Biological Treatment Of Oily Sludge Based On Bioleaching And Its Microbial Succession Mechanism

Oily sludge is a waste produced in the process of oil exploitation,storage and transportation,deep processing and storage and transportation of petrochemical products.It is usually characterized by high viscosity,rich in organic matter,heavy metals and high toxicity.Current oily sludge treatment technology includes physical,chemical and biological methods.Physical treatment methods include techniques such as centrifugation,precipitation and filtration,which are used to separate solids and liquids from the sludge.Chemical treatment methods involve the use of reagents such as acids,bases and oxidants to break down hydrocarbons and heavy metals in the sludge.Biological treatment methods involve the use of microorganisms to break down hydrocarbons in the sludge through aerobic or anaerobic processes.Among these treatment technologies,biological treatment has attracted attention due to its simple operation,low cost and environmentally friendly nature.Bioleaching technology utilizes the life activities of thiobacillus acidophilus bacteria to oxidize ferrous ions and reduced sulfur elements to high valence states,in this process,H⁺is generated and a strong oxidizing environment is created.Bioleaching strains are most commonly used in bioleaching,but because of their biological acid production and REDOX properties,they can also be used in other fields,such as advanced treatment of solid wastes.This study intends to adopt bioleaching technology to treat oily sludge,and realize the advanced treatment of oily sludge through the synergistic action between microbial populations.The dewatering,oil removal and heavy metal removal of oily sludge can be realized synchronously,and the deep harmless and reduced treatment of oily sludge can be realized.In the experiment,the optimal operating conditions of the process and the inhibitive factors and solutions for the long-term operation of the process were explored,and the microbial succession mechanism in the sludge treatment process was analyzed by means of high throughput technology.（1）Screening and domestication of functional floraAfter enrichment and isolation of 9K medium,Rhodococcus accounted for25.09%,and thiobacillus acidophilus accounted for nearly 67.96%,most of which were thiobacillus ferrooxidans.In the middle stage of oil sludge acclimation,the proportion of leach bacteria decreased,and the dominant species was Rhodococcus,that is,the bacteria degrading oil substances,but the bacteria at this stage still maintained the function of acid production.After acclimation,the structure of microbial population changed greatly,forming a system with multiple functional bacteria such as Rhodococcus（7.87%）,Thiobacillus acidophilus（42.57%）,Alicyclobacillus（12.19%）,Desulfohalotomaculum（13.38%）,etc.Functional bacteria still accounted for more than half.At this time,the functional microbial population has the function of producing acid,which can keep the system at high REDOX potential for a long time,and also has the function of degrading phenol and other organic pollutants,which provides functional bacteria for subsequent research.（2）Experimental parameters of oily sludge treatmentThrough the response surface method assisted process design,the conditions and parameters of biological treatment of oily sludge based on bioleaching technology were optimized.After optimization,the optimal operation conditions are Na₂S₂O₃·5H₂O5.00g/L,Fe SO₄·7H₂O 5.64g/L,aeration ratio（gas-water ratio）14.53,aeration interval is on for 5 minutes（min）,off for 10 minutes（min）,continuous operation,providing parameter conditions for the follow-up long cycle operation.（3）long-term process operation regulationUnder the above parameters,a long-term experiment on the advanced treatment of oily sludge was carried out by using the existing functional bacteria solution to explore the sustainability and long-term stability of the biological leaching technology for the treatment of oily sludge.The main limiting factor of the long-term operation of this process is the accumulation of heavy metal elements.Only 30%heavy metal removal rate can be achieved by carbon material adsorption method,which has adverse effects on the activity of bacterial community and population density.Functional bacteria liquid replacement method can achieve 3 consecutive cycles of stable operation in line with long-term operation requirements.To sum up,it is finally determined that bacterial solution replacement is the safeguard means in long-term operation,and the optimal replacement ratio is 80%.This replacement ratio can achieve the purpose of removing heavy metals and restoring microbial population activity.