Investigation of DCS in the recycling water of a recycled fiber mill

In this paper, the composition and accumulation characteristics of dissolved and colloidal substance (DCS) and the related parameters were investigated in the recycling water of a local recycled fiber mill with zero wastewater discharge, the internal relationships among these parameters were analyzed. The results showed that DS accounted for more than 80% of the DCS is the major components of the DCS, it is the main contributor to conductivity of the recycling water with 90% contribution to the charge value of DCS. Macromolecular colloid substances which diameter is bigger than 0.45 μm are the main components to affect turbidity of the water. The DCS diameter in wastewater discharged from pulping process is mainly distributed in the range of 0.4 μm to 0.5 μm. But which from paper-making process is mainly distributed from 0.2 μm to 0.4 μm. Then it is reduced to 0~0.1 μm after anaerobic unit, but increased to 0.5 μm~0.6 μm after aerobic unit. During the anaerobic treatment, the cationic charge demands of DS and DCS are decreased; the cationic charge demand ratio of DS/DCS shows the maximum value, which indicating that anionic trash removes evidently in anaerobic stage. However, DS, DCS, as well as the cationic charge demand ratio of DS/DCS increase after aerobic treatment, which can be interpreted that a large number of neutral CS and negatively charged DS are produced after aerobic oxidation.