Degradation mechanism of sludge organic matter treated in alkaline/acidic solution and its effect on long-term strength

Abstract

Sludge contains a little organic matter. Due to the action of microorganisms, organic matter was decomposed, and released humic acid. It can also affect lime or cement solidified sludge. Three categories of pH solution (pH = 4.0, 7.0, and 9.0) were prepared to soaking sludge. The organic matter and pH were observed for 78 days. The results showed that both acidic and alkaline buffer solutions can accelerate the consumption of organic matter, and change the molecule structure from tightness to loosening. In addition, the alkaline solution not only can promote humic acid releasing from organic matter, but also can consume it at the same time. This is a benefit to create alkaline pore water, and further improve the effect of lime or/and cement solidified sludge. The long-term strength indicated that solidified sludge without organic matter was almost unchanged throughout the curing time. From this view, pre-treatment organic matter with alkaline solution is an effective measurement for improving the long-term performance of cement/lime solidified sludge.