Aerobic granular sludge formation and stability in enhanced biological phosphorus removal system under antibiotics pressure: Performance, granulation mechanism, and microbial successions.

Wastewater containing antibiotics can pose a significant threat to biological wastewater treatment processes. This study investigated the establishment and stable operation of enhanced biological phosphorus removal (EBPR) by aerobic granular sludge (AGS) under mixed stress conditions induced by tetracycline (TC), sulfamethoxazole (SMX), ofloxacin (OFL), and roxithromycin (ROX). The results show that the AGS system was efficient in removing TP (98.0%), COD (96.1%), and NH4+-N (99.6%). The average removal efficiencies of the four antibiotics were 79.17% (TC), 70.86% (SMX), 25.73% (OFL), and 88.93% (ROX), respectively. The microorganisms in the AGS system secreted more polysaccharides, which contributed to the reactor's tolerance to antibiotics and facilitated granulation by enhancing the production of protein, particularly loosely bound protein. Illumina MiSeq sequencing revealed that putative phosphate accumulating organisms (PAOs)-related genera (Pseudomonas and Flavobacterium) were enormously beneficial to the mature AGS for TP removal. Based on the analysis of extracellular polymeric substances, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and microbial community, a three-stage granulation mechanism was proposed including adaption to the stress environment, formation of early aggregates and maturation of PAOs enriched microbial granules. Overall, the study demonstrated the stability of EBPR-AGS under mixed antibiotics pressure, providing insight into the granulation mechanism and the potential use of AGS for wastewater treatment containing antibiotics.

[Combined Remediation of Eutrophic Water by Phoslock® and Aerobic Denitrifying Bacteria].

Nitrogen and phosphorus are the leading causes of water eutrophication, and it is challenging to remove nitrogen and phosphorus effectively through a single water remediation method. In this study, an aerobic denitrifying bacterium (AD-19) isolated from eutrophic water was used to construct an immobilized biofilm and combined with Phoslock® to remove nitrogen and phosphorus from the water. The phosphorus control efficiency of Phoslock®, nitrogen removal performance of the denitrifying bacteria, and combined remediation performance for the eutrophic water were studied. The results demonstrated that the removal rate of PO43--P in the simulated eutrophic water reached 95% with a dosing ratio of 80 (mass ratio of Phoslock® to PO43--P), and phosphorus release from sediment was effectively inhibited at the same time. Strain AD-19, which was identified as Pseudomonas sp. Using the 16S rDNA method, had a good heterotrophic nitrification and aerobic denitrification ability, and more than 97% of the nitrogen was removed when NH4+-N or NO3--N was used as the nitrogen source. The feasibility of the combined remediation of the eutrophic water was demonstrated using a lake simulation device. Furthermore, this technique was used to restore a eutrophic pond in a park in Wuhan city. After 16 days of treatment, the water quality indices for nitrogen and phosphorus were improved from worse than Grade Ⅴ to Grade Ⅲ (GB 3838-2002, Ministry of Environmental Protection of China, 2002) and remained stable for more than 270 days, indicating that Phoslock® combined with the immobilized biofilm could quickly and effectively restore eutrophic water as well as maintain the water quality for long periods.

Simultaneous removal of nitrogen and phosphorus by a novel aerobic denitrifying phosphorus-accumulating bacterium, Pseudomonas stutzeri ADP-19.

A novel denitrifying phosphorus-accumulating bacterium was isolated from contaminated sediment and identified as Pseudomonas stutzeri ADP-19. Bio-safety assays demonstrated that the strain was γ-hemolytic, antibiotic-sensitive, and had no decarboxylase activity. It removed 96.5% of NH4+-N and 73.3% of PO43--P (at initial concentrations of 100 mg/L and 20 mg/L) under aerobic conditions, and the corresponding maximum removal rates were 3.44 and 0.41 mg/L/h, respectively. Nitrogen removal was achieved through a fully nitrification-denitrification pathway [NH4+-N â†’ NH2OH â†’ NO2--N â†’ NO3--N â†’ NO2--N → (NxO) â†’ N2], while phosphorus removal mainly depended on the phosphate assimilation and the excessive poly-P accumulation. Strain ADP-19 also showed a strong salt tolerance within a wide salinity range of 0-5%. The enhanced biological treatment of anaerobic-digested wastewater in a sequencing batch reactor (SBR) indicated that the strain improved the microbial diversity of the activated sludge and significantly enhanced the nitrogen and phosphorus removal efficiency.