How does moisture content regulate EPS dynamics and microbial interactions to mediate erosion resistance in sewer sediments?

The erosion resistance of sewer sediments is a key determinant of hydraulic efficiency and flood risks in urban drainage systems. In real sewer networks, sediment moisture content fluctuates substantially due to intermittent drainage, seasonal variation, and storm inflow pulses, yet its influence on microbially mediated sediment stability remains poorly understood. This study systematically investigated how moisture content regulates extracellular polymeric substances (EPS) dynamics, microbial community structure, and microbial interactions in sewer sediments across a moisture range of 10.10-59.09%. Sediments at intermediate moisture levels (29.17-40.91%) exhibited the highest erosion resistance, with EPS content strongly positively correlated with critical shear stress (R2 = 0.92). Moderate moisture also enriched key EPS-producing taxa and promoted a more cooperative microbial interaction pattern, thereby enhancing the capacity of the community to withstand scouring disturbance. These findings introduce the concept of "adaptive moisture window", representing the moisture range where microbial activity and EPS secretion are most favorable for sediment stability. This framework provides new insights into predicting sediment cohesion under variable sewer moisture regimes and offers new guidance for adaptive sediment management in urban drainage systems.