Yield of Ozone,Nitrite Nitrogen and Hydrogen Peroxide Versus Discharge Parameter Using APPJ Under Water

Discharge plasma in and in contact with water can be accompanied with ultraviolet radiation and electron impact, thus can generate hydroxyl radicals, ozone, nitrite nitrogen and hydrogen peroxide. In this paper, a non-equilibrium plasma processing system was established by means of an atmospheric pressure plasma jet immersed in water. The hydroxyl intensities and discharge energy waveforms were tested. The results show that the positive and negative discharge energy peaks were asymmetric, where the positive discharge energy peak was greater than the negative one. Meanwhile, the yield of ozone and nitrite nitrogen was enhanced with the increase of both the treatment time and the discharge energy. Moreover, the pH value of treated water was reduced rapidly and maintained at a lower level. The residual concentration of hydrogen peroxide in APPJ treated water was kept at a low level. Additionally, both the efficiency energy ratio of the yield of ozone and nitrite nitrogen and that of the removal of p-nitrophenol increased as a function of discharge energy and discharge voltage. The experimental results were fully analyzed and the chemical reaction equations and the physical processes of discharges in water were given.

Comparison between Spectrophotometry and Gas Phase Molecular Absorption Spectrometry for Determination of Nitrite Nitrogen in Flue Gas

Spectrophotometry and gas phase molecular absorption spectrometry for determination of nitrite nitrogen in flue gas were compared.KOH absorption solution was used to absorb nitrite nitrogen in flue gas,and the concentration of nitrite nitrogen in the absorption solution was determined by spectrophotometry and gas phase molecular absorption spectrometry to obtain the concentration of nitrite nitrogen in flue gas.The experiments show that both methods are accurate and reliable.

Achieving and maintaining biological nitrogen removal via nitrite under normal conditions

The principal aim of this paper is to develop an approach to realize stable biological nitrogen removal via nitrite under normal conditions. Validation of the new method was established on laboratory-scale experiments applying the sequencing batch reactor（SBR） activated sludge process to domestic wastewater with low C/N ratio. The addition of sodium chloride（NaCI） to influent was established to achieve nitrite build-up. The high nitrite accumulation, depending on the salinity in influent and the application duration of salt, was obtained in SBRs treating saline wastewater. The maintenance results indicated that the real-time SBRs can maintain stable nitrite accumulation, but conversion from shorter nitrification-denitrification to full nitrification-denitrification was observed after some operation cycles in the other SBR with fixed-time control. The presented method is valuable to offer a solution to realize and to maintain nitrogen removal via nitrite under normal conditions.

全程自养生物脱氮工艺机理及影响因素分析

全程自养生物脱氮工艺(completely autotrophic nitrogen removal over nitrite,CANON)具备有机碳源投加少、能耗低、占地面积小、操作简单等优点,成为污水处理领域的重要研究对象。因此综述了全程自养生物脱氮工艺的机理、影响因素,分析了温度、pH、溶解氧(dissolved oxygen,DO)、基质浓度等因素对脱氮效果的影响,为全程自养生物脱氮工艺优化提供参考。

Effects of Aeration on Nitrification Process in a Polluted Urban River

[Objective] The study aimed to discuss the effects of aeration on nitrification process in a polluted urban river, [Metbod] Through indoor simulation experiments, the effects of different aeration conditions （aerating water named Ew, aerating sediment named Es ） on nitrification process in a polluted urban river were studied.[ Result]The nitrification of the control group named Ec proceeded slowly, while two kinds of aeration promo- ted the process of nitrification, that is, the peak values of nitrate nitrogen of Ew and Es group were respectively 5.15 and 3.83 times that of Ec group. During aeration, NO2 --N accumulation in the overlying water of Ew and Es group lasted for 10 and 14 days separately, and the maximum concentrations reached 11.41 and 7.41 mg/L respectively. Nitrification process was not consistent during the two aeration conditions, that is, the rate of nitrite oxidation in Ew group was faster than that in Es group. Denitrification process was significant after aeration, and the concentration of nitrate nitrogen in Ew and Es group was 1.26 and 2.82 mg/L respectively at the end of the experiment. [ Conclusion]The research could provide scientific references for the restoration of polluted urban rivers.

Performance of a completely autotrophic nitrogen removal over nitrite process for treating wastewater with different substrates at ambient temperature

The stability and parameters of a bio-ceramic filter for completely autotrophic nitrogen removal were investigated. The completely autotrophic nitrogen removal over nitrite （CANON） reactor was fed with different concentrations of ammonia （400, 300, and 200 mg N/L） but constant influent ammonia load. The results showed that the CANON system can achieve good treatment performance at ambient temperature （15-23℃）. The average removal rate and removal loading of NH4＋-N and TN was 83.90%, 1.26 kg N/（m3.day）, and 70.14%, 1.09 kg N/（m3.day）, respectively. Among the influencing factors like pH, dissolved oxygen and alkalinity, it was indicated that the pH was the key parameter of the performance of the CANON system. Observing the variation of pH would contribute to better control of the CANON system in an intuitive and fast way. Denaturing gradient gel electrophoresis analysis of microorganisms further revealed that there were some significant changes in the community structure of ammonium oxidizing bacteria, which had low diversity in different stages, while the species of anaerobic ammonium oxidizing （anammox） bacteria were fewer and the community composition was relatively stable. These observations showed that anaerobic ammonia oxidation was more stable than the aerobic ammonia oxidation, which could explain that why the CANON system maintained a good removal efficiency under the changing substrate conditions.

Performance of completely autotrophic nitrogen removal over nitrite process under different aeration modes and dissolved oxygen

In this study,three sequential batch biofilm reactors(SBBRs)were operated for 155 days to evaluate the performance of completely autotrophic nitrogen removal over nitrite(CANON)process under different aeration modes and dissolved oxygen(DO).Synthetic wastewater with 160-mg NH_(4)^(+)-N/L was fed into the reactors.In the continuously-aerated reactor,the efficiency of the ammonium nitrogen conversion and total nitrogen(TN)removal reached 80% and 70%,respectively,with DO between 0.8–1.0 mg/L.Whereas in the intermittently-aerated reactor,at the aeration/non-aeration ratio of 1.0,ammonium was always under the detection limit and 86% of TN was removed with DO between 2.0–2.5 mg/L during the aeration time.Results show that CANON could be achieved in both continuous and intermittent aeration pattern.However,to achieve the same nitrogen removal efficiency,the DO needed in the intermittently-aerated sequential batch biofilm reactor(SBBR)during the aeration period was higher than that in the continuously-aerated SBBR.In addition,the DO in the CANON system should be adjusted to the aeration mode,and low DO was not a prerequisite to CANON process.

Aerobic N_2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.