Removal Effect of Nitrifying Bacteria on Ammonia Nitrogen in Water

[Objectives]To investigate the removal effect of nitrifying bacteria on ammonia nitrogen in water.[Methods]In this experiment,the treated water(referred to as raw water hereinafter)from the Changping Town Qiaoli Water Treatment Project in Dongguan City of Guangdong Province was used as the experimental water body,and the nitrifying bacteria liquid used in the project was taken as the experimental material,to explore the removal effect of the nitrifying bacteria liquid on the ammonia nitrogen in the water body.[Results]Under the condition that other variables remain unchanged,the more the amount of nitrifying bacteria liquid added,the higher the removal efficiency of nitrifying bacteria liquid;under the same conditions,the removal effect of ammonia nitrogen in a stirred water body is better than that in an unstirred water body;the removal effect of ammonia nitrogen in a water body with bio-media/carriers is better than that without bio-media/carriers.[Conclusions]Nitrifying bacteria have a better removal effect on the ammonia nitrogen in the water body.

Impact of 17β-Estradiol on Natural Water’s Heterotrophic Nitrifying Bacteria

In this research, bottom water samples were collected from nature water. After cultivating and selecting, bacteria which could use (NH4)2SO4 as the only nitrogen source had been selected. The bacteria were cultivated in BM cultures with 0, 0.1, 1, 10, 100 ng/L 17β-estradiol (E2), and the initial concentration of E2 is the only difference between cultures of each group. BM culture is a kind of bacteria culture with 100 mg/L of NH4-N as only nitrogen source. Every group’s N- NH4+, N- NO3-concentration and OD600 were measured. The result shows that compared with the control group, in which no E2 was added, the growth of heterotrophic nitrifying bacteria had been promoted when the concentration of E2 was in range of 1 - 100 ng/L. In addition, heterotrophic nitrifying bacteria’s growing speed has a positive correlation between the E2’s concentration. However, low concentration of E2 (like 0.1 ng/L), could inhibit the growth of heterotrophic nitrifying bacteria. Considering the impact of E2 on heterotrophic nitrifying bacteria, it is necessary to intensify the detection of E2 in the future.

Nitrification performance of nitrifying bacteria immobilized in waterborne polyurethane at low ammonia nitrogen concentrations

Suspended and waterborne polyurethane immobilized nitrifying bacteria have been adopted for evaluating the effects of environmental changes, such as temperature, dissolved oxygen （DO） concentration and pH, on nitrification characteristics under conditions of low ammonia concentrations. The results showed that nitrification was prone to complete with increasing pH, DO and temperature. Sensitivity analysis demonstrated the effects of temperature and pH on nitrification feature of suspended bacteria were slightly greater than those of immobilized nitrifying bacteria. Immobilized cells could achieve complete nitrification at low ammonia concentrations when DO was sufficient. Continuous experiments were carried out to discuss the removal of ammonia nitrogen from synthetic micropollute source water with the ammonia concentration of about 1mg/L using immobilized nitrifying bacteria pellets in an up-flow inner circulation reactor under different hydraulic retention times （HRT）. The continuous removal rate remains above 80% even under HRT 30 min. The results verified that the waterborne polyurethane immobilized nitrifying bacteria pellets had great potential applications for micro-pollution source water treatment.

Effect of organic carbon on nitrification effciency and community composition of nitrifying biofilms

The effects of organic carbon/inorganic nitrogen （C/N） ratio on the nitrification processes and the community shifts of nitrifying biofilms were investigated by kinetic comparison and denaturing gradient gel electrophoresis （DGGE） analysis. The results showed that the nitrification rate decreased with an increasing organic concentration. However, the effect became weak when the carbon concentration reached a sufficiently high level. Denitrification was detected after organic carbon was added. The 12 h ammonium removal rate ranged from 85% to 30% at C/N = 0.5, 1, 2, 4, 8, and 16, as compared to the control （C/N = 0）. The loss of nitrogen after 24 h at C/N = 0.5, 1, 2, 4, 8, and 16 was 31%, 18%, 24%, 65%, 59%, and 62%, respectively. The sequence analysis of 16S rRNA gene fragments revealed that the dominant populations changed from nitrifying bacteria （Nitrosomonas europaea and Nitrobacter sp.） to denitrifying bacteria （Pseudomonas sp., Acidovorax sp. and Comamonas sp.） with an increasing C/N ratio. Although at high C/N ratio the denitrifying bacteria were the dominant populations, nitrifying bacteria grew simultaneously. Consequently, nitrification process coexisted with denitrification.

The impact of ultrasonic treatment on activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in activated sludge

The ultrasonic treatment of sludge has been considered as an effective method to facilitate the partial nitritation of municipal sewage.This study aims to reveal the effects of ultrasound on ammoniaoxidizing bacteria(AOB)and nitrite-oxidizing bacteria(NOB).The impact factors including ultrasonic irradiation time and intensity,sludge concentration,thermal effect and released free radicals were studied.The maximized difference between the changes in AOB and NOB activities were obtained with 10 g mixed liquor suspended solids(MLSS)/L,using 0.9 kJ/mL ultrasonic energy density and 12 h interval time.The increased ultrasonic intensity destroyed the floc structure of activated sludge,increased the microbial death,and decreased the cellular ATP level.Further,the mechanism exploration indicated that the mechanical shearing could be a critical factor in achieving the nitritation with inhibitory effect on nitrite oxidation.

Differences in distributions, assembly mechanisms, and putative interactions of AOB and NOB at a large spatial scale

Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) play crucial roles in removing nitrogen from sewage in wastewater treatment plants (WWTPs) to protect water resources. However, the differences in ecological properties and putative interactions of AOB and NOB in WWTPs at a large spatial scale remain unclear. Hence, 132 activated sludge (AS) samples collected from 11 cities across China were studied by utilizing 16S rRNA gene sequencing technology. Results indicated that Nitrosomonas and Nitrosospira accounted for similar ratios of the AOB community and might play nearly equal roles in ammonia oxidation in AS. However, Nitrospira greatly outnumbered other NOB genera, with proportions varying from 94.7% to 99.9% of the NOB community in all WWTPs. Similar compositions and, hence, a low distance–decay turnover rate of NOB (0.035) across China were observed. This scenario might have partly resulted from the high proportions of homogenizing dispersal (~13%). Additionally, drift presented dominant roles in AOB and NOB assembling mechanisms (85.2% and 81.6% for AOB and NOB, respectively). The partial Mantel test illustrated that sludge retention time and temperature were the primary environmental factors affecting AOB and NOB communities. Network results showed that NOB played a leading role in maintaining module structures and node connections in AS. Moreover, most links between NOB and other microorganisms were positive, indicating that NOB were involved in complex symbioses with bacteria in AS.

Micro-analysis of nitrogen transport and conversion inside activated sludge flocs using microelectro

To investigate the nitrogen transport and conversion inside activated sludge flocs,micro-profiles of O2,NHt 4,NO-2,NO-3,and pH were measured under different operating conditions.The flocs were obtained from a laboratory-scale sequencing batch reactor.Nitrification,as observed from interfacial ammonium and nitrate fluxes,was higher at pH 8.5,than at pH 6.5 and 7.5.At pH 8.5,heterotrophic bacteria used less oxygen than nitrifying bacteria,whereas at lower pH heterotrophic activity dominated.When the ratio of C to N was decreased from 20 to 10,the ammonium uptake increased.When dissolved oxygen(DO)concentration in the bulk liquid was decreased from 4 to 2 mg·L^(-1),nitrification decreased,and only 25%of the DO influx into the flocs was used for nitrification.This study indicated that nitrifying bacteria became more competitive at a higher DO concentration,a higher pH value(approximately 8.5)and a lower C/N.

Dynamics of nitrogenous compounds and their control in biofloc technology (BFT) systemsA review

Controlling toxic nitrogenous substances in biofloc technology(BFT)systems is critical for the success of this novel technology.To effectively control nitrogen accumulation in BFT systems,it is important to first understand the dynamics and the removal pathways of this element and its related compounds from aquaculture water.This review focuses on synthesizing the information of nitrogen dynamics in BFT systems to provide researchers and practitioners with a guide to the fate of nitrogen and its control methods.This paper discusses the different types of nitrogenous compounds in BFT water,the transformation processes of ammonia to nitrites and nitrates,the relationship between the two forms of ammonia(NH3 and NH4+)in water and the equilibrium between them.This paper also discusses nitrification as a major nitrogen removal pathway and the factors that influence the nitrification process.Notably,the control of nitrogen in BFT systems by manipulating the carbon to nitrogen ratio(C/N)using external carbohydrates is described in this paper.This paper suggests that further studies should focus on investigating the various factors that influence nitrogen dynamics in BFT systems and the means of controlling contaminants other than nitrogen.