| Sludge is an important product of sewage treatment,in which heavy metal sludge is heavily polluted,difficult to handle,and expensive to dispose of.Therefore,what is described above is an important problem in the sludge treatment industry.Solving the problem is very important and of great significance for our country’s carbon neutrality,sustainable development and ecological civilization construction.Our country’s leather production volume ranks first in the world,so a large amount of tannery sludge pollution is generated every year.Chromium is a toxic metal and an important element in the prevention and control of heavy metal pollution.Therefore,the treatment of tannery sludge is a key step in the effective treatment of tannery wastewater,which will provide an important guarantee for wastewater treatment in the tannery industry,and is directive and with reference value for the treatment of heavy metal chromium pollution.In recent years,the emerging biological leaching technology has solved the problems of land pollution,water pollution and air pollution caused by traditional sludge disposal methods such as incineration and landfill because of its green and low-carbon characteristics and can realize resource recycling and utilization.It has become an important sludge treatment method and has broad application prospects.Bioleaching technology utilizes the heavy metal leaching ability of Acidithiobacillus to dispose of and realize the resource utilization of sludge.It is widely used in biosphere sulfur cycle,biometallurgy and bioremediation.Biological leaching is a mixed process.However,Acidithiobacillus is affected by the nature of the sludge,possessing shortcomings and difficulties such as organic matter growth inhibition and long leaching period.The following researches have been carried out around this problem:1.Isolation and genomic analysis of a new species of AcidithiobacillusIn order to enrich the bacterial flora of Acidithiobacillus in sludge leaching,strains were isolated from the water of a tailings pit in Yantai,and new species were successfully discovered.After enrichment and screening of mineral samples,26 strains of Acidithiobacillus were identified.The phylogenetic tree,morphological description and physiological and biochemical analysis of the YTS05 strain showed that the strain was a new species of Acidithiobacillus and suggested to be named Acidithiobacillus yanwangming.The genome of strain YTS05 was sequenced and analyzed.The genome size was 2,741,152 bp,the G+C content was 58.71%,the plasmid size was 1,4321 bp,and the G+C content was 53.18%.The integrated genome data was annotated and analyzed in KEGG,CAZy,COG and other databases,and 1932,68,and 2336 related genes were annotated,and the carbon metabolism,sulfur oxidation,two-component signaling system and secretion system.2.Study on the leaching process of tannery sludge with the mixed bacteria of AcidithiobacillusUsing the screened strains and Acidithiobacillus stored in the laboratory,a mixed flora was constructed,and the physiological and biochemical indicators such as pH value,COD and Cr content in the leachate were studied during the process of leaching the tannery sludge with the mixed flora.It was found that the pH value of the leaching process showed a trend of first rise and then a rapid decline,reaching the highest at 2 days,and the sludge pH value dropped below 2 on the 8th day;in the detection of COD,the phenomenon of first falling and then rising appeared,it is speculated that the main reason is that the heterotrophic bacteria consume a large amount of organic matter in the sludge,which leads to a decrease in COD,and the death of the bacteria produces a large amount of remains,which leads to an increase in COD.In terms of Cr leaching rate,the smaller the pH,the greater the Cr leaching rate,and the final leaching rate reaches 90%above.Relevant data show that the environmental adaptability and metabolic acid production capacity of Acidithiobacillus metabolism play a central role in the entire leaching process,which directly affects the leaching effect and efficiency,and improves the growth adaptability of Acidithiobacillus in the sludge organic matter environment.3.Heterotrophic acid-tolerant yeast selection and genome research of key strains in sludge leaching systemIn order to reduce the restrictive effect of the sludge organic matter environment on Thiobacillus acidophilus and better play the role of Acidithiobacillus in sludge leaching,the screening work of acid-resistant heterotrophic bacteria in the sludge leaching system was carried out,in order to pass the heterotrophic acidophilic bacteria.The synergy of the trophic and autotrophic flora can degrade the organic matter of the sludge and provide a suitable environment for the growth of Acidithiobacillus.5 strains of Candida tropicalis,4 strains of Rhodotorula mucilaginosa,and 1 strain of Candida palmioleophila were successfully screened and identified in the acidic sludge,and adaptive laboratory evolution(ALE)was performed on the strains of tropical yeast and Rhodotorula spp.An extremely acid-tolerant strain that can tolerate pH 1.7 is bred.A strain of Candida tropicalis CBW-2 was found among the screened acid-fast yeasts.It has a good temperature adaptation range(30～40℃)and has good application value.The strain was analyzed by Illumina Hiseq+PacBio sequencing technology.Whole genome sequencing.The genome size of the strain is 14.8 Mb,and the GC content is 33.25%.The organic matter metabolism process of the strain is mainly analyzed,and the relevant results are for further systematic application.Provide background knowledge.4.Synergistic research and analysis of small molecule metabolism of acid-fast yeast and AcidithiobacillusA systematic study was carried out on the synergistic effect of acid-fast yeast and Acidithiobacillus in the presence of small molecular organic matter,in order to improve the adaptability of the organic matter environment of Acidithiobacillus.Firstly,the effects of small molecular organic compounds such as acetic acid,formic acid,methanol,glucose,butyric acid and citric acid on the growth of Acidithiobacillus were studied.At a certain concentration,it was found that acetic acid,butyric acid and formic acid completely inhibited the growth of Acidithiobacillus,while methanol,glucose and citric acid completely inhibited the growth of Acidithiobacillus.No obvious effect on its growth.Then,by adding acid-fast yeast,it was found that Candida tropicalis can grow synergistically with autotrophic bacteria and consume the organic small molecular acids.The reasons for the inhibition of autotrophic bacteria by small molecular organics were analyzed by using the genome information system,which provided the knowledge base for constructing the theory of synergistic growth of autotrophic and heterotrophic flora. |
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