Impacts of biological activities on erosion of sewer sediments

Experimental studies were conducted to investigate the influences of biological processes on the erosion behaviour of organic-rich sanitary sewer sediments. The results show that biological activities can make sediments expand and their bulk densities decrease. The experimental results also illustrate that sewer sediment erosion is a very complex process influenced by gravitational consolidation and biostabilisation. Aerobic biological processes can weaken a sediment bed and affect the erosion patterns for sediments rich in volatile solids, whereas the same processes can increase the resistance to erosion of sediments with lower volatile solid contents. Under anaerobic conditions, two sediment layers with different physical properties and erosion-resistance capabilities would form as a result of biological activities. Under low temperature and aerobic conditions, however, gravitational consolidation was identified as the major factor controlling the erosion behaviour of sediments.