不同曝气位点对微氧强化硫酸盐还原-反硝化脱硫效果及群落结构的影响

微氧强化硫酸盐还原-反硝化脱硫(SR-DSR)工艺因具有同步处理废水中COD、NO~-_3、SO■生成S~0且运行成本低、流程短的优势而受到关注.但因不同曝气方式而在反应器中形成的不同微氧区的位置对反应器运行效能、S~0转化率和群落结构的影响尚不明确.因此,本文以5 mL·min~(-1)·L~(-1)曝气速率、10.4 mmol·L~(-1)硫酸钠、31 mmol·L~(-1)乳酸钠和8 mmol·L~(-1)硝酸钾连续运行膨胀颗粒污泥床(EGSB)反应器,对比研究了回流槽中(底部)曝气(微氧区位于反应器下部)和反应区上部曝气(微氧区分别位于反应器上部和下部但DO更低)运行稳定后,反应器的运行效能、S~0转化率和功能微生物的演替规律.结果表明,上部曝气时乳酸盐去除率为100%,出水中乙酸盐浓度为9.1 mmol·L~(-1),丙酸盐浓度为3.7 mmol·L~(-1),NO~-_3去除率为100%,出水中NO~-_2浓度为0.35 mmol·L~(-1),SO■去除率为84%,出水中S~(2-)浓度为2.6 mmol·L~(-1),S~0转化率为59%.与底部曝气相比,上部曝气时出水中乙酸盐和丙酸盐浓度分别升高2.2和1.9 mmol·L~(-1),NO~-_2浓度下降0.15 mmol·L~(-1),S~(2-)浓度降低0.5 mmol·L~(-1),SO■去除率和S~0转化率分别下降6%和1%.上部曝气时,反应器下部和上部均存在相对减弱的微氧环境,使得反应器中硫酸盐还原菌(SRB)Desulfomicrobium和Desulfobulbus的总丰度分别增加9%和5%,硫氧化反硝化菌(soNRB)Halothiobacillaceae和Sulfurovum的丰度均减小3.1%,异养反硝化菌(hNRB)Comamonas的丰度升高0.2%,互营菌Synergistaceae的丰度减少37%.其中,反应器下部的SRB和soNRB总丰度分别升高28%和3%,为SO■还原和S~0转化提供了充分条件,而反应器上部的微氧环境又减弱了SO■还原过程,从而降低了反应器出水中的S~(2-).因此,在碳源充足的条件下,可以采取反应器上部曝气的方式创造微氧环境,既可以保证较高的S~0转化率,又可以减少出水中S~(2-)和NO~-_2的浓度.

Effects of aeration position on performance and microbial zonation of SR-DSR process under the micro-aerobic condition

It has attracted wide attention for the advantages of sulfate reduction-denitrifying sulfide removal (SR-DSR) under micro-aerobic for simultaneous treatment of COD, NO₃^-, SO₄^2- to S⁰ in wastewater with low operation cost and short process. However, it is still unclear that the effect of different micro-aerobic zones formed in the bioreactor due to different aeration modes on the bioreactor operation efficiency, S⁰ transformation efficiency and microorganism community. Therefore, an EGSB bioreactor was continuously operated as SR-DSR progress with the aeration rate of 5 mL·min^-1·L^-1 and the influent of 10.4 mmol·L^-1 NaSO₄, 31 mmol·L^-1 sodium lactate and 8 mmol·L^-1 KNO₃. Compared and studied the operation efficiency, S⁰ transformation efficiency and functional microorganism succession rule of the bioreactor when the quality of effluent was stable with the aeration in the reflux tank (micro-aerobic zone at the bottom of the bioreactor) and aeration in the top of the reaction zone (micro-aerobic zone at the top and bottom of the bioreactor with lower DO). The results showed that the removal efficiency of lactate, NO₃^- and SO₄^2- were respectively 100%, 100% and 84%, with the concentration of acetate, propionate, NO₂^- and S^2- in effluent were respectively 9.1 mmol·L^-1, 3.7 mmol·L^-1, 0.35 mmol·L^-1 and 2.6 mmol·L^-1 and 59% S⁰ transformation. The relatively weak micro-aerobic environment at lower and upper parts of the bioreactor, which due to aeration in the top of the reaction zone, increased the total abundances of SRB Desulfomicrobium and Desulfobulbus by 9% and 5%, respectively, and both decreased the abundances of soNRB Halothiobacillaceae and Sulfovum by 3.1%, respectively, increased the abundance of hNRB Bacteroidetes_vadin HA17 and Comamonas by 3.5% and 0.2%, respectively, and decreased the abundance of Synergistaceae by 37%. Further more, the total abundance of SRB and soNRB in the lower part of the bioreactor increased by 28% and 3%, respectively, which provided sufficient conditions for SO₄^2- reduction and S⁰ transformation. At the same time, the micro-aerobic environment in the upper part of the bioreactor weakened the SO₄^2- reduction process, reduced the concentration of SO₄^2- in the effluent. As a result, compared with aeration in the reflux tank, the concentration of acetate and propionate in effluent increased 2.2 and 1.9 mmol·L^-1, respectively, the concentration of NO₂^- and S^2- decreased 0.15 and 0.5 mmol·L^-1, respectively, the removal rate of SO₄^2- and the conversion rate of S⁰ decreased 6% and 1%, respectively in the aeration in the top of the reaction zone one. Therefore,under the condition of sufficient carbon source, aeration at the upper part of the bioreactor can not only ensure a high transformation of S⁰, but also reduce the concentration of S^2- and NO₂^- in the effluent.