[On the effect of hydrocyanic acid on chemical synthesis].
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Hydrochloric Acid↗
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[Research on chemical synthesis].
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Carbon Dioxide↗
[On the mechanism of chemosynthesis].
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Nitrobacter↗
Effects of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as end product.
The effect of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as the end product was studied by using a SBR. Experimental results indicated that the growth of nitrobacteria was inhibited and very high levels of nitrite accumulation at different salinities were achieved under the conditions of 25-28 degrees C, pH 7.5-8.0, and the influent ammonia nitrogen of 40-70 mg/L when seawater flow used to flush toilet was less than 35% (salinity 12393 mg/L, Cl- 6778 mg/L) of total domestic wastewater flow, which is mainly ascribed to much high chlorine concentration of seawater. Results showed that high seawater salinity is available for short-range nitrification to nitrite as the end product. When the seawater flow used to flush toilet accounting for above 70% of the total domestic wastewater flow, the removal efficiency of ammonia was still above 80% despite the removal of organics declined obviously (less than 60%). It was found that the effect of seawater salinity on the removal of organics was negative rather than positive one as shown for ammonia removal.
Ammonia↗
Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes.
Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30 degrees C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2-/gN-NH4+, and 0.4gN-NO2-/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.
Biofilms↗
[Nitrification and denitrification in the integrated vertical flow constructed wetlands].
Nitrification and denitrification in the different layers of the integrated vertical flow constructed wetlands (IVCW) are studied. The results show the constants rate of nitrification and denitrification in the strata of IVCW were 0.01 - 6.35microg x (gxd)-1 and 3.37 - 4.19microg x (gxd)-1 respectively. The most probable number (MPN) method are employed to determine the number and distribution of nitrifying and denitrifying bacteria in the strata of the system. The results show that the numbers of nitrifying and denitrifying bacteria were 7.5 x 10(3) - 1.1 x 10(5) MPN x g(-1) and 7.5 x 10(6) - 1.1 x 10 MPN x g(-1) respectively. The positive correlation between bacteria and their action was obvious (r = 0.9661, p < 0.001, r = 0.7722, p < 0.025). It is also observed that the number of nitrifying bacteria and nitrification rate was decreased along the direction of the water in the IVCW, while denitrifying bacteria and denitrification rate was increased. And there was the significant negative correlation between nitrification and denitrification rate(r = -0.9776, p < 0.001).
Biodegradation, Environmental↗
[Stability of shortcut nitrification-denitrification].
The effects of temperature and aeration time on the stability of shortcut nitrification-denitrification are studied specially in some experiments are carried on a sequencing batch reactor (SBR) fed with soybean wastewater. Results show that shortcut nitrification-denitrification achieved by controlling temperature was not stable until the temperature was more than 28 degrees C. In addition, for the first time strong effect of excess aeration on shortcut nitrification-denitrification is observed. When the system run under excess aeration for twelve days, the type of nitrification turned from shortcut nitrification which nitrosation rate (NO2(-)-N/NOx(-) -N) was more than 96% to complete nitrification which nitrosation rate (NO2(-) -N/NOx(-) -N) was less than 39.3%. So, in order to make shortcut nitrification-denitrification run stably, real-time process control must be used.
Bioreactors↗
[Potential of nitrification and denitrification in water purification system with hydroponic bio-filter method].
The potential of nitrification and denitrification of sediment and the density of ammonium-oxidizing bacteria and nitrite-oxidizing bacteria in sediment in water quality purifying system with hydroponic bio-filter method (HBFM) were measured. The variation of nitrification and denitrification potential of the sediment along the stream way was quantitatively studied. The results show that among the sediments from front, middle and retral part of the stream way, the sediment from middle part reached a maximum nitrification potential . nitrification potential of 4.76 x 10(-6) g/(g x h), while the sediment from front part reached a maximum denitrification potential of 8 .1 x 10(-7) g/(g x h). The distribution of nitrification potential accords with the ammonium-oxidizing bacteria density. The key for improving nitrogen removal efficiency of HBFM system consists in changing nitrification & denitrification region distributing and accordingly enhances denitrification process.
Biofilms↗
[Operation performance of membrane nitrification bioreactor for ammonia-containing wastewater].
The operation performance of membrane nitrification bioreactor to treat ammonia-containing wastewater as well as the capabilities of separation and filtration of polypropylene membrane modules were tested. The removal efficiency of ammonia was kept higher than 95% when the hydraulic retention time was set at 1 day, the influent concentration was increased up to 80 mmol (NH4+ -N) x L(-1) and the volume loading rate was increased up to 1.12 kg (NH4+ -N) x m(-3) x d(-1). The biomass in the reactor was accumulated from 5 g x L(-1) to 10 g x L(-1) within 50 days, which indicated that polypropylene membrane modules were efficient in retaining biomass. The biomass attached to the membrane also contributed to the conversion of ammonia and nitrite. When the hydraulic pressure was lower than 80cm, the increase of hydraulic pressure improved the permeation of membrane. However, when the hydraulic pressure was beyond 80cm, the increase of hydraulic pressure did not significantly improve the permeation of membrane. The permeate flux was the highest 2.51 (L x m (-2) x h(-1)) but the resistance was the lowest (2.63 x 10(-5)) m(-1) when the hydraulic pressure was about 20 cm. The results showed that the membrane nitrification bioreactor could be run normally without extra energy input.
Biodegradation, Environmental↗
[Effect of osmotic pressure on nitrification].
The effect of osmotic pressure on nitrification was investigated in the internal-loop air-lift nitrifying reactor. When influent ammonia concentration is kept at 420mg x L(-1) and influent osmotic pressure is increased from 4.3 to 18.8 x 10(5) Pa, the ammonia conversion of the nitrifying bioreactor is maintained between 93% and 100%. After influent osmotic pressure is further increased to 19.2 x 10(5)Pa, the ammonia conversion goes down to 69.2%. The influence of osmotic pressure on nitrification takes place without any alarm and the critical osmotic pressure is between 18.8 x 10(5) and 19.2 x 10(5) Pa. During osmotic stress, the nitrifying bacterial populations in the activated sludge become simplified, the cell size becomes smaller, the inner membrane becomes less and some unknown inclusion particles are formed. The cell structure is restored as soon as the osmotic pressure is removed. Addition of potassium is able to relieve the effect of osmotic pressure on nitrification. The nitrifying activity of the activated sludge is stimulated by the osmotic stress, and the specific ammonia conversion is increased from 0.083 kg x kg(-1) x d(-1) to 0.509 kg x kg(-1) x d(-1) and 2.569 kg x kg(-1) x d(-1), respectively.
Bioreactors↗
[Nitrification and denitrification in BACF for treating high ammonia source water].
A high ammonia micropolluted source water advanced treatment for ammonia removal by biological activated carbon filter was tested. The removal rate of ammonia was high than 95% when influent concentration was under 1.0 mg/L. The removal rate decreased with the influent concentration increased when the ammonia concentration was in range of 1.5 - 4.9 mg/L and the influent DO was under 10 mg/L, and the minimum removal rate was about 30%. The key factor of restrict nitrification in BACF was the influent DO. When the influent ammonia concentration was high, the DO in water was depleted quickly by nitrify and hetetrophic bacteria in 0.4 m deep of filter and the filter layer was divided to aerobic zone and anoxic zone. The denitrification was occurred in the anoxic zone, and because of very low concentration of electron donor led to accumulation of the denitrification intermediates such as NO2-. Aerobic bacteria was existed in the anoxic zone.
Ammonia↗
[Isolation and characterization of heterotrophic nitrifying bacteria].
Method of isolating the heterotrophic nitrifiers and the characterization of the heterotrophic nitrification were studied. Two heterotrophic nitrifiers were newly isolated from a membrane bioreactor (MBR) in which the TN removal efficiency was 80.1%. The batch test results indicate that Bacillus sp. LY and Brevibacillus sp. LY could utilize the organic carbon as the source of assimilation when they grew on glucose and ammonium chloride medium companying the formation of oxidized-nitrogen. After 24 days incubation, the removal efficiencies of the COD by Bacillus sp. LY and Brevibacillus sp. LY were 71.7% and 52.6%, respectively. The removal efficiencies of ammonium nitrogen by the two isolates were 78.2% and 51.2% and the TN removal efficiencies by the two isolates were 61.2% and 35.6%, respectively.
Biofilms↗
[Start-up experiment on nitrification of mid-low ammonia concentration wastewater in SBR biofilm reactor].
The start-up experiment on nitrification of mid-low NH4+ -N concentration wastewater was carried out in four SBR biofilm reactors for the establishment of completely autotrophic nitrogen removal process by the control of DO and HRT and different medias. The results show that on the conditions of temperature 30 degrees C +/-2 degrees C, ammonia concentration 60-120 mg/L, DO 0.8 - 1.0 mg/L and hydraulic retention time 24 h, the inoculating general active aerobic sludge and anaerobic sludge was nitrified stably after 130 days, and the YJZH media was more suitable for microorganism coherence.
Ammonia↗
[Community structure of nitrification bacteria in aerobic short-cut nitrification granule].
By using a lab-scale aerated upflow sludge bed reactor, the inoculated anaerobic granule was cultivated to aerobic nitrification granule, and then converted to short-cut nitrification granule with the short-cut nitrification efficiencies above 90%. Appling real-time quantity PCR, and florescent in situ hybridization techniques, the ecological community structure of nitrification bacteria in aerobic granules were studied. The results show that there existed a layered structure in the aerobic granule, the ammonia oxidizing bacteria (AOB) was mainly located in the surface area of the granule, and the nitrite oxidizing bacteria (NOB) was mainly located in the inner area of the granule, was just adjacent to the AOB. There was no active bacteria in the inner core area. The amount of AOB in the granules increased, as the ammonia loading rate of the reactor was increased gradually. The percentage of AOB in the total amount of Eubacteria in the granule was 0.45%, 5.20%, 15.37%, 48.55% respectively, as the ammonia loading rate of the reactor were 0, 0.4, 1.0 and 2.2 kg/(m3 x d) respectively, and the nitrosofication efficiency were 0%, 35%, 50%, 99% relatively.
Aerobiosis↗
[Effects of hydraulic retention time (HRT) on nitrification performance and microbial community of conventional activated sludge (CAS)].
A conventional activated sludge system was used to treat the ammonium-bearing inorganic wastewater for 260 days under decreased HRTs. When treating 500 mg x L(-1) NH4+ -N wastewater, over 98% ammonia removal could be obtained at HRT > or =20 h. Sharp washout of biomass occurred when HRT was further decreased, resulting in the accumulation of ammonium and nitrite. Changes in the community structure were monitored by microbial quinone and conventional analytical methods. Quinone profiles indicated that ammonia-oxidizing bacteria (AOB) in beta-Protevbacteria and Nitrobacteria in alpha-Proteobacteria were the predominant species to oxidize ammonia and nitrite, respectively. The number of AOB decreased with the reduction of biomass in bioreactor, while that of nitrite-oxidizing bacteria (NOB) changed little and fluctuated at 10(5) CFU x L(-1)
Biodiversity↗
[Ability of obligate methylotrophs to perform nitrogen fixation].
The ability for nitrification was studied among mesophilic and thermophilic cultures of obligate methylotrophs Methylobacter ucrainicus, Methylomonas methanica, and Methylococcus thermophilus. The strains were almost incapable of nitrification under autotrophic conditions. In the presence of methane, however, they oxidized NH+4 TO NO-2: over 150 mg/litre NO-2 nitrogen was found in the cultural broth. Therefore, obligate methylotrophs are capable of heterotrophic nitrification. The level of nitrification suggests that it is not a side reaction but a necessary stage of the metabolism of obligate methylotrophs. The phenotype relation between obligate methylotrophs and nitrifying organisms is discussed.
Bacteria↗
[Resistance testing of the pathogens in urinary tract infections on agar dip-slides].
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Agar↗