| Medical wastewater is a toxic and infectious wastewater produced by medical institutions in the provision of medical care and medical services.it contains a large number of pathogenic pollutants such as viruses,bacteria and parasite eggs.If medical wastewater containing pathogenic pollutants is directly discharged without disinfection and sterilization,it will cause serious water and soil pollution.It may also become a way to spread diseases and pose a serious threat to people's lives.Therefore,how to scientifically and effectively treat medical wastewater has become an urgent environmental problem.In this paper,low temperature plasma technology was used to simulate the inactivation of bacterial contaminants in medical wastewater.On the one hand,the effect of high pressure DC discharge induced plasma treatment of Staphylococcus aureus in water was studied,which provides effective technological support for the end sterilization of medical wastewater.On the other hand,the inactivation effect and mechanism of the in vitro cultured S.aureus biofilm was studied by using low temperature plasma activated water.It is intended to provide a valuable reference for the application of plasma activated water in the sterilization of medical devices,surgical tools,chronic wounds,etc.as well as a theoretical basis for effectively reducing the source of bacteria in medical wastewater.The specific research results is as follows:?1?The inactivation of Staphylococcus aureus in water treated by low temperature plasma was studied.The inactivation effect of bacteria was evaluated by the measure of culturability,metabolic capacity,and integrity of bacterial cell membrane.The study finds that Plasma treatment can cause an obvious deactivation effect on Staphylococcus aureus in water.With the increase of treatment time by plasma,the bacteria with culturability?metabolic capacity and intact cell membrane structure in aqueous solution showed a downward trend,and fell to the lowest point after 30 minutes'plasma treatment,respectively,0log10 CFU·mL-1,5.13%,9.31%.?2?The presence of active particles such as atomic oxygen?O?in low temperature plasma was detected by emission spectroscopy.The concentration of representative long-lived active components?H2O2?NO3-?NO2-?O3?in activated water induced by low temperature plasma after discharge at different times was investigated.The results showed that the concentration of the long-lived active groups like H2O2?NO3-?NO2-?O3 in the activated water obtained different degrees of accumulation with the increasing discharge time,and reached its maximum point after 60 minutes'discharge,which were 227.23mg·L-1,164.33mg·L-1,180.21mg·L-1,5.84 mg·L-1.?3?The inactivation effect and mechanism of in vitro cultured S.aureus biofilm treated by plasma-induced activation water were studied.The effects on Staphylococcus aureus biofilm under plasma treatment or activated water soaking at different time were studied.The culturability,metabolic capacity,membrane integrity and intracellular ROS content of Staphylococcus aureus were also accessed.The study finds that the activated water has obvious deactivation effect,and prolonging the plasma treatment time and the activation water soaking time can enhance the deactivation effect.After activated water treatment,the intracellular ROS content of bacteria increased significantly.The synergistic effect of a large number of active groups accumulated in activated water and bacterial intracellular ROS may be the main reason for biofilm inactivation.?4?The ability to regenerate biofilms of viable bacteria after plasma activated water treatment was evaluated by measuring the culturability,metabolic capacity,and total biomass of the regenerated biofilm.The results showed that after the plasma activated water treatment,the three indexes decreased significantly,the ability of the surviving bacteria to regenerate the biofilm was significantly reduced,and the plasma activated water had a long-term inhibitory effect on the S.aureus biofilm. |
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