零价铁自养反硝化过程活性污泥矿化及解决措施

Activated Sludge Mineralization and Solutions in the Process of Zero-Valent Iron Autotrophic Denitrification

本研究通过接种生活污水处理厂活性污泥,在升流式厌氧反应器内启动了零价铁还原硝酸盐的反应,经过52d的运行后实现氮去除速率29.3 g·(m^3·d)^(-1).针对运行过程中形成的三价铁及铁氧化物对污泥的包裹,致使污泥矿化,导致活性降低的问题,进行了流加污泥和改变回流两种防矿化方式的可行性研究.采用流加方式,经过22 d运行,硝酸盐氮转化速率在33.0 g·(m^3·d)^(-1)左右,出水亚硝酸盐氮平均浓度16.50 mg·L^(-1),此两者和矿化时期相比均无较大变化,而出水氨氮平均浓度从12.38 mg·L^(-1)下降到3.58 mg·L^(-1),氮去除速率从9.9 g·(m^3·d)^(-1)恢复至15.0 g·(m^3·d)^(-1),生物反应减弱了化学还原硝酸盐过程;采用改变回流方式,反应柱外部设置回流池,利用回流池上部水进行水力循环和上升冲刷,将生成的三价铁及铁氧化物随出水流出并沉积在外部回流池内,在上升流速3.49 m·h-1的条件下,转化硝酸盐对应生成的三价铁量有大约58%通过回流沉淀在外部回流池内,硝酸盐氮反应速率在34.3 g·(m^3·d)^(-1),出水亚硝酸盐氮、氨氮浓度分别为0.22 mg·L^(-1)、0.75mg·L^(-1),未出现氨和亚硝酸盐的大量积累,实现氮去除速率在33.4 g·(m^3·d)^(-1),实现了长期运行中污泥矿化问题的解决.对比两种方式,从处理效果看改变回流模式处理污泥矿化问题优于污泥流加方式.

We studied the inoculation of activated sludge from domestic sewage treatment plants. The reaction of reducing nitrate by zero-valent iron was started in the up-flow anaerobic reactor. After 52 d of operation,a nitrogen removal rate of 29. 3 g·（ m^3·d）^-1was achieved. Ferric iron and iron oxide coated on the sludge formed in the operation process caused the mineralization and slowly decreased the sludge activity. The methods of the＂supplement and replacement of the sludge in the reactor＂and＂changing the reflux mode of the reactor＂were applied. Using the method of the supplement and replacement of the sludge in the reactor,by discharging a part of the sludge in the reactor and adding the extra dosage from the anaerobic denitrifying sludge for the treatment of wastewater,after22 d of operation,the conversion rate of nitrate-nitrogen was 33. 0 g·（ m^3·d）^-1and the concentration of nitrite-nitrogen was 16. 50mg·L^-1. The effluent average concentration of ammonia-nitrogen decreased from 12. 38 mg·L^-1to 3. 58 mg·L^-1and the nitrogen removal rate was recovered from 9. 9 g·（ m^3·d）^-1to 15. 0 g·（ m^3·d）^-1. The biological reaction weakened the chemical reduction of nitrate by zero-valent iron. Using the method of changing the reflux mode of the reactor,the reflux tank was arranged outside the reaction column using hydraulic circulation. The increase in the erosion of the upper layer of the sedimentation tank would bring out ferric iron and iron oxide with the outflow water and they would be deposited in the reflux tank. The corresponding ferric iron of transformation of nitrate settled in the external reflux tank was 58% at the ascending velocity of 3. 49 m·h-1. The nitrate-nitrogen conversion rate was 34. 3 g·（ m^3·d）^-1,the effluent concentration of nitrite-nitrogen was 0. 22 mg·L^-1,and ammonia-nitrogen was0. 75 mg·L^-1. Ammonia and nitrite did not extensively accumulate. The nitrogen removal rate was 33. 4 g·（ m^3·d）^-1,which solved the problem of the mineralized sludge in the long-term reactor operation. In summary,the method of reforming the reflux mode of the reactor performed better than the method of the supplement and replacement of sludge in the reactor.