【作者】 丁文川；

【导师】 龙腾锐；

【作者基本信息】 重庆大学 ， 市政工程， 2007， 博士

【摘要】 近年来,低强度超声波辐射提高生物细胞或酶活性的作用效应被大量研究所证实,从而开辟了超声波应用的新领域。将低强度超声波的生物效应运用于强化废水生物处理过程,目前国内外才开始进行探索,相关研究还不深入。论文对频率21kHz~40kHz低强度超声波辐射提高污泥生物活性的影响参数和作用机制进行了试验研究;考察了低强度超声波预处理活性污泥对废水有机污染物生物降解过程的作用效应;借助分子生物学研究手段,揭示了低强度超声波辐射对污泥微生物群落结构的影响;研究了低强度超声波辐射强化污泥好氧消化工艺,并推导出超声波输入能量与消化反应速率关系的经验式。主要研究成果如下:①采用频率21kHz~40kHz超声波对活性污泥进行辐射,在一定的功率和辐射时间范围内,可有效提高污泥的生物活性。当采用功率40W(功率密度0.05W/mL)、频率28kHz超声波辐射污泥10min后,污泥OUR较辐射前提高129%,蛋白水解酶活力提高23.7%,污泥脱氢酶活性提高24.6%,且强化效应具有时间上的持续性。试验结果表明,超声功率、频率、辐射时间以及污泥的浓度和性质等都对超声波提高污泥活性效果造成显著影响,相同的超声辐射参数对不同生物酶产生促进或抑制作用,并且超声辐射对污泥生物活性的强化作用在一个较窄的超声参数范围内。②低强度超声辐射预处理活性污泥后,会干扰活性污泥在废水净化过程中对糖类、蛋白质等物质的正常合成代谢,使污泥胞外聚合物(EPS)组成成分含量发生明显变化。当采用频率21kHz和28kHz,功率20W和40W(功率密度分别为0.02W/mL和0.04W/mL),辐射时间10min对活性污泥进行超声预处理后,污泥EPS中多糖含量均明显小于对照,仅为对照的77.6%~90.4%;而蛋白质含量高于对照,为对照的110.0%~133.5%。③采用适当的辐射参数直接对活性污泥进行超声预处理,然后再与废水混合反应,可以提高活性污泥对废水有机物的去除。在试验中发现,当采用频率28kHz,功率40W(功率密度0.02W/mL),辐射时间2min参数组合预处理活性污泥,运行6h后反应器混合液SCOD去除率较对照提高了8.2%,而污泥表观产率系数为0.489 gMLSS/gCOD小于对照0.554 gMLSS/gCOD,产生出类似污泥“解偶联”机制的现象,这对于污水处理过程中污泥减量具有一定意义;但超声预处理使污泥絮凝效果变差,在活性污泥工艺中需要对泥水分离单元进行改进(如采用膜分离),以保证良好的出水水质。④在污泥好氧消化过程中引入低强度超声波辐射的试验结果表明,超声波辐射能显著提高污泥好氧消化效率,选用功率密度0.045W/mL~0.09W/mL超声对污泥间歇辐射处理,每次辐射时间10min~20min,可使污泥消化反应的Kd值较对照提高40%~90%,剩余污泥的好氧消化稳定时间提前3~7d;超声波能量输入对消化速率影响与温度对酶促反应的影响有着惊人的相似,并存在最适的输入能量和最大反应速率,超声波辐射后可改善消化液的沉降性能。⑤低强度超声波提高污泥生物活性机制可能在于超声波能量输入、机械效应和空化效应等强化了污泥混合液固-液对氧的传质、提高酶活性以及增加了溶液中可利用基质;但同时超声空化作用产生大量自由基,会对污泥微生物活性产生抑制或破坏,因此低强度超声辐射对污泥活性影响是促进效应和抑制效应共同作用下的综合表现。采用ERIC-PCR指纹图谱对污泥微生物群落结构分析表明,低强度超声预处理不会迅速改变污泥优势种群组成,但可能造成一些种群微生物代谢受到抑制,改变了各种群个体数量增长平衡,从而引起污泥整体代谢特征的变化。更多还原

【Abstract】 In recent years the effect of low intensity ultrasound (US) irradiation on improving the activity of biological cells or enzymes has been confirmed by a great number of studies, which leads to opening up a new field of ultrasound application. The application of the bio-effect caused by the low intensity ultrasound to intensify the biological process in waste water treatment is only in the primary stage of investigation both at home and abroad and related studies have not been advanced in depth yet. In this thesis the experimental study on application of low intensity ultrasound irradiation with frequency of 21kHz ~ 40kHz to enhancing the activity of the sludge is introduced, the factors influencing the activity of the sludge and the mechanism of ultrasound action are explored. In this study the effect of active sludge pretreated by low intensity ultrasound on the bio-degradation of organic pollutant in wastewater was investigated. The influence of low intensity ultrasound irradiation on the structure of microbe community in sludge has been revealed. A technology of sludge aerobic digestion enhanced by low intensity ultrasound irradiation is suggested. An empirical formula for the relationship between input energy of ultrasound and the digestion rate has been deduced. The conclusions of this study are as follows:①The activity of sludge could be effectively enhanced by US irradiation with frequency of 21kHz ~ 40kHz under certain range of power input and irradiation time, for example, after pretreatment of the sludge by low intensity US with a power input of 40W (power density 0.05W/mL)and frequency of 28kHz for 10 min, its OUR, proteases activity and dehydrogenases activity were increased by 129%, 23.7% and 24.6% respectively and the intensifying effect was a continuous process. Test results show that the power, frequency and irradiation time of the ultrasound as well as the concentration and property of the sludge have significant influence on the effect of the ultrasound on enhancing the activity of the sludge. For different biological enzymes the same irradiation parameters of the ultrasound may produce promoting or inhibiting effect. Therefore, the intensifying effect of the ultrasound irradiation on the activity of the sludge may exist only in a narrow range of its parameters.②After pretreatment of activated sludge by low intensity US, the normal synthesis metabolism of the sugars and protein of activated sludge during the wastewater purification may be disturbed, which leads to obvious variation of the sludge extracellular polymeric substances (EPS) composition, for example, when the sludge pretreated by US at the frequency of 21 kHz and 28 kHz, power input of 20 W and 40 W (power density 0.02W/mL and 0.04W/mL) with exposure time of 10 min, the polysaccharose concentration in the sludge EPS is less than that in the control one and consists of 77.6%~90.4% of the latter, but the protein content is more and consists of 110.0%~133.5% of the control sample.③The sludge, pretreated by US with proper irradiation parameters and then mixed with wastewater, can enhance the removal rate of organic substances in waste water. An important phenomenon has been observed that when the sludge was pretreated by US at the frequency of 28 kHz, power input of 40 W with exposure time of 2 min, after 6h of operation, the supernatant SCOD removal rate of the reactor was increased by 8.2% compared with that of the control one, but the yield coefficient of the sludge was 0.489 gMLSS/gCOD, smaller than 0.554gMLSS/ gCOD for that of the control one, a phenomena similar to the "uncoupling" mechanism of the sludge was observed, which has certain meaning for sludge reduction during wastewater purifying. However, the US pretreatment made the flocculation effect of the sludge worsen, therefore, the separating unit in the active sludge technology should be improved (e.g. using film separation) to ensure the quality of the effluent in process.④The experiment results of sludge aerobic digestion with low intensity ultrasonic irradiation show that when the excess sludge was irradiated by low intensity ultrasound intermittently at a power density of 0.045W/mL or 0.09 W/mL with exposure duration of 10min~20min each time, the Kd of its digestion process was increased by 40%~90%. The US irradiation is able to improve the aerobic digestion efficiency of the sludge and the stabilization time for the excess sludge aerobic digestion can be shortened by 3~7 d. The influence of acoustic energy input on the digestion rate is quite similar to that of temperature on the enzyme reaction and there existed optimal energy input and maximal reaction velocity and the ultrasound irradiation can improve the sedimentation of the digestion mixture.⑤The experiments results show that the mechanism of enhancing biological activity of the sludge by the low intensity US is possibly attributed to the energy effect, mechanical effect and cavitation effect, which can improve the liquid-solid mass transfer of the sludge, enhance the activity of biological enzyme and increase the biodegradable substance in mixture. On the other hand, free radicals in high concentration were generated by ultrasonic cavitation, which can inhibit or even damage the biological activity of the cells. Therefore, the effect of low intensity US irradiation on the sludge activity is a synthesized performance of enhancing and inhibiting action. The ERIC- PCR fingerprint diagram for the microbe population structure indicated that the low intensity ultrasonic pretreatment cannot alter the prevailing sludge group composition rapidly, but the biological metabolism of some microbe groups might be depressed which result in change of the quantity balance of the populations, and the whole metabolic characteristic of sludge would be varied. .更多还原