Study On Deep Treatment Technology Of Pulp And Paper Mill Effluents

There are still some COD and color in pulp and paper mill effluent. As discharge standard of water pollutants for pulp and paper industry (GB3544-2008) was published and implementated, papermaking enterprises are facing serious challenges. Therefore, it is very important to study on deep treatment technology of pulp and paper mill effluents for efficient treatment and reuse of the pulp and paper mill effluent. The dissolved organic matters in the pulp and paper mill effluent could be classified to four types:Hydrophobic acids, Non-acid hydrophobics, Transphilics and Hydrophilics by XAD-4/XAD-8 adsorption resin. With TOC, UV254 and color as indicators, the proportion of the four dissolved organic matters and the removal behaviors of the four dissolved organic matters in coagulation, activated carbon adsorption, coagulation-activated carbon adsorption and Fenton oxidation process were investigated and then the causes of high COD and high color were analysised. The research results could provide the basis for selecting deep treatment process of pulp and paper mill effluents.The results showed that, in the pulp and paper mill effluents, the hydrophobic acids were the dominant organic matters of 55%-82%, and the hydrophobic acids contained the most plenty of unsaturated bonds organic matters or aromatic compounds, of 60%～80% and color was caused mainly by hydrophobic acids, of 57%～76%. The chosed four coagulants, aluminum sulfate, ferric chloride, PAC and PFS, could achieve the first step of the new standard in the optimized conditions. As the same dosage of the coagulant, iron series were better than aluminum series, but only considering the cost, PFS was the cheapest. The selected three activated carbon, bamboo, coconut and coal-based, could achieve the first step of the new standard in the optimized conditions, but the coal-based carbon per unit mass could give the best removal efficiency. The removal efficiency of TOC, UV254 and color was 72.9%, 89.4% and 100% by the combination of coagulation and activated carbon adsorption. And comparison with coagulation, it improved 7.8%,7.6% and 9.8% respectively while with activated carbon adsorption, it raised 59.0%,62.0% and 73.9% respectively. The optimized conditions of Fenton oxidation were pH value of 4.0±0.1, the concentration of ferrous ion of 0.20mM, the molar ratio of hydrogen peroxide and ferrous ion of 10:1 and the reaction time of 30 minutes. And in the conditions, the removal efficiency of COD, UV254, color and TOC was 80.6%,79.1%,100% and 53.8%.The research results on removal characterization of DOM fractions by different treatments showed that, the hydrophobic matters, especially hydrophobic acids, were good removed by coagulation and Fenton oxidation while the proportion of hydrophobics was down and the proportion of hydrophilics was up after the treatment. The hydrophilics were well removed by activated carbon adsorption while the proportion of hydrophilics was down and the proportion of hydrophobics was up. The four organic matters were excellently removed by the combination of coagulation and activated carbon adsorption while the proportion of hydrophobics was down and the proportion of hydrophilics was up after the treatment.