Concentration Of Free Ammonium Research Articles

Multi-chambers of pilot-scale reactor enhanced partial nitritation performance

Nowadays, applying anammox to treat high nitrogenous side-stream wastewater has taken a step forward. However, the partial nitritation process is sensitive to the ammonium concentration and the nitrogen loading rate, which significantly influences the nitrogen removal performance. This study investigated the performance of a novel nitritation pilot-scale reactor which was divided into four chambers. The nitrite accumulation efficiency reached more than 90 % in the rural wastewater treatment process. As the reactor was divided into four chambers, the comprehensive statistical results showed that the concentration of free ammonium in the front chambers had been effectively improved. The proportion of free ammonium concentration (>0.1 mg NH3·L−1), which could inhibit the activity of nitrite oxidizing bacteria, in first chamber (PN1) was 2 times higher than in the last chamber (PN4). Meanwhile, Nitrosomonas, responsible for ammonium oxidation to nitrite, was highly enriched in the first two chambers even though the dissolved oxygen was maintained at 1.5 ± 0.3 mg·L−1. Compare to conventional reactor, the resistance of the novel reactor to volumetric shock loading has been enhanced. Even though the ammonium loading rate fluctuated greatly, the effluent was still stable and could meet the demand following the anammox process. This study demonstrated that the reactor with multi-chambers could effectively improve the nitrite accumulation efficiency in the partial nitritation process and thus provide a new perspective on the partial nitritation process in a single reactor and further promote the anammox performance in the wastewater treatment process.

Carbon and nitrogen metabolism in young Tachigali vulgaris plants subjected to water deficit

Plants’ biochemical responses to water deficit are associated with their ability to synthesize accumulate osmolytes compatible to regulatory properties of water potential. The aim of the current study is to evaluate carbon and nitrogen metabolism in Tachigali vulgaris plants subjected to three water suspension periods. The experiment was carried out in greenhouse and followed a completely randomized design, at 3 x 2 factorial arrangement (three times: zero, five and ten water suspension days; and two water conditions: control and water deficit), with 4 repetitions; results were subjected to analysis of variance and means were compared through t-test at 5% probability level, in statistical package (Assistat 7.7 beta). The following variables recorded decreased values: relative water content RWC in leaf tissue (by 32.14%); nitrate ion in leaves (by 18.67%) and in roots (by 14.40%); nitrate reductase enzyme activity in leaves (by 17.06%) and roots (by 15.77%); starch concentration in leaf tissue (by 44.98%) and roots (by 21.07%). On the other hand, the following variables recorded increased values: free ammonium concentration in leaves (by 64.83%) and roots (by 1.61%); total soluble amino acids in leaf tissue (by 28.03%) and roots (by 8.42%); total soluble carbohydrates in leaves (by 3.12%) and roots (by 11.05%); sucrose in leaves (by 4.77%) and roots (by 24.77%); proline in leaves (by 193.58%) and roots (by 57.26%). Biochemical processes observed in T. vulgaris plants were affected by water deficit, which indicated that this species is capable of adopting mechanisms and strategies in order to survive under stressful conditions.

Start-up of PN-anammox system under low inoculation quantity and its restoration after low-loading rate shock

Partial nitritation (PN)-anaerobic ammonium oxidation (anammox) is a promising pathway for the biological treatment of wastewater. However, the destruction of the system caused by excessive accumulation of nitrate in long-term operation remains a challenge. In this study, PN-anammox was initialized with low inoculation quantity in an air-lift reactor. The nitrogen removal rate of 0.71 kgN/(m3 · d) was obtained, which was far higher than the seed sludge (0.3 kgN/(m3 · d)). Thereafter, excess nitrate build-up was observed under low-loading conditions, and recovery strategies for the PN-anammox system were investigated. Experimental results suggest that increasing the nitrogen loading rate as well as the concentration of free ammonium failed to effectively suppress the nitrite oxidation bacteria (NOB) after the PN-anammox system was disrupted. Afterwards, effluent back-flow was added into the reactor to control the up-flow velocity. As a result, an aggressive discharge of sludge that promoted the synergetic growth of functional bacteria was achieved, leading to the successful restoration of the PN-anammox system. The partial nitritation and anammox activity were in balance, and an increase in nitrogen removal rate up to 1.07 kgN/(m3 · d) was obtained with a nitrogen removal efficiency of 82.4% after recovery. Besides, the proportion of granular sludge (over 200 µm) increased from 33.67% to 82.82%. Ammonium oxidation bacteria (AOB) along with anammox bacteria were enriched in the granular sludge during the recovery period, which was crucial for the recovery and stable operation of the PN-anammox system.

Effect of free ammonium and free nitrous acid on the activity, aggregate morphology and extracellular polymeric substance distribution of ammonium oxidizing bacteria in partial nitrification

Successful partial nitrification not only guarantees the inhibition of nitrite oxidation, but also does not excessively retard the ammonia oxidation rate. Therefore, the performance of ammonium oxidizing bacteria (AOB) during partial nitrification is fundamental to this process. In this study, two lab-scale partial nitrification bioreactors containing different inhibition conditions-one with free ammonium (FA) inhibition, the other with free nitrous acid (FNA) inhibition-were used to compare the differences between activity, quantity, aggregation morphology and extracellular polymeric substance (EPS) distribution of AOB. The results showed that although stable, long-term, partial nitrification was achieved in both reactors, there were differences in AOB activity, microbial spatial distribution and EPS characteristic. In the FA bioreactor, FA concentration was conducted at more than 40mg/L, which had a strong impact on the metabolism of AOB. The activity and quantity decreased by 50%. Higher EPS (42.44±2.31mgg-1 mixed liquor volatile suspended solids [MLVSS]) and protein were introduced into the EPS matrix. However, in the FNA bioreactor, the FNA concentration was about 0.23mg/L. It did not reach a level to affect AOB metabolism. The AOB activity and quantity were maintained at high levels and the total EPS content was 28.29±2.04mgg-1 MLVSS. Additionally, the microscopic results showed that in the FA bioreactor, AOB cells aggregated in microcolonies, while they appeared to be self-flocculating with no specific conformation in the other reactor. β-polysaccharides located inside sludge flocs in the FA bioreactor but only accumulated around the outer layer of activated sludge flocs in the FNA condition.

Modelling combined effect of chloramine and copper on ammonia-oxidizing microbial activity using a biostability approach

Continuous and batch laboratory experiments were used to evaluate the combined effects of copper and chloramine on ammonia oxidizing microbes present in otherwise high nitrifying water samples. The experimental data were analyzed using a biostability concept and quantified with the biostable residual concentratrion (BRC) of monochloramine, or the concentration that prevents the onset of nitrification. In the batch experiments, copper dosing ≥0.25 mg-Cu L−1 resulted in complete inhibition of nitrification, and a lower copper dosing (0.1 mg-Cu L−1) delayed nitrification. The BRC was systematically lowered with the addition of copper. For example, a free-ammonium concentration of 0.1 mg-N L−1 had a BRC of 0.73 mg-Cl2 L−1 with no Cu, but addition of 0.1 mg-Cu L−1 lowered the BRC to 0.16 mg-Cl2 L−1, while addition of 0.25 mg-Cu L−1 eliminated the need to add chloramine (BRC = 0). A non-competitive inhibition model fit the experimental data well with a copper threshold of 0.044 mg-Cu L−1 and can be used to estimate Cu doses needed to prevent nitrification based on the chloramine concentration. Full scale systems applications need further study.

Aqueous mixtures of di-n-decyldimethylammonium chloride/polyoxyethylene alkyl ether: Dramatic influence of tail/tail and head/head interactions on co-micellization and biocidal activity

Mixed aggregate formation and synergistic interactions of binary surfactant mixtures of di-n-decyldimethylammonium chloride, [DiC10][Cl], with polyoxyethylene alkyl ethers, CiEj (i=10, 12, j=4, 6, 8), have been investigated for various [DiC10][Cl]/CiEj ratios. The critical aggregation concentration of the binary mixtures has been determined by tensiometry, and the aggregate characteristics (i.e., size and composition, free ammonium concentration) have been estimated using the pulsed field gradient NMR spectroscopy and a [DiC10]-selective electrode. Diffusion coefficient measurements of micelles confirmed the synergistic interaction between the surfactants. It is thus shown that the formation of surface monolayers and mixed aggregates from [DiC10][Cl]/C10Ej mixtures is driven by both tail/tail and head/head interactions, whereas [DiC10][Cl]/C12Ej co-aggregation is mainly driven by tail/tail interactions. As a consequence, the co-aggregation phenomenon notably influences the biocidal activity of [DiC10][Cl] on the Candida albicans fungi. In the presence of C12Ej, the biocidal activity of the ammonium salt is inhibited due to the trapping of the cationic surfactants in the mixed aggregates, whereas in the presence of C10Ej, the biocidal activity of the surfactant mixture is maintained. The mode of action is also confirmed by a faster increase in the zeta potential of a C. albicans suspension in the presence of [DiC10][Cl]/C10E8 than in the presence of [DiC10][Cl]/C12E8. Therefore, a judicious adjustment of the alkyl (i) and polyoxyethylene (j) chain lengths of CiEj avoids its antagonistic effect on the biocidal activity of [DiC10][Cl].

Partial Nitrification in an Airlift Activated Sludge Reactor with Experimental and Theoretical Assessments of the pH Gradient inside the Sponge Support Medium

An airlift-type activated sludge reactor using a sponge support medium was fed with wastewater containing 500 mg-N/L of NH4 +-N. In order to establish partial nitrification, the reactor was kept at 35°C. Moreover, the reactor was started up with the NaHCO3 solution as an alkali agent to supply inorganic carbon for enhancement of partial nitrification. The partial nitrification was established during the period when NaHCO3 was used as an alkali agent. However, soon after changing the alkali agent to a mixture of Na2HPO4 and NaOH, the production of NO2 --N started to decrease. The change in pH inside the sponge medium revealed by the model simulation and microelectrode study showed relatively high free ammonium concentration inside the medium. Thus, partial nitrification was proved to be affected by inorganic carbon in the alkali agent. Furthermore, it was suggested that the establishment of partial nitrification in this study was due to the combination of high operating temperatures, addition of inorganic carbon, and the inhibition of NOB by the free ammonium concentration.

Nitrogen removal from wastewater with high ammonia nitrogen concentration via shorter nitrification and denitrification

Shorter nitrification is reached through Nitrobacter bacteria activity inhibition. Nitrobacter bacteria responsible for nitrite nitrogen oxidation are sensitive to free ammonium. The presence of free ammonium depended on a high ammonia nitrogen concentration in wastewater and its pH. It was the pH of the wastewater that was the decisive parameter in Nitrobacter bacteria activity inhibition in stable temperatures and at stable ammonia nitrogen concentrations. Reaction control in the aeration phase of the treatment process guaranteed the concentration of free ammonium within the 1 to 6 mg NH3/l range and at the same time concentration of free nitrous acid did not exceed 0.04 mg HNO2/l. It allowed nitrification to be significantly shortened and to receive build-up of nitrite nitrogen up to 300 mg NO2-N/l. Nitrification rate was about 0.06 g N/g MLSS·d. Measured oxidation rates of particular groups of nitrifying bacteria as oxygen uptake rates by Nitrosomonas and Nitrobacter bacteria respectively made control of shorter nitrification easier and gave insight into the activity of both nitrifier groups.

Ammonium Tolerance and Carbohydrate Status in Maize Cultivars

Four maize (Zea maysL.) hybrids were grown hydroponically for 4 weeks with 20 mmammonium or nitrate as the sole nitrogen source. Dry matter production was strongly depressed by ammonium nutrition in the hybrid Helga relative to plants grown on nitrate, and moderately decreased in the hybrid Melina. Ammonium had no inhibitory effect on total yield in the other two hybrids (Ramses and DK 261). The relative growth rate (RGR) of roots and shoots of the sensitive hybrid Helga decreased significantly under ammonium nutrition during the first 2 weeks of the experiment, while at the end of the experiment nitrogen form had no effect on the RGR in any of the four hybrids. The strong reduction in RGR of Helga in the early seedling stage was correlated with the accumulation of twice the concentration of free ammonium in the shoot tissue relative to the other hybrids. Helga was therefore unable to sufficiently detoxify ammonia in the roots. Root concentrations of water soluble carbohydrates (WSC) in Helga and Melina in the early seedling stage did not differ under ammonium and nitrate nutrition. In contrast, Ramses and DK 261 both had elevated WSC concentrations in ammonium-fed roots. It is hypothesized that a sufficient supply of carbon skeletons for ammonium assimilation in the roots is required for maximum growth under high ammonium concentrations, and that there is genotypic variability in this physiological trait.

Nitrogen removal from wastewater with high ammonia nitrogen concentration via shorter nitrification and denitrification

Shorter nitrification is reached through Nitrobacter bacteria activity inhibition. Nitrobacter bacteria responsible for nitrite nitrogen oxidation are sensitive to free ainmonium. The presence of free ammonium depended on a high ammonia nitrogen concentration in wastewater and its pH. It was the pH of the wastewater that was the decisive parameter in Nitrobacter bacteria activity inhibition in stable temperatures and at stable ammonia nitrogen concentrations. Reaction control in the aeration phase of the treatment process guaranteed the concentration of free ammonium within the I to 6 mg NH3/l range and at the same time concentration of free nitrous acid did not exceed 0.04 mg HNO2/l. It allowed nitrification to be significantly shortened and to receive build-up of nitrite nitrogen up to 300 mg NO2-N/l. Nitrification rate was about 0.06 g N/g MLSS·d.Measured oxidation rates of particular groups of nitrifying bacteria as oxygen uptake rates by Nitrosomonas and Nitrobacter bacteria respectively made control of shorter nitrification easier and gave insight into the activity of both nitrifier groups.

Nitrogen and Phosphorus in the Sediments of a Tidal, Freshwater Marsh in Massachusetts

Total organic nitrogen (TON) and phosphorus (TOP) were measured as a function of depth in 14 cores taken from a New England, tidal, freshwater marsh. TON and TOP ranged from 1.56 to 1.97% and 0.11 to 0.30% of dry weight sediments, respectively. The variation in both pool sizes over time was small and TON varied inconsistently with depth; however, TOP decreased regularly down to 20 cm. Consequently, the TON: TOP ratio increased linearly from 14∶1 at the surface to 32∶1 at 20 cm, then was nearly constant to 70 cm. This pattern may be a general feature of marsh sediments and may indicate 1) that phosphorus is recycled less efficiently than nitrogen, 2) that over time proportionately more introgen than phosphorus is incorporated into recalcitrant compounds, or 3) that phosphorus is more mobile than nitrogen in these marsh sediments. The total inorganic nitrogen pool was measured in this marsh also and was dominated by ammonium (97% of total). The annual average free ammonium concentration was 3.70±0.64 mg N per 1 at the surface and decreased to 0.92±0.18 mg N per 1 at 20 to 22 cm in the sediments. Sorptiondesorption studies showed that, on a fresh sediment volume basis, sediment sorbed ammonium was roughly equivalent to free porewater ammonium (K=0.8). The relationship between free and sorbed ammonium was linear between 0.4 and 24.0 mg NH4·N per 1 of pore water. The depth distribution of ammonium in these sediments is probably maintained by a dynamic balance between net microbial mineralization of litter, plant uptake, transpiration, diffusion, and porewater advection.