污泥中磷和氮的厌氧溶出及其改性赤泥晶种结晶法回收工艺

Process of Phosphorus and Nitrogen Dissolution from Sludge by Anaerobic Digestion and Their Recovery by Modified Red Mud Seeded Crystallization

为从污泥中回收磷和氮,研究了污泥中磷和氮的厌氧消化溶出及改性赤泥晶种诱导磷酸铵镁结晶法回收磷和氮的工艺,考察了污泥混合液中pH、温度和厌氧消化时间对厌氧消化溶出正磷酸盐(PO3-4-P)和氨氮(NH+4-N)的影响。结果表明,当温度为50℃,厌氧消化时间为5～7d,不改变污泥混合液的pH,污泥厌氧消化可溶出的PO3-4-P为200.0mg/L,NH+4-N为245.0mg/L,N与P摩尔比为2.5∶1。采用改性赤泥作为晶种诱导磷酸铵镁结晶的方法,对厌氧消化上清液中的PO3-4-P和NH+4-N进行固定化回收,考察了改性赤泥投加量、反应时间、搅拌速度和沉淀时间对厌氧消化过程中磷和氮回收效果的影响。结果表明,在改性赤泥投加量为10g/L、反应时间为90min、搅拌速度为200r/min的条件下,PO3-4-P的回收率为98.8%,NH+4-N的回收率为39.9%。用扫描电子显微镜-能谱分析和X-射线衍射对固定化磷回收产物进行的表征显示,改性赤泥表面生成了磷酸铵镁。

On purpose of phosphorus （P） and nitrogen （N） recovery from sludge, the P and N release by anaerobic digestion from sludge, and their recovery by modified red mud seeded crystallization of magnesium ammonium phosphate （MAP） were studied. The effects of sludge mixture pH, temperature and anaerobic digestion time on the release of phosphate and ammonia nitrogen were investigated. It showed that under the conditions of 50 ℃, 5-7 days of anaerobic time and without pH adjustment, the sludge mixture could release around 200.0 mg/L phosphate, 245.0 mg/L ammonia nitrogen, and the N：P molar ratio was 2.5：1. Taking the modified red mud as inducing seed crystal, the phosphate and ammonia nitrogen in the supernatant of the digested sludge were fixed and recovered by MAP crystallization, and the effects of modified red mud dosage, reaction time, stirring speed and precipitating time on the recovery efficiency were investigated. It showed that under the conditions of 10 g/L red mud, 90 minutes reaction time and 200 r/min stirring, the recovery efficiency of P and N was 98. 8% and 39.9%, respectively. The electron scanning microscopy and X-ray diffraction were employed to characterize the fixed products of the above process, and it showed that MAP was formed on the surface of the modified red mud.