mgHNO(2)-N . L(-1), and the data suggested that the biosynthesis was completely stopped at an FNA concentration of 0.40 mgHNO(2)-N . L(-1). The inhibition on energy generation initiated at a slightly lower level but the Nitrosomonas culture was still oxidizing ammonia at half of the maximum rate at an FNA concentration of 0.50-0.63 mgHNO(2)-N . L(-1). The affinity constant of the Nitrosomonas culture with respect to ammonia was determined to be 0.36 mgNH(3)-N . L(-1), independent of the presence or absence of inorganic carbon.

Nitrification in fixed-bed reactors treating saline wastewater

“…Furthermore, it was suggested that the inhibitory effect on energy generation (catabolic processes) and growth processes (anabolic processes) D i s c u s s i o n | 137 should be investigated separately (Vadivelu et al 2006). Simply comparing the overall substrate utilization rates, as conducted in our study, might have seriously under-estimated the inhibitory effects, certainly in relation to growth inhibition.…”

Producing free nitrous acid – A green and renewable biocidal agent – From anaerobic digester liquor

“…As shown in the titration curve, there was no indication of residual bicarbonate since no buffering capacity was observed at the pH range of 6.0-4.0 (Figure 2). While the ammonium oxidation rate was also slowed down at this low pH (Figure 3), likely due to the low bicarbonate availability [23] or possibly due to partial inhibition by FNA [2,24], complete nitritation was still achieved with the gradual bicarbonate dosing used in this study.…”

“…It has been reported that, at parts per billion (ppb) levels, FNA has inhibitory effects on: 1) the anabolic and catabolic activities of ammonia and nitrite oxidising bacteria [2,3]; 2) growth, nitrate and nitrite reduction activities of denitrifying bacteria in activated sludge [4] and 3) aerobic and anoxic phosphorus uptake by polyphosphate accumulating organisms [5,6]. In addition, FNA has also been shown to inhibit methanogens [7], pathogens [8] and yeast [9].…”

Simultaneous Elimination of Carbon and Nitrogen Compounds of Petrochemical Effluents by Nitrification and Denitrification

“…At alkaline pH values, the availability of NH 3 is not limited and this would be favorable for nitrification considering that NH 3 is the substrate for AMO (Suzuki et al, 1974). However, it is also known that high concentrations of free ammonia inhibit nitrification (Anthonisen et al, 1976;Vadivelu et al, 2006b). In aerobic nitrifying reactors operated under constant aeration and agitation, NH 3 can be lost from the system by volatilization.…”

“…It has been observed that high concentrations of nitrite can inhibit the nitrification process and that could be mainly related to the pH values through the formation of HNO 2 . Nitrous acid is known to inhibit nitrification, thus, low pH values must be avoided in nitrifying processes (Anthonisen et al, 1976;Vadivelu et al, 2006aVadivelu et al, , 2006b. Recently, Silva et al (2011) reported that the nitrite-oxidizing process was more sensitive to the presence of nitrite than the ammonium-oxidizing process, suggesting that nitrite accumulation in nitrification systems should be controlled to avoid a higher accumulation of nitrite and a decrease in nitrate yield.…”