Accumulation of dissolved and colloidal substances in water recycled during papermaking

As fresh water consumption in pulp and paper industry processes is reduced, dissolved and colloidal substances (DCS) gradually accumulate, which has a serious adverse impact on the production and quality of the paper product. Using laboratory simulations of the recycling filtration process of papermaking, we have studied changes in different water quality parameters with the increasing amount of water recycling to describe the accumulation of DCS. The accumulation factors (AFs) and release factors (RFs) of the different water quality parameters are also analyzed. The results indicate that the accumulation of DCS, the ultraviolet absorbance factor (UV280) and the concentration of the main inorganic ions increase in line with the increasing number of times the water is recycled. Comparing the AFs of the different water quality parameters, colloidal substances and dissolved lignin are the contaminants that accumulate most in the recycling water. The AF of the Al3+ in inorganic ions is the largest, at 10–20 times that of other ions. According to the RFs, the release rate of the colloidal substances and the dissolved lignin decreases with the increasing number of times the water is recycled. Dissolved and colloidal lignins were more affected by the contamination load increasing in the water than the other pollutants were. The release rates of calcium and magnesium were higher than the other inorganic pollutants analyzed. The major influence of the inorganic pollutant load of the water on the release rate comes from aluminum.