超声破解污泥对硝酸盐还原酶活力的影响

Effect of Ultrasonic Disintegration of Sludge on Nitrate Reductase Activity

硝酸盐还原酶是生物脱氮过程中最为重要的一种酶,而超声波预处理活性污泥可改变酶促反应速率。采用超声破解污泥,研究了探头式超声反应器在控温与未控温条件下硝酸盐还原酶活力的变化。研究发现,未控温条件下,采用低声能密度(0.48 k W/L)破解污泥,硝酸盐还原酶活力随破解时间的延长而上升,此时絮体尺寸减小为其主要作用;在0.96和1.44 k W/L声能密度下破解污泥,随超声破解时间的延长,硝酸盐还原酶活力先上升后下降,此时絮体尺寸减小、温度上升与细胞膜破裂作用同时存在;在高声能密度条件下破解污泥,由于温度上升过大会使硝酸盐还原酶彻底失活,温度成为影响硝酸盐还原酶活力的关键因素。另外,采用槽式超声反应器考察了超声频率对硝酸盐还原酶活力的影响。研究发现,在相同比能下,硝酸盐还原酶活力受频率的影响较大,超声频率为20 k Hz有利于增加硝酸盐还原酶活力。

Ultrasonic sludge pretreatment can change the enzymatic reaction rate, while nitrate re- ductase is an important enzyme during biological denitrification process in the wastewater treatment plant. The change of nitrate reductase activity caused by ultrasonic disintegration of sludge at controlled tempera- ture and uncontrolled temperature was studied respectively by using a probe type ultrasonic reactor. It was found that when sludge was pretreated with low ultrasonic energy density of 0.48 kW/L at uncontrolled temperature, the nitrate reductase activity would increase with disintegration time. Under such a condi- tion, uhrasonication mainly contributed to the decrease of floe size. When sludge was pretreated with high ultrasonic energy density such as 0.96 kW/L and 1.44 kW/L at uncontrolled temperature, nitrate redue- tase activity would increase first and then decrease. In this case, the decrease of floc size, the increase of temperature and the breakage of cell membrane existed simultaneously. When pretreated with high ultra- sonic energy density, temperature became the dominant factor influencing nitrate reductase activity, be- cause excessive heat caused by ultrasonication would deactivate nitrate reductase activity. In addition,the effect of ultrasonic frequency on nitrate reductase activity was also studied by using a trench type ul- trasonic reactor. It was found that if sludge was pretreated with a fixed ultrasonic energy density, nitrate reductase activity would be affected greatly by ultrasonic frequency, and 20 kHz would benefit the in- crease of nitrate reductase activity.