冻融对污水河道沉积物特性及脱水性能的影响

为了降低污水河道治理过程中污染沉积物的含水率以减少其对环境的二次污染,对污水河道沉积物在自然条件下和人为条件下进行冻融实验研究,通过冻融前后沉积物比阻抗、含水率、颗粒分布及渗出液中污染物含量等实验说明冻融对污染沉积物脱水性能及其特性有影响.研究表明,冻融过程使沉积物的比表面积变小,体均粒径变大,泥水明显分离,含水率从冻前83%～85%降到融后的50%～60%;大量间隙水、毛细结合水和表面粘附水游离出来,提高了沉积物的脱水性能;比阻值由(1.2～4.1)×10⁹s²/g降为(3.8～5.2)×10⁷s²/g;同时渗出液的SS含量由1 000～1 200mg/kg降到340～380 mg/kg、氨氮含量由150～170 mg/kg降到100～120 mg/kg、BOD含量由300～310 mg/kg降到50～60 mg/kg,但渗出液中油类物质含量由1～2mg/kg提高到11～12 mg/kg,即如果沉积物不是被油类物质污染,冻融可使渗出液污染程度小于冻前沉积物的渗出液.

Effect of Freeze-Thaw Treatment on Characteristics and Dewaterability of Sewage River Sediment

This research employed the freeze-thaw treatment method under nature and manual condition to reduce the moisture content of the contaminated sewage river sediment, thus reduce the secondary pollution to environment during remediation of sewage river. Experimental results show that the freeze-thaw treatment influences the sediment dewaterability and characteristics, such as specific resistance to filtration, moisture content, granule distribution, pollutant content of leachate. After freeze-thaw treatment, the surface area of the sediment became decreased, average granule diameter increased and the solid and water separated clearly. Moisture content was decreased from 83% - 85% to 50% - 60%. Volume cavernous water, capillary water and adhesion water dissociated from the sediment, thus sediment dewaterability is enhanced greatly. The specific resistance was reduced from (1.2 - 4.1) x 10(9)s(2)/g to (3.8 - 5.2) x 10(7)s(2)/g. On the other hand, leachate characteristics changed a lot: suspend solid (SS) content was reduced from 1 000 - 1 200 mg/kg to 340 - 380 mg/kg, ammonia nitrogen content was reduced from 150 - 170 mg/kg to 100 - 120 mg/kg, BOD5 content was reduced from 300 - 310 mg/kg to 50 - 60 mg/kg, however oil content was increased from 1 - 2 mg/kg to 11 - 12 mg/kg. Therefore, if the sediment is not contaminated by oil, the leachate pollution can be reduced by freeze-thaw treatment method.