China's dual-carbon goals challenges wastewater treatment plants (WWTPs), requiring integrated pollution control and carbon emission reduction. Critical gaps hinder China's strategies for WWTPs, particularly in identifying upgrade needs, optimizing performance, and assessing the local benchmark plants as references. This study addresses these gaps through greenhouse gas (GHG) emission accounting and impact factor analysis, using monthly data from 2232 WWTPs across China. A tiered assessment methodology was developed to evaluate the synergy between pollution reduction and carbon mitigation, including indicators, methodologies, and assessment criteria. Results indicate that indirect emissions from electricity and chemical consumption accounted for 59.9% of total GHG emissions. Key factors influencing these indirect emissions included plant scale, treatment processes, geographic area, operational load, electricity consumption, and influent quality. Through the tiered assessment, WWTPs were classified into three categories: priority control (861 plants), general control (730 plants), and maintenance (641 plants). Furthermore, 222 benchmark plants were identified as exhibiting optimal synergy between pollution control and carbon reduction. For 80% of the benchmark plants, the ranges for carbon emission intensity, influent COD, influent C/N ratio, electricity consumption intensity, and operating load were 0.258–0.482 ​kg CO₂e/t, 175–338 ​mg/L, 6.13–10.9, 0.149–0.260 ​kWh per tonne of influent, and 88.0%–110%, respectively. Achieving these benchmark standards across all WWTPs could lead to a 30% reduction in total GHG emissions. Finally, the study proposes targeted policies to enhance the synergy between pollution control and carbon reduction strategies in China's urban wastewater treatment systems.

Antibiotic resistance is currently a major global public health issue. In particular, the emergence and transfer of antibiotic resistance genes (ARGs) is a matter of primary concern. This study presented a method for ruling out the transfer of naked DNA (plasmid RP4 lysed from donor cells) during the cell-to-cell conjugation, using a modified “U-tube”. A series of gene transfer assays was conducted in both flask and modified U-tube, using Pseudomonas putida KT2440 (P. putida (RP4)) harboring the RP4 plasmid as the donor strain, Escherichia coli (E. coli, ATCC 25922) in pure culture as sole recipient, and bacteria from reclaimed water microcosms as multi-recipients. The verification experiments showed that the U-tube device could prevent direct contact of bacteria without affecting the exchange of free plasmid. In the experiments involving a sole recipient, the transconjugants were obtained in flask samples, but not in modified U-tube. Furthermore, in experiments involving multi-recipients, transfer of naked DNA in the modified U-tube accounted for 5.18% in the transfer frequency of the flask transfer experiment. The modified U-tube proved to be useful for monitoring the interference of naked DNA in the research of conjugative transfer and calculating the exact conjugative transfer rate. This device is identified as a promising candidate for distinguishing different gene transfers in practical application because of its convenient use and easy and simple manufacture.