Wastewater sample
At the end of the reaction cycle, mixed liquor samples from each experimental group and the control group were collected and immediately stored at -80C in an ultra-low temperature freezer. DNA extraction was performed using the FastDNA SPIN Kit for Soil (MP Biomedicals) strictly according to the manufacturer's instructions to obtain high-quality total microbial DNA. The concentration and purity of the extracted DNA were assessed by agarose gel electrophoresis and NanoDrop analysis. Subsequently, library construction and sequencing were commissioned to Majorbio Bio-Pharm Technology Co., Ltd. (Shanghai, China). Paired-end sequencing was performed on the Illumina NovaSeq platform to construct a paired-end library with an insert size of approximately 350 bp. Raw sequencing data were first quality-filtered using Fastp software to remove low-quality sequences and adapters.