| Saline organic wastewater is widely used in petrochemical industry,printing and dyeing,medical treatment and other industries.It contains not only refractory organic pollutants,but also a large amount of salt.Higher salinity in wastewater can poison microorganisms,thus reducing the efficiency of wastewater treatment by traditional biological methods.Salt-tolerant microorganism has been widely studied for its good survival in high salt environment,which greatly improves the efficiency of the degradation of high-salt wastewater.This paper based on activated sludge domesticated ceaselessly,to explore the properties of activated sludge and the change of the biological community with the increase of salinity system,and through the study of salt tolerance mechanism,the treatment conditions of high-salt organic wastewater were further optimized.The experimental results showed that with the increasing salinity of the system,the diversity of the microbial community was significantly reduced,the proportion of Gram-positive bacteria remained stable basically,and the dominant position of Gram-negative bacteria was gradually replaced by actinomycetes and fungi.The proportions of Dechloromonas,Phycicoccus,Dokdonella,and Nitrospira in the flora decreased,and the proportion of Rhodanobacter,Acidocella,Winogradskyella,and Parvibaculum increased in the community.The SVI value of the activated sludge and the SOUR were getting smaller and smaller,and the sedimentation performance of the sludge was significantly reduced.When the salinity was 2.0%,the SVI value of activated sludge decreased from 89.1mL·g-1in the initial period of acclimation to 34.8mL·g-1.The sludge SOUR decreased from 27.87 mgO2/gVSS·h in the initial period of acclimation to 14.91mg O2/gVSS·h,and the treatment rate of COD and NH3-N in the system was stable at 80%and 75%.Two salt-tolerant strains were isolated and screened from salt-tolerant sludge,named as strain A and strain B.After some physiological and biochemical experiments and DNA sequencing,strain A was Bacillus cereus and strain B was Bacillus anthracis.Taking strain A as an example to investigate its salt tolerance mechanism,it was found that in the high salinity environment,Bacillus cereus not only transported and absorbed cell-compatible substances such as proline,glycine,trehalose,and betaine from the environment,but also produced a large amount of protein and a certain amount of sugars in a short time to maintain their osmotic pressure.In addition,the integrity of the cell membrane was not easily affected by impact,and relatively stable permeability was maintained under high salt,maintaining cell osmotic pressure and normal membrane potential.When the influent COD concentration was 8000 mg/L,the temperature was35°C,the pH was 9,the salinity was 4%,and the inoculum amount of the suspension was 6%,the COD removal rate of the wastewater by the strain A after 24 hours was65.36%.When the influent COD concentration was 10000 mg/L,the temperature was 35°C,the pH was 9,the salinity was 6%,and the inoculum amount of the suspension was 8%,the COD removal rate of the wastewater by the strain B after 24hours was 61.50%.Sodium alginate was used to further study the immobilization of strains.The experimental results showed that the treatment rate of high-salt simulated wastewater COD by strain A was 57.32%under optimum conditions,and it could be reused for 6 times.It was still 80%of the original treatment efficiency.The COD removal rate of the simulated wastewater by the strain B was 48.2%,and the reuse effect after 7 times could reach about 80%of the original treatment efficiency. |
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