Search

Hydrazine is an important intermediate for anaerobic ammonium oxidation (anammox), in which ammonium and nitrite are converted to nitrogen gas. Hydrazine addition is known to improve the nitrogen removal capacity in anammox-based processes. However, the underlying mechanism remains unknown. This study investigated the effects of hydrazine addition on conversion performance for normal anammox substrates (ammonium, nitrite and nitrate) using batch experiments with various combinations of nitrogenous as substrates for the anammox bacteria in the presence or absence of hydrazine. Hydrazine addition improved specific anammox activity (SAA) by 42%, of which 5% was attributed to increased ammonium removal by strengthening anammox, 25% to acceleration of nitrite degradation by the bioreaction where exogenous hydrazine was reacted with nitrite to generate azide, and 12% to reducing nitrate production rate through selective inhibition of nitrite-nitrate oxidoreductase (NXR) activity by generating azide. A model in which hydrazine addition enhances the nitrogen removal capacity in an anammox system was established, which can provide theoretical guidance for engineering applications of anammox with trace hydrazine addition. [ABSTRACT FROM AUTHOR]

Co-occurrence of organic matter (OM) and nitrogen in industrial and domestic wastewaters is a major obstacle in field scale application of anammox process- a novel technology for biological nitrogen removal. This study explored a new symbiosis amongst different consortium i.e., denitrifiers, anammox and anaerobes, which together minimized the inhibition caused due to OM through its concurrent utilization via other metabolic pathways. This symbiosis was achieved by seeding anaerobic granular sludge in existing anammox hybrid reactors at different seed ratios, i.e., 0.2, 0.4, 0.6 and 0.8. COD/TN and seed ratio played a vital role in controlling the overall dynamics of the three different pathways, i.e., denitrification, anammox and anaerobic degradation. The seed ratio of 0.6 was found ideal for synergistic removal of both OM (95.4%) and nitrogen (97.4%). At higher COD/TN ratio, anaerobes were more prevalent and outcompeted anammox bacteria which showed predominance at lower COD/TN ratio. The process performance data were analysed using multi-linear regression (MLR) and non-linear regression models. Biasness of the models were analysed using t -test which dictated MLR model was unbiased and statistically more precise than non-linear regression model. A new mathematical model coceptualised on the mass balance of substrate predicted N 2 and biogas with least error of precision. [ABSTRACT FROM AUTHOR]

An integrated partial nitrification, sludge fermentation and denitrification process in a sequencing batch reactor (PNSFD-SBR), was developed to enhance nitrogen removal from domestic wastewater with low C/N (i.e. SCOD/TN) between 2 to 3 and to reutilize/reduce external waste activated sludge (WAS). Average ammonium removal efficiency of 95.9%, total nitrogen removal efficiency of 93.5%, and external WAS reduction rate of 21.6% was achieved during long-term experiment at 30 ± 1 °C. Real-time pH-DO (dissolved oxygen) monitor and control played an important role in the PNSFD achievement. A batch test indicated that micro-aeration (less than 1 mg/L) sustained partial nitrification, which further facilitated subsequent sludge fermentation and denitrification processes. Moreover, Illumina MiSeq analysis demonstrated the predominant bacteria were Rhodocyclaceae , Anaerolineaceae and Saprospiraceae on family level and they were key to partial nitrification, denitrification and sludge fermentation, by which the feasibility of PNSFD process to achieve simultaneous nitrogen removal and external WAS reutilization/reduction was verified. [ABSTRACT FROM AUTHOR]

The combined anammox (anaerobic ammonium oxidation) and autotrophic desulfurization–denitrification (AADD) process represents a promising innovative technology for biological nitrogen and sulfur removal. In this study, an up-flow anaerobic sludge blanket reactor, which was started with anammox and methanogenic granules, was operated for 245 days to evaluate the co-treatment of wastewater containing nitrogen and sulfur. The reactor demonstrated good performance in terms of nitrogen and sulfide removal and exhibited excellent behavior for removal of NH 4 + -N, NO 2 − -N and S 2− -S exceeding 252, 333 and 330 mg L −1 , respectively. The highest nitrogen removal rate and sulfide removal rate attained were 4.00 kgN m −3 d −1 and 2.39 kgS m −3 d −1 , respectively, which were also the highest reported values for a coupling-system. The influent NH 4 + -N:S 2− -S and NO 2 − -N:S 2− -S ratios set at 1.74 and 2.20–2.27 are suitable for maintaining system stability. The specific activities of anammox and autotrophic desulfurization–denitrification (SAA and SADD), extracellular polymeric substance (EPS), heme c (an important cofactor of some anammox bacterial enzymes) and the diversity of anammox and autotrophic desulfurization–denitrification (ADD) bacteria were investigated during the operation. The SAA and SADD are regarded as key factors for high efficiency. The granules contained many EPS (128.4–204.5 mg g −1 VSS) and minor heme c content (1.17 μmol g −1 VSS). The dominant bacteria belonged to members of Brocadiaceae and Hydrogenophilaceae , a majority of which were anammox bacteria and ADD bacteria, respectively. These observations suggest a new removal process for ammonia, nitrite and sulfide utilizing an uncommon mechanism involving simultaneous anammox and ADD. [ABSTRACT FROM AUTHOR]

Efficient biological nitrogen removal from high salinity wastewater has been focused recently. The present study comparatively investigated the effects of temperature, salinity and calcium concentration on the performance of anaerobic ammonium oxidation (anammox) processes using anammox granular sludge to treat synthetic wastewater. Four upflow anaerobic sludge blanket reactors were operated in parallel at ambient temperatures evolving from 25 to 9 °C (reactor R 1 ) and thermostatic room temperatures of 35 ± 2 °C (reactors R 2 , R 3 and R 4 ). The results demonstrated that low ambient temperature and high sodium levels impair the nitrogen removal performance of anammox granular sludge. The anaerobic ammonium-oxidizing bacteria gradually adapted to a salt concentration of 15 g L −1 at low ambient temperature, and a nitrogen removal rate of 1.34 ± 0.12 kg N m −3 d −1 was achieved. A nitrogen removal rate of 1.90 ± 0.01 kg N m −3 d −1 in R 4 was achieved at a salt concentration of 15 g L −1 . Moreover, 152 mg L −1 calcium relieved the high salinity inhibition of anaerobic ammonium-oxidizing bacteria. Furthermore, the fractal dimension and permeability of anammox granules were also investigated with settling experiment, which indicated that the anammox granules were porous and permeable. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium-oxidizing (anammox) is a novel wastewater treatment process, which can realize efficient nitrogen removal with low operational cost. The anammox process is usually executed at 35 °C by heating devices. The potential effects of overheating on anammox culture are still remained as an open question. In this study, we share experiences about behavior detection and activity recovery of damaged anammox culture after accidental overheating. When anammox culture suffered 48 °C for 1 h, flocculating and deflocculating occurred, resulting in the suspended culture and the settled. Fluorescence in situ Hybridization, Flow Cytometry and Non-invasive Micro-test Technique showed that the settled culture contained more anammox bacteria than the suspended, leading to its higher death probability as time course, higher bulk liquid H + flux rate and faster activity restoration for nitrogen removal after overheating. The autofluorescence of Candidatus Brocadia fulgida varied during this process and could be considered as a characteristic fingerprint for these anammox bacteria. Experimental results also indicated the shear force produced by 150 rpm stir would contribute to the further damage of the heated bacteria. Reducing shear stress by low stirring rates and static cultivation might potentially be used as effective strategies in the repair of damaged anammox culture. [ABSTRACT FROM AUTHOR]

The performance and hydrodynamic features of a staged up-flow ANAMMOX (anaerobic ammonium oxidation) sludge bed (SUASB) reactor was evaluated. When the reactor was at steady-state conditions, the nitrogen loading rate (NLR) and nitrogen removal rate (NRR) were 5.63 and 4.82 kg N m-3 d-1, respectively. The reactor could withstand a 1.5-fold substrate or hydraulic shock. The modified Stover-Kincannon model was used for the kinetic analysis, and the saturation value (KB) and maximum total substrate utilization rate (Umax) were 14.5 and 14.8 kg N m-3 d-1, respectively. Moreover, the C(t)-Θ curve showed the existence of dead zones in the SUASB at the hydraulic retention times (HRTs) of 3 and 12 h, and the flow pattern performance of the SUASB fell between those of a continuous stirred tank reactor (CSTR) and a plug flow reactor (PFR). [ABSTRACT FROM AUTHOR]