Physicochemical and ecological characteristics of the granular sludge during start-up of Anammox reactor / 生物工程学报

The anaerobic granular sludge from an Internal Circulation (IC) reactor of a paper mill wastewater treatment plant were seeded in an Anammox upflow anaerobic sludge blanket reactor. After 185 days operation, the reactor was finally started up by increasing the influent ammonium and nitrite concentrations to 224 mg/L and 255 mg/L, respectively, with volumetric nitrogen removal rate increasing to 3.76 kg/(m3·d). The physicochemical characteristics of the cultivated Anammox granules were observed by scanning electron microscope, transmission electron microscope and Fourier Transform infrared spectroscopy (FTIR). Results suggested that during the start-up course, the granular sludge initially disintegrated and then re-aggregated. FTIR spectra results revealed that the Anammox granular sludge contained abundant functional groups, indicating that it may also possess good adsorption properties. The ecological structure of the granular sludge, analyzed by the metagenomic sequencing methods, suggested that the relative abundance of the dominant bacterial community in the seeding sludge, i.e., Proteobacteria, Firmicutes, Bacteroidetes, significantly reduced, while Planctomycetes which contains anaerobic ammonium oxidation bacteria remarkably increased from 1.59% to 23.24% in the Anammox granules.

Performances of anammox-EGSB bioreactors started up with three different seeding sludges / 生物工程学报

In order to select better seeding sludge and promote start-up of Anammox reactors, we studied the start-up performances of three Anammox-EGSB bioreactors inoculated with anaerobic methanogenic sludge (AMS) (R1), Fresh Anammox sludge (FAS) (R2) and stored Anammox sludge (SAS) (R3), respectively. Results showed that these three seeding sludges could start up Anammox-EGSB bioreactors successfully, but the start-up progresses showed different characteristics. The start-up course of R1 could be divided into three phases including autolysis phase (15 d), lag phase (54 d) and activity elevation phase (40 d). However, the start-up courses of R2 and R3 only included lag phase (2 d and 12 d, respectively) and activity elevation phase (15 d and 57 d, respectively). Besides, the performance of R3 was better than that of R1, but worse than that of R2. Furthermore, bathing the Anammox sludge in the effluent of bioreactors was a convenient and effective way to keep the activity of the Anammox sludge. The ammonia removal efficiency, percentage of denitrification and the stoichiometric ratios of NH4(+)-Nr/NO2(-)-Nr and NO3(-)-Np/NH4(+)-Nr could serve as indicators to monitor the start-up of Anammox bioreactors.

Effect of sequential biocatalyst addition on Anammox process / 生物工程学报

Anaerobic ammonium oxidation (Anammox) process is a high-rate nitrogen removal technology that has been applied in sludge dewatering effluents treatment with nitrogen removal rate as high as 9.5 kg/(m x d). However, due to the slow growth rate of the autotrophic Anammox bacteria and the susceptivity to environmental conditions, the start-up of Anammox process is very long; the operation is unstable; and the nitrogen removal from organic-containing and/or toxicant-containing ammonium-rich wastewaters using Anammox process becomes difficult. Thus, the application of this high-rate process is significantly limited. In this paper, a newly-developed Anammox process with sequential biocatalyst (Anammox biomass) addition was established based on the procedure in fermentation engineering. We introduced the Anammox process with sequential biocatalyst addition on start-up, stable operation and the treatment of organic-containing and toxicant-containing ammonium-rich wastewaters. Results show that supplementing high-activity Anammox biomass into reactors will increase the amount of as well as the ratio of Anammox bacteria. Thus, the innovative Anammox process with sequential biocatalyst addition not only accelerates the start-up course, but also enhances the stability of Anammox process. Furthermore, it overcomes the drawbacks of wastewaters containing high organic content and toxic substances. Therefore, the application of Anammox process may be further enlarged.

Start-up and process control of a pilot-scale Anammox bioreactor at ambient temperature / 生物工程学报

Start-up and process control of a pilot-scale anaerobic ammonium-oxidizing (Anammox) bioreactor were studied at ambient temperature. Inoculated with a mixture of nitrification-denitrification sludge, nitritation sludge, anaerobic floc sludge and anaerobic granular sludge, the pilot-scale Anammox bioreactor was successfully started up within 255 days at 5 degrees C-27 degrees C. The nitrogen removal rate reached 1.30 kg/(m3 x d). Three facets were taken into account to facilitate the process initiation. First, in terms of alkalization in Anammox, influent pH was kept at about 6.8. Besides, nitrite concentration was kept as low as 13-36 mg/L. Finally, 2% (volumetric ratio) of Anammox sludge from lab-scale bioreactors was supplemented to the pilot-scale one.

Performance of lab-scale SPAC anaerobic bioreactor with high loading rate / 生物工程学报

The performance of a novel anaerobic bioreactor, spiral automatic circulation (SPAC) reactor, was investigated in lab-scale. The results showed that the average COD removal efficiency was 93.6% (91.1%-95.7%), with influent concentration increased from 8000 mg/L to 20 000 mg/L, at 30 degrees C and hydraulic retention time (HRT) of 12 h. The removal efficiency remained at 96.0%-78.7% when HRT was shortened from 5.95 h to 1.57 h, as the influent concentration was kept constantly at 20 000 mg/L. The highest organic loading rate (OLR), volumetric COD removal rate and volumetric biogas production of the SPAC reactor were 306 gCOD/(L x d), 240 g/(L x d) and 131 L/(L x d), respectively. When increasing influent COD concentration (from 8000 mg/L to 20 000 mg/L), the effluent COD concentration maintained at low level (852 mg/L for average) with volumetric COD removal rate increased by 162% and volumetric biogas production increased by 119%. With reduced HRT (from 5.95 h to 1.57 h), the volumetric COD removal rate and volumetric biogas production were increased by 191% and 195%, respectively. The SPAC reactor shows good performances in adapting the continuous change of influent COD and HRT.