[Ammonia Nitrogen Removal Performance with Parallel Operation of Conventional and Inverted A2/O Sewage Treatment Processes in Winter].

Ammonia nitrogen (NH4+-N) removal capacities of the A2/O and inverted A2/O processes were analyzed with the same inlet and parallel operation during winter. When the operating water temperature was 14℃, the inverted A2/O process exhibited lower NH4+-N removal from the volumetric load[0.13 kg ·(m3 ·d)-1vs. 0.29 kg ·(m3 ·d)-1] and a lower ammonia oxidation rate (AOR)[0.07 kg ·(kg ·d)-1 vs. 0.11 kg ·(kg ·d)-1] than the A2/O process, whereas the two processes exhibited similar performance at 26℃.The quantitative results for the ammonia oxidizing bacteria (AOB) population were almost the same in the two parallel processes (3.2%±0.24% for the inverted A2/O process and 3.4%±0.31% for the A2/O process). Clone library analysis showed that at low temperatures, the inverted A2/O process had a lower capacity for ammonia nitrogen removal than A2/O process. This is because the particular AOB species[spirillum (Nitrosospira)] facilitated the slower AOR type (K-growth strategy) of nitrosation in the inverted A2/O process, whereas in the A2/O process, the faster AOR type (r-growth strategy) of nitrosation was facilitated by bacterium (Nitrosomonas). At 26℃, the dominant species in the two processes were Nitrosomonas. Through comprehensive analysis of the pollutants during the removal process, we found that although temperature is the leading cause of AOB advantage in species succession, the changes in the inverted A2/O process structure, caused by the aerobic unit, resulted in high COD load and high NH4+-N concentration, which were unfavorable for the growth of AOB. This shows that under conventional sewage conditions, the K-growth strategy is advantageous for the AOB species. Therefore, the structure of the inverted A2/O process for heterotrophic bacteria (phosphorus accumulating bacteria and denitrifying bacteria) indirectly affects the population distribution and succession of autotrophic ammonia-oxidizing bacteria, through COD load and other factors, thereby leading to weakened nitrification capacity at low temperatures.

[Distribution of Antibiotic Concentration in Domestic Wastewater Treatment Facilities in Villages and Towns].

Antibiotics discharged into the environment cause increased environmental resistance. Four types of antibiotics (quinolones, tetracyclines, macrolides, and ß-lactams) were selected for this study. In a comparison with the municipal wastewater plant, the concentration and removal of antibiotics in influent and effluent of domestic wastewater treatment facilities of different scales in villages and towns was investigated using high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS). The results showed that the highest amount of ofloxacin in rural wastewater treatment facilities reached 32663.5 ng·L-1. Due to the different situations of influent fluctuation, discharge requirements, and management between urban and rural wastewater plants, only 33% of the rural domestic wastewater facilities detected an antibiotics removal rate of more than 60%. The effective removal of some antibiotics can be achieved when the rural domestic wastewater treatment facilities maintain the standard discharge of conventional pollutants.