Development of a post-treatment system using a downflow hanging sponge reactor - an upflow anaerobic reactor for natural rubber processing wastewater treatment.

This study aimed to evaluate the nitrogen removal of a post-treatment system for natural rubber processing wastewater (NRPW) under low chemical oxygen demand to total nitrogen (COD/TN) ratios without any supplemental external carbon source. The system including a downflow hanging sponge (DHS) reactor and an upflow anaerobic reactor (UAR) was operated in two phases. In phase 1 (day 0-102), under a nitrogen loading rate (NLR) of 0.23 ± 0.06 kgN m-3 d-1 and COD/TN ratio of 0.63 ± 0.47, the DHS-UAR system removed 82.5 ± 11.8% and 83.9 ± 7.6% of TN and ammonium concentrations, respectively. In phase 2 (day 103-229), higher COD/TN ratio of 1.96 ± 0.28 was applied to remove increasing NLRs. At the highest NLR of 0.51 kgN m-3 d-1, the system achieved TN and ammonium removal efficiencies of 93.2% and 93.7%, respectively. Nitrogen profiles and the 16S rRNA high-throughput sequencing data suggested that ammonium, a major nitrogen compound in NRPW, was utilized by nitrifying and ammonium assimilation bacteria in DHS, then removed by heterotrophic denitrifying and anammox bacteria in the UAR. The predominance of Acinetobacter detected in both reactors suggested its essential role for the nitrogen conversion.

Simultaneous partial nitrification, anammox, and denitrification in an upflow microaerobic membrane bioreactor treating middle concentration of ammonia nitrogen wastewater with low COD/TN ratio.

The rapid start-up and operating characteristics of simultaneous partial nitrification, anammox, and denitrification (SNAD) process was investigated using synthetic wastewater with a low C/N ratio (COD: NH4+-N = 200 mg/L: 200 mg/L) in a novel upflow microaerobic membrane bioreactor (UMMBR). The average removal efficiencies of COD, NH4+-N, and TN in the stable phase were 89%, 96%, and 86%, respectively. Carmine granule, which coexisted with sludge floc, appeared on day 83. The high sludge concentration (12.9-17.2 g/L) and the upflow mode of the UMMBR could establish some anaerobicregions for anammox process. The anammox bacteria and short-cut denitrification (NO2-→N2) bacteria with activities of 4.46 mg NH4+-N/gVSS·h and 2.57 mg NO2--N/gVSS·h contributed TN removal of 39% and 61% on day 129, respectively. High-throughput sequencing analysis revealed that the ammonia-oxidizing archaea (AOA, 49.45% in granule and 17.05% in sludge floc) and ammonia-oxidizing bacterial (AOB, 1.30% in sludge floc) dominated the nitrifying microbial community. Candidatus Jettenia (47.14%) and Denitratisoma (10.92%) mainly existed in granule with positive correlations. Some heterotrophic bacteria (OLB13, SJA-15, 1-20, SBR1031, and SJA-28) in sludge floc benefited system stability and sludge activity and protected Candidatus Jettenia from adverse environments.

Performance and nitrogen removal mechanism in a novel aerobic-microaerobic combined process treating manure-free piggery wastewater.

A novel combined sequencing batch reactor (SBR) - up-flow microaerobic sludge reactor (UMSR) process was developed to treat manure-free piggery wastewater characterized by low COD/TN ratio and high NH4+-N. The front-end SBR was designed to get an effluent with COD/TN ≤ 1 by removing COD, allowing the back-end UMSR to practice anammox for the simultaneous removal of TN and NH4+-N. Fed with the raw piggery wastewater, the combined SBR-UMSR process was started up at 27℃ with a reflux ratio of 15:1 in the UMSR. After 230-days running, the removal of COD, TN, and NH4+-N in the combined SBR-UMSR process reached 78.41%,85.05%, and 92.21%, respectively. 50.22% of COD in the wastewater was removed in the SBR, while 87.11% of NH4+-N and 79.69% of TN were removed in the UMSR. Stoichiometry and bacterial function analysis revealed that the partial nitrification - anammox process was the dominant nitrogen removal approach in the UMSR.

Effect of the method of falling water aeration-reflux on nitrogen removal and applicability in a novel upflow microaerobic sludge reactor treating low carbon-to-nitrogen ratio wastewater.

A novel falling water aeration-external reflux upflow microaerobic sludge reactor (UMSR) was designed to treat wastewater with the low chemical oxygen demand (COD) to total nitrogen (TN) ratio. The result showed the concentration of dissolved oxygen (DO) in the reactor could be accurately controlled by adjusting the reflux ratio of oxygenated water. The higher aeration efficiency in pollutant removal could be obtained by the reoxygenation mode of the small height falling water. At the reflux ratio of 5:1, the ammonium, nitrite and nitrate nitrogen concentrations in the effluent of UMSR were 6.0, 0.4 and 6.1 mg/L on average, respectively. The removal efficiency of ammonium nitrogen and total nitrogen reached 90.53% and 80.77%, respectively with the influent COD/TN as being 1.0. The structure of the microbial community confirmed the existence of partial-denitrification/anaerobic ammonium oxidation (anammox) bacteria, autotrophic and heterotrophic denitrifiers contributed to nitrogen and carbon removal in UMSR.