污泥热水解过程中磷的释放规律与影响因素

Phosphate Release and Influencing Factors Analysis during Sludge Thermal Hydrolysis

剩余污泥中富含磷物质,具有较大的回收利用价值。从污泥中高效回收磷最重要的步骤是将磷尽可能地释放到溶液中。以含固率为5%的剩余污泥(干污泥中磷占比为1. 1%)为研究对象,进行了热水解磷释放规律研究。结果显示:当采用低温水解与投加酸联合处理剩余污泥时,污泥絮体被破坏,磷的释放量显著增加。当温度为75℃、加热时间为1 h、pH值为3时,TP和IP的释放量可达到最大,分别为311. 9 mg/L和293. 8 mg/L,是原污泥液相中TP和IP含量的7. 9倍和8. 4倍。将经上述条件处理的污泥混合液在35℃下静置24 h,污泥液相中NH+4-N浓度由96. 0 mg/L提高到318. 7 mg/L,同时伴随着SCOD浓度的明显减小。因此,通过低温短时热水解联合酸处理可显著提高污泥中磷和氨氮的释放量,可为后续以鸟粪石沉淀法回收磷创造有利条件。

The phosphorus （P） in excess sludge （ES） produced by the sewage treatment plant has huge recycling value. The most important step of P recovery from the ES is to release as much P as possible into the solution. In this work, the ES with a solid content of 5% was used to study P release during the thermal hydrolysis. The results showed that when the ES was treated with low-temperature and pretreated with acid, the floc of the sludge was destroyed, and the release of P increased significantly. When the temperature was 75 ℃ for 1 h, the release of the total P （TP）and dissolving inorganic P （IP） in the liquid phase of raw sludge reached the maximum level, 311.9 mg/L and 293.8 mg/L, respective- ly, and was increased by 7.9 times and 8.4 times compared with raw sludge. When the sludge mixture was allowed to stand for 24 h at 35 ~C, the concentration of ammonia nitrogen （ NH4^＋ - N） increased from 96.0 mg/L to 318.7 mg/L, accompanied by a significant decrease in the concentration of soluble chemical oxygen demand （SCOD）. These results demonstrated that the combination of low-temperature and short-time thermal and acid pretreatment could significantly increase the P and NH4^＋ -N release in the sludge, which created favorable conditions for P recovery by struvite precipitation.