药剂真空预压法在工程废浆处理中的防淤堵作用

为探讨药剂真空预压法的防淤堵作用,对上海某场地的原始废浆和添加药剂的废浆均分别进行了沉降柱试验和真空预压试验。在沉降柱试验中研究了原始废浆和添加不同药剂后废浆的沉降和浊度特性,结果显示添加CPAM的废浆固液分离最快,上清液浊度最低;添加PAFC的废浆固液分离最慢,上清液浊度最高。在真空预压试验中研究了出水量、含水率、颗粒分布及孔隙变化,颗分结果表明加药沉淀后废浆中的细颗粒会"生长"成粗颗粒;压汞试验反映了原始泥浆、加药絮凝、真空预压各个阶段孔隙的变化过程;出水量测试显示普通真空预压开始不久出水速率便迅速衰减,而药剂真空预压的出水速率一直很大,说明药剂真空预压法具有非常好的防淤堵作用。最后,从废浆中的土颗粒生长、游离细颗粒流失和降低水流阻力三方面对药剂真空预压的防淤堵作用进行了解释。

Anti-clogging function of vacuum preloading with flocculants in solid-liquid separation of construction waste slurry

The settling column tests and the vacuum preloading model tests are performed on the waste slurry of a construction site in Shanghai and the additive agent slurry. The sediment and turbidity characteristics of slurries with four different agents are studied. The test results show that the turbidity of supernatant decreases after adding agents. The waste slurry mixed with CPAM has the fastest speed in solid-liquid separation and the lowest turbidity of supernatant, and that mixed with PAFC has the slowest speed in solid-liquid separation and the highest turbidity of supernatant. The water yield, water content, particle-size distribution, void ratio and variation of pore-size distribution are studied in the vacuum preloading model tests. The test results show that the small-size particles become larger, and the particles with size larger than 75 mm increase by 13.01% after adding agents and increase to 23.68% after vacuum preloading. The results of mercury intrusion porosimetry tests show exactly the process of pore change during adding of agents and vacuum preloading. The water velocity of slurry with common vacuum preloading decreases quickly after starting of vacuum preloading, and drain channels are clogged by particles. The water velocity of slurry with additive agents combined with vacuum preloading decreases slowly and it exhibits great anti-clogging effect of additive agents. The water yield of slurry with additive agents combined with vacuum preloading is nine times larger than that with common vacuum preloading. Finally, the reasons for anti-clogging effect of additive agent combined with vacuum preloading are explained by the variation of particle size, loss of small particles, and reduction of flow resistance.