垃圾渗滤液的延时搅拌造粒混凝处理特性研究

Treatment characteristics of the delayed stirring pelleting coagulation of landfill leachate

混凝沉淀在垃圾渗滤液的深度处理工艺中是非常必要的预处理环节。传统的混凝工艺处理垃圾渗滤液普遍存在水资源回收率低、污染物去除率低、絮凝体松散等缺点。基于收缩脱水絮体致密化理论,提出了垃圾渗滤液的延时搅拌造粒工艺,通过长时间高强度的机械搅拌实现悬浮物的均一化。研究结果表明,在pH=12、搅拌强度为1500 r/min、PAC和PAM投加量分别为3000 mg/L和60 mg/L的最佳条件下,SS、浊度、COD的去除率分别可达92.33%、99.92%、35.84%。通过图像粒子测算系统测得最佳条件下絮凝体d_(50)为3.76 mm,沉速为20.08 mm/s,与常规混凝相比,沉速提升约60%。基于絮体沉速、投影面积、有效粒径等数据,计算得到三维分形维数为2.8909,有效密度为0.0876 g/cm^(3)。延时搅拌造粒生成的絮体沉速快、密度大,混凝后的上清液回收率可由常规混凝的45%提升至85%。

Coagulation sedimentation is a critical pretreatment step in the advanced treatment of landfill leachate.Traditional coagulation processes for treating landfill leachate have drawbacks such as low water recovery,loose flocs,and low pollutant removal efficiency.A delayed stirring pelleting coagulation process of landfill leachate was put forwarded based on the theory of mechanical syneresis.Through long periods of high-intensity mechanical agita⁃tion,it could homogenize suspended solids.The results showed that the removal efficiency of SS,turbidity,and COD could reach 92.33%,99.92%,and 35.84%under optimal conditions of pH=12,stirring strength of 1500 r/min,PAC and PAM dosage of 3000 mg/L and 60 mg/L.The image particle measurement system revealed that under optimal conditions,the d_(50) of floc was 3.76 mm and the sedimentation velocity was 20.08 mm/s,which was approximately 60%higher than that of conventional coagulation.According to the floc sedimentation rate,projection area and effec⁃tive particle size,the three-dimensional fractal dimension was 2.8909 and the effective density was 0.0876 g/cm^(3).It was found that the floc produced by delayed stirring pelleting coagulation had fast sedimentation speed and high density,and the supernatant recovery rate after floc could increase from 45%conventional coagulation to 85%.