| High yield pulping is widely accepted because of its high utilization of natural fibers and less pollutant discharge. High yield pulping process represented by APMP, PRC-APMP and BCTMP has become the mainstream of international pulp and paper industry development. But the high load of COD and BOD and the deeper color of the effluent bring a certain degree of difficulty to improve the quality of the treated water.Biological treatment is the most common and effective method of abatement pollutants such as COD. But its contribution to the color removal is very small, in most cases, it can even make the treated water darker. Improving the quality of treated pulping effluent and expanding the scope and scale of wastewater reuse are important to solve the water-saving problem of pulp and paper industry. Therefore, it is necessary to figure out the generated and transformed process of color substances during biological treatment. That is also important for solving all of color problems which is caused by biological treatment of paper effluent, food and fermentation wastewater.In this study, high yield pulp wastewater was treated with activated sludge to explore the transformation of colored substance by changing process conditionsIn this study, eucalyptus APMP wastewater was treated with activated sludge.The CODcr of raw wastewater was 4181mg/L and the color was 2541CU.. The CODCr removal and color were influenced by changing the culture time, pH, temperature, nutrients, dissolved oxygen, and sludge concentration.In most cases, the color of treated wastewater was increased compared with the initial wastewater. The lowest color of treated wastewater was 1557 CU. when the conditions were proper. The proper conditions were:reaction time 3 days, pH 6.0, temperature 35℃,C:N:P=150:5:1, liquid volume 150 ml(250ml flask) and sludge concentration 30%.After the wastewater is treated in proper conditions, the absorbance intensity both at visible and ultraviolet wavelength were decreased obviously. Infrared spectra showed that the content of-CH2-in treated water was increased comparing with the raw wastewater, and the weak absorption band near 2350 cm-1 indicated the existence of nitrogen compounds in wastewater,and the lignin was removed effectively because of the disappear of absorption band near 923 cm-1. Furthermore,The new substances containing group C=C or C=O may lead to the darker treated water when they were accumulated in water.The raw effluent and treated effluent were filtrated by hollow-fiber ultra-filtration membranes with 10000 same MWCO of membranes at the same concentration ratio.The entrapment rate for color substances of raw water was 86.85%. And the entrapment rate for color substances of raw water was 84.38%.The eucalyptus APMP wastewater mainly contained acids, phenols, alcohols and other organic matter. The content of long chain fatty acid was about 40%,and the content of dicarboxylic acid was 16.6%,and substances with a benzene ring content 15.3%.These made the raw water coloured.A large amount of organic matter was removed by activated sludge treatment. The 2,6-di-t-butyl phenol was the main matter that made the treated water coloured... |
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