Distinction of biofilm bacterial communities in practical rural sewers under different sewage sources

Although separate collection of sewage is efficient for rural sewage treatment, it may affect sewer biofilms associated with sewer operation and maintenance. To elucidate the variability of the bacterial communities in sewer biofilms from rural sewage with different characteristics, three rural drainage sewers, each conducting a different type of sewage (toilet black water, toilet grey water, or kitchen grey water), were studied. Additionally, the bacterial communities of the sewer biofilms were characterized using Illumina HiSeq high-throughput sequencing technology. The analysis demonstrated that the bacterial communities in rural sewer biofilms from different sewage types were significantly different. All three sewer biofilms contained abundant denitrifying bacteria but lacked ammonia-oxidizing and nitrite-oxidizing bacteria (relative abundance <0.1%). Moreover, the three analyzed sewers were in an aerobic environment, thus inducing a low abundance of sulfate-reducing bacteria in their biofilms (approximately 0.01%) and a low risk of H₂S accumulation. The biofilm and sewage in the grey water sewers also exhibited a relatively high abundance of pathogenic bacteria, including Legionella and Aeromonas, thereby suggesting that grey water biosafety should be considered during its reuse.