Study On The Treatment Of Tannery Wastewater With Combined Process

As the pillar industry of China’s light industry, the rapid development of leather industry has caused widespread concern on treatment of its wastewater. Traditional treatment of this kind wastewater combined the physical-chemical methods and biological methods. But the fluctuation of water quality, high concentration of pollutants, and disturbance of hexavalent chrome and sulfide make tannery wastewater difficult to treat, otherwise, accumulation of ammonia nitrogen and weather change also adverse to the system. Unstable of process, ammonia nitrogen exceed the discharge standard because of low efficiency of biological section occurred in practical operation, and with the increasingly stringent of discharge standard, optimal physical-chemical-biological-a dvanced treatment with high stability is expected to solve the problems above.The purpose of this study is to investigate the possibility of the combination of pretreatment, biological treatment and advanced treatment, and optimize the combination form and operation parameters. In the pretreatment, twice flocculent precipitate was used to enhance the removal of total chrome and sulfide, pre-precipitate and chemical precipitate were participate for the first flocculent, PAM added in the inlet to help the flocculent, FeSO4was added simultaneously to remove sulfide, then PAM was chose for the secondary flocculent. Results showed that about90%of total chrome and sulfide could be removed, which reduced the burden of following process. The whole process started in four steps, which enhanced the nitrification and denitrification. Optimized operation to shorten the residence time, PACT was used simultaneously to enhance the biological treatment. About90%of the main pollutants were removed, and the denitrogenation efficiency could achieve about95%. Combined the subentry process properly, used the alkali wastewater to treat the chrome-contained wastewater and advanced treatment process was employed to improve the system’s stability. Results indicated the combined process has a higher efficiency and more stable than ordinary tannery wastewater treat system, could meet the secondary standard limitation of "the comprehensive discharge standard of Haihe basin in Shandong province" economically.