Jiachun Yang

High-rate nitrogen removal by the Anammox process with a sufficient inorganic carbon source.

This study focused on high-rate nitrogen removal by the anaerobic ammonium oxidation (Anammox) process with a sufficient inorganic carbon (IC) source. Experiments were carried out in an up-flow column Anammox reactor fed with synthetic inorganic wastewater for 110 days. The IC source was added into the influent tank in the form of bicarbonate. The results confirmed the positive impact of inorganic matter on stimulating Anammox activity. After the addition of sufficient IC, the nitrogen removal rate sharply increased from 5.2 to 11.8 kg-Nm(-3)day(-1) within only 32 days. NO(2)-N inhibition was not observed even at NO(2)-N concentrations greater than 460 mgN/L, indicating the enriched Anammox consortium adapted to high NO(2)-N concentrations. The ratio of NO(2)-N removal, NO(3)-N production and NH(4)-N removal for the reactor was correspondingly changed from 1.21:0.21:1 to 1.24:0.18:1. Simultaneously, the sludge volume index of the Anammox granules decreased markedly from 36.8 to 21.5 mL/g, which was attributed to the implementation of proper operational strategy. In addition, DNA analysis revealed that a shift from the KSU-1 strain to the KU2 strain occurred in the Anammox community.

High-rate partial nitrification treatment of reject water as a pretreatment for anaerobic ammonium oxidation (anammox).

In this study, a lab-scale swim-bed partial nitrification reactor was developed to treat ammonium-rich reject water to achieve an appropriate NO(2)(-)-N/NH(4)(+)-N mixture that could serve as a pretreatment for anaerobic ammonium oxidation (anammox). Strictly controlling the DO concentration was adopted as the main operational strategy. In addition, the influent concentrations of inorganic carbon/ammonium (IC/NH(4)(+)) and alkalinity/ammonium (Alk/NH(4)(+)) that were approximately 0.8 and 4.8, respectively, were regarded as the suitable ratios for the steady and high-rate operation of the reactor in this study. When reject water that was not diluted was introduced to this system, the maximum nitrogen loading rate was 5.9 kg-N/m(3)/day, the ammonium conversion rate was 3.1 kg-N/m(3)/day, and the effluent NO(2)-N/(NO(2)-N+NO(3)-N) percentage ratio was over 99.9%. Furthermore, DNA analysis confirmed the existence of AOB, which was responsible for the stable performance that was achieved in the PN reactor.

Anammox treatment of high-salinity wastewater at ambient temperature

The present study aims to provide a realistic understanding of how the anammox bacterial community and nitrogen removal performance are affected by increasing salt concentrations at ambient temperature. A laboratory-scale investigation was conducted for 92 days, during which the reactor was fed with synthetic inorganic wastewater composed mainly of NH(4)(+)-N and NO(2)(-)-N. A stable nitrogen removal rate of 4.5±0.1 kg Nm(-3) day(-1) was obtained at a NaCl concentration of 30 g/L, suggesting that the enriched anammox consortium adapted to high salt concentrations. This NRR level is the highest level ever reported at high salt concentration. The addition of salt in the influent was expected to improve the physical properties of the biomass. The anammox bacterium KU2, which was confirmed to adapt to high salt concentrations, was considered to be responsible for the stable nitrogen removal performance. The successful application of anammox technology in this study provides an alternative for the treatment of wastewater containing high concentrations of salt and nitrogen.

Treatment capability of an up-flow anammox column reactor using polyethylene sponge strips as biomass carrier.

The feasibility of applying a polyethylene (PE) sponge as a biomass carrier in an anaerobic ammonium oxidation (anammox) reactor and its nitrogen removal performance were also investigated. Experiments were carried out in an up-flow column reactor with synthetic inorganic wastewater. Experimental results indicate that reactor containing PE sponge biomass carriers showed a high nitrogen removal capability and exhibited stable performance. In addition, the reactor with 8 strips PE sponge as biomass carrier exhibited greater adaptation capacity compared to that with 6 strips and could achieve a high TN removal rate within a very short period. The ratio of NO(2)-N removal and NO(3)-N production to NH(4)-N removal for the reactor was 1.26:0.21. Furthermore, to investigate the bacterial composition of the mature community, 16S rRNA sequences were amplified by PCR and analyses were conducted using DNA databases. Results showed that a new kind of anammox microorganism (Kumadai-1) was the dominant species in the reactor when using PE sponge as a biomass carrier.

Stable and high-rate nitrogen removal from reject water by partial nitrification and subsequent anammox

A combined process of partial nitrification (PN) and anaerobic ammonium oxidation (anammox) was carried out to treat reject water with a high concentration of ammonium and a low level of hardly biodegraded organic carbon. Stable treatment performance was obtained under high nitrogen loading rates of 5.7 kg-N/m3/day and 10.5 kg-N/m3/day for the PN and anammox reactors for more than 2 months, respectively. Successful nitrite accumulation was observed in the PN reactor, with an effluent NH4-N/NO2-N ratio of 1:1.1 and marginal nitrate production, which is suitable for the subsequent anammox process. The strict control of DO concentration was adopted as the main manipulating strategy for the stable running of the PN reactor. And results indicated that the value of FA and FNA within a favorable range was essential for the successful operation of PN reactor. The anammox process was carried out in an up-flow fixed-bed reactor. The influent NH4-N/NO2-N ratio played a vital role in obtaining efficient nitrogen removal. The anammox reactor was successfully operated with a nitrogen removal rate of 9.1 kg-N/m3/day for 2 months, indicating high operational stability. Inorganic carbon was shown to have a positive impact on the high nitrogen removal rate during the combined process. In addition, the characteristics of the sludge in both reactors were investigated. The Stover-Kincannon model was used for kinetics studies. KB and Umax were determined as 30.1 g/L/day and 13.9 g/L/day, respectively, for the PN reactor and 42.1 g/L/day and 31.2 g/L/day, respectively, for the anammox reactor.

High-rate nitrogen removal by the Anammox process at ambient temperature

The purpose of this study is to investigate the nitrogen removal performance of the anaerobic ammonium oxidation (Anammox) process and the microbial community that enables the Anammox system to function well at ambient temperatures. A reactor with a novel spiral structure was used as the gas-solid separator. The reactor was fed with synthetic inorganic wastewater composed mainly of NH4+-N and NO2--N, and operated for 92 days. Stable nitrogen removal rates (NRR) of 16.3 and 17.5 kg-N m(-3) d(-1) were obtained at operating temperatures of 33±1 and 23±2°C, respectively. To our knowledge, such a high NRR at ambient temperatures has not been reported previously. In addition, the experiments presented herein confirm that high influent NO2--N concentration of 460 mg L(-1) did not noticeably inhibit the Anammox activity. Furthermore, the freshwater Anammox bacterium KU2, which was identified as the dominant bacterial species in the consortium by 16S rRNA gene analysis, is considered to be responsible for the stable nitrogen removal performance at ambient temperatures.

High rate partial nitrification treatment of reject wastewater.

Partial nitrification (PN) treatments on reject wastewater were carried out. Dissolved oxygen concentration was limited by controlling air flowrate, which was the main operational strategy in this study. Stable PN performance was obtained during continuous operation for 80 days, with a maximum nitrogen loading rate (NLR) of 4.2 kg-N m(-3) day(-1) and ammonium conversion rate of 2.1 kg-Nm(-3) day(-1). The production of nitrite oxidizers was assumed to be responsible for the nitrogen loss in the reactor. The ratios of NO2--N/ (NO2--N+NO3--N) were always above 99.9%, and BOD removal efficiencies were also stable at around 70% even if a sharp increase in NLR was applied during the stable period. Additionally, bacterial consortia analysis showed ammonium-oxidizing bacteria were the dominant microorganisms, which provided evidence for the long-term stable performance of this PN reactor. During the experiment, sludge setting properties deteriorated due to the absence of a biomass carrier. The stable performance of partial nitrification from reject wastewater demonstrated the feasibility of the operation strategy in this study.

High-rate nitrogen removal from anaerobic digester liquor using an up-flow anammox reactor with polyethylene sponge as a biomass carrier

Here, the stable performance of nitrogen removal from digester liquor after partial nitrification was experimentally demonstrated in an up-flow anammox reactor with polyethylene sponge (PE sponge) as a biomass carrier. A high nitrogen loading rate of 8.4 kg-N/m(3)/day with a TN removal rate of 7.6 kg-N/m(3)/day was obtained in this study, indicating PE sponge carrier is effective to attain high nitrogen removal performance. This high NLR should be mainly attributed to the successfully operational strategy, the biomass carrier with strong adsorption as well as the functional microbial community. The reaction ratio of NH(4)(+):NO(2)(-):NO(3)(-) using the anaerobic digester liquor as feeding media was 1:1.09:0.14. In addition, the channeling phenomenon was investigated in this study, and the problem could be solved through keeping the sludge bed lower than 2/3 of the effective height of the reactor. Furthermore, the settling property of the anammox granules was enhanced significantly and the bacteria community was verified by DNA analysis. The new species of anammox bacteria (kumadai-1) and KSU-1 were confirmed to be the predominant species after stable anammox performance was obtained.

High rate nitrogen removal by the CANON process at ambient temperature.

Completely autotrophic nitrogen removal over nitrite (CANON) is a cost-effective nitrogen removal process. Implementation of the CANON process relies on the cooperation of ammonium-oxidizing and Anammox bacteria, as well as the inhibition of nitrite-oxidizing bacteria. Strict limitations on dissolved oxygen (DO) concentration in the reactor, and the addition of sufficient inorganic carbon in the influent, were adopted as the main operational strategies. The reactor was fed with synthetic inorganic wastewater composed mainly of NH(4)(+)-N, and operated for 106 days. Stable nitrogen removal rates (NRR) of around 1.4 kg N m(-3) d(-1) were obtained at ambient temperature. Morphological characteristics and analysis of bacterial community confirmed the formation of functional outer aerobic and inner anaerobic granular sludge, providing evidence of stable nitrogen removal.