Study On The Characteristics Of Activated Sludge And Its Salt Tolerance Under Pressure

Currently,few studies had concentrated on salt tolerance behaviors of microorganisms under pressure environment,e.g.deep sea,the sediment of salt lake,salty underground water pressure,pressurized biological process etc.Pressurized biochemical methods could overcome the negative impact of the high salt environment on dissolved oxygen,and it had some advantages in dealing with high salinity organic wastewater.This subject,using activated sludge system as the research object,systematically investigated the characteristics and salt-resistant property of activated sludge under pressure in bench-scale batch reactors.The main conclusions of this paper were summarized as follows:Studies about the effect of instantaneous pressure on activated sludge characteristics showed that pressurized environment had the high oxygen transfer driving force,which could increase the concentration of dissolved oxygen(DO)and improve the degradation rate of organic matter under the same conditions.Also,the extracellular polymeric substances(EPS)and the CO2 concentration of pressurized activated sludge method were different from that of the normal environment.Whether the wastewater with salinity or not,the EPS of pressurized biochemical method was lower than that of atmospheric pressure.Lower EPS could reduce the output of excess sludge,which might be one of the important reasons for in-situ sludge reduction.Studies about the effect of instantaneous pressure on salt-resistant property of activated sludge showed that on one hand,under activated sludge systems without salt acclimation,pressure had different effects on the resistance ability of salinity shock of activated sludge.When salinity was less than 2.5%,systems had good microbial activity,and pressurized environment could degrade organics quickly and efficiently,which the pressure played a positive impact role on the salinity shock resistance of sludge.When the salinity was higher,sludge activity was inhibited,slowing the degradation rate of organics,and excessively high salinity even made organics within the reactor unable to degradation in the short time,the positive impact of pressure environment was not obvious.On the other hand,activated sludge system with salt acclimation could adapt to the high salt environment,and the high oxygen transfer driving force obtained by pressure could still increase the concentration of DO and promote the organics degradation rate of high salinity wastewater.During the process of salt acclimation of sludge under pressure,high salt environment(the salinity greater than 3%)showed obvious advantages.When the salinity was more than 3.5%,the pressure could reduce the negative impact of high viscosity caused by salinity on DO and promote aerobic degradation of organics,which made the TOC removal and dehydrogenase activity of sludge were higher than that of normal environment.Under pressure,the population structure was quite different from that of atmospheric one during salt acclimation process of sludge.The biological diversity under pressure was significantly higher than the normal one,and this result was consistent with the treatment effect.