Font Size: a A A

The Effect Of Cu And Zinc Ions On Activated Sludge Microbes And Its Analysis With Molecular Biological Technique

Posted on:2003-07-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:B XieFull Text:PDF
GTID:1101360095953837Subject:Environmental Engineering
Abstract/Summary:PDF Full Text Request
Heavy metals are commonly found in municipal sewage that contains industrial effluents. It is well documented that metal concentrations above toxic levels inhibit biological processes in municipal sewage treatment works and discharge of metals into surface waters can have severe impacts on the environment, ecosystems and public health.The effects of copper and zinc ions on activated sludge microorganisms of Sequence Batch Reactor (SBR) were investigated in this paper. The studies included the contents as followings: l).The effect of heavy metals on physicochemical index of SBR process; 2).The inhibition of bio-kinetic constants of substance degradation; 3).The effects of heavy metals on structure of activated sludge floes and protozoa; 4).The effect of heavy metals on bacterial community and its analysis by molecular biological technique. Of the research above, the study of analyzing bacterial community in heavy metal shocked biological system by molecular biological technique was mostly emphasized.Experimental results listed as followings:The inhibition was obviously observed when 20mg/l of copper ion was added to the unacclimated activated sludge, the turbidity of effluent was increased. The acclimation could help to improve the removal rate of organic substance. The Monod equation could be well used to describe the effect of inhibition of substance utilization. Ks could represent the inhibited degree of different process. The acclimation could improve the resistance of microorganism to toxicity of heavy metal. The addition of special nutrients and powder activated carbon (PAC) could reduced the effect of heavy metals on SBR process. 20mg/L Copper ion had little effect on ammonia removal rate.Zinc ion had inhibition on the degradation of ammonia and nitrite and organic substance, and zinc adding could seriously inhibit the transform of ammonia and nitrite, the acclimation couldn't relieve this inhibition.The toxicity of heavy metal on protozoa is obvious, especially when the experiment is acute toxicity test, but it is not suitable as an index of chronic experiment.Using the modified DNA extraction method, the crude bacterial DNA could be extracted from activated sludge efficiently. Higher quality and quantity of sludge DNA could be obtained rapidly and inexpensively from large number of sample, andthe PCR products obtained from this protocol wasn't affected by contaminated higher concentration of heavy metals.The variation of dominant species and diversity of bacterial community were analyzed using methods of 16SrDNA Length polymorphism. The results indicated that although the kinetic constant decreased, the dominant species changed little during the acclimation, while the dominant species had a great change in the acclimated system that was shocked by high concentration of copper. The change of diversity index was consistent with the kinetic constant and diversity index. Proteobacterial fi rand Gram positive bacteria were able to tolerate and accumulate higher concentration of copper ion.The diversity and similarity of bacterial community acclimated by zinc were analyzed by Random Amplified Polymorphism DNA (RAPD). The results showed DNA sequence diversity were different during the acclimation. The diversity of zinc loading unit is lower than the control one although both COD removal rate could reache the same at the end of acclimation. There existed much difference in diversity, richness, evenness and similarity between the end and the beginning of the acclimation. It could be known that some bacteria disappeared while some zinc ion tolerated species survive from the RAPD fingerprint.FISH (Fluorescent In Situ Hybridization) was a rapid and simple method to detect the distribution and relative quantities of nitrifying bacteria in the floe of activated sludge. The FISH results showed that the smaller magnitude of nitrifying bacteria in the experiment unit is the main reason leading to the lower transform rate of ammonia and nitrite.Combined the traditional and molecular biologica...
Keywords/Search Tags:Heavy Metals, Sequence Batch Reactor(SBR), 16S rDNA, Random Amplified Polymorphism DNA (RAPD), Fluorescent In Situ Hybridization (FISH).
PDF Full Text Request
Related items