| Nitrate as one of the most common non-point source pollutants,exist with orther contaminants mostly,like Cr???.This phenomenon has impacted on the environment and increased the difficulty of governance.The present study is mainly about simultaneous removal of Cr???and nitrate,research on the effect of Cr???on nitrate removal is less.This study used UASB reactor to culture denitrifying granular sludge and chromium-resistant denitrifying granular sludge.The removing ability of nitrate and the granule characteristics were investigated,the optimal Cr???concentration and the optimal rising flow rate was determined.Start four UASB reactors,the operating conditions was:R1 and R2 was inoculated with denitrifying granular sludge,nitrate influent concentration was 200 mg·L-1;R3 and R4was inoculated with chromium-resistant denitrifying granular sludge,nitrate influent concentration was 100 mg·L-1.The rising velocity of R1 and R3 was L·h-1,R2 and R4 was2 L·h-1.In order to investigated the effects of different Cr???influent concentration on denitrification process,we increased Cr???influent concentration from 10 mg·L-1 to 30mg·L-1gradually.The major conclusions are as follows:1)Used activated sludge from the secondary sedimentation tank of a sewage treatment plant as inoculate sludge to culture denitrified granular sludge and the chrome-resistant denitrifying granule sludge,respectively.R1 cultivated denitrified granular sludge at about 54 d,R2 cultivated chromium-resistant denitrified granular sludge at about 60 d.The particle size of denitrified granular sludge and chromium-resistant denitrified granular sludge are mainly between 0.4251.9 mm,and the PN/PS value are 1.1.2)Stability in the operation of four reactor,when the Cr???influent concentration increased from 10 mg·L-1 to 30 mg·L-1,the nitrate removal rate of R1 and R2 was 87.5%and 97.5%,respectively;R3 and R4 remained at 98%.The Cr???removal rate of R1 and R2 was 83.33%and 91.67%,respectively;R3 and R4 remained at 95%.The Zeta potentials in R2 and R4 reactors are lower than those in R1 and R3 reactors,respectively,and the relative hydrophobicity is higher than that of R1 and R3 reactors.The wet density of the four reactors was stable at about 1.0 g·L-1.3)During the recovery of the four reactors,R1,R2 and R3 did not add Cr???in the influent,and the removal ability of nitrate was improved.While the nitrate removal rate of R4 reactor is not very different from the stable operation.The particle size of the granular sludge in the four reactors is mainly distributed between 0.851.9 mm;the wet density and Zeta potentials is not quite different from stability in the operation of four reactor.In this paper,the effects of different rising flow rates and Cr???influent concentration on the denitrification process in the reactor were studied by cultivating denitrifying granular sludge and chrome-resistant denitrifying granular sludge.The results will provide theory and technique basic for nitrate removal in groundwater. |
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