Study Of Advanced Treatment Of Tannery Wastewater By Biological Activated Carbon

Tanning industry is one of the large-scale industrial which discharge large amount ofwastewater. The quality of the tannery wastewater treated with conventional secondaryprocessing can achieve the standard for discharge. However, the remaining pollutants willstill bring pollution to the containing water. Therefore, the deep treatment of tannerywastewater treated with secondary processing becomes necessary steps.This research mainly includes three parts. The first part was the optimization of theoperation parameters on the biological activated carbon （BAC） system. The optimal operationparameters of the system were determined by choosing different carbon layer height, waterflow velocity and pH of influent. The second part was the screening, interactive test andpreliminary appraisal of the high efficiency degradation bacterium for COD and NH₄⁺-Nremoval. The high efficiency degradation bacterium was inoculated in BAC system forbiological strengthening to improve the efficiency of the water treatment. Furthermore, thechemical dephosphorization method was investigated to remove the residual phosphorus ofthe effluent of BAC system.The results showed that the best operation parameters of the BAC system were: thecarbon layer height100cm, the water velocity0.144L/h and the influent pH7.5⁸.Two bacterium strains of high COD degradation efficiency （F21#, S22#） and twobacterium strains of high NH₄⁺-N degradation efficiency （F18#, F22#） were screeningedfrom the tan wastewater and the biomembrane of the BAC reactor. Meanwhile, the results ofthe interactive test showed that the COD and NH₄⁺-N degradation rate of the diffierentcombination on these strains were lower than the rate of the single strains. The result suggeststhat these four high efficiency degradation bacterium strains had no synergistic reaction.The capacity of tannery wastewater treatment by BAC system was enhanced usingbiological strengthening technology, by inoculating high efficiency degradation bacteriumstrains for COD and NH₄⁺-N into BAC system ordinally. After20d’s operation, the COD, TP,NH₄⁺-N and TN concentration of effluent were70.22mg/L,4.919mg/L,0.35mg/L,9.64mg/L respectively, which were lower than before.The effluent of BAC filter still contains TP （about4⁵mg/L）, thus aluminum sulfatewas added for deeply removal of TP. The result shows that the TP concentration could below0.1mg/L when the dosage of aluminum sulfate and TP molar ratio is3:1. Satisfied phosphorus removal achieved as the removal rate reached87.2%.