treatment of swine wastewater in aerobic granular reactors： comparison of different seed granules as factors

The granulation process, physic-chemical properties, pollution removal ability and bacterial com- munities of aerobic granules with different feed-waste- water （synthetic wastewater, R1; swine wastewater, R2）, and the change trend of some parameters of two types of granules in long-term operated reactors treating swine wastewater were investigated in this experiment. The result indicated that aerobic granulation with the synthetic wastewater had a faster rate compared with swine waste- water and that full granulation in R 1 and R2 was reached on the 30th day and 39th day, respectively. However, although the feed wastewater also had an obvious effect on the biomass fraction and extracellular polymeric sub- stances of the aerobic granules during the granulation process, these properties remained at a similar level after long-term operation. Moreover, a similar increasing trend could also be observed in terms of the nitrogen removal efficiencies of the aerobic granules in both reactors, and the average specific removal rates of the organics and ammonia nitrogen at the steady-state stage were 35.33mg.g^-1 VSS and 51.46mg.g^-1 VSS for R1, and 35.47mg.g^-1 VSS and 51.72mg.g^-1 VSS for R2, respectively. In addition, a shift in the bacterial diversity occurred in the granulation process, whereas bacterial communities in the aerobic granular reactor were not affected by the seed granules after long-term operation.

Pilot-scale studies of domestic wastewater treatment by typical constructed wetlands and their greenhouse gas emissions

Three typical constructed wetlands(CWs)including Vertical Flow(VF),Free Water Surface(FWS),and Subsurface Flow(SF),and combined VF-SF-FWS constructed wetlands were investigated for the treatment of domestic wastewater with low C/N ratio.The performance of nutrient removal and the characteristics of greenhouse gas emissions,such as CH4 and N2O,from these CWs were compared.The results indicated that the four types of CWs had high removal efficiencies for organic matter and suspended solid(SS).The combined wetland also showed a comparatively good performance for nitrogen and phosphorus removal,and the removal efficiencies for total nitrogen(TN)and total phosphorus(TP)were 81.3%and 84.5%,respectively.The combined CWs had a comparative lower global warming potential.The FWS CW had the highest tendency to emit CH4 and led to a higher global warming potential among the four types of CWs,which was about 586 mg CO_(2)/m^(2)·h.

Influence of hydraulic retention time on behavior of antibiotics and antibiotic resistance genes in aerobic granular reactor treating biogas slurry

The behavior of antibiotics and the corresponding resistance genes in aerobic granular reactors for treating biogas slurry under different hydraulic retention times (10.7 h, Rl;8 h, R2) was investigated in this study. The results indicated that the hydraulic retention time could affect the effluent concentrations and removal efficiencies of sulfonamides. The average removal rates of tetracyclines, fluoroquinolones, and sulfonamides were 63%, 46%, and 90% in Rl, and 62%, 46%, and 86% in R2, respectively. Although the removal efficiencies of tetracyclines and fluoroquinolones were similar in both reactors, the respective accumulated concentrations of tetracyclines and fluoroquinolones in R1 were 7.00 and 11.15μg/g SS, which were lower than those in R2 (8.92 and 13.37μg/g SS, respectively). The difference in the relative abundance of target antibiotic resistance genes between both reactors was not significant, yet the average relative abundances of all target resistance genes in R1 were higher than those in R2 after 45 days of operation. The results of this study suggested that a longer hydraulic retention time could enhance the antibiotic removal ability of aerobic granular sludge, yet it may also increase the risk of surplus sludge utilization from a resistance genes point of view.