Vacuum Dewatering Behaviours of Municipal Sewage Sludge

Vacuum dewatering tests for sewage sludge were conducted to investigate the effects of initial water content, quartz sand conditioning sludge and vacuum load on dewatering behaviours. Water content and settlement of sludge were measured and the factors influencing dewatering were analyzed. Combined with scanning electron microscopy results, the mechanisms of action for various influencing factors were discussed. The results show that quartz sand conditioning sludge has a significant effect on dewatering, followed by vacuum load, whereas the influence of the initial water content is less pronounced. Dewatering efficiency is proposed to quantify the dewatering performance. It is found that the dewatering efficiency changes little with the initial water content, but is strongly affected by conditioning and vacuum load. The dewatering efficiency increases with the dosage of quartz sand used to condition the sludge, and the recommended economical dosage of conditioning sludge is 20%. The dewatering efficiency is the highest at 50 kPa, next at 85 kPa, and the lowest at 30 kPa, so a reasonable vacuum load is 50 kPa. This study is expected to provide a theoretical foundation and technical support for vacuum dewatering of sewage sludge.